Next: Introduction [Contents][Index]
This manual documents the use of gfortran,
the GNU Fortran compiler. You can find in this manual how to invoke
gfortran, as well as its features and incompatibilities.
gfortranTMPDIR—Directory for scratch filesGFORTRAN_STDIN_UNIT—Unit number for standard inputGFORTRAN_STDOUT_UNIT—Unit number for standard outputGFORTRAN_STDERR_UNIT—Unit number for standard errorGFORTRAN_UNBUFFERED_ALL—Do not buffer I/O on all unitsGFORTRAN_UNBUFFERED_PRECONNECTED—Do not buffer I/O on preconnected unitsGFORTRAN_SHOW_LOCUS—Show location for runtime errorsGFORTRAN_OPTIONAL_PLUS—Print leading + where permittedGFORTRAN_LIST_SEPARATOR—Separator for list outputGFORTRAN_CONVERT_UNIT—Set endianness for unformatted I/OGFORTRAN_ERROR_BACKTRACE—Show backtrace on run-time errorsGFORTRAN_FORMATTED_BUFFER_SIZE—Set buffer size for formatted I/OGFORTRAN_UNFORMATTED_BUFFER_SIZE—Set buffer size for unformatted I/OX format descriptor without count fieldFORMAT specificationsFORMAT specificationsF, G and I format descriptorsQ exponent-letterLOGICAL and INTEGER valuesCONVERT specifier%VAL, %REF and %LOCSTRUCTURE and RECORDUNION and MAPAUTOMATIC and STATIC attributes_gfortran_set_args — Save command-line arguments_gfortran_set_options — Set library option flags_gfortran_set_convert — Set endian conversion_gfortran_set_record_marker — Set length of record markers_gfortran_set_fpe — Enable floating point exception traps_gfortran_set_max_subrecord_length — Set subrecord length_gfortran_caf_init — Initialiation function_gfortran_caf_finish — Finalization function_gfortran_caf_this_image — Querying the image number_gfortran_caf_num_images — Querying the maximal number of images_gfortran_caf_image_status — Query the status of an image_gfortran_caf_failed_images — Get an array of the indexes of the failed images_gfortran_caf_stopped_images — Get an array of the indexes of the stopped images_gfortran_caf_register — Registering coarrays_gfortran_caf_deregister — Deregistering coarrays_gfortran_caf_is_present — Query whether an allocatable or pointer component in a derived type coarray is allocated_gfortran_caf_send — Sending data from a local image to a remote image_gfortran_caf_get — Getting data from a remote image_gfortran_caf_sendget — Sending data between remote images_gfortran_caf_send_by_ref — Sending data from a local image to a remote image with enhanced referencing options_gfortran_caf_get_by_ref — Getting data from a remote image using enhanced references_gfortran_caf_sendget_by_ref — Sending data between remote images using enhanced references on both sides_gfortran_caf_lock — Locking a lock variable_gfortran_caf_lock — Unlocking a lock variable_gfortran_caf_event_post — Post an event_gfortran_caf_event_wait — Wait that an event occurred_gfortran_caf_event_query — Query event count_gfortran_caf_sync_all — All-image barrier_gfortran_caf_sync_images — Barrier for selected images_gfortran_caf_sync_memory — Wait for completion of segment-memory operations_gfortran_caf_error_stop — Error termination with exit code_gfortran_caf_error_stop_str — Error termination with string_gfortran_caf_fail_image — Mark the image failed and end its execution_gfortran_caf_atomic_define — Atomic variable assignment_gfortran_caf_atomic_ref — Atomic variable reference_gfortran_caf_atomic_cas — Atomic compare and swap_gfortran_caf_atomic_op — Atomic operation_gfortran_caf_co_broadcast — Sending data to all images_gfortran_caf_co_max — Collective maximum reduction_gfortran_caf_co_min — Collective minimum reduction_gfortran_caf_co_sum — Collective summing reduction_gfortran_caf_co_reduce — Generic collective reductionABORT — Abort the programABS — Absolute valueACCESS — Checks file access modesACHAR — Character in ASCII collating sequenceACOS — Arccosine functionACOSD — Arccosine function, degreesACOSH — Inverse hyperbolic cosine functionADJUSTL — Left adjust a stringADJUSTR — Right adjust a stringAIMAG — Imaginary part of complex numberAINT — Truncate to a whole numberALARM — Execute a routine after a given delayALL — All values in MASK along DIM are trueALLOCATED — Status of an allocatable entityAND — Bitwise logical ANDANINT — Nearest whole numberANY — Any value in MASK along DIM is trueASIN — Arcsine functionASIND — Arcsine function, degreesASINH — Inverse hyperbolic sine functionASSOCIATED — Status of a pointer or pointer/target pairATAN — Arctangent functionATAND — Arctangent function, degreesATAN2 — Arctangent functionATAN2D — Arctangent function, degreesATANH — Inverse hyperbolic tangent functionATOMIC_ADD — Atomic ADD operationATOMIC_AND — Atomic bitwise AND operationATOMIC_CAS — Atomic compare and swapATOMIC_DEFINE — Setting a variable atomicallyATOMIC_FETCH_ADD — Atomic ADD operation with prior fetchATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetchATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetchATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetchATOMIC_OR — Atomic bitwise OR operationATOMIC_REF — Obtaining the value of a variable atomicallyATOMIC_XOR — Atomic bitwise OR operationBACKTRACE — Show a backtraceBESSEL_J0 — Bessel function of the first kind of order 0BESSEL_J1 — Bessel function of the first kind of order 1BESSEL_JN — Bessel function of the first kindBESSEL_Y0 — Bessel function of the second kind of order 0BESSEL_Y1 — Bessel function of the second kind of order 1BESSEL_YN — Bessel function of the second kindBGE — Bitwise greater than or equal toBGT — Bitwise greater thanBIT_SIZE — Bit size inquiry functionBLE — Bitwise less than or equal toBLT — Bitwise less thanBTEST — Bit test functionC_ASSOCIATED — Status of a C pointerC_F_POINTER — Convert C into Fortran pointerC_F_PROCPOINTER — Convert C into Fortran procedure pointerC_FUNLOC — Obtain the C address of a procedureC_LOC — Obtain the C address of an objectC_SIZEOF — Size in bytes of an expressionCEILING — Integer ceiling functionCHAR — Character conversion functionCHDIR — Change working directoryCHMOD — Change access permissions of filesCMPLX — Complex conversion functionCO_BROADCAST — Copy a value to all images the current set of imagesCO_MAX — Maximal value on the current set of imagesCO_MIN — Minimal value on the current set of imagesCO_REDUCE — Reduction of values on the current set of imagesCO_SUM — Sum of values on the current set of imagesCOMMAND_ARGUMENT_COUNT — Get number of command line argumentsCOMPILER_OPTIONS — Options passed to the compilerCOMPILER_VERSION — Compiler version stringCOMPLEX — Complex conversion functionCONJG — Complex conjugate functionCOS — Cosine functionCOSD — Cosine function, degreesCOSH — Hyperbolic cosine functionCOTAN — Cotangent functionCOTAND — Cotangent function, degreesCOUNT — Count functionCPU_TIME — CPU elapsed time in secondsCSHIFT — Circular shift elements of an arrayCTIME — Convert a time into a stringDATE_AND_TIME — Date and time subroutineDBLE — Double conversion functionDCMPLX — Double complex conversion functionDIGITS — Significant binary digits functionDIM — Positive differenceDOT_PRODUCT — Dot product functionDPROD — Double product functionDREAL — Double real part functionDSHIFTL — Combined left shiftDSHIFTR — Combined right shiftDTIME — Execution time subroutine (or function)EOSHIFT — End-off shift elements of an arrayEPSILON — Epsilon functionERF — Error functionERFC — Error functionERFC_SCALED — Error functionETIME — Execution time subroutine (or function)EVENT_QUERY — Query whether a coarray event has occurredEXECUTE_COMMAND_LINE — Execute a shell commandEXIT — Exit the program with status.EXP — Exponential functionEXPONENT — Exponent functionEXTENDS_TYPE_OF — Query dynamic type for extensionFDATE — Get the current time as a stringFGET — Read a single character in stream mode from stdinFGETC — Read a single character in stream modeFINDLOC — Search an array for a valueFLOOR — Integer floor functionFLUSH — Flush I/O unit(s)FNUM — File number functionFPUT — Write a single character in stream mode to stdoutFPUTC — Write a single character in stream modeFRACTION — Fractional part of the model representationFREE — Frees memoryFSEEK — Low level file positioning subroutineFSTAT — Get file statusFTELL — Current stream positionGAMMA — Gamma functionGERROR — Get last system error messageGETARG — Get command line argumentsGET_COMMAND — Get the entire command lineGET_COMMAND_ARGUMENT — Get command line argumentsGETCWD — Get current working directoryGETENV — Get an environmental variableGET_ENVIRONMENT_VARIABLE — Get an environmental variableGETGID — Group ID functionGETLOG — Get login nameGETPID — Process ID functionGETUID — User ID functionGMTIME — Convert time to GMT infoHOSTNM — Get system host nameHUGE — Largest number of a kindHYPOT — Euclidean distance functionIACHAR — Code in ASCII collating sequenceIALL — Bitwise AND of array elementsIAND — Bitwise logical andIANY — Bitwise OR of array elementsIARGC — Get the number of command line argumentsIBCLR — Clear bitIBITS — Bit extractionIBSET — Set bitICHAR — Character-to-integer conversion functionIDATE — Get current local time subroutine (day/month/year)IEOR — Bitwise logical exclusive orIERRNO — Get the last system error numberIMAGE_INDEX — Function that converts a cosubscript to an image indexINDEX — Position of a substring within a stringINT — Convert to integer typeINT2 — Convert to 16-bit integer typeINT8 — Convert to 64-bit integer typeIOR — Bitwise logical orIPARITY — Bitwise XOR of array elementsIRAND — Integer pseudo-random numberIS_CONTIGUOUS — Test whether an array is contiguousIS_IOSTAT_END — Test for end-of-file valueIS_IOSTAT_EOR — Test for end-of-record valueISATTY — Whether a unit is a terminal device.ISHFT — Shift bitsISHFTC — Shift bits circularlyISNAN — Test for a NaNITIME — Get current local time subroutine (hour/minutes/seconds)KILL — Send a signal to a processKIND — Kind of an entityLBOUND — Lower dimension bounds of an arrayLCOBOUND — Lower codimension bounds of an arrayLEADZ — Number of leading zero bits of an integerLEN — Length of a character entityLEN_TRIM — Length of a character entity without trailing blank charactersLGE — Lexical greater than or equalLGT — Lexical greater thanLINK — Create a hard linkLLE — Lexical less than or equalLLT — Lexical less thanLNBLNK — Index of the last non-blank character in a stringLOC — Returns the address of a variableLOG — Natural logarithm functionLOG10 — Base 10 logarithm functionLOG_GAMMA — Logarithm of the Gamma functionLOGICAL — Convert to logical typeLONG — Convert to integer typeLSHIFT — Left shift bitsLSTAT — Get file statusLTIME — Convert time to local time infoMALLOC — Allocate dynamic memoryMASKL — Left justified maskMASKR — Right justified maskMATMUL — matrix multiplicationMAX — Maximum value of an argument listMAXEXPONENT — Maximum exponent of a real kindMAXLOC — Location of the maximum value within an arrayMAXVAL — Maximum value of an arrayMCLOCK — Time functionMCLOCK8 — Time function (64-bit)MERGE — Merge variablesMERGE_BITS — Merge of bits under maskMIN — Minimum value of an argument listMINEXPONENT — Minimum exponent of a real kindMINLOC — Location of the minimum value within an arrayMINVAL — Minimum value of an arrayMOD — Remainder functionMODULO — Modulo functionMOVE_ALLOC — Move allocation from one object to anotherMVBITS — Move bits from one integer to anotherNEAREST — Nearest representable numberNEW_LINE — New line characterNINT — Nearest whole numberNORM2 — Euclidean vector normsNOT — Logical negationNULL — Function that returns an disassociated pointerNUM_IMAGES — Function that returns the number of imagesOR — Bitwise logical ORPACK — Pack an array into an array of rank onePARITY — Reduction with exclusive ORPERROR — Print system error messagePOPCNT — Number of bits setPOPPAR — Parity of the number of bits setPRECISION — Decimal precision of a real kindPRESENT — Determine whether an optional dummy argument is specifiedPRODUCT — Product of array elementsRADIX — Base of a model numberRAN — Real pseudo-random numberRAND — Real pseudo-random numberRANDOM_INIT — Initialize a pseudo-random number generatorRANDOM_NUMBER — Pseudo-random numberRANDOM_SEED — Initialize a pseudo-random number sequenceRANGE — Decimal exponent rangeRANK — Rank of a data objectREAL — Convert to real typeRENAME — Rename a fileREPEAT — Repeated string concatenationRESHAPE — Function to reshape an arrayRRSPACING — Reciprocal of the relative spacingRSHIFT — Right shift bitsSAME_TYPE_AS — Query dynamic types for equalitySCALE — Scale a real valueSCAN — Scan a string for the presence of a set of charactersSECNDS — Time functionSECOND — CPU time functionSELECTED_CHAR_KIND — Choose character kindSELECTED_INT_KIND — Choose integer kindSELECTED_REAL_KIND — Choose real kindSET_EXPONENT — Set the exponent of the modelSHAPE — Determine the shape of an arraySHIFTA — Right shift with fillSHIFTL — Left shiftSHIFTR — Right shiftSIGN — Sign copying functionSIGNAL — Signal handling subroutine (or function)SIN — Sine functionSIND — Sine function, degreesSINH — Hyperbolic sine functionSIZE — Determine the size of an arraySIZEOF — Size in bytes of an expressionSLEEP — Sleep for the specified number of secondsSPACING — Smallest distance between two numbers of a given typeSPREAD — Add a dimension to an arraySQRT — Square-root functionSRAND — Reinitialize the random number generatorSTAT — Get file statusSTORAGE_SIZE — Storage size in bitsSUM — Sum of array elementsSYMLNK — Create a symbolic linkSYSTEM — Execute a shell commandSYSTEM_CLOCK — Time functionTAN — Tangent functionTAND — Tangent function, degreesTANH — Hyperbolic tangent functionTHIS_IMAGE — Function that returns the cosubscript index of this imageTIME — Time functionTIME8 — Time function (64-bit)TINY — Smallest positive number of a real kindTRAILZ — Number of trailing zero bits of an integerTRANSFER — Transfer bit patternsTRANSPOSE — Transpose an array of rank twoTRIM — Remove trailing blank characters of a stringTTYNAM — Get the name of a terminal device.UBOUND — Upper dimension bounds of an arrayUCOBOUND — Upper codimension bounds of an arrayUMASK — Set the file creation maskUNLINK — Remove a file from the file systemUNPACK — Unpack an array of rank one into an arrayVERIFY — Scan a string for characters not a given setXOR — Bitwise logical exclusive ORNext: GNU Fortran Command Options, Previous: Introduction, Up: Introduction [Contents][Index]
The GNU Fortran compiler front end was
designed initially as a free replacement for,
or alternative to, the Unix f95 command;
gfortran is the command you will use to invoke the compiler.
Next: GNU Fortran and GCC, Up: Introduction [Contents][Index]
The GNU Fortran compiler supports the Fortran 77, 90 and 95 standards completely, parts of the Fortran 2003, 2008 and 2018 standards, and several vendor extensions. The development goal is to provide the following features:
The compiler will also attempt to diagnose cases where the user’s program contains a correct usage of the language, but instructs the computer to do something questionable. This kind of diagnostics message is called a warning message.
gdb).
The GNU Fortran compiler consists of several components:
gcc command
(which also might be installed as the system’s cc command)
that also understands and accepts Fortran source code.
The gcc command is the driver program for
all the languages in the GNU Compiler Collection (GCC);
With gcc,
you can compile the source code of any language for
which a front end is available in GCC.
gfortran command itself,
which also might be installed as the
system’s f95 command.
gfortran is just another driver program,
but specifically for the Fortran compiler only.
The difference with gcc is that gfortran
will automatically link the correct libraries to your program.
gfortran compilation phase,
such as intrinsic functions and subroutines,
and routines for interaction with files and the operating system.
f951).
This is the GNU Fortran parser and code generator,
linked to and interfaced with the GCC backend library.
f951 “translates” the source code to
assembler code. You would typically not use this
program directly;
instead, the gcc or gfortran driver
programs will call it for you.
Next: Preprocessing and conditional compilation, Previous: About GNU Fortran, Up: Introduction [Contents][Index]
GNU Fortran is a part of GCC, the GNU Compiler Collection. GCC consists of a collection of front ends for various languages, which translate the source code into a language-independent form called GENERIC. This is then processed by a common middle end which provides optimization, and then passed to one of a collection of back ends which generate code for different computer architectures and operating systems.
Functionally, this is implemented with a driver program (gcc)
which provides the command-line interface for the compiler. It calls
the relevant compiler front-end program (e.g., f951 for
Fortran) for each file in the source code, and then calls the assembler
and linker as appropriate to produce the compiled output. In a copy of
GCC which has been compiled with Fortran language support enabled,
gcc will recognize files with .f, .for, .ftn,
.f90, .f95, .f03 and .f08 extensions as
Fortran source code, and compile it accordingly. A gfortran
driver program is also provided, which is identical to gcc
except that it automatically links the Fortran runtime libraries into the
compiled program.
Source files with .f, .for, .fpp, .ftn, .F, .FOR, .FPP, and .FTN extensions are treated as fixed form. Source files with .f90, .f95, .f03, .f08, .F90, .F95, .F03 and .F08 extensions are treated as free form. The capitalized versions of either form are run through preprocessing. Source files with the lower case .fpp extension are also run through preprocessing.
This manual specifically documents the Fortran front end, which handles the programming language’s syntax and semantics. The aspects of GCC which relate to the optimization passes and the back-end code generation are documented in the GCC manual; see Introduction in Using the GNU Compiler Collection (GCC). The two manuals together provide a complete reference for the GNU Fortran compiler.
Next: GNU Fortran and G77, Previous: GNU Fortran and GCC, Up: Introduction [Contents][Index]
Many Fortran compilers including GNU Fortran allow passing the source code through a C preprocessor (CPP; sometimes also called the Fortran preprocessor, FPP) to allow for conditional compilation. In the case of GNU Fortran, this is the GNU C Preprocessor in the traditional mode. On systems with case-preserving file names, the preprocessor is automatically invoked if the filename extension is .F, .FOR, .FTN, .fpp, .FPP, .F90, .F95, .F03 or .F08. To manually invoke the preprocessor on any file, use -cpp, to disable preprocessing on files where the preprocessor is run automatically, use -nocpp.
If a preprocessed file includes another file with the Fortran INCLUDE
statement, the included file is not preprocessed. To preprocess included
files, use the equivalent preprocessor statement #include.
If GNU Fortran invokes the preprocessor, __GFORTRAN__
is defined. The macros __GNUC__, __GNUC_MINOR__ and
__GNUC_PATCHLEVEL__ can be used to determine the version of the
compiler. See Overview in The C Preprocessor for details.
GNU Fortran supports a number of INTEGER and REAL kind types
in additional to the kind types required by the Fortran standard.
The availability of any given kind type is architecture dependent. The
following pre-defined preprocessor macros can be used to conditionally
include code for these additional kind types: __GFC_INT_1__,
__GFC_INT_2__, __GFC_INT_8__, __GFC_INT_16__,
__GFC_REAL_10__, and __GFC_REAL_16__.
While CPP is the de-facto standard for preprocessing Fortran code, Part 3 of the Fortran 95 standard (ISO/IEC 1539-3:1998) defines Conditional Compilation, which is not widely used and not directly supported by the GNU Fortran compiler. You can use the program coco to preprocess such files (http://www.daniellnagle.com/coco.html).
Next: Project Status, Previous: Preprocessing and conditional compilation, Up: Introduction [Contents][Index]
The GNU Fortran compiler is the successor to g77, the Fortran
77 front end included in GCC prior to version 4. It is an entirely new
program that has been designed to provide Fortran 95 support and
extensibility for future Fortran language standards, as well as providing
backwards compatibility for Fortran 77 and nearly all of the GNU language
extensions supported by g77.
Next: Standards, Previous: GNU Fortran and G77, Up: Introduction [Contents][Index]
As soon as
gfortrancan parse all of the statements correctly, it will be in the “larva” state. When we generate code, the “puppa” state. Whengfortranis done, we’ll see if it will be a beautiful butterfly, or just a big bug....–Andy Vaught, April 2000
The start of the GNU Fortran 95 project was announced on the GCC homepage in March 18, 2000 (even though Andy had already been working on it for a while, of course).
The GNU Fortran compiler is able to compile nearly all standard-compliant Fortran 95, Fortran 90, and Fortran 77 programs, including a number of standard and non-standard extensions, and can be used on real-world programs. In particular, the supported extensions include OpenMP, Cray-style pointers, some old vendor extensions, and several Fortran 2003 and Fortran 2008 features, including TR 15581. However, it is still under development and has a few remaining rough edges. There also is initial support for OpenACC.
At present, the GNU Fortran compiler passes the NIST Fortran 77 Test Suite, and produces acceptable results on the LAPACK Test Suite. It also provides respectable performance on the Polyhedron Fortran compiler benchmarks and the Livermore Fortran Kernels test. It has been used to compile a number of large real-world programs, including the HARMONIE and HIRLAM weather forecasting code and the Tonto quantum chemistry package; see https://gcc.gnu.org/wiki/GfortranApps for an extended list.
Among other things, the GNU Fortran compiler is intended as a replacement for G77. At this point, nearly all programs that could be compiled with G77 can be compiled with GNU Fortran, although there are a few minor known regressions.
The primary work remaining to be done on GNU Fortran falls into three categories: bug fixing (primarily regarding the treatment of invalid code and providing useful error messages), improving the compiler optimizations and the performance of compiled code, and extending the compiler to support future standards—in particular, Fortran 2003, Fortran 2008 and Fortran 2018.
Previous: Project Status, Up: Introduction [Contents][Index]
The GNU Fortran compiler implements ISO/IEC 1539:1997 (Fortran 95). As such, it can also compile essentially all standard-compliant Fortran 90 and Fortran 77 programs. It also supports the ISO/IEC TR-15581 enhancements to allocatable arrays.
GNU Fortran also have a partial support for ISO/IEC 1539-1:2004
(Fortran 2003), ISO/IEC 1539-1:2010 (Fortran 2008), the Technical
Specification Further Interoperability of Fortran with C
(ISO/IEC TS 29113:2012). Full support of those standards and future
Fortran standards is planned. The current status of the support is
can be found in the Fortran 2003 status, Fortran 2008 status and Status of Fortran 2018 support sections of the documentation.
Additionally, the GNU Fortran compilers supports the OpenMP specification (version 4.5 and partial support of the features of the 5.0 version, http://openmp.org/openmp-specifications/). There also is support for the OpenACC specification (targeting version 2.6, http://www.openacc.org/). See https://gcc.gnu.org/wiki/OpenACC for more information.
The Fortran 95 standard specifies in Part 2 (ISO/IEC 1539-2:2000) varying length character strings. While GNU Fortran currently does not support such strings directly, there exist two Fortran implementations for them, which work with GNU Fortran. They can be found at http://www.fortran.com/iso_varying_string.f95 and at ftp://ftp.nag.co.uk/sc22wg5/ISO_VARYING_STRING/.
Deferred-length character strings of Fortran 2003 supports part of
the features of ISO_VARYING_STRING and should be considered as
replacement. (Namely, allocatable or pointers of the type
character(len=:).)
Next: Runtime: Influencing runtime behavior with environment variables, Previous: Introduction, Up: Introduction [Contents][Index]
The gfortran command supports all the options supported by the
gcc command. Only options specific to GNU Fortran are documented
here.
See GCC Command Options in Using the GNU Compiler
Collection (GCC), for information
on the non-Fortran-specific aspects of the gcc command (and,
therefore, the gfortran command).
All GCC and GNU Fortran options
are accepted both by gfortran and by gcc
(as well as any other drivers built at the same time,
such as g++),
since adding GNU Fortran to the GCC distribution
enables acceptance of GNU Fortran options
by all of the relevant drivers.
In some cases, options have positive and negative forms; the negative form of -ffoo would be -fno-foo. This manual documents only one of these two forms, whichever one is not the default.
gfortranHere is a summary of all the options specific to GNU Fortran, grouped by type. Explanations are in the following sections.
See Options controlling Fortran dialect.
-fall-intrinsics -fallow-argument-mismatch -fallow-invalid-boz -fbackslash -fcray-pointer -fd-lines-as-code -fd-lines-as-comments -fdec -fdec-char-conversions -fdec-structure -fdec-intrinsic-ints -fdec-static -fdec-math -fdec-include -fdec-format-defaults -fdec-blank-format-item -fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 -fdefault-real-10 -fdefault-real-16 -fdollar-ok -ffixed-line-length-n -ffixed-line-length-none -fpad-source -ffree-form -ffree-line-length-n -ffree-line-length-none -fimplicit-none -finteger-4-integer-8 -fmax-identifier-length -fmodule-private -ffixed-form -fno-range-check -fopenacc -fopenmp -freal-4-real-10 -freal-4-real-16 -freal-4-real-8 -freal-8-real-10 -freal-8-real-16 -freal-8-real-4 -std=std -ftest-forall-temp
See Enable and customize preprocessing.
-A-question[=answer] -Aquestion=answer -C -CC -Dmacro[=defn] -H -P -Umacro -cpp -dD -dI -dM -dN -dU -fworking-directory -imultilib dir -iprefix file -iquote -isysroot dir -isystem dir -nocpp -nostdinc -undef
See Options to request or suppress errors and warnings.
-Waliasing -Wall -Wampersand -Warray-bounds -Wc-binding-type -Wcharacter-truncation -Wconversion -Wdo-subscript -Wfunction-elimination -Wimplicit-interface -Wimplicit-procedure -Wintrinsic-shadow -Wuse-without-only -Wintrinsics-std -Wline-truncation -Wno-align-commons -Wno-overwrite-recursive -Wno-tabs -Wreal-q-constant -Wsurprising -Wunderflow -Wunused-parameter -Wrealloc-lhs -Wrealloc-lhs-all -Wfrontend-loop-interchange -Wtarget-lifetime -fmax-errors=n -fsyntax-only -pedantic -pedantic-errors
See Options for debugging your program or GNU Fortran.
-fbacktrace -fdump-fortran-optimized -fdump-fortran-original -fdebug-aux-vars -fdump-fortran-global -fdump-parse-tree -ffpe-trap=list -ffpe-summary=list
See Options for directory search.
-Idir -Jdir -fintrinsic-modules-path dir
See Options for influencing the linking step.
-static-libgfortran
See Options for influencing runtime behavior.
-fconvert=conversion -fmax-subrecord-length=length -frecord-marker=length -fsign-zero
See Options for interoperability.
-fc-prototypes -fc-prototypes-external
See Options for code generation conventions.
-faggressive-function-elimination -fblas-matmul-limit=n -fbounds-check -ftail-call-workaround -ftail-call-workaround=n -fcheck-array-temporaries -fcheck=<all|array-temps|bits|bounds|do|mem|pointer|recursion> -fcoarray=<none|single|lib> -fexternal-blas -ff2c -ffrontend-loop-interchange -ffrontend-optimize -finit-character=n -finit-integer=n -finit-local-zero -finit-derived -finit-logical=<true|false> -finit-real=<zero|inf|-inf|nan|snan> -finline-matmul-limit=n -finline-arg-packing -fmax-array-constructor=n -fmax-stack-var-size=n -fno-align-commons -fno-automatic -fno-protect-parens -fno-underscoring -fsecond-underscore -fpack-derived -frealloc-lhs -frecursive -frepack-arrays -fshort-enums -fstack-arrays
Next: Enable and customize preprocessing, Previous: Option summary, Up: GNU Fortran Command Options [Contents][Index]
The following options control the details of the Fortran dialect accepted by the compiler:
-ffree-form ¶-ffixed-formSpecify the layout used by the source file. The free form layout was introduced in Fortran 90. Fixed form was traditionally used in older Fortran programs. When neither option is specified, the source form is determined by the file extension.
-fall-intrinsics ¶This option causes all intrinsic procedures (including the GNU-specific
extensions) to be accepted. This can be useful with -std=f95 to
force standard-compliance but get access to the full range of intrinsics
available with gfortran. As a consequence, -Wintrinsics-std
will be ignored and no user-defined procedure with the same name as any
intrinsic will be called except when it is explicitly declared EXTERNAL.
-fallow-argument-mismatch ¶Some code contains calls to external procedures with mismatches between the calls and the procedure definition, or with mismatches between different calls. Such code is non-conforming, and will usually be flagged with an error. This options degrades the error to a warning, which can only be disabled by disabling all warnings via -w. Only a single occurrence per argument is flagged by this warning. -fallow-argument-mismatch is implied by -std=legacy.
Using this option is strongly discouraged. It is possible to
provide standard-conforming code which allows different types of
arguments by using an explicit interface and TYPE(*).
-fallow-invalid-boz ¶A BOZ literal constant can occur in a limited number of contexts in standard conforming Fortran. This option degrades an error condition to a warning, and allows a BOZ literal constant to appear where the Fortran standard would otherwise prohibit its use.
-fd-lines-as-code ¶-fd-lines-as-commentsEnable special treatment for lines beginning with d or D
in fixed form sources. If the -fd-lines-as-code option is
given they are treated as if the first column contained a blank. If the
-fd-lines-as-comments option is given, they are treated as
comment lines.
-fdec ¶DEC compatibility mode. Enables extensions and other features that mimic the default behavior of older compilers (such as DEC). These features are non-standard and should be avoided at all costs. For details on GNU Fortran’s implementation of these extensions see the full documentation.
Other flags enabled by this switch are: -fdollar-ok -fcray-pointer -fdec-char-conversions -fdec-structure -fdec-intrinsic-ints -fdec-static -fdec-math -fdec-include -fdec-blank-format-item -fdec-format-defaults
If -fd-lines-as-code/-fd-lines-as-comments are unset, then -fdec also sets -fd-lines-as-comments.
-fdec-char-conversions ¶Enable the use of character literals in assignments and DATA statements
for non-character variables.
-fdec-structure ¶Enable DEC STRUCTURE and RECORD as well as UNION,
MAP, and dot (’.’) as a member separator (in addition to ’%’). This is
provided for compatibility only; Fortran 90 derived types should be used
instead where possible.
-fdec-intrinsic-ints ¶Enable B/I/J/K kind variants of existing integer functions (e.g. BIAND, IIAND, JIAND, etc...). For a complete list of intrinsics see the full documentation.
-fdec-math ¶Enable legacy math intrinsics such as COTAN and degree-valued trigonometric functions (e.g. TAND, ATAND, etc...) for compatability with older code.
-fdec-static ¶Enable DEC-style STATIC and AUTOMATIC attributes to explicitly specify the storage of variables and other objects.
-fdec-include ¶Enable parsing of INCLUDE as a statement in addition to parsing it as INCLUDE line. When parsed as INCLUDE statement, INCLUDE does not have to be on a single line and can use line continuations.
-fdec-format-defaults ¶Enable format specifiers F, G and I to be used without width specifiers, default widths will be used instead.
-fdec-blank-format-item ¶Enable a blank format item at the end of a format specification i.e. nothing following the final comma.
-fdollar-ok ¶Allow ‘$’ as a valid non-first character in a symbol name. Symbols
that start with ‘$’ are rejected since it is unclear which rules to
apply to implicit typing as different vendors implement different rules.
Using ‘$’ in IMPLICIT statements is also rejected.
-fbackslash ¶Change the interpretation of backslashes in string literals from a single
backslash character to “C-style” escape characters. The following
combinations are expanded \a, \b, \f, \n,
\r, \t, \v, \\, and \0 to the ASCII
characters alert, backspace, form feed, newline, carriage return,
horizontal tab, vertical tab, backslash, and NUL, respectively.
Additionally, \xnn, \unnnn and
\Unnnnnnnn (where each n is a hexadecimal digit) are
translated into the Unicode characters corresponding to the specified code
points. All other combinations of a character preceded by \ are
unexpanded.
-fmodule-private ¶Set the default accessibility of module entities to PRIVATE.
Use-associated entities will not be accessible unless they are explicitly
declared as PUBLIC.
-ffixed-line-length-n ¶Set column after which characters are ignored in typical fixed-form
lines in the source file, and, unless -fno-pad-source, through which
spaces are assumed (as if padded to that length) after the ends of short
fixed-form lines.
Popular values for n include 72 (the standard and the default), 80 (card image), and 132 (corresponding to “extended-source” options in some popular compilers). n may also be ‘none’, meaning that the entire line is meaningful and that continued character constants never have implicit spaces appended to them to fill out the line. -ffixed-line-length-0 means the same thing as -ffixed-line-length-none.
-fno-pad-source ¶By default fixed-form lines have spaces assumed (as if padded to that length) after the ends of short fixed-form lines. This is not done either if -ffixed-line-length-0, -ffixed-line-length-none or if -fno-pad-source option is used. With any of those options continued character constants never have implicit spaces appended to them to fill out the line.
-ffree-line-length-n ¶Set column after which characters are ignored in typical free-form lines in the source file. The default value is 132. n may be ‘none’, meaning that the entire line is meaningful. -ffree-line-length-0 means the same thing as -ffree-line-length-none.
-fmax-identifier-length=n ¶Specify the maximum allowed identifier length. Typical values are 31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008).
-fimplicit-none ¶Specify that no implicit typing is allowed, unless overridden by explicit
IMPLICIT statements. This is the equivalent of adding
implicit none to the start of every procedure.
-fcray-pointer ¶Enable the Cray pointer extension, which provides C-like pointer functionality.
-fopenacc ¶Enable the OpenACC extensions. This includes OpenACC !$acc
directives in free form and c$acc, *$acc and
!$acc directives in fixed form, !$ conditional
compilation sentinels in free form and c$, *$ and
!$ sentinels in fixed form, and when linking arranges for the
OpenACC runtime library to be linked in.
-fopenmp ¶Enable the OpenMP extensions. This includes OpenMP !$omp directives
in free form
and c$omp, *$omp and !$omp directives in fixed form,
!$ conditional compilation sentinels in free form
and c$, *$ and !$ sentinels in fixed form,
and when linking arranges for the OpenMP runtime library to be linked
in. The option -fopenmp implies -frecursive.
-fno-range-check ¶Disable range checking on results of simplification of constant
expressions during compilation. For example, GNU Fortran will give
an error at compile time when simplifying a = 1. / 0.
With this option, no error will be given and a will be assigned
the value +Infinity. If an expression evaluates to a value
outside of the relevant range of [-HUGE():HUGE()],
then the expression will be replaced by -Inf or +Inf
as appropriate.
Similarly, DATA i/Z'FFFFFFFF'/ will result in an integer overflow
on most systems, but with -fno-range-check the value will
“wrap around” and i will be initialized to -1 instead.
-fdefault-integer-8 ¶Set the default integer and logical types to an 8 byte wide type. This option
also affects the kind of integer constants like 42. Unlike
-finteger-4-integer-8, it does not promote variables with explicit
kind declaration.
-fdefault-real-8 ¶Set the default real type to an 8 byte wide type. This option also affects
the kind of non-double real constants like 1.0. This option promotes
the default width of DOUBLE PRECISION and double real constants
like 1.d0 to 16 bytes if possible. If -fdefault-double-8
is given along with fdefault-real-8, DOUBLE PRECISION
and double real constants are not promoted. Unlike -freal-4-real-8,
fdefault-real-8 does not promote variables with explicit kind
declarations.
-fdefault-real-10 ¶Set the default real type to an 10 byte wide type. This option also affects
the kind of non-double real constants like 1.0. This option promotes
the default width of DOUBLE PRECISION and double real constants
like 1.d0 to 16 bytes if possible. If -fdefault-double-8
is given along with fdefault-real-10, DOUBLE PRECISION
and double real constants are not promoted. Unlike -freal-4-real-10,
fdefault-real-10 does not promote variables with explicit kind
declarations.
-fdefault-real-16 ¶Set the default real type to an 16 byte wide type. This option also affects
the kind of non-double real constants like 1.0. This option promotes
the default width of DOUBLE PRECISION and double real constants
like 1.d0 to 16 bytes if possible. If -fdefault-double-8
is given along with fdefault-real-16, DOUBLE PRECISION
and double real constants are not promoted. Unlike -freal-4-real-16,
fdefault-real-16 does not promote variables with explicit kind
declarations.
-fdefault-double-8 ¶Set the DOUBLE PRECISION type and double real constants
like 1.d0 to an 8 byte wide type. Do nothing if this
is already the default. This option prevents -fdefault-real-8,
-fdefault-real-10, and -fdefault-real-16,
from promoting DOUBLE PRECISION and double real constants like
1.d0 to 16 bytes.
-finteger-4-integer-8 ¶Promote all INTEGER(KIND=4) entities to an INTEGER(KIND=8)
entities. If KIND=8 is unavailable, then an error will be issued.
This option should be used with care and may not be suitable for your codes.
Areas of possible concern include calls to external procedures,
alignment in EQUIVALENCE and/or COMMON, generic interfaces,
BOZ literal constant conversion, and I/O. Inspection of the intermediate
representation of the translated Fortran code, produced by
-fdump-tree-original, is suggested.
-freal-4-real-8 ¶-freal-4-real-10-freal-4-real-16-freal-8-real-4-freal-8-real-10-freal-8-real-16Promote all REAL(KIND=M) entities to REAL(KIND=N) entities.
If REAL(KIND=N) is unavailable, then an error will be issued.
The -freal-4- flags also affect the default real kind and the
-freal-8- flags also the double-precision real kind. All other
real-kind types are unaffected by this option. The promotion is also
applied to real literal constants of default and double-precision kind
and a specified kind number of 4 or 8, respectively.
However, -fdefault-real-8, -fdefault-real-10,
-fdefault-real-10, and -fdefault-double-8 take precedence
for the default and double-precision real kinds, both for real literal
constants and for declarations without a kind number.
Note that for REAL(KIND=KIND(1.0)) the literal may get promoted and
then the result may get promoted again.
These options should be used with care and may not be suitable for your
codes. Areas of possible concern include calls to external procedures,
alignment in EQUIVALENCE and/or COMMON, generic interfaces,
BOZ literal constant conversion, and I/O and calls to intrinsic procedures
when passing a value to the kind= dummy argument. Inspection of the
intermediate representation of the translated Fortran code, produced by
-fdump-fortran-original or -fdump-tree-original, is suggested.
-std=std ¶Specify the standard to which the program is expected to conform, which may be one of ‘f95’, ‘f2003’, ‘f2008’, ‘f2018’, ‘gnu’, or ‘legacy’. The default value for std is ‘gnu’, which specifies a superset of the latest Fortran standard that includes all of the extensions supported by GNU Fortran, although warnings will be given for obsolete extensions not recommended for use in new code. The ‘legacy’ value is equivalent but without the warnings for obsolete extensions, and may be useful for old non-standard programs. The ‘f95’, ‘f2003’, ‘f2008’, and ‘f2018’ values specify strict conformance to the Fortran 95, Fortran 2003, Fortran 2008 and Fortran 2018 standards, respectively; errors are given for all extensions beyond the relevant language standard, and warnings are given for the Fortran 77 features that are permitted but obsolescent in later standards. The deprecated option ‘-std=f2008ts’ acts as an alias for ‘-std=f2018’. It is only present for backwards compatibility with earlier gfortran versions and should not be used any more.
-ftest-forall-temp ¶Enhance test coverage by forcing most forall assignments to use temporary.
Next: Options to request or suppress errors and warnings, Previous: Options controlling Fortran dialect, Up: GNU Fortran Command Options [Contents][Index]
Preprocessor related options. See section
Preprocessing and conditional compilation for more detailed
information on preprocessing in gfortran.
-cpp ¶-nocppEnable preprocessing. The preprocessor is automatically invoked if the file extension is .fpp, .FPP, .F, .FOR, .FTN, .F90, .F95, .F03 or .F08. Use this option to manually enable preprocessing of any kind of Fortran file.
To disable preprocessing of files with any of the above listed extensions, use the negative form: -nocpp.
The preprocessor is run in traditional mode. Any restrictions of the file-format, especially the limits on line length, apply for preprocessed output as well, so it might be advisable to use the -ffree-line-length-none or -ffixed-line-length-none options.
-dM ¶Instead of the normal output, generate a list of '#define'
directives for all the macros defined during the execution of the
preprocessor, including predefined macros. This gives you a way
of finding out what is predefined in your version of the preprocessor.
Assuming you have no file foo.f90, the command
touch foo.f90; gfortran -cpp -E -dM foo.f90
will show all the predefined macros.
-dD ¶Like -dM except in two respects: it does not include the
predefined macros, and it outputs both the #define directives
and the result of preprocessing. Both kinds of output go to the
standard output file.
-dN ¶Like -dD, but emit only the macro names, not their expansions.
-dU ¶Like dD except that only macros that are expanded, or whose
definedness is tested in preprocessor directives, are output; the
output is delayed until the use or test of the macro; and '#undef'
directives are also output for macros tested but undefined at the time.
-dI ¶Output '#include' directives in addition to the result
of preprocessing.
-fworking-directory ¶Enable generation of linemarkers in the preprocessor output that will
let the compiler know the current working directory at the time of
preprocessing. When this option is enabled, the preprocessor will emit,
after the initial linemarker, a second linemarker with the current
working directory followed by two slashes. GCC will use this directory,
when it is present in the preprocessed input, as the directory emitted
as the current working directory in some debugging information formats.
This option is implicitly enabled if debugging information is enabled,
but this can be inhibited with the negated form
-fno-working-directory. If the -P flag is present
in the command line, this option has no effect, since no #line
directives are emitted whatsoever.
-idirafter dir ¶Search dir for include files, but do it after all directories
specified with -I and the standard system directories have
been exhausted. dir is treated as a system include directory.
If dir begins with =, then the = will be replaced by
the sysroot prefix; see --sysroot and -isysroot.
-imultilib dir ¶Use dir as a subdirectory of the directory containing target-specific C++ headers.
-iprefix prefix ¶Specify prefix as the prefix for subsequent -iwithprefix
options. If the prefix represents a directory, you should include
the final '/'.
-isysroot dir ¶This option is like the --sysroot option, but applies only to header files. See the --sysroot option for more information.
-iquote dir ¶Search dir only for header files requested with #include "file";
they are not searched for #include <file>, before all directories
specified by -I and before the standard system directories. If
dir begins with =, then the = will be replaced by the
sysroot prefix; see --sysroot and -isysroot.
-isystem dir ¶Search dir for header files, after all directories specified by
-I but before the standard system directories. Mark it as a
system directory, so that it gets the same special treatment as is
applied to the standard system directories. If dir begins with
=, then the = will be replaced by the sysroot prefix;
see --sysroot and -isysroot.
-nostdinc ¶Do not search the standard system directories for header files. Only the directories you have specified with -I options (and the directory of the current file, if appropriate) are searched.
-undef ¶Do not predefine any system-specific or GCC-specific macros. The standard predefined macros remain defined.
-Apredicate=answer ¶Make an assertion with the predicate predicate and answer answer. This form is preferred to the older form -A predicate(answer), which is still supported, because it does not use shell special characters.
-A-predicate=answer ¶Cancel an assertion with the predicate predicate and answer answer.
-C ¶Do not discard comments. All comments are passed through to the output file, except for comments in processed directives, which are deleted along with the directive.
You should be prepared for side effects when using -C; it causes
the preprocessor to treat comments as tokens in their own right. For example,
comments appearing at the start of what would be a directive line have the
effect of turning that line into an ordinary source line, since the first
token on the line is no longer a '#'.
Warning: this currently handles C-Style comments only. The preprocessor does not yet recognize Fortran-style comments.
-CC ¶Do not discard comments, including during macro expansion. This is like -C, except that comments contained within macros are also passed through to the output file where the macro is expanded.
In addition to the side-effects of the -C option, the -CC option causes all C++-style comments inside a macro to be converted to C-style comments. This is to prevent later use of that macro from inadvertently commenting out the remainder of the source line. The -CC option is generally used to support lint comments.
Warning: this currently handles C- and C++-Style comments only. The preprocessor does not yet recognize Fortran-style comments.
-Dname ¶Predefine name as a macro, with definition 1.
-Dname=definition ¶The contents of definition are tokenized and processed as if they
appeared during translation phase three in a '#define' directive.
In particular, the definition will be truncated by embedded newline
characters.
If you are invoking the preprocessor from a shell or shell-like program you may need to use the shell’s quoting syntax to protect characters such as spaces that have a meaning in the shell syntax.
If you wish to define a function-like macro on the command line, write
its argument list with surrounding parentheses before the equals sign
(if any). Parentheses are meaningful to most shells, so you will need
to quote the option. With sh and csh, -D'name(args...)=definition'
works.
-D and -U options are processed in the order they are given on the command line. All -imacros file and -include file options are processed after all -D and -U options.
-H ¶Print the name of each header file used, in addition to other normal
activities. Each name is indented to show how deep in the '#include'
stack it is.
-P ¶Inhibit generation of linemarkers in the output from the preprocessor. This might be useful when running the preprocessor on something that is not C code, and will be sent to a program which might be confused by the linemarkers.
-Uname ¶Cancel any previous definition of name, either built in or provided with a -D option.
Next: Options for debugging your program or GNU Fortran, Previous: Enable and customize preprocessing, Up: GNU Fortran Command Options [Contents][Index]
Errors are diagnostic messages that report that the GNU Fortran compiler cannot compile the relevant piece of source code. The compiler will continue to process the program in an attempt to report further errors to aid in debugging, but will not produce any compiled output.
Warnings are diagnostic messages that report constructions which are not inherently erroneous but which are risky or suggest there is likely to be a bug in the program. Unless -Werror is specified, they do not prevent compilation of the program.
You can request many specific warnings with options beginning -W, for example -Wimplicit to request warnings on implicit declarations. Each of these specific warning options also has a negative form beginning -Wno- to turn off warnings; for example, -Wno-implicit. This manual lists only one of the two forms, whichever is not the default.
These options control the amount and kinds of errors and warnings produced by GNU Fortran:
-fmax-errors=n ¶Limits the maximum number of error messages to n, at which point GNU Fortran bails out rather than attempting to continue processing the source code. If n is 0, there is no limit on the number of error messages produced.
-fsyntax-only ¶Check the code for syntax errors, but do not actually compile it. This will generate module files for each module present in the code, but no other output file.
-Wpedantic ¶-pedanticIssue warnings for uses of extensions to Fortran.
-pedantic also applies to C-language constructs where they
occur in GNU Fortran source files, such as use of ‘\e’ in a
character constant within a directive like #include.
Valid Fortran programs should compile properly with or without this option. However, without this option, certain GNU extensions and traditional Fortran features are supported as well. With this option, many of them are rejected.
Some users try to use -pedantic to check programs for conformance. They soon find that it does not do quite what they want—it finds some nonstandard practices, but not all. However, improvements to GNU Fortran in this area are welcome.
This should be used in conjunction with -std=f95, -std=f2003, -std=f2008 or -std=f2018.
-pedantic-errors ¶Like -pedantic, except that errors are produced rather than warnings.
-Wall ¶Enables commonly used warning options pertaining to usage that we recommend avoiding and that we believe are easy to avoid. This currently includes -Waliasing, -Wampersand, -Wconversion, -Wsurprising, -Wc-binding-type, -Wintrinsics-std, -Wtabs, -Wintrinsic-shadow, -Wline-truncation, -Wtarget-lifetime, -Winteger-division, -Wreal-q-constant, -Wunused and -Wundefined-do-loop.
-Waliasing ¶Warn about possible aliasing of dummy arguments. Specifically, it warns
if the same actual argument is associated with a dummy argument with
INTENT(IN) and a dummy argument with INTENT(OUT) in a call
with an explicit interface.
The following example will trigger the warning.
interface
subroutine bar(a,b)
integer, intent(in) :: a
integer, intent(out) :: b
end subroutine
end interface
integer :: a
call bar(a,a)
-Wampersand ¶Warn about missing ampersand in continued character constants. The warning is given with -Wampersand, -pedantic, -std=f95, -std=f2003, -std=f2008 and -std=f2018. Note: With no ampersand given in a continued character constant, GNU Fortran assumes continuation at the first non-comment, non-whitespace character after the ampersand that initiated the continuation.
-Warray-temporaries ¶Warn about array temporaries generated by the compiler. The information generated by this warning is sometimes useful in optimization, in order to avoid such temporaries.
-Wc-binding-type ¶Warn if the a variable might not be C interoperable. In particular, warn if
the variable has been declared using an intrinsic type with default kind
instead of using a kind parameter defined for C interoperability in the
intrinsic ISO_C_Binding module. This option is implied by
-Wall.
-Wcharacter-truncation ¶Warn when a character assignment will truncate the assigned string.
-Wline-truncation ¶Warn when a source code line will be truncated. This option is implied by -Wall. For free-form source code, the default is -Werror=line-truncation such that truncations are reported as error.
-Wconversion ¶Warn about implicit conversions that are likely to change the value of the expression after conversion. Implied by -Wall.
-Wconversion-extra ¶Warn about implicit conversions between different types and kinds. This option does not imply -Wconversion.
-Wextra ¶Enables some warning options for usages of language features which may be problematic. This currently includes -Wcompare-reals, -Wunused-parameter and -Wdo-subscript.
-Wfrontend-loop-interchange ¶Warn when using -ffrontend-loop-interchange for performing loop interchanges.
-Wimplicit-interface ¶Warn if a procedure is called without an explicit interface. Note this only checks that an explicit interface is present. It does not check that the declared interfaces are consistent across program units.
-Wimplicit-procedure ¶Warn if a procedure is called that has neither an explicit interface
nor has been declared as EXTERNAL.
-Winteger-division ¶Warn if a constant integer division truncates its result. As an example, 3/5 evaluates to 0.
-Wintrinsics-std ¶Warn if gfortran finds a procedure named like an intrinsic not
available in the currently selected standard (with -std) and treats
it as EXTERNAL procedure because of this. -fall-intrinsics can
be used to never trigger this behavior and always link to the intrinsic
regardless of the selected standard.
-Wno-overwrite-recursive ¶Do not warn when -fno-automatic is used with -frecursive. Recursion
will be broken if the relevant local variables do not have the attribute
AUTOMATIC explicitly declared. This option can be used to suppress the warning
when it is known that recursion is not broken. Useful for build environments that use
-Werror.
-Wreal-q-constant ¶Produce a warning if a real-literal-constant contains a q
exponent-letter.
-Wsurprising ¶Produce a warning when “suspicious” code constructs are encountered. While technically legal these usually indicate that an error has been made.
This currently produces a warning under the following circumstances:
CHARACTER variable is declared with negative length.
-Wtabs ¶By default, tabs are accepted as whitespace, but tabs are not members of the Fortran Character Set. For continuation lines, a tab followed by a digit between 1 and 9 is supported. -Wtabs will cause a warning to be issued if a tab is encountered. Note, -Wtabs is active for -pedantic, -std=f95, -std=f2003, -std=f2008, -std=f2018 and -Wall.
-Wundefined-do-loop ¶Warn if a DO loop with step either 1 or -1 yields an underflow or an overflow during iteration of an induction variable of the loop. This option is implied by -Wall.
-Wunderflow ¶Produce a warning when numerical constant expressions are encountered, which yield an UNDERFLOW during compilation. Enabled by default.
-Wintrinsic-shadow ¶Warn if a user-defined procedure or module procedure has the same name as an
intrinsic; in this case, an explicit interface or EXTERNAL or
INTRINSIC declaration might be needed to get calls later resolved to
the desired intrinsic/procedure. This option is implied by -Wall.
-Wuse-without-only ¶Warn if a USE statement has no ONLY qualifier and
thus implicitly imports all public entities of the used module.
-Wunused-dummy-argument ¶Warn about unused dummy arguments. This option is implied by -Wall.
-Wunused-parameter ¶Contrary to gcc’s meaning of -Wunused-parameter,
gfortran’s implementation of this option does not warn
about unused dummy arguments (see -Wunused-dummy-argument),
but about unused PARAMETER values. -Wunused-parameter
is implied by -Wextra if also -Wunused or
-Wall is used.
-Walign-commons ¶By default, gfortran warns about any occasion of variables being
padded for proper alignment inside a COMMON block. This warning can be turned
off via -Wno-align-commons. See also -falign-commons.
-Wfunction-elimination ¶Warn if any calls to impure functions are eliminated by the optimizations enabled by the -ffrontend-optimize option. This option is implied by -Wextra.
-Wrealloc-lhs ¶Warn when the compiler might insert code to for allocation or reallocation of
an allocatable array variable of intrinsic type in intrinsic assignments. In
hot loops, the Fortran 2003 reallocation feature may reduce the performance.
If the array is already allocated with the correct shape, consider using a
whole-array array-spec (e.g. (:,:,:)) for the variable on the left-hand
side to prevent the reallocation check. Note that in some cases the warning
is shown, even if the compiler will optimize reallocation checks away. For
instance, when the right-hand side contains the same variable multiplied by
a scalar. See also -frealloc-lhs.
-Wrealloc-lhs-all ¶Warn when the compiler inserts code to for allocation or reallocation of an allocatable variable; this includes scalars and derived types.
-Wcompare-reals ¶Warn when comparing real or complex types for equality or inequality. This option is implied by -Wextra.
-Wtarget-lifetime ¶Warn if the pointer in a pointer assignment might be longer than the its target. This option is implied by -Wall.
-Wzerotrip ¶Warn if a DO loop is known to execute zero times at compile
time. This option is implied by -Wall.
-Wdo-subscript ¶Warn if an array subscript inside a DO loop could lead to an out-of-bounds access even if the compiler cannot prove that the statement is actually executed, in cases like
real a(3)
do i=1,4
if (condition(i)) then
a(i) = 1.2
end if
end do
This option is implied by -Wextra.
-Werror ¶Turns all warnings into errors.
See Options to Request or Suppress Errors and
Warnings in Using the GNU Compiler Collection (GCC), for information on
more options offered by the GBE shared by gfortran, gcc
and other GNU compilers.
Some of these have no effect when compiling programs written in Fortran.
Next: Options for directory search, Previous: Options to request or suppress errors and warnings, Up: GNU Fortran Command Options [Contents][Index]
GNU Fortran has various special options that are used for debugging either your program or the GNU Fortran compiler.
-fdump-fortran-original ¶Output the internal parse tree after translating the source program into internal representation. This option is mostly useful for debugging the GNU Fortran compiler itself. The output generated by this option might change between releases. This option may also generate internal compiler errors for features which have only recently been added.
-fdump-fortran-optimized ¶Output the parse tree after front-end optimization. Mostly useful for debugging the GNU Fortran compiler itself. The output generated by this option might change between releases. This option may also generate internal compiler errors for features which have only recently been added.
-fdump-parse-tree ¶Output the internal parse tree after translating the source program
into internal representation. Mostly useful for debugging the GNU
Fortran compiler itself. The output generated by this option might
change between releases. This option may also generate internal
compiler errors for features which have only recently been added. This
option is deprecated; use -fdump-fortran-original instead.
-fdebug-aux-vars ¶Renames internal variables created by the gfortran front end and makes
them accessible to a debugger. The name of the internal variables then
start with upper-case letters followed by an underscore. This option is
useful for debugging the compiler’s code generation together with
-fdump-tree-original and enabling debugging of the executable
program by using -g or -ggdb3.
-fdump-fortran-global ¶Output a list of the global identifiers after translating into middle-end representation. Mostly useful for debugging the GNU Fortran compiler itself. The output generated by this option might change between releases. This option may also generate internal compiler errors for features which have only recently been added.
-ffpe-trap=list ¶Specify a list of floating point exception traps to enable. On most
systems, if a floating point exception occurs and the trap for that
exception is enabled, a SIGFPE signal will be sent and the program
being aborted, producing a core file useful for debugging. list
is a (possibly empty) comma-separated list of the following
exceptions: ‘invalid’ (invalid floating point operation, such as
SQRT(-1.0)), ‘zero’ (division by zero), ‘overflow’
(overflow in a floating point operation), ‘underflow’ (underflow
in a floating point operation), ‘inexact’ (loss of precision
during operation), and ‘denormal’ (operation performed on a
denormal value). The first five exceptions correspond to the five
IEEE 754 exceptions, whereas the last one (‘denormal’) is not
part of the IEEE 754 standard but is available on some common
architectures such as x86.
The first three exceptions (‘invalid’, ‘zero’, and ‘overflow’) often indicate serious errors, and unless the program has provisions for dealing with these exceptions, enabling traps for these three exceptions is probably a good idea.
If the option is used more than once in the command line, the lists will
be joined: ’ffpe-trap=list1 ffpe-trap=list2’
is equivalent to ffpe-trap=list1,list2.
Note that once enabled an exception cannot be disabled (no negative form).
Many, if not most, floating point operations incur loss of precision
due to rounding, and hence the ffpe-trap=inexact is likely to
be uninteresting in practice.
By default no exception traps are enabled.
-ffpe-summary=list ¶Specify a list of floating-point exceptions, whose flag status is printed
to ERROR_UNIT when invoking STOP and ERROR STOP.
list can be either ‘none’, ‘all’ or a comma-separated list
of the following exceptions: ‘invalid’, ‘zero’, ‘overflow’,
‘underflow’, ‘inexact’ and ‘denormal’. (See
-ffpe-trap for a description of the exceptions.)
If the option is used more than once in the command line, only the last one will be used.
By default, a summary for all exceptions but ‘inexact’ is shown.
-fno-backtrace ¶When a serious runtime error is encountered or a deadly signal is
emitted (segmentation fault, illegal instruction, bus error,
floating-point exception, and the other POSIX signals that have the
action ‘core’), the Fortran runtime library tries to output a
backtrace of the error. -fno-backtrace disables the backtrace
generation. This option only has influence for compilation of the
Fortran main program.
See Options for Debugging Your Program or GCC in Using the GNU Compiler Collection (GCC), for more information on debugging options.
Next: Influencing the linking step, Previous: Options for debugging your program or GNU Fortran, Up: GNU Fortran Command Options [Contents][Index]
These options affect how GNU Fortran searches
for files specified by the INCLUDE directive and where it searches
for previously compiled modules.
It also affects the search paths used by cpp when used to preprocess
Fortran source.
-Idir ¶These affect interpretation of the INCLUDE directive
(as well as of the #include directive of the cpp
preprocessor).
Also note that the general behavior of -I and
INCLUDE is pretty much the same as of -I with
#include in the cpp preprocessor, with regard to
looking for header.gcc files and other such things.
This path is also used to search for .mod files when previously
compiled modules are required by a USE statement.
See Options for Directory Search in Using the GNU Compiler Collection (GCC), for information on the -I option.
-Jdir ¶This option specifies where to put .mod files for compiled modules.
It is also added to the list of directories to searched by an USE
statement.
The default is the current directory.
-fintrinsic-modules-path dir ¶This option specifies the location of pre-compiled intrinsic modules, if they are not in the default location expected by the compiler.
Next: Influencing runtime behavior, Previous: Options for directory search, Up: GNU Fortran Command Options [Contents][Index]
These options come into play when the compiler links object files into an executable output file. They are meaningless if the compiler is not doing a link step.
-static-libgfortran ¶On systems that provide libgfortran as a shared and a static library, this option forces the use of the static version. If no shared version of libgfortran was built when the compiler was configured, this option has no effect.
Next: Options for code generation conventions, Previous: Influencing the linking step, Up: GNU Fortran Command Options [Contents][Index]
These options affect the runtime behavior of programs compiled with GNU Fortran.
-fconvert=conversion ¶Specify the representation of data for unformatted files. Valid values for conversion are: ‘native’, the default; ‘swap’, swap between big- and little-endian; ‘big-endian’, use big-endian representation for unformatted files; ‘little-endian’, use little-endian representation for unformatted files.
This option has an effect only when used in the main program.
The CONVERT specifier and the GFORTRAN_CONVERT_UNIT environment
variable override the default specified by -fconvert.
-frecord-marker=length ¶Specify the length of record markers for unformatted files.
Valid values for length are 4 and 8. Default is 4.
This is different from previous versions of gfortran,
which specified a default record marker length of 8 on most
systems. If you want to read or write files compatible
with earlier versions of gfortran, use -frecord-marker=8.
-fmax-subrecord-length=length ¶Specify the maximum length for a subrecord. The maximum permitted value for length is 2147483639, which is also the default. Only really useful for use by the gfortran testsuite.
-fsign-zero ¶When enabled, floating point numbers of value zero with the sign bit set
are written as negative number in formatted output and treated as
negative in the SIGN intrinsic. -fno-sign-zero does not
print the negative sign of zero values (or values rounded to zero for I/O)
and regards zero as positive number in the SIGN intrinsic for
compatibility with Fortran 77. The default is -fsign-zero.
Next: Options for interoperability with other languages, Previous: Influencing runtime behavior, Up: GNU Fortran Command Options [Contents][Index]
These machine-independent options control the interface conventions used in code generation.
Most of them have both positive and negative forms; the negative form of -ffoo would be -fno-foo. In the table below, only one of the forms is listed—the one which is not the default. You can figure out the other form by either removing no- or adding it.
-fno-automatic ¶Treat each program unit (except those marked as RECURSIVE) as if the
SAVE statement were specified for every local variable and array
referenced in it. Does not affect common blocks. (Some Fortran compilers
provide this option under the name -static or -save.)
The default, which is -fautomatic, uses the stack for local
variables smaller than the value given by -fmax-stack-var-size.
Use the option -frecursive to use no static memory.
Local variables or arrays having an explicit SAVE attribute are
silently ignored unless the -pedantic option is added.
-ff2c ¶Generate code designed to be compatible with code generated
by g77 and f2c.
The calling conventions used by g77 (originally implemented
in f2c) require functions that return type
default REAL to actually return the C type double, and
functions that return type COMPLEX to return the values via an
extra argument in the calling sequence that points to where to
store the return value. Under the default GNU calling conventions, such
functions simply return their results as they would in GNU
C—default REAL functions return the C type float, and
COMPLEX functions return the GNU C type complex.
Additionally, this option implies the -fsecond-underscore
option, unless -fno-second-underscore is explicitly requested.
This does not affect the generation of code that interfaces with
the libgfortran library.
Caution: It is not a good idea to mix Fortran code compiled with
-ff2c with code compiled with the default -fno-f2c
calling conventions as, calling COMPLEX or default REAL
functions between program parts which were compiled with different
calling conventions will break at execution time.
Caution: This will break code which passes intrinsic functions
of type default REAL or COMPLEX as actual arguments, as
the library implementations use the -fno-f2c calling conventions.
-fno-underscoring ¶Do not transform names of entities specified in the Fortran source file by appending underscores to them.
With -funderscoring in effect, GNU Fortran appends one underscore to external names with no underscores. This is done to ensure compatibility with code produced by many UNIX Fortran compilers.
Caution: The default behavior of GNU Fortran is
incompatible with f2c and g77, please use the
-ff2c option if you want object files compiled with
GNU Fortran to be compatible with object code created with these
tools.
Use of -fno-underscoring is not recommended unless you are experimenting with issues such as integration of GNU Fortran into existing system environments (vis-à-vis existing libraries, tools, and so on).
For example, with -funderscoring, and assuming that j() and
max_count() are external functions while my_var and
lvar are local variables, a statement like
I = J() + MAX_COUNT (MY_VAR, LVAR)
is implemented as something akin to:
i = j_() + max_count__(&my_var__, &lvar);
With -fno-underscoring, the same statement is implemented as:
i = j() + max_count(&my_var, &lvar);
Use of -fno-underscoring allows direct specification of user-defined names while debugging and when interfacing GNU Fortran code with other languages.
Note that just because the names match does not mean that the interface implemented by GNU Fortran for an external name matches the interface implemented by some other language for that same name. That is, getting code produced by GNU Fortran to link to code produced by some other compiler using this or any other method can be only a small part of the overall solution—getting the code generated by both compilers to agree on issues other than naming can require significant effort, and, unlike naming disagreements, linkers normally cannot detect disagreements in these other areas.
Also, note that with -fno-underscoring, the lack of appended underscores introduces the very real possibility that a user-defined external name will conflict with a name in a system library, which could make finding unresolved-reference bugs quite difficult in some cases—they might occur at program run time, and show up only as buggy behavior at run time.
In future versions of GNU Fortran we hope to improve naming and linking issues so that debugging always involves using the names as they appear in the source, even if the names as seen by the linker are mangled to prevent accidental linking between procedures with incompatible interfaces.
-fsecond-underscore ¶By default, GNU Fortran appends an underscore to external names. If this option is used GNU Fortran appends two underscores to names with underscores and one underscore to external names with no underscores. GNU Fortran also appends two underscores to internal names with underscores to avoid naming collisions with external names.
This option has no effect if -fno-underscoring is in effect. It is implied by the -ff2c option.
Otherwise, with this option, an external name such as MAX_COUNT
is implemented as a reference to the link-time external symbol
max_count__, instead of max_count_. This is required
for compatibility with g77 and f2c, and is implied
by use of the -ff2c option.
-fcoarray=<keyword> ¶Disable coarray support; using coarray declarations and image-control statements will produce a compile-time error. (Default)
Single-image mode, i.e. num_images() is always one.
Library-based coarray parallelization; a suitable GNU Fortran coarray library needs to be linked.
-fcheck=<keyword> ¶Enable the generation of run-time checks; the argument shall be a comma-delimited list of the following keywords. Prefixing a check with no- disables it if it was activated by a previous specification.
Enable all run-time test of -fcheck.
Warns at run time when for passing an actual argument a temporary array had to be generated. The information generated by this warning is sometimes useful in optimization, in order to avoid such temporaries.
Note: The warning is only printed once per location.
Enable generation of run-time checks for invalid arguments to the bit manipulation intrinsics.
Enable generation of run-time checks for array subscripts and against the declared minimum and maximum values. It also checks array indices for assumed and deferred shape arrays against the actual allocated bounds and ensures that all string lengths are equal for character array constructors without an explicit typespec.
Some checks require that -fcheck=bounds is set for the compilation of the main program.
Note: In the future this may also include other forms of checking, e.g., checking substring references.
Enable generation of run-time checks for invalid modification of loop iteration variables.
Enable generation of run-time checks for memory allocation.
Note: This option does not affect explicit allocations using the
ALLOCATE statement, which will be always checked.
Enable generation of run-time checks for pointers and allocatables.
Enable generation of run-time checks for recursively called subroutines and functions which are not marked as recursive. See also -frecursive. Note: This check does not work for OpenMP programs and is disabled if used together with -frecursive and -fopenmp.
Example: Assuming you have a file foo.f90, the command
gfortran -fcheck=all,no-array-temps foo.f90
will compile the file with all checks enabled as specified above except warnings for generated array temporaries.
-fbounds-check ¶Deprecated alias for -fcheck=bounds.
-ftail-call-workaround ¶-ftail-call-workaround=nSome C interfaces to Fortran codes violate the gfortran ABI by omitting the hidden character length arguments as described in See Argument passing conventions. This can lead to crashes because pushing arguments for tail calls can overflow the stack.
To provide a workaround for existing binary packages, this option disables tail call optimization for gfortran procedures with character arguments. With -ftail-call-workaround=2 tail call optimization is disabled in all gfortran procedures with character arguments, with -ftail-call-workaround=1 or equivalent -ftail-call-workaround only in gfortran procedures with character arguments that call implicitly prototyped procedures.
Using this option can lead to problems including crashes due to insufficient stack space.
It is very strongly recommended to fix the code in question. The -fc-prototypes-external option can be used to generate prototypes which conform to gfortran’s ABI, for inclusion in the source code.
Support for this option will likely be withdrawn in a future release of gfortran.
The negative form, -fno-tail-call-workaround or equivalent -ftail-call-workaround=0, can be used to disable this option.
Default is currently -ftail-call-workaround, this will change in future releases.
-fcheck-array-temporaries ¶Deprecated alias for -fcheck=array-temps.
-fmax-array-constructor=n ¶This option can be used to increase the upper limit permitted in array constructors. The code below requires this option to expand the array at compile time.
program test implicit none integer j integer, parameter :: n = 100000 integer, parameter :: i(n) = (/ (2*j, j = 1, n) /) print '(10(I0,1X))', i end program test
Caution: This option can lead to long compile times and excessively large object files.
The default value for n is 65535.
-fmax-stack-var-size=n ¶This option specifies the size in bytes of the largest array that will be put on the stack; if the size is exceeded static memory is used (except in procedures marked as RECURSIVE). Use the option -frecursive to allow for recursive procedures which do not have a RECURSIVE attribute or for parallel programs. Use -fno-automatic to never use the stack.
This option currently only affects local arrays declared with constant bounds, and may not apply to all character variables. Future versions of GNU Fortran may improve this behavior.
The default value for n is 65536.
-fstack-arrays ¶Adding this option will make the Fortran compiler put all arrays of unknown size and array temporaries onto stack memory. If your program uses very large local arrays it is possible that you will have to extend your runtime limits for stack memory on some operating systems. This flag is enabled by default at optimization level -Ofast unless -fmax-stack-var-size is specified.
-fpack-derived ¶This option tells GNU Fortran to pack derived type members as closely as possible. Code compiled with this option is likely to be incompatible with code compiled without this option, and may execute slower.
-frepack-arrays ¶In some circumstances GNU Fortran may pass assumed shape array sections via a descriptor describing a noncontiguous area of memory. This option adds code to the function prologue to repack the data into a contiguous block at runtime.
This should result in faster accesses to the array. However it can introduce significant overhead to the function call, especially when the passed data is noncontiguous.
-fshort-enums ¶This option is provided for interoperability with C code that was
compiled with the -fshort-enums option. It will make
GNU Fortran choose the smallest INTEGER kind a given
enumerator set will fit in, and give all its enumerators this kind.
-finline-arg-packing ¶When passing an assumed-shape argument of a procedure as actual
argument to an assumed-size or explicit size or as argument to a
procedure that does not have an explicit interface, the argument may
have to be packed, that is put into contiguous memory. An example is
the call to foo in
subroutine foo(a)
real, dimension(*) :: a
end subroutine foo
subroutine bar(b)
real, dimension(:) :: b
call foo(b)
end subroutine bar
When -finline-arg-packing is in effect, this packing will be performed by inline code. This allows for more optimization while increasing code size.
-finline-arg-packing is implied by any of the -O options except when optimizing for size via -Os. If the code contains a very large number of argument that have to be packed, code size and also compilation time may become excessive. If that is the case, it may be better to disable this option. Instances of packing can be found by using by using -Warray-temporaries.
-fexternal-blas ¶This option will make gfortran generate calls to BLAS functions
for some matrix operations like MATMUL, instead of using our own
algorithms, if the size of the matrices involved is larger than a given
limit (see -fblas-matmul-limit). This may be profitable if an
optimized vendor BLAS library is available. The BLAS library will have
to be specified at link time.
-fblas-matmul-limit=n ¶Only significant when -fexternal-blas is in effect.
Matrix multiplication of matrices with size larger than (or equal to) n
will be performed by calls to BLAS functions, while others will be
handled by gfortran internal algorithms. If the matrices
involved are not square, the size comparison is performed using the
geometric mean of the dimensions of the argument and result matrices.
The default value for n is 30.
-finline-matmul-limit=n ¶When front-end optimization is active, some calls to the MATMUL
intrinsic function will be inlined. This may result in code size
increase if the size of the matrix cannot be determined at compile
time, as code for both cases is generated. Setting
-finline-matmul-limit=0 will disable inlining in all cases.
Setting this option with a value of n will produce inline code
for matrices with size up to n. If the matrices involved are not
square, the size comparison is performed using the geometric mean of
the dimensions of the argument and result matrices.
The default value for n is 30. The -fblas-matmul-limit
can be used to change this value.
-frecursive ¶Allow indirect recursion by forcing all local arrays to be allocated on the stack. This flag cannot be used together with -fmax-stack-var-size= or -fno-automatic.
-finit-local-zero ¶-finit-derived-finit-integer=n-finit-real=<zero|inf|-inf|nan|snan>-finit-logical=<true|false>-finit-character=nThe -finit-local-zero option instructs the compiler to
initialize local INTEGER, REAL, and COMPLEX
variables to zero, LOGICAL variables to false, and
CHARACTER variables to a string of null bytes. Finer-grained
initialization options are provided by the
-finit-integer=n,
-finit-real=<zero|inf|-inf|nan|snan> (which also initializes
the real and imaginary parts of local COMPLEX variables),
-finit-logical=<true|false>, and
-finit-character=n (where n is an ASCII character
value) options.
With -finit-derived, components of derived type variables will be initialized according to these flags. Components whose type is not covered by an explicit -finit-* flag will be treated as described above with -finit-local-zero.
These options do not initialize
EQUIVALENCE statement.
(These limitations may be removed in future releases).
Note that the -finit-real=nan option initializes REAL
and COMPLEX variables with a quiet NaN. For a signalling NaN
use -finit-real=snan; note, however, that compile-time
optimizations may convert them into quiet NaN and that trapping
needs to be enabled (e.g. via -ffpe-trap).
The -finit-integer option will parse the value into an
integer of type INTEGER(kind=C_LONG) on the host. Said value
is then assigned to the integer variables in the Fortran code, which
might result in wraparound if the value is too large for the kind.
Finally, note that enabling any of the -finit-* options will silence warnings that would have been emitted by -Wuninitialized for the affected local variables.
-falign-commons ¶By default, gfortran enforces proper alignment of all variables in a
COMMON block by padding them as needed. On certain platforms this is mandatory,
on others it increases performance. If a COMMON block is not declared with
consistent data types everywhere, this padding can cause trouble, and
-fno-align-commons can be used to disable automatic alignment. The
same form of this option should be used for all files that share a COMMON block.
To avoid potential alignment issues in COMMON blocks, it is recommended to order
objects from largest to smallest.
-fno-protect-parens ¶By default the parentheses in expression are honored for all optimization
levels such that the compiler does not do any re-association. Using
-fno-protect-parens allows the compiler to reorder REAL and
COMPLEX expressions to produce faster code. Note that for the re-association
optimization -fno-signed-zeros and -fno-trapping-math
need to be in effect. The parentheses protection is enabled by default, unless
-Ofast is given.
-frealloc-lhs ¶An allocatable left-hand side of an intrinsic assignment is automatically (re)allocated if it is either unallocated or has a different shape. The option is enabled by default except when -std=f95 is given. See also -Wrealloc-lhs.
-faggressive-function-elimination ¶Functions with identical argument lists are eliminated within
statements, regardless of whether these functions are marked
PURE or not. For example, in
a = f(b,c) + f(b,c)
there will only be a single call to f. This option only works
if -ffrontend-optimize is in effect.
-ffrontend-optimize ¶This option performs front-end optimization, based on manipulating parts the Fortran parse tree. Enabled by default by any -O option except -O0 and -Og. Optimizations enabled by this option include:
MATMUL,
TRIM in comparisons and assignments,
TRIM(a) with a(1:LEN_TRIM(a)) and
.AND. and .OR.).
It can be deselected by specifying -fno-frontend-optimize.
-ffrontend-loop-interchange ¶Attempt to interchange loops in the Fortran front end where
profitable. Enabled by default by any -O option.
At the moment, this option only affects FORALL and
DO CONCURRENT statements with several forall triplets.
See Options for Code Generation Conventions in Using the GNU Compiler Collection (GCC), for information on more options
offered by the GBE
shared by gfortran, gcc, and other GNU compilers.
Next: Environment variables affecting gfortran, Previous: Options for code generation conventions, Up: GNU Fortran Command Options [Contents][Index]
This option will generate C prototypes from BIND(C) variable
declarations, types and procedure interfaces and writes them to
standard output. ENUM is not yet supported.
The generated prototypes may need inclusion of an appropriate header,
such as <stdint.h> or <stdlib.h>. For types which are
not specified using the appropriate kind from the iso_c_binding
module, a warning is added as a comment to the code.
For function pointers, a pointer to a function returning int
without an explicit argument list is generated.
Example of use:
$ gfortran -fc-prototypes -fsyntax-only foo.f90 > foo.h
where the C code intended for interoperating with the Fortran code
then uses #include "foo.h".
This option will generate C prototypes from external functions and
subroutines and write them to standard output. This may be useful for
making sure that C bindings to Fortran code are correct. This option
does not generate prototypes for BIND(C) procedures, use
-fc-prototypes for that.
The generated prototypes may need inclusion of an appropriate
header, such as as <stdint.h> or <stdlib.h>.
This is primarily meant for legacy code to ensure that existing C
bindings match what gfortran emits. The generated C
prototypes should be correct for the current version of the compiler,
but may not match what other compilers or earlier versions of
gfortran need. For new developments, use of the
BIND(C) features is recommended.
Example of use:
$ gfortran -fc-prototypes-external -fsyntax-only foo.f > foo.h
where the C code intended for interoperating with the Fortran code
then uses #include "foo.h".
Previous: Options for interoperability with other languages, Up: GNU Fortran Command Options [Contents][Index]
gfortranThe gfortran compiler currently does not make use of any environment
variables to control its operation above and beyond those
that affect the operation of gcc.
See Environment Variables Affecting GCC in Using the GNU Compiler Collection (GCC), for information on environment variables.
See Runtime: Influencing runtime behavior with environment variables, for environment variables that affect the run-time behavior of programs compiled with GNU Fortran.
Next: Fortran standards status, Previous: GNU Fortran Command Options, Up: Introduction [Contents][Index]
The behavior of the gfortran can be influenced by
environment variables.
Malformed environment variables are silently ignored.
TMPDIR—Directory for scratch filesGFORTRAN_STDIN_UNIT—Unit number for standard inputGFORTRAN_STDOUT_UNIT—Unit number for standard outputGFORTRAN_STDERR_UNIT—Unit number for standard errorGFORTRAN_UNBUFFERED_ALL—Do not buffer I/O on all unitsGFORTRAN_UNBUFFERED_PRECONNECTED—Do not buffer I/O on preconnected unitsGFORTRAN_SHOW_LOCUS—Show location for runtime errorsGFORTRAN_OPTIONAL_PLUS—Print leading + where permittedGFORTRAN_LIST_SEPARATOR—Separator for list outputGFORTRAN_CONVERT_UNIT—Set endianness for unformatted I/OGFORTRAN_ERROR_BACKTRACE—Show backtrace on run-time errorsGFORTRAN_FORMATTED_BUFFER_SIZE—Set buffer size for formatted I/OGFORTRAN_UNFORMATTED_BUFFER_SIZE—Set buffer size for unformatted I/O
Next: GFORTRAN_STDIN_UNIT—Unit number for standard input, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
TMPDIR—Directory for scratch filesWhen opening a file with STATUS='SCRATCH', GNU Fortran tries to
create the file in one of the potential directories by testing each
directory in the order below.
TMPDIR, if it exists.
GetTempPath
function. Alternatively, on the Cygwin target, the TMP and
TEMP environment variables, if they exist, in that order.
P_tmpdir macro if it is defined, otherwise the directory
/tmp.
Next: GFORTRAN_STDOUT_UNIT—Unit number for standard output, Previous: TMPDIR—Directory for scratch files, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_STDIN_UNIT—Unit number for standard inputThis environment variable can be used to select the unit number preconnected to standard input. This must be a positive integer. The default value is 5.
Next: GFORTRAN_STDERR_UNIT—Unit number for standard error, Previous: GFORTRAN_STDIN_UNIT—Unit number for standard input, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_STDOUT_UNIT—Unit number for standard outputThis environment variable can be used to select the unit number preconnected to standard output. This must be a positive integer. The default value is 6.
Next: GFORTRAN_UNBUFFERED_ALL—Do not buffer I/O on all units, Previous: GFORTRAN_STDOUT_UNIT—Unit number for standard output, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_STDERR_UNIT—Unit number for standard errorThis environment variable can be used to select the unit number preconnected to standard error. This must be a positive integer. The default value is 0.
Next: GFORTRAN_UNBUFFERED_PRECONNECTED—Do not buffer I/O on preconnected units, Previous: GFORTRAN_STDERR_UNIT—Unit number for standard error, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_UNBUFFERED_ALL—Do not buffer I/O on all unitsThis environment variable controls whether all I/O is unbuffered. If the first letter is ‘y’, ‘Y’ or ‘1’, all I/O is unbuffered. This will slow down small sequential reads and writes. If the first letter is ‘n’, ‘N’ or ‘0’, I/O is buffered. This is the default.
Next: GFORTRAN_SHOW_LOCUS—Show location for runtime errors, Previous: GFORTRAN_UNBUFFERED_ALL—Do not buffer I/O on all units, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_UNBUFFERED_PRECONNECTED—Do not buffer I/O on preconnected unitsThe environment variable named GFORTRAN_UNBUFFERED_PRECONNECTED controls
whether I/O on a preconnected unit (i.e. STDOUT or STDERR) is unbuffered. If
the first letter is ‘y’, ‘Y’ or ‘1’, I/O is unbuffered. This
will slow down small sequential reads and writes. If the first letter
is ‘n’, ‘N’ or ‘0’, I/O is buffered. This is the default.
Next: GFORTRAN_OPTIONAL_PLUS—Print leading + where permitted, Previous: GFORTRAN_UNBUFFERED_PRECONNECTED—Do not buffer I/O on preconnected units, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_SHOW_LOCUS—Show location for runtime errorsIf the first letter is ‘y’, ‘Y’ or ‘1’, filename and line numbers for runtime errors are printed. If the first letter is ‘n’, ‘N’ or ‘0’, do not print filename and line numbers for runtime errors. The default is to print the location.
Next: GFORTRAN_LIST_SEPARATOR—Separator for list output, Previous: GFORTRAN_SHOW_LOCUS—Show location for runtime errors, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_OPTIONAL_PLUS—Print leading + where permittedIf the first letter is ‘y’, ‘Y’ or ‘1’, a plus sign is printed where permitted by the Fortran standard. If the first letter is ‘n’, ‘N’ or ‘0’, a plus sign is not printed in most cases. Default is not to print plus signs.
Next: GFORTRAN_CONVERT_UNIT—Set endianness for unformatted I/O, Previous: GFORTRAN_OPTIONAL_PLUS—Print leading + where permitted, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_LIST_SEPARATOR—Separator for list outputThis environment variable specifies the separator when writing list-directed output. It may contain any number of spaces and at most one comma. If you specify this on the command line, be sure to quote spaces, as in
$ GFORTRAN_LIST_SEPARATOR=' , ' ./a.out
when a.out is the compiled Fortran program that you want to run.
Default is a single space.
Next: GFORTRAN_ERROR_BACKTRACE—Show backtrace on run-time errors, Previous: GFORTRAN_LIST_SEPARATOR—Separator for list output, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_CONVERT_UNIT—Set endianness for unformatted I/OBy setting the GFORTRAN_CONVERT_UNIT variable, it is possible
to change the representation of data for unformatted files.
The syntax for the GFORTRAN_CONVERT_UNIT variable is:
GFORTRAN_CONVERT_UNIT: mode | mode ';' exception | exception ; mode: 'native' | 'swap' | 'big_endian' | 'little_endian' ; exception: mode ':' unit_list | unit_list ; unit_list: unit_spec | unit_list unit_spec ; unit_spec: INTEGER | INTEGER '-' INTEGER ;
The variable consists of an optional default mode, followed by
a list of optional exceptions, which are separated by semicolons
from the preceding default and each other. Each exception consists
of a format and a comma-separated list of units. Valid values for
the modes are the same as for the CONVERT specifier:
NATIVE Use the native format. This is the default.
SWAP Swap between little- and big-endian.
LITTLE_ENDIAN Use the little-endian format
for unformatted files.
BIG_ENDIAN Use the big-endian format for unformatted files.
A missing mode for an exception is taken to mean BIG_ENDIAN.
Examples of values for GFORTRAN_CONVERT_UNIT are:
'big_endian' Do all unformatted I/O in big_endian mode.
'little_endian;native:10-20,25' Do all unformatted I/O
in little_endian mode, except for units 10 to 20 and 25, which are in
native format.
'10-20' Units 10 to 20 are big-endian, the rest is native.
Setting the environment variables should be done on the command
line or via the export
command for sh-compatible shells and via setenv
for csh-compatible shells.
Example for sh:
$ gfortran foo.f90 $ GFORTRAN_CONVERT_UNIT='big_endian;native:10-20' ./a.out
Example code for csh:
% gfortran foo.f90 % setenv GFORTRAN_CONVERT_UNIT 'big_endian;native:10-20' % ./a.out
Using anything but the native representation for unformatted data carries a significant speed overhead. If speed in this area matters to you, it is best if you use this only for data that needs to be portable.
See CONVERT specifier, for an alternative way to specify the
data representation for unformatted files. See Influencing runtime behavior, for
setting a default data representation for the whole program. The
CONVERT specifier overrides the -fconvert compile options.
Note that the values specified via the GFORTRAN_CONVERT_UNIT environment variable will override the CONVERT specifier in the open statement. This is to give control over data formats to users who do not have the source code of their program available.
Next: GFORTRAN_FORMATTED_BUFFER_SIZE—Set buffer size for formatted I/O, Previous: GFORTRAN_CONVERT_UNIT—Set endianness for unformatted I/O, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_ERROR_BACKTRACE—Show backtrace on run-time errorsIf the GFORTRAN_ERROR_BACKTRACE variable is set to ‘y’,
‘Y’ or ‘1’ (only the first letter is relevant) then a
backtrace is printed when a serious run-time error occurs. To disable
the backtracing, set the variable to ‘n’, ‘N’, ‘0’.
Default is to print a backtrace unless the -fno-backtrace
compile option was used.
Next: GFORTRAN_UNFORMATTED_BUFFER_SIZE—Set buffer size for unformatted I/O, Previous: GFORTRAN_ERROR_BACKTRACE—Show backtrace on run-time errors, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_FORMATTED_BUFFER_SIZE—Set buffer size for formatted I/OThe GFORTRAN_FORMATTED_BUFFER_SIZE environment variable
specifies buffer size in bytes to be used for formatted output.
The default value is 8192.
Previous: GFORTRAN_FORMATTED_BUFFER_SIZE—Set buffer size for formatted I/O, Up: Runtime: Influencing runtime behavior with environment variables [Contents][Index]
GFORTRAN_UNFORMATTED_BUFFER_SIZE—Set buffer size for unformatted I/OThe GFORTRAN_UNFORMATTED_BUFFER_SIZE environment variable
specifies buffer size in bytes to be used for unformatted output.
The default value is 131072.
Next: Compiler Characteristics, Previous: Runtime: Influencing runtime behavior with environment variables, Up: Introduction [Contents][Index]
Next: Fortran 2008 status, Up: Fortran standards status [Contents][Index]
GNU Fortran supports several Fortran 2003 features; an incomplete list can be found below. See also the wiki page about Fortran 2003.
PASS attribute.
PASS, PROCEDURE and GENERIC, and
operators bound to a type.
CLASS”) for derived types and unlimited
polymorphism (“CLASS(*)”) – including SAME_TYPE_AS,
EXTENDS_TYPE_OF and SELECT TYPE for scalars and arrays and
finalization.
ASSOCIATE construct.
ALLOCATE statement, allowing for a
type-specification with type parameter and for allocation and initialization
from a SOURCE= expression; ALLOCATE and DEALLOCATE
optionally return an error message string via ERRMSG=.
MOVE_ALLOC.
PRIVATE and PUBLIC attributes may be given individually
to derived-type components.
INTENT may be specified which affect the
association status not the value of the pointer target.
command_argument_count, get_command,
get_command_argument, and get_environment_variable.
SELECTED_CHAR_KIND and NEW_LINE intrinsic functions.
INT, REAL, CMPLX and DBLE.
[...] rather
than (/.../). Type-specification for array constructors like
(/ some-type :: ... /).
FLUSH statement.
IOMSG= specifier for I/O statements.
ENUM and ENUMERATOR statements. Interoperability with
gcc is guaranteed also for the case where the
-fshort-enums command line option is given.
ALLOCATABLE dummy arguments.
ALLOCATABLE function results
ALLOCATABLE components of derived types
OPEN statement supports the ACCESS='STREAM' specifier,
allowing I/O without any record structure.
strtod honours
the rounding mode, the rounding mode is also supported for input.
PROTECTED statement and attribute.
VALUE statement and attribute.
VOLATILE statement and attribute.
IMPORT statement, allowing to import
host-associated derived types.
ISO_FORTRAN_ENVIRONMENT is supported,
which contains parameters of the I/O units, storage sizes. Additionally,
procedures for C interoperability are available in the ISO_C_BINDING
module.
USE statement with INTRINSIC and NON_INTRINSIC
attribute; supported intrinsic modules: ISO_FORTRAN_ENV,
ISO_C_BINDING, OMP_LIB and OMP_LIB_KINDS,
and OPENACC.
USE statement.
Next: Status of Fortran 2018 support, Previous: Fortran 2003 status, Up: Fortran standards status [Contents][Index]
The latest version of the Fortran standard is ISO/IEC 1539-1:2010, informally known as Fortran 2008. The official version is available from International Organization for Standardization (ISO) or its national member organizations. The the final draft (FDIS) can be downloaded free of charge from http://www.nag.co.uk/sc22wg5/links.html. Fortran is developed by the Working Group 5 of Sub-Committee 22 of the Joint Technical Committee 1 of the International Organization for Standardization and the International Electrotechnical Commission (IEC). This group is known as WG5.
The GNU Fortran compiler supports several of the new features of Fortran 2008; the wiki has some information about the current Fortran 2008 implementation status. In particular, the following is implemented.
OPEN statement now supports the NEWUNIT= option,
which returns a unique file unit, thus preventing inadvertent use of the
same unit in different parts of the program.
g0 format descriptor and unlimited format items.
ASINH, ACOSH, ATANH,
ERF, ERFC, GAMMA, LOG_GAMMA, BESSEL_J0,
BESSEL_J1, BESSEL_JN, BESSEL_Y0, BESSEL_Y1,
BESSEL_YN, HYPOT, NORM2, and ERFC_SCALED.
TAN, SINH, COSH,
TANH, ASIN, ACOS, and ATAN is now possible;
ATAN(Y,X) is now an alias for ATAN2(Y,X).
PARITY intrinsic functions.
LEADZ and TRAILZ for
counting the number of leading and trailing zero bits, POPCNT and
POPPAR for counting the number of one bits and returning the parity;
BGE, BGT, BLE, and BLT for bitwise comparisons;
DSHIFTL and DSHIFTR for combined left and right shifts,
MASKL and MASKR for simple left and right justified masks,
MERGE_BITS for a bitwise merge using a mask, SHIFTA,
SHIFTL and SHIFTR for shift operations, and the
transformational bit intrinsics IALL, IANY and IPARITY.
EXECUTE_COMMAND_LINE intrinsic subroutine.
STORAGE_SIZE intrinsic inquiry function.
INT{8,16,32} and REAL{32,64,128} kind type
parameters and the array-valued named constants INTEGER_KINDS,
LOGICAL_KINDS, REAL_KINDS and CHARACTER_KINDS of
the intrinsic module ISO_FORTRAN_ENV.
C_SIZEOF of the intrinsic module
ISO_C_BINDINGS and COMPILER_VERSION and COMPILER_OPTIONS
of ISO_FORTRAN_ENV.
MODULEs do not
produce the smod file needed by the descendent SUBMODULEs unless they
contain at least one MODULE PROCEDURE interface. The reason for this is
that SUBMODULEs are useless without MODULE PROCEDUREs. See
http://j3-fortran.org/doc/meeting/207/15-209.txt for a discussion and a draft
interpretation. Adopting this interpretation has the advantage that code that
does not use submodules does not generate smod files.
DO CONCURRENT construct is supported.
BLOCK construct is supported.
STOP and the new ERROR STOP statements now
support all constant expressions. Both show the signals which were signaling
at termination.
CONTIGUOUS attribute.
ALLOCATE with MOLD.
IMPURE attribute for procedures, which
allows for ELEMENTAL procedures without the restrictions of
PURE.
NULL()) and not-allocated variables
can be used as actual argument to optional non-pointer, non-allocatable
dummy arguments, denoting an absent argument.
TARGET attribute can be used as
actual argument to POINTER dummies with INTENT(IN).
NULL.
EXIT statement (with construct-name) can be now be
used to leave not only the DO but also the ASSOCIATE,
BLOCK, IF, SELECT CASE and SELECT TYPE
constructs.
ENTRY with
-std=f2008; a line may start with a semicolon; for internal
and module procedures END can be used instead of
END SUBROUTINE and END FUNCTION; SELECTED_REAL_KIND
now also takes a RADIX argument; intrinsic types are supported
for TYPE(intrinsic-type-spec); multiple type-bound procedures
can be declared in a single PROCEDURE statement; implied-shape
arrays are supported for named constants (PARAMETER).
Previous: Fortran 2008 status, Up: Fortran standards status [Contents][Index]
ERROR STOP statement is permitted in a PURE
procedure.
IMPLICIT NONE statement with an
implicit-none-spec-list.
The behavior of the INQUIRE statement with the RECL=
specifier now conforms to Fortran 2018.
GNU Fortran supports some of the new features of the Technical Specification (TS) 29113 on Further Interoperability of Fortran with C. The wiki has some information about the current TS 29113 implementation status. In particular, the following is implemented.
See also Further Interoperability of Fortran with C.
OPTIONAL attribute is allowed for dummy arguments
of BIND(C) procedures.
RANK intrinsic is supported.
ASYNCHRONOUS
attribute is compatible with TS 29113.
TYPE(*)).
DIMENSION(..)).
~prefix/lib/gcc/$target/$version.
GNU Fortran supports the following new features of the Technical Specification 18508 on Additional Parallel Features in Fortran:
CO_MIN and CO_MAX and SUM reduction intrinsics.
And the CO_BROADCAST and CO_REDUCE intrinsic, except that those
do not support polymorphic types or types with allocatable, pointer or
polymorphic components.
EVENT POST, EVENT WAIT, EVENT_QUERY)
FAIL IMAGE, IMAGE_STATUS,
FAILED_IMAGES, STOPPED_IMAGES)
Next: Extensions, Previous: Fortran standards status, Up: Introduction [Contents][Index]
This chapter describes certain characteristics of the GNU Fortran compiler, that are not specified by the Fortran standard, but which might in some way or another become visible to the programmer.
The KIND type parameters supported by GNU Fortran for the primitive
data types are:
INTEGER1, 2, 4, 8*, 16*, default: 4**
LOGICAL1, 2, 4, 8*, 16*, default: 4**
REAL4, 8, 10*, 16*, default: 4***
COMPLEX4, 8, 10*, 16*, default: 4***
DOUBLE PRECISION4, 8, 10*, 16*, default: 8***
CHARACTER1, 4, default: 1
* not available on all systems
** unless -fdefault-integer-8 is used
*** unless -fdefault-real-8 is used (see Options controlling Fortran dialect)
The KIND value matches the storage size in bytes, except for
COMPLEX where the storage size is twice as much (or both real and
imaginary part are a real value of the given size). It is recommended to use
the SELECTED_CHAR_KIND — Choose character kind, SELECTED_INT_KIND — Choose integer kind and
SELECTED_REAL_KIND — Choose real kind intrinsics or the INT8, INT16,
INT32, INT64, REAL32, REAL64, and REAL128
parameters of the ISO_FORTRAN_ENV module instead of the concrete values.
The available kind parameters can be found in the constant arrays
CHARACTER_KINDS, INTEGER_KINDS, LOGICAL_KINDS and
REAL_KINDS in the ISO_FORTRAN_ENV module. For C interoperability,
the kind parameters of the ISO_C_BINDING module should be used.
Next: Evaluation of logical expressions, Previous: KIND Type Parameters, Up: Compiler Characteristics [Contents][Index]
The Fortran standard does not specify how variables of LOGICAL
type are represented, beyond requiring that LOGICAL variables
of default kind have the same storage size as default INTEGER
and REAL variables. The GNU Fortran internal representation is
as follows.
A LOGICAL(KIND=N) variable is represented as an
INTEGER(KIND=N) variable, however, with only two permissible
values: 1 for .TRUE. and 0 for
.FALSE.. Any other integer value results in undefined behavior.
See also Argument passing conventions and Interoperability with C.
Next: MAX and MIN intrinsics with REAL NaN arguments, Previous: Internal representation of LOGICAL variables, Up: Compiler Characteristics [Contents][Index]
The Fortran standard does not require the compiler to evaluate all parts of an
expression, if they do not contribute to the final result. For logical
expressions with .AND. or .OR. operators, in particular, GNU
Fortran will optimize out function calls (even to impure functions) if the
result of the expression can be established without them. However, since not
all compilers do that, and such an optimization can potentially modify the
program flow and subsequent results, GNU Fortran throws warnings for such
situations with the -Wfunction-elimination flag.
Next: Thread-safety of the runtime library, Previous: Evaluation of logical expressions, Up: Compiler Characteristics [Contents][Index]
The Fortran standard does not specify what the result of the
MAX and MIN intrinsics are if one of the arguments is a
NaN. Accordingly, the GNU Fortran compiler does not specify
that either, as this allows for faster and more compact code to be
generated. If the programmer wishes to take some specific action in
case one of the arguments is a NaN, it is necessary to
explicitly test the arguments before calling MAX or MIN,
e.g. with the IEEE_IS_NAN function from the intrinsic module
IEEE_ARITHMETIC.
Next: Data consistency and durability, Previous: MAX and MIN intrinsics with REAL NaN arguments, Up: Compiler Characteristics [Contents][Index]
GNU Fortran can be used in programs with multiple threads, e.g. by
using OpenMP, by calling OS thread handling functions via the
ISO_C_BINDING facility, or by GNU Fortran compiled library code
being called from a multi-threaded program.
The GNU Fortran runtime library, (libgfortran), supports being
called concurrently from multiple threads with the following
exceptions.
During library initialization, the C getenv function is used,
which need not be thread-safe. Similarly, the getenv
function is used to implement the GET_ENVIRONMENT_VARIABLE and
GETENV intrinsics. It is the responsibility of the user to
ensure that the environment is not being updated concurrently when any
of these actions are taking place.
The EXECUTE_COMMAND_LINE and SYSTEM intrinsics are
implemented with the system function, which need not be
thread-safe. It is the responsibility of the user to ensure that
system is not called concurrently.
For platforms not supporting thread-safe POSIX functions, further functionality might not be thread-safe. For details, please consult the documentation for your operating system.
The GNU Fortran runtime library uses various C library functions that
depend on the locale, such as strtod and snprintf. In
order to work correctly in locale-aware programs that set the locale
using setlocale, the locale is reset to the default “C”
locale while executing a formatted READ or WRITE
statement. On targets supporting the POSIX 2008 per-thread locale
functions (e.g. newlocale, uselocale,
freelocale), these are used and thus the global locale set
using setlocale or the per-thread locales in other threads are
not affected. However, on targets lacking this functionality, the
global LC_NUMERIC locale is set to “C” during the formatted I/O.
Thus, on such targets it’s not safe to call setlocale
concurrently from another thread while a Fortran formatted I/O
operation is in progress. Also, other threads doing something
dependent on the LC_NUMERIC locale might not work correctly if a
formatted I/O operation is in progress in another thread.
Next: Files opened without an explicit ACTION= specifier, Previous: Thread-safety of the runtime library, Up: Compiler Characteristics [Contents][Index]
This section contains a brief overview of data and metadata consistency and durability issues when doing I/O.
With respect to durability, GNU Fortran makes no effort to ensure that
data is committed to stable storage. If this is required, the GNU
Fortran programmer can use the intrinsic FNUM to retrieve the
low level file descriptor corresponding to an open Fortran unit. Then,
using e.g. the ISO_C_BINDING feature, one can call the
underlying system call to flush dirty data to stable storage, such as
fsync on POSIX, _commit on MingW, or fcntl(fd,
F_FULLSYNC, 0) on Mac OS X. The following example shows how to call
fsync:
! Declare the interface for POSIX fsync function
interface
function fsync (fd) bind(c,name="fsync")
use iso_c_binding, only: c_int
integer(c_int), value :: fd
integer(c_int) :: fsync
end function fsync
end interface
! Variable declaration
integer :: ret
! Opening unit 10
open (10,file="foo")
! ...
! Perform I/O on unit 10
! ...
! Flush and sync
flush(10)
ret = fsync(fnum(10))
! Handle possible error
if (ret /= 0) stop "Error calling FSYNC"
With respect to consistency, for regular files GNU Fortran uses
buffered I/O in order to improve performance. This buffer is flushed
automatically when full and in some other situations, e.g. when
closing a unit. It can also be explicitly flushed with the
FLUSH statement. Also, the buffering can be turned off with the
GFORTRAN_UNBUFFERED_ALL and
GFORTRAN_UNBUFFERED_PRECONNECTED environment variables. Special
files, such as terminals and pipes, are always unbuffered. Sometimes,
however, further things may need to be done in order to allow other
processes to see data that GNU Fortran has written, as follows.
The Windows platform supports a relaxed metadata consistency model,
where file metadata is written to the directory lazily. This means
that, for instance, the dir command can show a stale size for a
file. One can force a directory metadata update by closing the unit,
or by calling _commit on the file descriptor. Note, though,
that _commit will force all dirty data to stable storage, which
is often a very slow operation.
The Network File System (NFS) implements a relaxed consistency model
called open-to-close consistency. Closing a file forces dirty data and
metadata to be flushed to the server, and opening a file forces the
client to contact the server in order to revalidate cached
data. fsync will also force a flush of dirty data and metadata
to the server. Similar to open and close, acquiring and
releasing fcntl file locks, if the server supports them, will
also force cache validation and flushing dirty data and metadata.
Next: File operations on symbolic links, Previous: Data consistency and durability, Up: Compiler Characteristics [Contents][Index]
The Fortran standard says that if an OPEN statement is executed
without an explicit ACTION= specifier, the default value is
processor dependent. GNU Fortran behaves as follows:
ACTION='READWRITE'
ACTION='READ'
ACTION='WRITE'
Next: File format of unformatted sequential files, Previous: Files opened without an explicit ACTION= specifier, Up: Compiler Characteristics [Contents][Index]
This section documents the behavior of GNU Fortran for file operations on symbolic links, on systems that support them.
INQUIRE(FILE="foo",EXIST=ex) will set ex to .true. if
foo is a symbolic link pointing to an existing file, and .false.
if foo points to an non-existing file (“dangling” symbolic link).
OPEN statement with a STATUS="NEW" specifier
on a symbolic link will result in an error condition, whether the symbolic
link points to an existing target or is dangling.
CLOSE statement
with a STATUS="DELETE" specifier will cause the symbolic link itself
to be deleted, not its target.
Next: Asynchronous I/O, Previous: File operations on symbolic links, Up: Compiler Characteristics [Contents][Index]
Unformatted sequential files are stored as logical records using record markers. Each logical record consists of one of more subrecords.
Each subrecord consists of a leading record marker, the data written by the user program, and a trailing record marker. The record markers are four-byte integers by default, and eight-byte integers if the -fmax-subrecord-length=8 option (which exists for backwards compability only) is in effect.
The representation of the record markers is that of unformatted files
given with the -fconvert option, the CONVERT specifier
in an open statement or the GFORTRAN_CONVERT_UNIT—Set endianness for unformatted I/O environment
variable.
The maximum number of bytes of user data in a subrecord is 2147483639 (2 GiB - 9) for a four-byte record marker. This limit can be lowered with the -fmax-subrecord-length option, altough this is rarely useful. If the length of a logical record exceeds this limit, the data is distributed among several subrecords.
The absolute of the number stored in the record markers is the number of bytes of user data in the corresponding subrecord. If the leading record marker of a subrecord contains a negative number, another subrecord follows the current one. If the trailing record marker contains a negative number, then there is a preceding subrecord.
In the most simple case, with only one subrecord per logical record, both record markers contain the number of bytes of user data in the record.
The format for unformatted sequential data can be duplicated using unformatted stream, as shown in the example program for an unformatted record containing a single subrecord:
program main use iso_fortran_env, only: int32 implicit none integer(int32) :: i real, dimension(10) :: a, b call random_number(a) open (10,file='test.dat',form='unformatted',access='stream') inquire (iolength=i) a write (10) i, a, i close (10) open (10,file='test.dat',form='unformatted') read (10) b if (all (a == b)) print *,'success!' end program main
Previous: File format of unformatted sequential files, Up: Compiler Characteristics [Contents][Index]
Asynchronous I/O is supported if the program is linked against the POSIX thread library. If that is not the case, all I/O is performed as synchronous. On systems which do not support pthread condition variables, such as AIX, I/O is also performed as synchronous.
On some systems, such as Darwin or Solaris, the POSIX thread library is always linked in, so asynchronous I/O is always performed. On other sytems, such as Linux, it is necessary to specify -pthread, -lpthread or -fopenmp during the linking step.
Next: Mixed-Language Programming, Previous: Compiler Characteristics, Up: Introduction [Contents][Index]
The two sections below detail the extensions to standard Fortran that are implemented in GNU Fortran, as well as some of the popular or historically important extensions that are not (or not yet) implemented. For the latter case, we explain the alternatives available to GNU Fortran users, including replacement by standard-conforming code or GNU extensions.
Next: Extensions not implemented in GNU Fortran, Up: Extensions [Contents][Index]
GNU Fortran implements a number of extensions over standard Fortran. This chapter contains information on their syntax and meaning. There are currently two categories of GNU Fortran extensions, those that provide functionality beyond that provided by any standard, and those that are supported by GNU Fortran purely for backward compatibility with legacy compilers. By default, -std=gnu allows the compiler to accept both types of extensions, but to warn about the use of the latter. Specifying either -std=f95, -std=f2003, -std=f2008, or -std=f2018 disables both types of extensions, and -std=legacy allows both without warning. The special compile flag -fdec enables additional compatibility extensions along with those enabled by -std=legacy.
X format descriptor without count fieldFORMAT specificationsFORMAT specificationsF, G and I format descriptorsQ exponent-letterLOGICAL and INTEGER valuesCONVERT specifier%VAL, %REF and %LOCSTRUCTURE and RECORDUNION and MAPAUTOMATIC and STATIC attributesNext: Old-style variable initialization, Up: Extensions implemented in GNU Fortran [Contents][Index]
GNU Fortran allows old-style kind specifications in declarations. These look like:
TYPESPEC*size x,y,z
where TYPESPEC is a basic type (INTEGER, REAL,
etc.), and where size is a byte count corresponding to the
storage size of a valid kind for that type. (For COMPLEX
variables, size is the total size of the real and imaginary
parts.) The statement then declares x, y and z to
be of type TYPESPEC with the appropriate kind. This is
equivalent to the standard-conforming declaration
TYPESPEC(k) x,y,z
where k is the kind parameter suitable for the intended precision. As
kind parameters are implementation-dependent, use the KIND,
SELECTED_INT_KIND and SELECTED_REAL_KIND intrinsics to retrieve
the correct value, for instance REAL*8 x can be replaced by:
INTEGER, PARAMETER :: dbl = KIND(1.0d0) REAL(KIND=dbl) :: x
Next: Extensions to namelist, Previous: Old-style kind specifications, Up: Extensions implemented in GNU Fortran [Contents][Index]
GNU Fortran allows old-style initialization of variables of the form:
INTEGER i/1/,j/2/
REAL x(2,2) /3*0.,1./
The syntax for the initializers is as for the DATA statement, but
unlike in a DATA statement, an initializer only applies to the
variable immediately preceding the initialization. In other words,
something like INTEGER I,J/2,3/ is not valid. This style of
initialization is only allowed in declarations without double colons
(::); the double colons were introduced in Fortran 90, which also
introduced a standard syntax for initializing variables in type
declarations.
Examples of standard-conforming code equivalent to the above example are:
! Fortran 90
INTEGER :: i = 1, j = 2
REAL :: x(2,2) = RESHAPE((/0.,0.,0.,1./),SHAPE(x))
! Fortran 77
INTEGER i, j
REAL x(2,2)
DATA i/1/, j/2/, x/3*0.,1./
Note that variables which are explicitly initialized in declarations
or in DATA statements automatically acquire the SAVE
attribute.
Next: X format descriptor without count field, Previous: Old-style variable initialization, Up: Extensions implemented in GNU Fortran [Contents][Index]
GNU Fortran fully supports the Fortran 95 standard for namelist I/O including array qualifiers, substrings and fully qualified derived types. The output from a namelist write is compatible with namelist read. The output has all names in upper case and indentation to column 1 after the namelist name. Two extensions are permitted:
Old-style use of ‘$’ instead of ‘&’
$MYNML X(:)%Y(2) = 1.0 2.0 3.0 CH(1:4) = "abcd" $END
It should be noted that the default terminator is ‘/’ rather than ‘&END’.
Querying of the namelist when inputting from stdin. After at least one space, entering ‘?’ sends to stdout the namelist name and the names of the variables in the namelist:
? &mynml x x%y ch &end
Entering ‘=?’ outputs the namelist to stdout, as if
WRITE(*,NML = mynml) had been called:
=? &MYNML X(1)%Y= 0.000000 , 1.000000 , 0.000000 , X(2)%Y= 0.000000 , 2.000000 , 0.000000 , X(3)%Y= 0.000000 , 3.000000 , 0.000000 , CH=abcd, /
To aid this dialog, when input is from stdin, errors send their
messages to stderr and execution continues, even if IOSTAT is set.
PRINT namelist is permitted. This causes an error if
-std=f95 is used.
PROGRAM test_print REAL, dimension (4) :: x = (/1.0, 2.0, 3.0, 4.0/) NAMELIST /mynml/ x PRINT mynml END PROGRAM test_print
Expanded namelist reads are permitted. This causes an error if -std=f95 is used. In the following example, the first element of the array will be given the value 0.00 and the two succeeding elements will be given the values 1.00 and 2.00.
&MYNML X(1,1) = 0.00 , 1.00 , 2.00 /
When writing a namelist, if no DELIM= is specified, by default a
double quote is used to delimit character strings. If -std=F95, F2003,
or F2008, etc, the delim status is set to ’none’. Defaulting to
quotes ensures that namelists with character strings can be subsequently
read back in accurately.
Next: Commas in FORMAT specifications, Previous: Extensions to namelist, Up: Extensions implemented in GNU Fortran [Contents][Index]
X format descriptor without count fieldTo support legacy codes, GNU Fortran permits the count field of the
X edit descriptor in FORMAT statements to be omitted.
When omitted, the count is implicitly assumed to be one.
PRINT 10, 2, 3 10 FORMAT (I1, X, I1)
Next: Missing period in FORMAT specifications, Previous: X format descriptor without count field, Up: Extensions implemented in GNU Fortran [Contents][Index]
FORMAT specificationsTo support legacy codes, GNU Fortran allows the comma separator
to be omitted immediately before and after character string edit
descriptors in FORMAT statements. A comma with no following format
decriptor is permited if the -fdec-blank-format-item is given on
the command line. This is considered non-conforming code and is
discouraged.
PRINT 10, 2, 3
10 FORMAT ('FOO='I1' BAR='I2)
print 20, 5, 6
20 FORMAT (I3, I3,)
Next: Default widths for F, G and I format descriptors, Previous: Commas in FORMAT specifications, Up: Extensions implemented in GNU Fortran [Contents][Index]
FORMAT specificationsTo support legacy codes, GNU Fortran allows missing periods in format specifications if and only if -std=legacy is given on the command line. This is considered non-conforming code and is discouraged.
REAL :: value
READ(*,10) value
10 FORMAT ('F4')
Next: I/O item lists, Previous: Missing period in FORMAT specifications, Up: Extensions implemented in GNU Fortran [Contents][Index]
F, G and I format descriptorsTo support legacy codes, GNU Fortran allows width to be omitted from format specifications if and only if -fdec-format-defaults is given on the command line. Default widths will be used. This is considered non-conforming code and is discouraged.
REAL :: value1
INTEGER :: value2
WRITE(*,10) value1, value1, value2
10 FORMAT ('F, G, I')
Next: Q exponent-letter, Previous: Default widths for F, G and I format descriptors, Up: Extensions implemented in GNU Fortran [Contents][Index]
To support legacy codes, GNU Fortran allows the input item list
of the READ statement, and the output item lists of the
WRITE and PRINT statements, to start with a comma.
Next: BOZ literal constants, Previous: I/O item lists, Up: Extensions implemented in GNU Fortran [Contents][Index]
Q exponent-letterGNU Fortran accepts real literal constants with an exponent-letter
of Q, for example, 1.23Q45. The constant is interpreted
as a REAL(16) entity on targets that support this type. If
the target does not support REAL(16) but has a REAL(10)
type, then the real-literal-constant will be interpreted as a
REAL(10) entity. In the absence of REAL(16) and
REAL(10), an error will occur.
Next: Real array indices, Previous: Q exponent-letter, Up: Extensions implemented in GNU Fortran [Contents][Index]
Besides decimal constants, Fortran also supports binary (b),
octal (o) and hexadecimal (z) integer constants. The
syntax is: ‘prefix quote digits quote’, were the prefix is
either b, o or z, quote is either ' or
" and the digits are 0 or 1 for binary,
between 0 and 7 for octal, and between 0 and
F for hexadecimal. (Example: b'01011101'.)
Up to Fortran 95, BOZ literal constants were only allowed to initialize
integer variables in DATA statements. Since Fortran 2003 BOZ literal
constants are also allowed as actual arguments to the REAL,
DBLE, INT and CMPLX intrinsic functions.
The BOZ literal constant is simply a string of bits, which is padded
or truncated as needed, during conversion to a numeric type. The
Fortran standard states that the treatment of the sign bit is processor
dependent. Gfortran interprets the sign bit as a user would expect.
As a deprecated extension, GNU Fortran allows hexadecimal BOZ literal
constants to be specified using the X prefix. That the BOZ literal
constant can also be specified by adding a suffix to the string, for
example, Z'ABC' and 'ABC'X are equivalent. Additionally,
as extension, BOZ literals are permitted in some contexts outside of
DATA and the intrinsic functions listed in the Fortran standard.
Use -fallow-invalid-boz to enable the extension.
Next: Unary operators, Previous: BOZ literal constants, Up: Extensions implemented in GNU Fortran [Contents][Index]
As an extension, GNU Fortran allows the use of REAL expressions
or variables as array indices.
Next: Implicitly convert LOGICAL and INTEGER values, Previous: Real array indices, Up: Extensions implemented in GNU Fortran [Contents][Index]
As an extension, GNU Fortran allows unary plus and unary minus operators to appear as the second operand of binary arithmetic operators without the need for parenthesis.
X = Y * -Z
Next: Hollerith constants support, Previous: Unary operators, Up: Extensions implemented in GNU Fortran [Contents][Index]
LOGICAL and INTEGER valuesAs an extension for backwards compatibility with other compilers, GNU
Fortran allows the implicit conversion of LOGICAL values to
INTEGER values and vice versa. When converting from a
LOGICAL to an INTEGER, .FALSE. is interpreted as
zero, and .TRUE. is interpreted as one. When converting from
INTEGER to LOGICAL, the value zero is interpreted as
.FALSE. and any nonzero value is interpreted as .TRUE..
LOGICAL :: l
l = 1
INTEGER :: i
i = .TRUE.
However, there is no implicit conversion of INTEGER values in
if-statements, nor of LOGICAL or INTEGER values
in I/O operations.
Next: Character conversion, Previous: Implicitly convert LOGICAL and INTEGER values, Up: Extensions implemented in GNU Fortran [Contents][Index]
GNU Fortran supports Hollerith constants in assignments, DATA
statements, function and subroutine arguments. A Hollerith constant is
written as a string of characters preceded by an integer constant
indicating the character count, and the letter H or
h, and stored in bytewise fashion in a numeric (INTEGER,
REAL, or COMPLEX), LOGICAL or CHARACTER variable.
The constant will be padded with spaces or truncated to fit the size of
the variable in which it is stored.
Examples of valid uses of Hollerith constants:
complex*16 x(2)
data x /16Habcdefghijklmnop, 16Hqrstuvwxyz012345/
x(1) = 16HABCDEFGHIJKLMNOP
call foo (4h abc)
Examples of Hollerith constants:
integer*4 a
a = 0H ! Invalid, at least one character is needed.
a = 4HAB12 ! Valid
a = 8H12345678 ! Valid, but the Hollerith constant will be truncated.
a = 3Hxyz ! Valid, but the Hollerith constant will be padded.
In general, Hollerith constants were used to provide a rudimentary
facility for handling character strings in early Fortran compilers,
prior to the introduction of CHARACTER variables in Fortran 77;
in those cases, the standard-compliant equivalent is to convert the
program to use proper character strings. On occasion, there may be a
case where the intent is specifically to initialize a numeric variable
with a given byte sequence. In these cases, the same result can be
obtained by using the TRANSFER statement, as in this example.
integer(kind=4) :: a
a = transfer ("abcd", a) ! equivalent to: a = 4Habcd
The use of the -fdec option extends support of Hollerith constants to comparisons:
integer*4 a
a = 4hABCD
if (a .ne. 4habcd) then
write(*,*) "no match"
end if
Supported types are numeric (INTEGER, REAL, or COMPLEX),
and CHARACTER.
Next: Cray pointers, Previous: Hollerith constants support, Up: Extensions implemented in GNU Fortran [Contents][Index]
Allowing character literals to be used in a similar way to Hollerith constants
is a non-standard extension. This feature is enabled using
-fdec-char-conversions and only applies to character literals of kind=1.
Character literals can be used in DATA statements and assignments with
numeric (INTEGER, REAL, or COMPLEX) or LOGICAL
variables. Like Hollerith constants they are copied byte-wise fashion. The
constant will be padded with spaces or truncated to fit the size of the
variable in which it is stored.
Examples:
integer*4 x
data x / 'abcd' /
x = 'A' ! Will be padded.
x = 'ab1234' ! Will be truncated.
Next: CONVERT specifier, Previous: Character conversion, Up: Extensions implemented in GNU Fortran [Contents][Index]
Cray pointers are part of a non-standard extension that provides a C-like pointer in Fortran. This is accomplished through a pair of variables: an integer "pointer" that holds a memory address, and a "pointee" that is used to dereference the pointer.
Pointer/pointee pairs are declared in statements of the form:
pointer ( <pointer> , <pointee> )
or,
pointer ( <pointer1> , <pointee1> ), ( <pointer2> , <pointee2> ), ...
The pointer is an integer that is intended to hold a memory address.
The pointee may be an array or scalar.
If an assumed-size array is permitted within the scoping unit, a
pointee can be an assumed-size array.
That is, the last dimension may be left unspecified by using a *
in place of a value. A pointee cannot be an assumed shape array.
No space is allocated for the pointee.
The pointee may have its type declared before or after the pointer statement, and its array specification (if any) may be declared before, during, or after the pointer statement. The pointer may be declared as an integer prior to the pointer statement. However, some machines have default integer sizes that are different than the size of a pointer, and so the following code is not portable:
integer ipt
pointer (ipt, iarr)
If a pointer is declared with a kind that is too small, the compiler will issue a warning; the resulting binary will probably not work correctly, because the memory addresses stored in the pointers may be truncated. It is safer to omit the first line of the above example; if explicit declaration of ipt’s type is omitted, then the compiler will ensure that ipt is an integer variable large enough to hold a pointer.
Pointer arithmetic is valid with Cray pointers, but it is not the same as C pointer arithmetic. Cray pointers are just ordinary integers, so the user is responsible for determining how many bytes to add to a pointer in order to increment it. Consider the following example:
real target(10)
real pointee(10)
pointer (ipt, pointee)
ipt = loc (target)
ipt = ipt + 1
The last statement does not set ipt to the address of
target(1), as it would in C pointer arithmetic. Adding 1
to ipt just adds one byte to the address stored in ipt.
Any expression involving the pointee will be translated to use the value stored in the pointer as the base address.
To get the address of elements, this extension provides an intrinsic
function LOC(). The LOC() function is equivalent to the
& operator in C, except the address is cast to an integer type:
real ar(10)
pointer(ipt, arpte(10))
real arpte
ipt = loc(ar) ! Makes arpte is an alias for ar
arpte(1) = 1.0 ! Sets ar(1) to 1.0
The pointer can also be set by a call to the MALLOC intrinsic
(see MALLOC — Allocate dynamic memory).
Cray pointees often are used to alias an existing variable. For example:
integer target(10)
integer iarr(10)
pointer (ipt, iarr)
ipt = loc(target)
As long as ipt remains unchanged, iarr is now an alias for
target. The optimizer, however, will not detect this aliasing, so
it is unsafe to use iarr and target simultaneously. Using
a pointee in any way that violates the Fortran aliasing rules or
assumptions is illegal. It is the user’s responsibility to avoid doing
this; the compiler works under the assumption that no such aliasing
occurs.
Cray pointers will work correctly when there is no aliasing (i.e., when they are used to access a dynamically allocated block of memory), and also in any routine where a pointee is used, but any variable with which it shares storage is not used. Code that violates these rules may not run as the user intends. This is not a bug in the optimizer; any code that violates the aliasing rules is illegal. (Note that this is not unique to GNU Fortran; any Fortran compiler that supports Cray pointers will “incorrectly” optimize code with illegal aliasing.)
There are a number of restrictions on the attributes that can be applied
to Cray pointers and pointees. Pointees may not have the
ALLOCATABLE, INTENT, OPTIONAL, DUMMY,
TARGET, INTRINSIC, or POINTER attributes. Pointers
may not have the DIMENSION, POINTER, TARGET,
ALLOCATABLE, EXTERNAL, or INTRINSIC attributes, nor
may they be function results. Pointees may not occur in more than one
pointer statement. A pointee cannot be a pointer. Pointees cannot occur
in equivalence, common, or data statements.
A Cray pointer may also point to a function or a subroutine. For example, the following excerpt is valid:
implicit none external sub pointer (subptr,subpte) external subpte subptr = loc(sub) call subpte() [...] subroutine sub [...] end subroutine sub
A pointer may be modified during the course of a program, and this will change the location to which the pointee refers. However, when pointees are passed as arguments, they are treated as ordinary variables in the invoked function. Subsequent changes to the pointer will not change the base address of the array that was passed.
Next: OpenMP, Previous: Cray pointers, Up: Extensions implemented in GNU Fortran [Contents][Index]
CONVERT specifierGNU Fortran allows the conversion of unformatted data between little-
and big-endian representation to facilitate moving of data
between different systems. The conversion can be indicated with
the CONVERT specifier on the OPEN statement.
See GFORTRAN_CONVERT_UNIT—Set endianness for unformatted I/O, for an alternative way of specifying
the data format via an environment variable.
Valid values for CONVERT are:
CONVERT='NATIVE' Use the native format. This is the default.
CONVERT='SWAP' Swap between little- and big-endian.
CONVERT='LITTLE_ENDIAN' Use the little-endian representation
for unformatted files.
CONVERT='BIG_ENDIAN' Use the big-endian representation for
unformatted files.
Using the option could look like this:
open(file='big.dat',form='unformatted',access='sequential', &
convert='big_endian')
The value of the conversion can be queried by using
INQUIRE(CONVERT=ch). The values returned are
'BIG_ENDIAN' and 'LITTLE_ENDIAN'.
CONVERT works between big- and little-endian for
INTEGER values of all supported kinds and for REAL
on IEEE systems of kinds 4 and 8. Conversion between different
“extended double” types on different architectures such as
m68k and x86_64, which GNU Fortran
supports as REAL(KIND=10) and REAL(KIND=16), will
probably not work.
Note that the values specified via the GFORTRAN_CONVERT_UNIT environment variable will override the CONVERT specifier in the open statement. This is to give control over data formats to users who do not have the source code of their program available.
Using anything but the native representation for unformatted data carries a significant speed overhead. If speed in this area matters to you, it is best if you use this only for data that needs to be portable.
Next: OpenACC, Previous: CONVERT specifier, Up: Extensions implemented in GNU Fortran [Contents][Index]
OpenMP (Open Multi-Processing) is an application programming interface (API) that supports multi-platform shared memory multiprocessing programming in C/C++ and Fortran on many architectures, including Unix and Microsoft Windows platforms. It consists of a set of compiler directives, library routines, and environment variables that influence run-time behavior.
GNU Fortran strives to be compatible to the OpenMP Application Program Interface v4.5.
To enable the processing of the OpenMP directive !$omp in
free-form source code; the c$omp, *$omp and !$omp
directives in fixed form; the !$ conditional compilation sentinels
in free form; and the c$, *$ and !$ sentinels
in fixed form, gfortran needs to be invoked with the
-fopenmp. This also arranges for automatic linking of the
GNU Offloading and Multi Processing Runtime Library
libgomp in GNU Offloading and Multi Processing Runtime
Library.
The OpenMP Fortran runtime library routines are provided both in a
form of a Fortran 90 module named omp_lib and in a form of
a Fortran include file named omp_lib.h.
An example of a parallelized loop taken from Appendix A.1 of the OpenMP Application Program Interface v2.5:
SUBROUTINE A1(N, A, B)
INTEGER I, N
REAL B(N), A(N)
!$OMP PARALLEL DO !I is private by default
DO I=2,N
B(I) = (A(I) + A(I-1)) / 2.0
ENDDO
!$OMP END PARALLEL DO
END SUBROUTINE A1
Please note:
-Wl,--whole-archive -lpthread -Wl,--no-whole-archive is added
to the command line. However, this is not supported by gcc and
thus not recommended.
Next: Argument list functions %VAL, %REF and %LOC, Previous: OpenMP, Up: Extensions implemented in GNU Fortran [Contents][Index]
OpenACC is an application programming interface (API) that supports offloading of code to accelerator devices. It consists of a set of compiler directives, library routines, and environment variables that influence run-time behavior.
GNU Fortran strives to be compatible to the OpenACC Application Programming Interface v2.6.
To enable the processing of the OpenACC directive !$acc in
free-form source code; the c$acc, *$acc and !$acc
directives in fixed form; the !$ conditional compilation
sentinels in free form; and the c$, *$ and !$
sentinels in fixed form, gfortran needs to be invoked with
the -fopenacc. This also arranges for automatic linking of
the GNU Offloading and Multi Processing Runtime Library
libgomp in GNU Offloading and Multi Processing Runtime
Library.
The OpenACC Fortran runtime library routines are provided both in a
form of a Fortran 90 module named openacc and in a form of a
Fortran include file named openacc_lib.h.
Next: Read/Write after EOF marker, Previous: OpenACC, Up: Extensions implemented in GNU Fortran [Contents][Index]
%VAL, %REF and %LOCGNU Fortran supports argument list functions %VAL, %REF
and %LOC statements, for backward compatibility with g77.
It is recommended that these should be used only for code that is
accessing facilities outside of GNU Fortran, such as operating system
or windowing facilities. It is best to constrain such uses to isolated
portions of a program–portions that deal specifically and exclusively
with low-level, system-dependent facilities. Such portions might well
provide a portable interface for use by the program as a whole, but are
themselves not portable, and should be thoroughly tested each time they
are rebuilt using a new compiler or version of a compiler.
%VAL passes a scalar argument by value, %REF passes it by
reference and %LOC passes its memory location. Since gfortran
already passes scalar arguments by reference, %REF is in effect
a do-nothing. %LOC has the same effect as a Fortran pointer.
An example of passing an argument by value to a C subroutine foo.:
C
C prototype void foo_ (float x);
C
external foo
real*4 x
x = 3.14159
call foo (%VAL (x))
end
For details refer to the g77 manual https://gcc.gnu.org/onlinedocs/gcc-3.4.6/g77/index.html#Top.
Also, c_by_val.f and its partner c_by_val.c of the
GNU Fortran testsuite are worth a look.
Next: STRUCTURE and RECORD, Previous: Argument list functions %VAL, %REF and %LOC, Up: Extensions implemented in GNU Fortran [Contents][Index]
Some legacy codes rely on allowing READ or WRITE after the
EOF file marker in order to find the end of a file. GNU Fortran normally
rejects these codes with a run-time error message and suggests the user
consider BACKSPACE or REWIND to properly position
the file before the EOF marker. As an extension, the run-time error may
be disabled using -std=legacy.
Next: UNION and MAP, Previous: Read/Write after EOF marker, Up: Extensions implemented in GNU Fortran [Contents][Index]
STRUCTURE and RECORDRecord structures are a pre-Fortran-90 vendor extension to create user-defined aggregate data types. Support for record structures in GNU Fortran can be enabled with the -fdec-structure compile flag. If you have a choice, you should instead use Fortran 90’s “derived types”, which have a different syntax.
In many cases, record structures can easily be converted to derived types.
To convert, replace STRUCTURE /structure-name/
by TYPE type-name. Additionally, replace
RECORD /structure-name/ by
TYPE(type-name). Finally, in the component access,
replace the period (.) by the percent sign (%).
Here is an example of code using the non portable record structure syntax:
! Declaring a structure named ``item'' and containing three fields: ! an integer ID, an description string and a floating-point price. STRUCTURE /item/ INTEGER id CHARACTER(LEN=200) description REAL price END STRUCTURE ! Define two variables, an single record of type ``item'' ! named ``pear'', and an array of items named ``store_catalog'' RECORD /item/ pear, store_catalog(100) ! We can directly access the fields of both variables pear.id = 92316 pear.description = "juicy D'Anjou pear" pear.price = 0.15 store_catalog(7).id = 7831 store_catalog(7).description = "milk bottle" store_catalog(7).price = 1.2 ! We can also manipulate the whole structure store_catalog(12) = pear print *, store_catalog(12)
This code can easily be rewritten in the Fortran 90 syntax as following:
! ``STRUCTURE /name/ ... END STRUCTURE'' becomes ! ``TYPE name ... END TYPE'' TYPE item INTEGER id CHARACTER(LEN=200) description REAL price END TYPE ! ``RECORD /name/ variable'' becomes ``TYPE(name) variable'' TYPE(item) pear, store_catalog(100) ! Instead of using a dot (.) to access fields of a record, the ! standard syntax uses a percent sign (%) pear%id = 92316 pear%description = "juicy D'Anjou pear" pear%price = 0.15 store_catalog(7)%id = 7831 store_catalog(7)%description = "milk bottle" store_catalog(7)%price = 1.2 ! Assignments of a whole variable do not change store_catalog(12) = pear print *, store_catalog(12)
GNU Fortran implements STRUCTURES like derived types with the following rules and exceptions:
SEQUENCE attribute.
Otherwise they may contain no specifiers.
%FILL.
This will create an anonymous component which cannot be accessed but occupies
space just as if a component of the same type was declared in its place, useful
for alignment purposes. As an example, the following structure will consist
of at least sixteen bytes:
structure /padded/ character(4) start character(8) %FILL character(4) end end structure
structure /header/ ! ... end structure record /header/ header
structure /type-name/
...
structure [/<type-name>/] <field-list>
...
The type name may be ommitted, in which case the structure type itself is anonymous, and other structures of the same type cannot be instantiated. The following shows some examples:
structure /appointment/
! nested structure definition: app_time is an array of two 'time'
structure /time/ app_time (2)
integer(1) hour, minute
end structure
character(10) memo
end structure
! The 'time' structure is still usable
record /time/ now
now = time(5, 30)
...
structure /appointment/
! anonymous nested structure definition
structure start, end
integer(1) hour, minute
end structure
character(10) memo
end structure
UNION blocks. For more detail see the
section on UNION and MAP.
<literal-integer> * <constant-initializer>. The value of the integer
indicates the number of times to repeat the constant initializer when expanding
the initializer list.
Next: Type variants for integer intrinsics, Previous: STRUCTURE and RECORD, Up: Extensions implemented in GNU Fortran [Contents][Index]
UNION and MAPUnions are an old vendor extension which were commonly used with the
non-standard STRUCTURE and RECORD extensions. Use of UNION and
MAP is automatically enabled with -fdec-structure.
A UNION declaration occurs within a structure; within the definition of
each union is a number of MAP blocks. Each MAP shares storage
with its sibling maps (in the same union), and the size of the union is the
size of the largest map within it, just as with unions in C. The major
difference is that component references do not indicate which union or map the
component is in (the compiler gets to figure that out).
Here is a small example:
structure /myunion/
union
map
character(2) w0, w1, w2
end map
map
character(6) long
end map
end union
end structure
record /myunion/ rec
! After this assignment...
rec.long = 'hello!'
! The following is true:
! rec.w0 === 'he'
! rec.w1 === 'll'
! rec.w2 === 'o!'
The two maps share memory, and the size of the union is ultimately six bytes:
0 1 2 3 4 5 6 Byte offset ------------------------------- | | | | | | | ------------------------------- ^ W0 ^ W1 ^ W2 ^ \-------/ \-------/ \-------/ ^ LONG ^ \---------------------------/
Following is an example mirroring the layout of an Intel x86_64 register:
structure /reg/
union ! U0 ! rax
map
character(16) rx
end map
map
character(8) rh ! rah
union ! U1
map
character(8) rl ! ral
end map
map
character(8) ex ! eax
end map
map
character(4) eh ! eah
union ! U2
map
character(4) el ! eal
end map
map
character(4) x ! ax
end map
map
character(2) h ! ah
character(2) l ! al
end map
end union
end map
end union
end map
end union
end structure
record /reg/ a
! After this assignment...
a.rx = 'AAAAAAAA.BBB.C.D'
! The following is true:
a.rx === 'AAAAAAAA.BBB.C.D'
a.rh === 'AAAAAAAA'
a.rl === '.BBB.C.D'
a.ex === '.BBB.C.D'
a.eh === '.BBB'
a.el === '.C.D'
a.x === '.C.D'
a.h === '.C'
a.l === '.D'
Next: AUTOMATIC and STATIC attributes, Previous: UNION and MAP, Up: Extensions implemented in GNU Fortran [Contents][Index]
Similar to the D/C prefixes to real functions to specify the input/output types, GNU Fortran offers B/I/J/K prefixes to integer functions for compatibility with DEC programs. The types implied by each are:
B-INTEGER(kind=1)I-INTEGER(kind=2)J-INTEGER(kind=4)K-INTEGER(kind=8)
GNU Fortran supports these with the flag -fdec-intrinsic-ints. Intrinsics for which prefixed versions are available and in what form are noted in Intrinsic Procedures. The complete list of supported intrinsics is here:
| Intrinsic | B | I | J | K |
|---|---|---|---|---|
| BABS | IIABS | JIABS | KIABS |
| BBTEST | BITEST | BJTEST | BKTEST |
| BIAND | IIAND | JIAND | KIAND |
| BBCLR | IIBCLR | JIBCLR | KIBCLR |
| BBITS | IIBITS | JIBITS | KIBITS |
| BBSET | IIBSET | JIBSET | KIBSET |
| BIEOR | IIEOR | JIEOR | KIEOR |
| BIOR | IIOR | JIOR | KIOR |
| BSHFT | IISHFT | JISHFT | KISHFT |
| BSHFTC | IISHFTC | JISHFTC | KISHFTC |
| BMOD | IMOD | JMOD | KMOD |
| BNOT | INOT | JNOT | KNOT |
| -- | FLOATI | FLOATJ | FLOATK |
Next: Extended math intrinsics, Previous: Type variants for integer intrinsics, Up: Extensions implemented in GNU Fortran [Contents][Index]
AUTOMATIC and STATIC attributesWith -fdec-static GNU Fortran supports the DEC extended attributes
STATIC and AUTOMATIC to provide explicit specification of entity
storage. These follow the syntax of the Fortran standard SAVE attribute.
STATIC is exactly equivalent to SAVE, and specifies that
an entity should be allocated in static memory. As an example, STATIC
local variables will retain their values across multiple calls to a function.
Entities marked AUTOMATIC will be stack automatic whenever possible.
AUTOMATIC is the default for local variables smaller than
-fmax-stack-var-size, unless -fno-automatic is given. This
attribute overrides -fno-automatic, -fmax-stack-var-size, and
blanket SAVE statements.
Examples:
subroutine f integer, automatic :: i ! automatic variable integer x, y ! static variables save ... endsubroutine
subroutine f integer a, b, c, x, y, z static :: x save y automatic z, c ! a, b, c, and z are automatic ! x and y are static endsubroutine
! Compiled with -fno-automatic subroutine f integer a, b, c, d automatic :: a ! a is automatic; b, c, and d are static endsubroutine
Next: Form feed as whitespace, Previous: AUTOMATIC and STATIC attributes, Up: Extensions implemented in GNU Fortran [Contents][Index]
GNU Fortran supports an extended list of mathematical intrinsics with the compile flag -fdec-math for compatability with legacy code. These intrinsics are described fully in Intrinsic Procedures where it is noted that they are extensions and should be avoided whenever possible.
Specifically, -fdec-math enables the COTAN — Cotangent function intrinsic, and
trigonometric intrinsics which accept or produce values in degrees instead of
radians. Here is a summary of the new intrinsics:
* Enabled with -fdec-math.
For advanced users, it may be important to know the implementation of these functions. They are simply wrappers around the standard radian functions, which have more accurate builtin versions. These functions convert their arguments (or results) to degrees (or radians) by taking the value modulus 360 (or 2*pi) and then multiplying it by a constant radian-to-degree (or degree-to-radian) factor, as appropriate. The factor is computed at compile-time as 180/pi (or pi/180).
Next: TYPE as an alias for PRINT, Previous: Extended math intrinsics, Up: Extensions implemented in GNU Fortran [Contents][Index]
Historically, legacy compilers allowed insertion of form feed characters (’\f’, ASCII 0xC) at the beginning of lines for formatted output to line printers, though the Fortran standard does not mention this. GNU Fortran supports the interpretation of form feed characters in source as whitespace for compatibility.
Next: %LOC as an rvalue, Previous: Form feed as whitespace, Up: Extensions implemented in GNU Fortran [Contents][Index]
For compatibility, GNU Fortran will interpret TYPE statements as
PRINT statements with the flag -fdec. With this flag asserted,
the following two examples are equivalent:
TYPE *, 'hello world'
PRINT *, 'hello world'
Next: .XOR. operator, Previous: TYPE as an alias for PRINT, Up: Extensions implemented in GNU Fortran [Contents][Index]
Normally %LOC is allowed only in parameter lists. However the intrinsic
function LOC does the same thing, and is usable as the right-hand-side of
assignments. For compatibility, GNU Fortran supports the use of %LOC as
an alias for the builtin LOC with -std=legacy. With this
feature enabled the following two examples are equivalent:
integer :: i, l l = %loc(i) call sub(l)
integer :: i call sub(%loc(i))
Next: Bitwise logical operators, Previous: %LOC as an rvalue, Up: Extensions implemented in GNU Fortran [Contents][Index]
GNU Fortran supports .XOR. as a logical operator with -std=legacy
for compatibility with legacy code. .XOR. is equivalent to
.NEQV.. That is, the output is true if and only if the inputs differ.
Next: Extended I/O specifiers, Previous: .XOR. operator, Up: Extensions implemented in GNU Fortran [Contents][Index]
With -fdec, GNU Fortran relaxes the type constraints on logical operators to allow integer operands, and performs the corresponding bitwise operation instead. This flag is for compatibility only, and should be avoided in new code. Consider:
INTEGER :: i, j i = z'33' j = z'cc' print *, i .AND. j
In this example, compiled with -fdec, GNU Fortran will
replace the .AND. operation with a call to the intrinsic
IAND — Bitwise logical andi and j.
Note that this conversion will occur if at least one operand is of integral
type. As a result, a logical operand will be converted to an integer when the
other operand is an integer in a logical operation. In this case,
.TRUE. is converted to 1 and .FALSE. to 0.
Here is the mapping of logical operator to bitwise intrinsic used with -fdec:
| Operator | Intrinsic | Bitwise operation |
|---|---|---|
.NOT. | | complement |
.AND. | | intersection |
.OR. | | union |
.NEQV. | | exclusive or |
.EQV. | | complement of exclusive or |
Next: Legacy PARAMETER statements, Previous: Bitwise logical operators, Up: Extensions implemented in GNU Fortran [Contents][Index]
GNU Fortran supports the additional legacy I/O specifiers
CARRIAGECONTROL, READONLY, and SHARE with the
compile flag -fdec, for compatibility.
CARRIAGECONTROLThe CARRIAGECONTROL specifier allows a user to control line
termination settings between output records for an I/O unit. The specifier has
no meaning for readonly files. When CARRAIGECONTROL is specified upon
opening a unit for formatted writing, the exact CARRIAGECONTROL setting
determines what characters to write between output records. The syntax is:
OPEN(..., CARRIAGECONTROL=cc)
Where cc is a character expression that evaluates to one of the following values:
'LIST' | One line feed between records (default) |
'FORTRAN' | Legacy interpretation of the first character (see below) |
'NONE' | No separator between records |
With CARRIAGECONTROL='FORTRAN', when a record is written, the first
character of the input record is not written, and instead determines the output
record separator as follows:
| Leading character | Meaning | Output separating character(s) |
|---|---|---|
'+' | Overprinting | Carriage return only |
'-' | New line | Line feed and carriage return |
'0' | Skip line | Two line feeds and carriage return |
'1' | New page | Form feed and carriage return |
'$' | Prompting | Line feed (no carriage return) |
CHAR(0) | Overprinting (no advance) | None |
READONLYThe READONLY specifier may be given upon opening a unit, and is
equivalent to specifying ACTION='READ', except that the file may not be
deleted on close (i.e. CLOSE with STATUS="DELETE"). The syntax
is:
OPEN(..., READONLY)
SHAREThe SHARE specifier allows system-level locking on a unit upon opening
it for controlled access from multiple processes/threads. The SHARE
specifier has several forms:
OPEN(..., SHARE=sh) OPEN(..., SHARED) OPEN(..., NOSHARED)
Where sh in the first form is a character expression that evaluates to a value as seen in the table below. The latter two forms are aliases for particular values of sh:
| Explicit form | Short form | Meaning |
|---|---|---|
SHARE='DENYRW' | NOSHARED | Exclusive (write) lock |
SHARE='DENYNONE' | SHARED | Shared (read) lock |
In general only one process may hold an exclusive (write) lock for a given file at a time, whereas many processes may hold shared (read) locks for the same file.
The behavior of locking may vary with your operating system. On POSIX systems,
locking is implemented with fcntl. Consult your corresponding operating
system’s manual pages for further details. Locking via SHARE= is not
supported on other systems.
Next: Default exponents, Previous: Extended I/O specifiers, Up: Extensions implemented in GNU Fortran [Contents][Index]
For compatibility, GNU Fortran supports legacy PARAMETER statements without parentheses with -std=legacy. A warning is emitted if used with -std=gnu, and an error is acknowledged with a real Fortran standard flag (-std=f95, etc...). These statements take the following form:
implicit real (E) parameter e = 2.718282 real c parameter c = 3.0e8
Previous: Legacy PARAMETER statements, Up: Extensions implemented in GNU Fortran [Contents][Index]
For compatibility, GNU Fortran supports a default exponent of zero in real
constants with -fdec. For example, 9e would be
interpreted as 9e0, rather than an error.
Previous: Extensions implemented in GNU Fortran, Up: Extensions [Contents][Index]
The long history of the Fortran language, its wide use and broad userbase, the large number of different compiler vendors and the lack of some features crucial to users in the first standards have lead to the existence of a number of important extensions to the language. While some of the most useful or popular extensions are supported by the GNU Fortran compiler, not all existing extensions are supported. This section aims at listing these extensions and offering advice on how best make code that uses them running with the GNU Fortran compiler.
ENCODE and DECODE statementsFORMAT expressionsCOMMON blocksOPEN( ... NAME=)Q edit descriptorENCODE and DECODE statementsGNU Fortran does not support the ENCODE and DECODE
statements. These statements are best replaced by READ and
WRITE statements involving internal files (CHARACTER
variables and arrays), which have been part of the Fortran standard since
Fortran 77. For example, replace a code fragment like
INTEGER*1 LINE(80)
REAL A, B, C
c ... Code that sets LINE
DECODE (80, 9000, LINE) A, B, C
9000 FORMAT (1X, 3(F10.5))
with the following:
CHARACTER(LEN=80) LINE
REAL A, B, C
c ... Code that sets LINE
READ (UNIT=LINE, FMT=9000) A, B, C
9000 FORMAT (1X, 3(F10.5))
Similarly, replace a code fragment like
INTEGER*1 LINE(80)
REAL A, B, C
c ... Code that sets A, B and C
ENCODE (80, 9000, LINE) A, B, C
9000 FORMAT (1X, 'OUTPUT IS ', 3(F10.5))
with the following:
CHARACTER(LEN=80) LINE
REAL A, B, C
c ... Code that sets A, B and C
WRITE (UNIT=LINE, FMT=9000) A, B, C
9000 FORMAT (1X, 'OUTPUT IS ', 3(F10.5))
Next: Alternate complex function syntax, Previous: ENCODE and DECODE statements, Up: Extensions not implemented in GNU Fortran [Contents][Index]
FORMAT expressionsA variable FORMAT expression is format statement which includes
angle brackets enclosing a Fortran expression: FORMAT(I<N>). GNU
Fortran does not support this legacy extension. The effect of variable
format expressions can be reproduced by using the more powerful (and
standard) combination of internal output and string formats. For example,
replace a code fragment like this:
WRITE(6,20) INT1 20 FORMAT(I<N+1>)
with the following:
c Variable declaration
CHARACTER(LEN=20) FMT
c
c Other code here...
c
WRITE(FMT,'("(I", I0, ")")') N+1
WRITE(6,FMT) INT1
or with:
c Variable declaration
CHARACTER(LEN=20) FMT
c
c Other code here...
c
WRITE(FMT,*) N+1
WRITE(6,"(I" // ADJUSTL(FMT) // ")") INT1
Next: Volatile COMMON blocks, Previous: Variable FORMAT expressions, Up: Extensions not implemented in GNU Fortran [Contents][Index]
Some Fortran compilers, including g77, let the user declare
complex functions with the syntax COMPLEX FUNCTION name*16(), as
well as COMPLEX*16 FUNCTION name(). Both are non-standard, legacy
extensions. gfortran accepts the latter form, which is more
common, but not the former.
Next: OPEN( ... NAME=), Previous: Alternate complex function syntax, Up: Extensions not implemented in GNU Fortran [Contents][Index]
COMMON blocksSome Fortran compilers, including g77, let the user declare
COMMON with the VOLATILE attribute. This is
invalid standard Fortran syntax and is not supported by
gfortran. Note that gfortran accepts
VOLATILE variables in COMMON blocks since revision 4.3.
Next: Q edit descriptor, Previous: Volatile COMMON blocks, Up: Extensions not implemented in GNU Fortran [Contents][Index]
OPEN( ... NAME=)Some Fortran compilers, including g77, let the user declare
OPEN( ... NAME=). This is
invalid standard Fortran syntax and is not supported by
gfortran. OPEN( ... NAME=) should be replaced
with OPEN( ... FILE=).
Previous: OPEN( ... NAME=), Up: Extensions not implemented in GNU Fortran [Contents][Index]
Q edit descriptorSome Fortran compilers provide the Q edit descriptor, which
transfers the number of characters left within an input record into an
integer variable.
A direct replacement of the Q edit descriptor is not available
in gfortran. How to replicate its functionality using
standard-conforming code depends on what the intent of the original
code is.
Options to replace Q may be to read the whole line into a
character variable and then counting the number of non-blank
characters left using LEN_TRIM. Another method may be to use
formatted stream, read the data up to the position where the Q
descriptor occurred, use INQUIRE to get the file position,
count the characters up to the next NEW_LINE and then start
reading from the position marked previously.
Next: Coarray Programming, Previous: Extensions, Up: Introduction [Contents][Index]
This chapter is about mixed-language interoperability, but also applies if one links Fortran code compiled by different compilers. In most cases, use of the C Binding features of the Fortran 2003 standard is sufficient, and their use is highly recommended.
Since Fortran 2003 (ISO/IEC 1539-1:2004(E)) there is a
standardized way to generate procedure and derived-type
declarations and global variables which are interoperable with C
(ISO/IEC 9899:1999). The bind(C) attribute has been added
to inform the compiler that a symbol shall be interoperable with C;
also, some constraints are added. Note, however, that not
all C features have a Fortran equivalent or vice versa. For instance,
neither C’s unsigned integers nor C’s functions with variable number
of arguments have an equivalent in Fortran.
Note that array dimensions are reversely ordered in C and that arrays in
C always start with index 0 while in Fortran they start by default with
1. Thus, an array declaration A(n,m) in Fortran matches
A[m][n] in C and accessing the element A(i,j) matches
A[j-1][i-1]. The element following A(i,j) (C: A[j-1][i-1];
assuming i < n) in memory is A(i+1,j) (C: A[j-1][i]).
Next: Derived Types and struct, Up: Interoperability with C [Contents][Index]
In order to ensure that exactly the same variable type and kind is used
in C and Fortran, the named constants shall be used which are defined in the
ISO_C_BINDING intrinsic module. That module contains named constants
for kind parameters and character named constants for the escape sequences
in C. For a list of the constants, see ISO_C_BINDING.
For logical types, please note that the Fortran standard only guarantees
interoperability between C99’s _Bool and Fortran’s C_Bool-kind
logicals and C99 defines that true has the value 1 and false
the value 0. Using any other integer value with GNU Fortran’s LOGICAL
(with any kind parameter) gives an undefined result. (Passing other integer
values than 0 and 1 to GCC’s _Bool is also undefined, unless the
integer is explicitly or implicitly casted to _Bool.)
Next: Interoperable Global Variables, Previous: Intrinsic Types, Up: Interoperability with C [Contents][Index]
For compatibility of derived types with struct, one needs to use
the BIND(C) attribute in the type declaration. For instance, the
following type declaration
USE ISO_C_BINDING TYPE, BIND(C) :: myType INTEGER(C_INT) :: i1, i2 INTEGER(C_SIGNED_CHAR) :: i3 REAL(C_DOUBLE) :: d1 COMPLEX(C_FLOAT_COMPLEX) :: c1 CHARACTER(KIND=C_CHAR) :: str(5) END TYPE
matches the following struct declaration in C
struct {
int i1, i2;
/* Note: "char" might be signed or unsigned. */
signed char i3;
double d1;
float _Complex c1;
char str[5];
} myType;
Derived types with the C binding attribute shall not have the sequence
attribute, type parameters, the extends attribute, nor type-bound
procedures. Every component must be of interoperable type and kind and may not
have the pointer or allocatable attribute. The names of the
components are irrelevant for interoperability.
As there exist no direct Fortran equivalents, neither unions nor structs with bit field or variable-length array members are interoperable.
Next: Interoperable Subroutines and Functions, Previous: Derived Types and struct, Up: Interoperability with C [Contents][Index]
Variables can be made accessible from C using the C binding attribute,
optionally together with specifying a binding name. Those variables
have to be declared in the declaration part of a MODULE,
be of interoperable type, and have neither the pointer nor
the allocatable attribute.
MODULE m
USE myType_module
USE ISO_C_BINDING
integer(C_INT), bind(C, name="_MyProject_flags") :: global_flag
type(myType), bind(C) :: tp
END MODULE
Here, _MyProject_flags is the case-sensitive name of the variable
as seen from C programs while global_flag is the case-insensitive
name as seen from Fortran. If no binding name is specified, as for
tp, the C binding name is the (lowercase) Fortran binding name.
If a binding name is specified, only a single variable may be after the
double colon. Note of warning: You cannot use a global variable to
access errno of the C library as the C standard allows it to be
a macro. Use the IERRNO intrinsic (GNU extension) instead.
Next: Working with Pointers, Previous: Interoperable Global Variables, Up: Interoperability with C [Contents][Index]
Subroutines and functions have to have the BIND(C) attribute to
be compatible with C. The dummy argument declaration is relatively
straightforward. However, one needs to be careful because C uses
call-by-value by default while Fortran behaves usually similar to
call-by-reference. Furthermore, strings and pointers are handled
differently. Note that in Fortran 2003 and 2008 only explicit size
and assumed-size arrays are supported but not assumed-shape or
deferred-shape (i.e. allocatable or pointer) arrays. However, those
are allowed since the Technical Specification 29113, see
Further Interoperability of Fortran with C
To pass a variable by value, use the VALUE attribute.
Thus, the following C prototype
int func(int i, int *j)
matches the Fortran declaration
integer(c_int) function func(i,j)
use iso_c_binding, only: c_int
integer(c_int), VALUE :: i
integer(c_int) :: j
Note that pointer arguments also frequently need the VALUE attribute,
see Working with Pointers.
Strings are handled quite differently in C and Fortran. In C a string
is a NUL-terminated array of characters while in Fortran each string
has a length associated with it and is thus not terminated (by e.g.
NUL). For example, if one wants to use the following C function,
#include <stdio.h>
void print_C(char *string) /* equivalent: char string[] */
{
printf("%s\n", string);
}
to print “Hello World” from Fortran, one can call it using
use iso_c_binding, only: C_CHAR, C_NULL_CHAR
interface
subroutine print_c(string) bind(C, name="print_C")
use iso_c_binding, only: c_char
character(kind=c_char) :: string(*)
end subroutine print_c
end interface
call print_c(C_CHAR_"Hello World"//C_NULL_CHAR)
As the example shows, one needs to ensure that the
string is NUL terminated. Additionally, the dummy argument
string of print_C is a length-one assumed-size
array; using character(len=*) is not allowed. The example
above uses c_char_"Hello World" to ensure the string
literal has the right type; typically the default character
kind and c_char are the same and thus "Hello World"
is equivalent. However, the standard does not guarantee this.
The use of strings is now further illustrated using the C library
function strncpy, whose prototype is
char *strncpy(char *restrict s1, const char *restrict s2, size_t n);
The function strncpy copies at most n characters from
string s2 to s1 and returns s1. In the following
example, we ignore the return value:
use iso_c_binding
implicit none
character(len=30) :: str,str2
interface
! Ignore the return value of strncpy -> subroutine
! "restrict" is always assumed if we do not pass a pointer
subroutine strncpy(dest, src, n) bind(C)
import
character(kind=c_char), intent(out) :: dest(*)
character(kind=c_char), intent(in) :: src(*)
integer(c_size_t), value, intent(in) :: n
end subroutine strncpy
end interface
str = repeat('X',30) ! Initialize whole string with 'X'
call strncpy(str, c_char_"Hello World"//C_NULL_CHAR, &
len(c_char_"Hello World",kind=c_size_t))
print '(a)', str ! prints: "Hello WorldXXXXXXXXXXXXXXXXXXX"
end
The intrinsic procedures are described in Intrinsic Procedures.
Next: Further Interoperability of Fortran with C, Previous: Interoperable Subroutines and Functions, Up: Interoperability with C [Contents][Index]
C pointers are represented in Fortran via the special opaque derived type
type(c_ptr) (with private components). Thus one needs to
use intrinsic conversion procedures to convert from or to C pointers.
For some applications, using an assumed type (TYPE(*)) can be an
alternative to a C pointer; see
Further Interoperability of Fortran with C.
For example,
use iso_c_binding
type(c_ptr) :: cptr1, cptr2
integer, target :: array(7), scalar
integer, pointer :: pa(:), ps
cptr1 = c_loc(array(1)) ! The programmer needs to ensure that the
! array is contiguous if required by the C
! procedure
cptr2 = c_loc(scalar)
call c_f_pointer(cptr2, ps)
call c_f_pointer(cptr2, pa, shape=[7])
When converting C to Fortran arrays, the one-dimensional SHAPE argument
has to be passed.
If a pointer is a dummy-argument of an interoperable procedure, it usually
has to be declared using the VALUE attribute. void*
matches TYPE(C_PTR), VALUE, while TYPE(C_PTR) alone
matches void**.
Procedure pointers are handled analogously to pointers; the C type is
TYPE(C_FUNPTR) and the intrinsic conversion procedures are
C_F_PROCPOINTER and C_FUNLOC.
Let us consider two examples of actually passing a procedure pointer from C to Fortran and vice versa. Note that these examples are also very similar to passing ordinary pointers between both languages. First, consider this code in C:
/* Procedure implemented in Fortran. */
void get_values (void (*)(double));
/* Call-back routine we want called from Fortran. */
void
print_it (double x)
{
printf ("Number is %f.\n", x);
}
/* Call Fortran routine and pass call-back to it. */
void
foobar ()
{
get_values (&print_it);
}
A matching implementation for get_values in Fortran, that correctly
receives the procedure pointer from C and is able to call it, is given
in the following MODULE:
MODULE m
IMPLICIT NONE
! Define interface of call-back routine.
ABSTRACT INTERFACE
SUBROUTINE callback (x)
USE, INTRINSIC :: ISO_C_BINDING
REAL(KIND=C_DOUBLE), INTENT(IN), VALUE :: x
END SUBROUTINE callback
END INTERFACE
CONTAINS
! Define C-bound procedure.
SUBROUTINE get_values (cproc) BIND(C)
USE, INTRINSIC :: ISO_C_BINDING
TYPE(C_FUNPTR), INTENT(IN), VALUE :: cproc
PROCEDURE(callback), POINTER :: proc
! Convert C to Fortran procedure pointer.
CALL C_F_PROCPOINTER (cproc, proc)
! Call it.
CALL proc (1.0_C_DOUBLE)
CALL proc (-42.0_C_DOUBLE)
CALL proc (18.12_C_DOUBLE)
END SUBROUTINE get_values
END MODULE m
Next, we want to call a C routine that expects a procedure pointer argument and pass it a Fortran procedure (which clearly must be interoperable!). Again, the C function may be:
int
call_it (int (*func)(int), int arg)
{
return func (arg);
}
It can be used as in the following Fortran code:
MODULE m
USE, INTRINSIC :: ISO_C_BINDING
IMPLICIT NONE
! Define interface of C function.
INTERFACE
INTEGER(KIND=C_INT) FUNCTION call_it (func, arg) BIND(C)
USE, INTRINSIC :: ISO_C_BINDING
TYPE(C_FUNPTR), INTENT(IN), VALUE :: func
INTEGER(KIND=C_INT), INTENT(IN), VALUE :: arg
END FUNCTION call_it
END INTERFACE
CONTAINS
! Define procedure passed to C function.
! It must be interoperable!
INTEGER(KIND=C_INT) FUNCTION double_it (arg) BIND(C)
INTEGER(KIND=C_INT), INTENT(IN), VALUE :: arg
double_it = arg + arg
END FUNCTION double_it
! Call C function.
SUBROUTINE foobar ()
TYPE(C_FUNPTR) :: cproc
INTEGER(KIND=C_INT) :: i
! Get C procedure pointer.
cproc = C_FUNLOC (double_it)
! Use it.
DO i = 1_C_INT, 10_C_INT
PRINT *, call_it (cproc, i)
END DO
END SUBROUTINE foobar
END MODULE m
Previous: Working with Pointers, Up: Interoperability with C [Contents][Index]
The Technical Specification ISO/IEC TS 29113:2012 on further
interoperability of Fortran with C extends the interoperability support
of Fortran 2003 and Fortran 2008. Besides removing some restrictions
and constraints, it adds assumed-type (TYPE(*)) and assumed-rank
(dimension) variables and allows for interoperability of
assumed-shape, assumed-rank and deferred-shape arrays, including
allocatables and pointers.
Note: Currently, GNU Fortran does not use internally the array descriptor (dope vector) as specified in the Technical Specification, but uses an array descriptor with different fields. Assumed type and assumed rank formal arguments are converted in the library to the specified form. The ISO_Fortran_binding API functions (also Fortran 2018 18.4) are implemented in libgfortran. Alternatively, the Chasm Language Interoperability Tools, http://chasm-interop.sourceforge.net/, provide an interface to GNU Fortran’s array descriptor.
The Technical Specification adds the following new features, which are supported by GNU Fortran:
ASYNCHRONOUS attribute has been clarified and
extended to allow its use with asynchronous communication in
user-provided libraries such as in implementations of the
Message Passing Interface specification.
C_LOC and C_F_POINTER intrinsics.
OPTIONAL attribute is now allowed for dummy
arguments; an absent argument matches a NULL pointer.
TYPE(*)) have been added, which may
only be used for dummy arguments. They are unlimited polymorphic
but contrary to CLASS(*) they do not contain any type
information, similar to C’s void * pointers. Expressions
of any type and kind can be passed; thus, it can be used as
replacement for TYPE(C_PTR), avoiding the use of
C_LOC in the caller.
Note, however, that TYPE(*) only accepts scalar arguments,
unless the DIMENSION is explicitly specified. As
DIMENSION(*) only supports array (including array elements) but
no scalars, it is not a full replacement for C_LOC. On the
other hand, assumed-type assumed-rank dummy arguments
(TYPE(*), DIMENSION(..)) allow for both scalars and arrays, but
require special code on the callee side to handle the array descriptor.
DIMENSION(..)) as dummy argument
allow that scalars and arrays of any rank can be passed as actual
argument. As the Technical Specification does not provide for direct
means to operate with them, they have to be used either from the C side
or be converted using C_LOC and C_F_POINTER to scalars
or arrays of a specific rank. The rank can be determined using the
RANK intrinisic.
Currently unimplemented:
ISO_Fortran_binding.h header file and the C functions it
specifies are not available.
BIND(C) procedures is not fully supported. In particular,
C interoperable strings of other length than one are not supported
as this requires the new array descriptor.
Next: Non-Fortran Main Program, Previous: Interoperability with C, Up: Mixed-Language Programming [Contents][Index]
Next: UNROLL directive, Up: GNU Fortran Compiler Directives [Contents][Index]
The Fortran standard describes how a conforming program shall behave; however, the exact implementation is not standardized. In order to allow the user to choose specific implementation details, compiler directives can be used to set attributes of variables and procedures which are not part of the standard. Whether a given attribute is supported and its exact effects depend on both the operating system and on the processor; see C Extensions in Using the GNU Compiler Collection (GCC) for details.
For procedures and procedure pointers, the following attributes can be used to change the calling convention:
CDECL – standard C calling convention
STDCALL – convention where the called procedure pops the stack
FASTCALL – part of the arguments are passed via registers
instead using the stack
Besides changing the calling convention, the attributes also influence the decoration of the symbol name, e.g., by a leading underscore or by a trailing at-sign followed by the number of bytes on the stack. When assigning a procedure to a procedure pointer, both should use the same calling convention.
On some systems, procedures and global variables (module variables and
COMMON blocks) need special handling to be accessible when they
are in a shared library. The following attributes are available:
DLLEXPORT – provide a global pointer to a pointer in the DLL
DLLIMPORT – reference the function or variable using a
global pointer
For dummy arguments, the NO_ARG_CHECK attribute can be used; in
other compilers, it is also known as IGNORE_TKR. For dummy arguments
with this attribute actual arguments of any type and kind (similar to
TYPE(*)), scalars and arrays of any rank (no equivalent
in Fortran standard) are accepted. As with TYPE(*), the argument
is unlimited polymorphic and no type information is available.
Additionally, the argument may only be passed to dummy arguments
with the NO_ARG_CHECK attribute and as argument to the
PRESENT intrinsic function and to C_LOC of the
ISO_C_BINDING module.
Variables with NO_ARG_CHECK attribute shall be of assumed-type
(TYPE(*); recommended) or of type INTEGER, LOGICAL,
REAL or COMPLEX. They shall not have the ALLOCATE,
CODIMENSION, INTENT(OUT), POINTER or VALUE
attribute; furthermore, they shall be either scalar or of assumed-size
(dimension(*)). As TYPE(*), the NO_ARG_CHECK attribute
requires an explicit interface.
NO_ARG_CHECK – disable the type, kind and rank checking
DEPRECATED – print a warning when using a such-tagged
deprecated procedure, variable or parameter; the warning can be suppressed
with -Wno-deprecated-declarations.
The attributes are specified using the syntax
!GCC$ ATTRIBUTES attribute-list :: variable-list
where in free-form source code only whitespace is allowed before !GCC$
and in fixed-form source code !GCC$, cGCC$ or *GCC$ shall
start in the first column.
For procedures, the compiler directives shall be placed into the body of the procedure; for variables and procedure pointers, they shall be in the same declaration part as the variable or procedure pointer.
Next: BUILTIN directive, Previous: ATTRIBUTES directive, Up: GNU Fortran Compiler Directives [Contents][Index]
The syntax of the directive is
!GCC$ unroll N
You can use this directive to control how many times a loop should be unrolled.
It must be placed immediately before a DO loop and applies only to the
loop that follows. N is an integer constant specifying the unrolling factor.
The values of 0 and 1 block any unrolling of the loop.
Next: IVDEP directive, Previous: UNROLL directive, Up: GNU Fortran Compiler Directives [Contents][Index]
The syntax of the directive is
!GCC$ BUILTIN (B) attributes simd FLAGS IF('target')
You can use this directive to define which middle-end built-ins provide vector
implementations. B is name of the middle-end built-in. FLAGS
are optional and must be either "(inbranch)" or "(notinbranch)".
IF statement is optional and is used to filter multilib ABIs
for the built-in that should be vectorized. Example usage:
!GCC$ builtin (sinf) attributes simd (notinbranch) if('x86_64')
The purpose of the directive is to provide an API among the GCC compiler and the GNU C Library which would define vector implementations of math routines.
Next: VECTOR directive, Previous: BUILTIN directive, Up: GNU Fortran Compiler Directives [Contents][Index]
The syntax of the directive is
!GCC$ ivdep
This directive tells the compiler to ignore vector dependencies in the
following loop. It must be placed immediately before a DO loop
and applies only to the loop that follows.
Sometimes the compiler may not have sufficient information to decide whether a particular loop is vectorizable due to potential dependencies between iterations. The purpose of the directive is to tell the compiler that vectorization is safe.
This directive is intended for annotation of existing code. For new code it is recommended to consider OpenMP SIMD directives as potential alternative.
Next: NOVECTOR directive, Previous: IVDEP directive, Up: GNU Fortran Compiler Directives [Contents][Index]
The syntax of the directive is
!GCC$ vector
This directive tells the compiler to vectorize the following loop. It
must be placed immediately before a DO loop and applies only to
the loop that follows.
Previous: VECTOR directive, Up: GNU Fortran Compiler Directives [Contents][Index]
The syntax of the directive is
!GCC$ novector
This directive tells the compiler to not vectorize the following loop.
It must be placed immediately before a DO loop and applies only
to the loop that follows.
Next: Naming and argument-passing conventions, Previous: GNU Fortran Compiler Directives, Up: Mixed-Language Programming [Contents][Index]
Even if you are doing mixed-language programming, it is very likely that you do not need to know or use the information in this section. Since it is about the internal structure of GNU Fortran, it may also change in GCC minor releases.
When you compile a PROGRAM with GNU Fortran, a function
with the name main (in the symbol table of the object file)
is generated, which initializes the libgfortran library and then
calls the actual program which uses the name MAIN__, for
historic reasons. If you link GNU Fortran compiled procedures
to, e.g., a C or C++ program or to a Fortran program compiled by
a different compiler, the libgfortran library is not initialized
and thus a few intrinsic procedures do not work properly, e.g.
those for obtaining the command-line arguments.
Therefore, if your PROGRAM is not compiled with
GNU Fortran and the GNU Fortran compiled procedures require
intrinsics relying on the library initialization, you need to
initialize the library yourself. Using the default options,
gfortran calls _gfortran_set_args and
_gfortran_set_options. The initialization of the former
is needed if the called procedures access the command line
(and for backtracing); the latter sets some flags based on the
standard chosen or to enable backtracing. In typical programs,
it is not necessary to call any initialization function.
If your PROGRAM is compiled with GNU Fortran, you shall
not call any of the following functions. The libgfortran
initialization functions are shown in C syntax but using C
bindings they are also accessible from Fortran.
_gfortran_set_args — Save command-line arguments_gfortran_set_options — Set library option flags_gfortran_set_convert — Set endian conversion_gfortran_set_record_marker — Set length of record markers_gfortran_set_fpe — Enable floating point exception traps_gfortran_set_max_subrecord_length — Set subrecord length
Next: _gfortran_set_options — Set library option flags, Up: Non-Fortran Main Program [Contents][Index]
_gfortran_set_args — Save command-line arguments_gfortran_set_args saves the command-line arguments; this
initialization is required if any of the command-line intrinsics
is called. Additionally, it shall be called if backtracing is
enabled (see _gfortran_set_options).
void _gfortran_set_args (int argc, char *argv[])
| argc | number of command line argument strings |
| argv | the command-line argument strings; argv[0] is the pathname of the executable itself. |
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
return 0;
}
Next: _gfortran_set_convert — Set endian conversion, Previous: _gfortran_set_args — Save command-line arguments, Up: Non-Fortran Main Program [Contents][Index]
_gfortran_set_options — Set library option flags_gfortran_set_options sets several flags related to the Fortran
standard to be used, whether backtracing should be enabled
and whether range checks should be performed. The syntax allows for
upward compatibility since the number of passed flags is specified; for
non-passed flags, the default value is used. See also
see Options for code generation conventions. Please note that not all flags are actually
used.
void _gfortran_set_options (int num, int options[])
| num | number of options passed |
| argv | The list of flag values |
| option[0] | Allowed standard; can give run-time errors
if e.g. an input-output edit descriptor is invalid in a given
standard. Possible values are (bitwise or-ed) GFC_STD_F77 (1),
GFC_STD_F95_OBS (2), GFC_STD_F95_DEL (4),
GFC_STD_F95 (8), GFC_STD_F2003 (16), GFC_STD_GNU
(32), GFC_STD_LEGACY (64), GFC_STD_F2008 (128),
GFC_STD_F2008_OBS (256), GFC_STD_F2008_TS (512),
GFC_STD_F2018 (1024), GFC_STD_F2018_OBS (2048), and
GFC_STD=F2018_DEL (4096). Default: GFC_STD_F95_OBS |
GFC_STD_F95_DEL | GFC_STD_F95 | GFC_STD_F2003 | GFC_STD_F2008 |
GFC_STD_F2008_TS | GFC_STD_F2008_OBS | GFC_STD_F77 | GFC_STD_F2018 |
GFC_STD_F2018_OBS | GFC_STD_F2018_DEL | GFC_STD_GNU | GFC_STD_LEGACY. |
| option[1] | Standard-warning flag; prints a warning to
standard error. Default: GFC_STD_F95_DEL | GFC_STD_LEGACY. |
| option[2] | If non zero, enable pedantic checking. Default: off. |
| option[3] | Unused. |
| option[4] | If non zero, enable backtracing on run-time
errors. Default: off. (Default in the compiler: on.)
Note: Installs a signal handler and requires command-line
initialization using _gfortran_set_args. |
| option[5] | If non zero, supports signed zeros. Default: enabled. |
| option[6] | Enables run-time checking. Possible values are (bitwise or-ed): GFC_RTCHECK_BOUNDS (1), GFC_RTCHECK_ARRAY_TEMPS (2), GFC_RTCHECK_RECURSION (4), GFC_RTCHECK_DO (8), GFC_RTCHECK_POINTER (16), GFC_RTCHECK_MEM (32), GFC_RTCHECK_BITS (64). Default: disabled. |
| option[7] | Unused. |
| option[8] | Show a warning when invoking STOP and
ERROR STOP if a floating-point exception occurred. Possible values
are (bitwise or-ed) GFC_FPE_INVALID (1), GFC_FPE_DENORMAL (2),
GFC_FPE_ZERO (4), GFC_FPE_OVERFLOW (8),
GFC_FPE_UNDERFLOW (16), GFC_FPE_INEXACT (32). Default: None (0).
(Default in the compiler: GFC_FPE_INVALID | GFC_FPE_DENORMAL |
GFC_FPE_ZERO | GFC_FPE_OVERFLOW | GFC_FPE_UNDERFLOW.) |
/* Use gfortran 4.9 default options. */
static int options[] = {68, 511, 0, 0, 1, 1, 0, 0, 31};
_gfortran_set_options (9, &options);
Next: _gfortran_set_record_marker — Set length of record markers, Previous: _gfortran_set_options — Set library option flags, Up: Non-Fortran Main Program [Contents][Index]
_gfortran_set_convert — Set endian conversion_gfortran_set_convert set the representation of data for
unformatted files.
void _gfortran_set_convert (int conv)
| conv | Endian conversion, possible values: GFC_CONVERT_NATIVE (0, default), GFC_CONVERT_SWAP (1), GFC_CONVERT_BIG (2), GFC_CONVERT_LITTLE (3). |
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_convert (1);
return 0;
}
Next: _gfortran_set_fpe — Enable floating point exception traps, Previous: _gfortran_set_convert — Set endian conversion, Up: Non-Fortran Main Program [Contents][Index]
_gfortran_set_record_marker — Set length of record markers_gfortran_set_record_marker sets the length of record markers
for unformatted files.
void _gfortran_set_record_marker (int val)
| val | Length of the record marker; valid values are 4 and 8. Default is 4. |
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_record_marker (8);
return 0;
}
Next: _gfortran_set_max_subrecord_length — Set subrecord length, Previous: _gfortran_set_record_marker — Set length of record markers, Up: Non-Fortran Main Program [Contents][Index]
_gfortran_set_fpe — Enable floating point exception traps_gfortran_set_fpe enables floating point exception traps for
the specified exceptions. On most systems, this will result in a
SIGFPE signal being sent and the program being aborted.
void _gfortran_set_fpe (int val)
| option[0] | IEEE exceptions. Possible values are
(bitwise or-ed) zero (0, default) no trapping,
GFC_FPE_INVALID (1), GFC_FPE_DENORMAL (2),
GFC_FPE_ZERO (4), GFC_FPE_OVERFLOW (8),
GFC_FPE_UNDERFLOW (16), and GFC_FPE_INEXACT (32). |
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
/* FPE for invalid operations such as SQRT(-1.0). */
_gfortran_set_fpe (1);
return 0;
}
Previous: _gfortran_set_fpe — Enable floating point exception traps, Up: Non-Fortran Main Program [Contents][Index]
_gfortran_set_max_subrecord_length — Set subrecord length_gfortran_set_max_subrecord_length set the maximum length
for a subrecord. This option only makes sense for testing and
debugging of unformatted I/O.
void _gfortran_set_max_subrecord_length (int val)
| val | the maximum length for a subrecord; the maximum permitted value is 2147483639, which is also the default. |
int main (int argc, char *argv[])
{
/* Initialize libgfortran. */
_gfortran_set_args (argc, argv);
_gfortran_set_max_subrecord_length (8);
return 0;
}
Previous: Non-Fortran Main Program, Up: Mixed-Language Programming [Contents][Index]
This section gives an overview about the naming convention of procedures and global variables and about the argument passing conventions used by GNU Fortran. If a C binding has been specified, the naming convention and some of the argument-passing conventions change. If possible, mixed-language and mixed-compiler projects should use the better defined C binding for interoperability. See see Interoperability with C.
According the Fortran standard, valid Fortran names consist of a letter
between A to Z, a to z, digits 0,
1 to 9 and underscores (_) with the restriction
that names may only start with a letter. As vendor extension, the
dollar sign ($) is additionally permitted with the option
-fdollar-ok, but not as first character and only if the
target system supports it.
By default, the procedure name is the lower-cased Fortran name with an
appended underscore (_); using -fno-underscoring no
underscore is appended while -fsecond-underscore appends two
underscores. Depending on the target system and the calling convention,
the procedure might be additionally dressed; for instance, on 32bit
Windows with stdcall, an at-sign @ followed by an integer
number is appended. For the changing the calling convention, see
see GNU Fortran Compiler Directives.
For common blocks, the same convention is used, i.e. by default an
underscore is appended to the lower-cased Fortran name. Blank commons
have the name __BLNK__.
For procedures and variables declared in the specification space of a
module, the name is formed by __, followed by the lower-cased
module name, _MOD_, and the lower-cased Fortran name. Note that
no underscore is appended.
Previous: Naming conventions, Up: Naming and argument-passing conventions [Contents][Index]
Subroutines do not return a value (matching C99’s void) while
functions either return a value as specified in the platform ABI or
the result variable is passed as hidden argument to the function and
no result is returned. A hidden result variable is used when the
result variable is an array or of type CHARACTER.
Arguments are passed according to the platform ABI. In particular,
complex arguments might not be compatible to a struct with two real
components for the real and imaginary part. The argument passing
matches the one of C99’s _Complex. Functions with scalar
complex result variables return their value and do not use a
by-reference argument. Note that with the -ff2c option,
the argument passing is modified and no longer completely matches
the platform ABI. Some other Fortran compilers use f2c
semantic by default; this might cause problems with
interoperablility.
GNU Fortran passes most arguments by reference, i.e. by passing a pointer to the data. Note that the compiler might use a temporary variable into which the actual argument has been copied, if required semantically (copy-in/copy-out).
For arguments with ALLOCATABLE and POINTER
attribute (including procedure pointers), a pointer to the pointer
is passed such that the pointer address can be modified in the
procedure.
For dummy arguments with the VALUE attribute: Scalar arguments
of the type INTEGER, LOGICAL, REAL and
COMPLEX are passed by value according to the platform ABI.
(As vendor extension and not recommended, using %VAL() in the
call to a procedure has the same effect.) For TYPE(C_PTR) and
procedure pointers, the pointer itself is passed such that it can be
modified without affecting the caller.
For Boolean (LOGICAL) arguments, please note that GCC expects
only the integer value 0 and 1. If a GNU Fortran LOGICAL
variable contains another integer value, the result is undefined.
As some other Fortran compilers use -1 for .TRUE.,
extra care has to be taken – such as passing the value as
INTEGER. (The same value restriction also applies to other
front ends of GCC, e.g. to GCC’s C99 compiler for _Bool
or GCC’s Ada compiler for Boolean.)
For arguments of CHARACTER type, the character length is passed
as a hidden argument at the end of the argument list. For
deferred-length strings, the value is passed by reference, otherwise
by value. The character length has the C type size_t (or
INTEGER(kind=C_SIZE_T) in Fortran). Note that this is
different to older versions of the GNU Fortran compiler, where the
type of the hidden character length argument was a C int. In
order to retain compatibility with older versions, one can e.g. for
the following Fortran procedure
subroutine fstrlen (s, a) character(len=*) :: s integer :: a print*, len(s) end subroutine fstrlen
define the corresponding C prototype as follows:
#if __GNUC__ > 7 typedef size_t fortran_charlen_t; #else typedef int fortran_charlen_t; #endif void fstrlen_ (char*, int*, fortran_charlen_t);
In order to avoid such compiler-specific details, for new code it is instead recommended to use the ISO_C_BINDING feature.
Note with C binding, CHARACTER(len=1) result variables are
returned according to the platform ABI and no hidden length argument
is used for dummy arguments; with VALUE, those variables are
passed by value.
For OPTIONAL dummy arguments, an absent argument is denoted
by a NULL pointer, except for scalar dummy arguments of type
INTEGER, LOGICAL, REAL and COMPLEX
which have the VALUE attribute. For those, a hidden Boolean
argument (logical(kind=C_bool),value) is used to indicate
whether the argument is present.
Arguments which are assumed-shape, assumed-rank or deferred-rank
arrays or, with -fcoarray=lib, allocatable scalar coarrays use
an array descriptor. All other arrays pass the address of the
first element of the array. With -fcoarray=lib, the token
and the offset belonging to nonallocatable coarrays dummy arguments
are passed as hidden argument along the character length hidden
arguments. The token is an opaque pointer identifying the coarray
and the offset is a passed-by-value integer of kind C_PTRDIFF_T,
denoting the byte offset between the base address of the coarray and
the passed scalar or first element of the passed array.
The arguments are passed in the following order
CHARACTER and no C binding is used
CHARACTER or a nonallocatable coarray dummy
argument, followed by the hidden arguments of the next dummy argument
of such a type
Next: Intrinsic Procedures, Previous: Mixed-Language Programming, Up: Introduction [Contents][Index]
Next: Function ABI Documentation, Up: Coarray Programming [Contents][Index]
Next: caf_register_t, Up: Type and enum ABI Documentation [Contents][Index]
caf_token_tTypedef of type void * on the compiler side. Can be any data
type on the library side.
Next: caf_deregister_t, Previous: caf_token_t, Up: Type and enum ABI Documentation [Contents][Index]
caf_register_tIndicates which kind of coarray variable should be registered.
typedef enum caf_register_t {
CAF_REGTYPE_COARRAY_STATIC,
CAF_REGTYPE_COARRAY_ALLOC,
CAF_REGTYPE_LOCK_STATIC,
CAF_REGTYPE_LOCK_ALLOC,
CAF_REGTYPE_CRITICAL,
CAF_REGTYPE_EVENT_STATIC,
CAF_REGTYPE_EVENT_ALLOC,
CAF_REGTYPE_COARRAY_ALLOC_REGISTER_ONLY,
CAF_REGTYPE_COARRAY_ALLOC_ALLOCATE_ONLY
}
caf_register_t;
The values CAF_REGTYPE_COARRAY_ALLOC_REGISTER_ONLY and
CAF_REGTYPE_COARRAY_ALLOC_ALLOCATE_ONLY are for allocatable components
in derived type coarrays only. The first one sets up the token without
allocating memory for allocatable component. The latter one only allocates the
memory for an allocatable component in a derived type coarray. The token
needs to be setup previously by the REGISTER_ONLY. This allows to have
allocatable components un-allocated on some images. The status whether an
allocatable component is allocated on a remote image can be queried by
_caf_is_present which used internally by the ALLOCATED
intrinsic.
Next: caf_reference_t, Previous: caf_register_t, Up: Type and enum ABI Documentation [Contents][Index]
caf_deregister_ttypedef enum caf_deregister_t {
CAF_DEREGTYPE_COARRAY_DEREGISTER,
CAF_DEREGTYPE_COARRAY_DEALLOCATE_ONLY
}
caf_deregister_t;
Allows to specifiy the type of deregistration of a coarray object. The
CAF_DEREGTYPE_COARRAY_DEALLOCATE_ONLY flag is only allowed for
allocatable components in derived type coarrays.
Next: caf_team_t, Previous: caf_deregister_t, Up: Type and enum ABI Documentation [Contents][Index]
caf_reference_tThe structure used for implementing arbitrary reference chains.
A CAF_REFERENCE_T allows to specify a component reference or any kind
of array reference of any rank supported by gfortran. For array references all
kinds as known by the compiler/Fortran standard are supported indicated by
a MODE.
typedef enum caf_ref_type_t {
/* Reference a component of a derived type, either regular one or an
allocatable or pointer type. For regular ones idx in caf_reference_t is
set to -1. */
CAF_REF_COMPONENT,
/* Reference an allocatable array. */
CAF_REF_ARRAY,
/* Reference a non-allocatable/non-pointer array. I.e., the coarray object
has no array descriptor associated and the addressing is done
completely using the ref. */
CAF_REF_STATIC_ARRAY
} caf_ref_type_t;
typedef enum caf_array_ref_t {
/* No array ref. This terminates the array ref. */
CAF_ARR_REF_NONE = 0,
/* Reference array elements given by a vector. Only for this mode
caf_reference_t.u.a.dim[i].v is valid. */
CAF_ARR_REF_VECTOR,
/* A full array ref (:). */
CAF_ARR_REF_FULL,
/* Reference a range on elements given by start, end and stride. */
CAF_ARR_REF_RANGE,
/* Only a single item is referenced given in the start member. */
CAF_ARR_REF_SINGLE,
/* An array ref of the kind (i:), where i is an arbitrary valid index in the
array. The index i is given in the start member. */
CAF_ARR_REF_OPEN_END,
/* An array ref of the kind (:i), where the lower bound of the array ref
is given by the remote side. The index i is given in the end member. */
CAF_ARR_REF_OPEN_START
} caf_array_ref_t;
/* References to remote components of a derived type. */
typedef struct caf_reference_t {
/* A pointer to the next ref or NULL. */
struct caf_reference_t *next;
/* The type of the reference. */
/* caf_ref_type_t, replaced by int to allow specification in fortran FE. */
int type;
/* The size of an item referenced in bytes. I.e. in an array ref this is
the factor to advance the array pointer with to get to the next item.
For component refs this gives just the size of the element referenced. */
size_t item_size;
union {
struct {
/* The offset (in bytes) of the component in the derived type.
Unused for allocatable or pointer components. */
ptrdiff_t offset;
/* The offset (in bytes) to the caf_token associated with this
component. NULL, when not allocatable/pointer ref. */
ptrdiff_t caf_token_offset;
} c;
struct {
/* The mode of the array ref. See CAF_ARR_REF_*. */
/* caf_array_ref_t, replaced by unsigend char to allow specification in
fortran FE. */
unsigned char mode[GFC_MAX_DIMENSIONS];
/* The type of a static array. Unset for array's with descriptors. */
int static_array_type;
/* Subscript refs (s) or vector refs (v). */
union {
struct {
/* The start and end boundary of the ref and the stride. */
index_type start, end, stride;
} s;
struct {
/* nvec entries of kind giving the elements to reference. */
void *vector;
/* The number of entries in vector. */
size_t nvec;
/* The integer kind used for the elements in vector. */
int kind;
} v;
} dim[GFC_MAX_DIMENSIONS];
} a;
} u;
} caf_reference_t;
The references make up a single linked list of reference operations. The
NEXT member links to the next reference or NULL to indicate the end of
the chain. Component and array refs can be arbitrarily mixed as long as they
comply to the Fortran standard.
NOTES
The member STATIC_ARRAY_TYPE is used only when the TYPE is
CAF_REF_STATIC_ARRAY. The member gives the type of the data referenced.
Because no array descriptor is available for a descriptor-less array and
type conversion still needs to take place the type is transported here.
At the moment CAF_ARR_REF_VECTOR is not implemented in the front end for
descriptor-less arrays. The library caf_single has untested support for it.
Previous: caf_reference_t, Up: Type and enum ABI Documentation [Contents][Index]
caf_team_tOpaque pointer to represent a team-handle. This type is a stand-in for the future implementation of teams. It is about to change without further notice.
Previous: Type and enum ABI Documentation, Up: Coarray Programming [Contents][Index]
_gfortran_caf_init — Initialiation function_gfortran_caf_finish — Finalization function_gfortran_caf_this_image — Querying the image number_gfortran_caf_num_images — Querying the maximal number of images_gfortran_caf_image_status — Query the status of an image_gfortran_caf_failed_images — Get an array of the indexes of the failed images_gfortran_caf_stopped_images — Get an array of the indexes of the stopped images_gfortran_caf_register — Registering coarrays_gfortran_caf_deregister — Deregistering coarrays_gfortran_caf_is_present — Query whether an allocatable or pointer component in a derived type coarray is allocated_gfortran_caf_send — Sending data from a local image to a remote image_gfortran_caf_get — Getting data from a remote image_gfortran_caf_sendget — Sending data between remote images_gfortran_caf_send_by_ref — Sending data from a local image to a remote image with enhanced referencing options_gfortran_caf_get_by_ref — Getting data from a remote image using enhanced references_gfortran_caf_sendget_by_ref — Sending data between remote images using enhanced references on both sides_gfortran_caf_lock — Locking a lock variable_gfortran_caf_lock — Unlocking a lock variable_gfortran_caf_event_post — Post an event_gfortran_caf_event_wait — Wait that an event occurred_gfortran_caf_event_query — Query event count_gfortran_caf_sync_all — All-image barrier_gfortran_caf_sync_images — Barrier for selected images_gfortran_caf_sync_memory — Wait for completion of segment-memory operations_gfortran_caf_error_stop — Error termination with exit code_gfortran_caf_error_stop_str — Error termination with string_gfortran_caf_fail_image — Mark the image failed and end its execution_gfortran_caf_atomic_define — Atomic variable assignment_gfortran_caf_atomic_ref — Atomic variable reference_gfortran_caf_atomic_cas — Atomic compare and swap_gfortran_caf_atomic_op — Atomic operation_gfortran_caf_co_broadcast — Sending data to all images_gfortran_caf_co_max — Collective maximum reduction_gfortran_caf_co_min — Collective minimum reduction_gfortran_caf_co_sum — Collective summing reduction_gfortran_caf_co_reduce — Generic collective reduction
Next: _gfortran_caf_finish — Finalization function, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_init — Initialiation functionThis function is called at startup of the program before the Fortran main
program, if the latter has been compiled with -fcoarray=lib.
It takes as arguments the command-line arguments of the program. It is
permitted to pass two NULL pointers as argument; if non-NULL,
the library is permitted to modify the arguments.
void _gfortran_caf_init (int *argc, char ***argv)
| argc | intent(inout) An integer pointer with the number of
arguments passed to the program or NULL. |
| argv | intent(inout) A pointer to an array of strings with the
command-line arguments or NULL. |
The function is modelled after the initialization function of the Message Passing Interface (MPI) specification. Due to the way coarray registration works, it might not be the first call to the library. If the main program is not written in Fortran and only a library uses coarrays, it can happen that this function is never called. Therefore, it is recommended that the library does not rely on the passed arguments and whether the call has been done.
Next: _gfortran_caf_this_image — Querying the image number, Previous: _gfortran_caf_init — Initialiation function, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_finish — Finalization functionThis function is called at the end of the Fortran main program, if it has been compiled with the -fcoarray=lib option.
void _gfortran_caf_finish (void)
For non-Fortran programs, it is recommended to call the function at the end of the main program. To ensure that the shutdown is also performed for programs where this function is not explicitly invoked, for instance non-Fortran programs or calls to the system’s exit() function, the library can use a destructor function. Note that programs can also be terminated using the STOP and ERROR STOP statements; those use different library calls.
Next: _gfortran_caf_num_images — Querying the maximal number of images, Previous: _gfortran_caf_finish — Finalization function, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_this_image — Querying the image numberThis function returns the current image number, which is a positive number.
int _gfortran_caf_this_image (int distance)
| distance | As specified for the this_image intrinsic
in TS18508. Shall be a non-negative number. |
If the Fortran intrinsic this_image is invoked without an argument, which
is the only permitted form in Fortran 2008, GCC passes 0 as
first argument.
Next: _gfortran_caf_image_status — Query the status of an image, Previous: _gfortran_caf_this_image — Querying the image number, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_num_images — Querying the maximal number of imagesThis function returns the number of images in the current team, if distance is 0 or the number of images in the parent team at the specified distance. If failed is -1, the function returns the number of all images at the specified distance; if it is 0, the function returns the number of nonfailed images, and if it is 1, it returns the number of failed images.
int _gfortran_caf_num_images(int distance, int failed)
| distance | the distance from this image to the ancestor. Shall be positive. |
| failed | shall be -1, 0, or 1 |
This function follows TS18508. If the num_image intrinsic has no arguments,
then the compiler passes distance=0 and failed=-1 to the function.
Next: _gfortran_caf_failed_images — Get an array of the indexes of the failed images, Previous: _gfortran_caf_num_images — Querying the maximal number of images, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_image_status — Query the status of an imageGet the status of the image given by the id image of the team given by
team. Valid results are zero, for image is ok, STAT_STOPPED_IMAGE
from the ISO_FORTRAN_ENV module to indicate that the image has been stopped and
STAT_FAILED_IMAGE also from ISO_FORTRAN_ENV to indicate that the image
has executed a FAIL IMAGE statement.
int _gfortran_caf_image_status (int image, caf_team_t * team)
| image | the positive scalar id of the image in the current TEAM. |
| team | optional; team on the which the inquiry is to be performed. |
This function follows TS18508. Because team-functionality is not yet implemented a null-pointer is passed for the team argument at the moment.
Next: _gfortran_caf_stopped_images — Get an array of the indexes of the stopped images, Previous: _gfortran_caf_image_status — Query the status of an image, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_failed_images — Get an array of the indexes of the failed imagesGet an array of image indexes in the current team that have failed. The array is sorted ascendingly. When team is not provided the current team is to be used. When kind is provided then the resulting array is of that integer kind else it is of default integer kind. The returns an unallocated size zero array when no images have failed.
int _gfortran_caf_failed_images (caf_team_t * team, int * kind)
| team | optional; team on the which the inquiry is to be performed. |
| image | optional; the kind of the resulting integer array. |
This function follows TS18508. Because team-functionality is not yet implemented a null-pointer is passed for the team argument at the moment.
Next: _gfortran_caf_register — Registering coarrays, Previous: _gfortran_caf_failed_images — Get an array of the indexes of the failed images, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_stopped_images — Get an array of the indexes of the stopped imagesGet an array of image indexes in the current team that have stopped. The array is sorted ascendingly. When team is not provided the current team is to be used. When kind is provided then the resulting array is of that integer kind else it is of default integer kind. The returns an unallocated size zero array when no images have failed.
int _gfortran_caf_stopped_images (caf_team_t * team, int * kind)
| team | optional; team on the which the inquiry is to be performed. |
| image | optional; the kind of the resulting integer array. |
This function follows TS18508. Because team-functionality is not yet implemented a null-pointer is passed for the team argument at the moment.
Next: _gfortran_caf_deregister — Deregistering coarrays, Previous: _gfortran_caf_stopped_images — Get an array of the indexes of the stopped images, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_register — Registering coarraysRegisters memory for a coarray and creates a token to identify the coarray. The
routine is called for both coarrays with SAVE attribute and using an
explicit ALLOCATE statement. If an error occurs and STAT is a
NULL pointer, the function shall abort with printing an error message
and starting the error termination. If no error occurs and STAT is
present, it shall be set to zero. Otherwise, it shall be set to a positive
value and, if not-NULL, ERRMSG shall be set to a string describing
the failure. The routine shall register the memory provided in the
DATA-component of the array descriptor DESC, when that component
is non-NULL, else it shall allocate sufficient memory and provide a
pointer to it in the DATA-component of DESC. The array descriptor
has rank zero, when a scalar object is to be registered and the array
descriptor may be invalid after the call to _gfortran_caf_register.
When an array is to be allocated the descriptor persists.
For CAF_REGTYPE_COARRAY_STATIC and CAF_REGTYPE_COARRAY_ALLOC,
the passed size is the byte size requested. For CAF_REGTYPE_LOCK_STATIC,
CAF_REGTYPE_LOCK_ALLOC and CAF_REGTYPE_CRITICAL it is the array
size or one for a scalar.
When CAF_REGTYPE_COARRAY_ALLOC_REGISTER_ONLY is used, then only a token
for an allocatable or pointer component is created. The SIZE parameter
is not used then. On the contrary when
CAF_REGTYPE_COARRAY_ALLOC_ALLOCATE_ONLY is specified, then the
token needs to be registered by a previous call with regtype
CAF_REGTYPE_COARRAY_ALLOC_REGISTER_ONLY and either the memory specified
in the DESC’s data-ptr is registered or allocate when the data-ptr is
NULL.
void caf_register (size_t size, caf_register_t type, caf_token_t *token,
gfc_descriptor_t *desc, int *stat, char *errmsg, size_t errmsg_len)
| size | For normal coarrays, the byte size of the coarray to be allocated; for lock types and event types, the number of elements. |
| type | one of the caf_register_t types. |
| token | intent(out) An opaque pointer identifying the coarray. |
| desc | intent(inout) The (pseudo) array descriptor. |
| stat | intent(out) For allocatable coarrays, stores the STAT=;
may be NULL |
| errmsg | intent(out) When an error occurs, this will be set to
an error message; may be NULL |
| errmsg_len | the buffer size of errmsg. |
Nonallocatable coarrays have to be registered prior use from remote images. In order to guarantee this, they have to be registered before the main program. This can be achieved by creating constructor functions. That is what GCC does such that also for nonallocatable coarrays the memory is allocated and no static memory is used. The token permits to identify the coarray; to the processor, the token is a nonaliasing pointer. The library can, for instance, store the base address of the coarray in the token, some handle or a more complicated struct. The library may also store the array descriptor DESC when its rank is non-zero.
For lock types, the value shall only be used for checking the allocation
status. Note that for critical blocks, the locking is only required on one
image; in the locking statement, the processor shall always pass an
image index of one for critical-block lock variables
(CAF_REGTYPE_CRITICAL). For lock types and critical-block variables,
the initial value shall be unlocked (or, respectively, not in critical
section) such as the value false; for event types, the initial state should
be no event, e.g. zero.
Next: _gfortran_caf_is_present — Query whether an allocatable or pointer component in a derived type coarray is allocated, Previous: _gfortran_caf_register — Registering coarrays, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_deregister — Deregistering coarraysCalled to free or deregister the memory of a coarray; the processor calls this
function for automatic and explicit deallocation. In case of an error, this
function shall fail with an error message, unless the STAT variable is
not null. The library is only expected to free memory it allocated itself
during a call to _gfortran_caf_register.
void caf_deregister (caf_token_t *token, caf_deregister_t type,
int *stat, char *errmsg, size_t errmsg_len)
| token | the token to free. |
| type | the type of action to take for the coarray. A
CAF_DEREGTYPE_COARRAY_DEALLOCATE_ONLY is allowed only for allocatable or
pointer components of derived type coarrays. The action only deallocates the
local memory without deleting the token. |
| stat | intent(out) Stores the STAT=; may be NULL |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL |
| errmsg_len | the buffer size of errmsg. |
For nonalloatable coarrays this function is never called. If a cleanup is required, it has to be handled via the finish, stop and error stop functions, and via destructors.
Next: _gfortran_caf_send — Sending data from a local image to a remote image, Previous: _gfortran_caf_deregister — Deregistering coarrays, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_is_present — Query whether an allocatable or pointer component in a derived type coarray is allocatedUsed to query the coarray library whether an allocatable component in a derived type coarray is allocated on a remote image.
void _gfortran_caf_is_present (caf_token_t token, int image_index,
gfc_reference_t *ref)
| token | An opaque pointer identifying the coarray. |
| image_index | The ID of the remote image; must be a positive number. |
| ref | A chain of references to address the allocatable or pointer component in the derived type coarray. The object reference needs to be a scalar or a full array reference, respectively. |
Next: _gfortran_caf_get — Getting data from a remote image, Previous: _gfortran_caf_is_present — Query whether an allocatable or pointer component in a derived type coarray is allocated, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_send — Sending data from a local image to a remote imageCalled to send a scalar, an array section or a whole array from a local to a remote image identified by the image_index.
void _gfortran_caf_send (caf_token_t token, size_t offset,
int image_index, gfc_descriptor_t *dest, caf_vector_t *dst_vector,
gfc_descriptor_t *src, int dst_kind, int src_kind, bool may_require_tmp,
int *stat)
| token | intent(in) An opaque pointer identifying the coarray. |
| offset | intent(in) By which amount of bytes the actual data is shifted compared to the base address of the coarray. |
| image_index | intent(in) The ID of the remote image; must be a positive number. |
| dest | intent(in) Array descriptor for the remote image for the
bounds and the size. The base_addr shall not be accessed. |
| dst_vector | intent(in) If not NULL, it contains the vector subscript of the destination array; the values are relative to the dimension triplet of the dest argument. |
| src | intent(in) Array descriptor of the local array to be transferred to the remote image |
| dst_kind | intent(in) Kind of the destination argument |
| src_kind | intent(in) Kind of the source argument |
| may_require_tmp | intent(in) The variable is false when
it is known at compile time that the dest and src either cannot
overlap or overlap (fully or partially) such that walking src and
dest in element wise element order (honoring the stride value) will not
lead to wrong results. Otherwise, the value is true. |
| stat | intent(out) when non-NULL give the result of the operation, i.e., zero on success and non-zero on error. When NULL and an error occurs, then an error message is printed and the program is terminated. |
It is permitted to have image_index equal the current image; the memory
of the send-to and the send-from might (partially) overlap in that case. The
implementation has to take care that it handles this case, e.g. using
memmove which handles (partially) overlapping memory. If
may_require_tmp is true, the library might additionally create a
temporary variable, unless additional checks show that this is not required
(e.g. because walking backward is possible or because both arrays are
contiguous and memmove takes care of overlap issues).
Note that the assignment of a scalar to an array is permitted. In addition, the library has to handle numeric-type conversion and for strings, padding and different character kinds.
Next: _gfortran_caf_sendget — Sending data between remote images, Previous: _gfortran_caf_send — Sending data from a local image to a remote image, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_get — Getting data from a remote imageCalled to get an array section or a whole array from a remote, image identified by the image_index.
void _gfortran_caf_get (caf_token_t token, size_t offset,
int image_index, gfc_descriptor_t *src, caf_vector_t *src_vector,
gfc_descriptor_t *dest, int src_kind, int dst_kind, bool may_require_tmp,
int *stat)
| token | intent(in) An opaque pointer identifying the coarray. |
| offset | intent(in) By which amount of bytes the actual data is shifted compared to the base address of the coarray. |
| image_index | intent(in) The ID of the remote image; must be a positive number. |
| dest | intent(out) Array descriptor of the local array to store the data retrieved from the remote image |
| src | intent(in) Array descriptor for the remote image for the
bounds and the size. The base_addr shall not be accessed. |
| src_vector | intent(in) If not NULL, it contains the vector subscript of the source array; the values are relative to the dimension triplet of the src argument. |
| dst_kind | intent(in) Kind of the destination argument |
| src_kind | intent(in) Kind of the source argument |
| may_require_tmp | intent(in) The variable is false when
it is known at compile time that the dest and src either cannot
overlap or overlap (fully or partially) such that walking src and
dest in element wise element order (honoring the stride value) will not
lead to wrong results. Otherwise, the value is true. |
| stat | intent(out) When non-NULL give the result of the operation, i.e., zero on success and non-zero on error. When NULL and an error occurs, then an error message is printed and the program is terminated. |
It is permitted to have image_index equal the current image; the memory of
the send-to and the send-from might (partially) overlap in that case. The
implementation has to take care that it handles this case, e.g. using
memmove which handles (partially) overlapping memory. If
may_require_tmp is true, the library might additionally create a
temporary variable, unless additional checks show that this is not required
(e.g. because walking backward is possible or because both arrays are
contiguous and memmove takes care of overlap issues).
Note that the library has to handle numeric-type conversion and for strings, padding and different character kinds.
Next: _gfortran_caf_send_by_ref — Sending data from a local image to a remote image with enhanced referencing options, Previous: _gfortran_caf_get — Getting data from a remote image, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_sendget — Sending data between remote imagesCalled to send a scalar, an array section or a whole array from a remote image identified by the src_image_index to a remote image identified by the dst_image_index.
void _gfortran_caf_sendget (caf_token_t dst_token, size_t dst_offset,
int dst_image_index, gfc_descriptor_t *dest, caf_vector_t *dst_vector,
caf_token_t src_token, size_t src_offset, int src_image_index,
gfc_descriptor_t *src, caf_vector_t *src_vector, int dst_kind, int src_kind,
bool may_require_tmp, int *stat)
| dst_token | intent(in) An opaque pointer identifying the destination coarray. |
| dst_offset | intent(in) By which amount of bytes the actual data is shifted compared to the base address of the destination coarray. |
| dst_image_index | intent(in) The ID of the destination remote image; must be a positive number. |
| dest | intent(in) Array descriptor for the destination
remote image for the bounds and the size. The base_addr shall not be
accessed. |
| dst_vector | intent(int) If not NULL, it contains the vector subscript of the destination array; the values are relative to the dimension triplet of the dest argument. |
| src_token | intent(in) An opaque pointer identifying the source coarray. |
| src_offset | intent(in) By which amount of bytes the actual data is shifted compared to the base address of the source coarray. |
| src_image_index | intent(in) The ID of the source remote image; must be a positive number. |
| src | intent(in) Array descriptor of the local array to be transferred to the remote image. |
| src_vector | intent(in) Array descriptor of the local array to be transferred to the remote image |
| dst_kind | intent(in) Kind of the destination argument |
| src_kind | intent(in) Kind of the source argument |
| may_require_tmp | intent(in) The variable is false when
it is known at compile time that the dest and src either cannot
overlap or overlap (fully or partially) such that walking src and
dest in element wise element order (honoring the stride value) will not
lead to wrong results. Otherwise, the value is true. |
| stat | intent(out) when non-NULL give the result of the operation, i.e., zero on success and non-zero on error. When NULL and an error occurs, then an error message is printed and the program is terminated. |
It is permitted to have the same image index for both src_image_index and
dst_image_index; the memory of the send-to and the send-from might
(partially) overlap in that case. The implementation has to take care that it
handles this case, e.g. using memmove which handles (partially)
overlapping memory. If may_require_tmp is true, the library
might additionally create a temporary variable, unless additional checks show
that this is not required (e.g. because walking backward is possible or because
both arrays are contiguous and memmove takes care of overlap issues).
Note that the assignment of a scalar to an array is permitted. In addition, the library has to handle numeric-type conversion and for strings, padding and different character kinds.
Next: _gfortran_caf_get_by_ref — Getting data from a remote image using enhanced references, Previous: _gfortran_caf_sendget — Sending data between remote images, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_send_by_ref — Sending data from a local image to a remote image with enhanced referencing optionsCalled to send a scalar, an array section or a whole array from a local to a remote image identified by the image_index.
void _gfortran_caf_send_by_ref (caf_token_t token, int image_index,
gfc_descriptor_t *src, caf_reference_t *refs, int dst_kind, int src_kind,
bool may_require_tmp, bool dst_reallocatable, int *stat, int dst_type)
| token | intent(in) An opaque pointer identifying the coarray. |
| image_index | intent(in) The ID of the remote image; must be a positive number. |
| src | intent(in) Array descriptor of the local array to be transferred to the remote image |
| refs | intent(in) The references on the remote array to store the data given by src. Guaranteed to have at least one entry. |
| dst_kind | intent(in) Kind of the destination argument |
| src_kind | intent(in) Kind of the source argument |
| may_require_tmp | intent(in) The variable is false when
it is known at compile time that the dest and src either cannot
overlap or overlap (fully or partially) such that walking src and
dest in element wise element order (honoring the stride value) will not
lead to wrong results. Otherwise, the value is true. |
| dst_reallocatable | intent(in) Set when the destination is of allocatable or pointer type and the refs will allow reallocation, i.e., the ref is a full array or component ref. |
| stat | intent(out) When non-NULL give the result of the
operation, i.e., zero on success and non-zero on error. When NULL and
an error occurs, then an error message is printed and the program is terminated. |
| dst_type | intent(in) Give the type of the destination. When the destination is not an array, than the precise type, e.g. of a component in a derived type, is not known, but provided here. |
It is permitted to have image_index equal the current image; the memory of
the send-to and the send-from might (partially) overlap in that case. The
implementation has to take care that it handles this case, e.g. using
memmove which handles (partially) overlapping memory. If
may_require_tmp is true, the library might additionally create a
temporary variable, unless additional checks show that this is not required
(e.g. because walking backward is possible or because both arrays are
contiguous and memmove takes care of overlap issues).
Note that the assignment of a scalar to an array is permitted. In addition, the library has to handle numeric-type conversion and for strings, padding and different character kinds.
Because of the more complicated references possible some operations may be unsupported by certain libraries. The library is expected to issue a precise error message why the operation is not permitted.
Next: _gfortran_caf_sendget_by_ref — Sending data between remote images using enhanced references on both sides, Previous: _gfortran_caf_send_by_ref — Sending data from a local image to a remote image with enhanced referencing options, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_get_by_ref — Getting data from a remote image using enhanced referencesCalled to get a scalar, an array section or a whole array from a remote image identified by the image_index.
void _gfortran_caf_get_by_ref (caf_token_t token, int image_index,
caf_reference_t *refs, gfc_descriptor_t *dst, int dst_kind, int src_kind,
bool may_require_tmp, bool dst_reallocatable, int *stat, int src_type)
| token | intent(in) An opaque pointer identifying the coarray. |
| image_index | intent(in) The ID of the remote image; must be a positive number. |
| refs | intent(in) The references to apply to the remote structure to get the data. |
| dst | intent(in) Array descriptor of the local array to store the data transferred from the remote image. May be reallocated where needed and when DST_REALLOCATABLE allows it. |
| dst_kind | intent(in) Kind of the destination argument |
| src_kind | intent(in) Kind of the source argument |
| may_require_tmp | intent(in) The variable is false when
it is known at compile time that the dest and src either cannot
overlap or overlap (fully or partially) such that walking src and
dest in element wise element order (honoring the stride value) will not
lead to wrong results. Otherwise, the value is true. |
| dst_reallocatable | intent(in) Set when DST is of allocatable or pointer type and its refs allow reallocation, i.e., the full array or a component is referenced. |
| stat | intent(out) When non-NULL give the result of the
operation, i.e., zero on success and non-zero on error. When NULL and an
error occurs, then an error message is printed and the program is terminated. |
| src_type | intent(in) Give the type of the source. When the source is not an array, than the precise type, e.g. of a component in a derived type, is not known, but provided here. |
It is permitted to have image_index equal the current image; the memory
of the send-to and the send-from might (partially) overlap in that case. The
implementation has to take care that it handles this case, e.g. using
memmove which handles (partially) overlapping memory. If
may_require_tmp is true, the library might additionally create a
temporary variable, unless additional checks show that this is not required
(e.g. because walking backward is possible or because both arrays are
contiguous and memmove takes care of overlap issues).
Note that the library has to handle numeric-type conversion and for strings, padding and different character kinds.
Because of the more complicated references possible some operations may be unsupported by certain libraries. The library is expected to issue a precise error message why the operation is not permitted.
Next: _gfortran_caf_lock — Locking a lock variable, Previous: _gfortran_caf_get_by_ref — Getting data from a remote image using enhanced references, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_sendget_by_ref — Sending data between remote images using enhanced references on both sidesCalled to send a scalar, an array section or a whole array from a remote image identified by the src_image_index to a remote image identified by the dst_image_index.
void _gfortran_caf_sendget_by_ref (caf_token_t dst_token,
int dst_image_index, caf_reference_t *dst_refs,
caf_token_t src_token, int src_image_index, caf_reference_t *src_refs,
int dst_kind, int src_kind, bool may_require_tmp, int *dst_stat,
int *src_stat, int dst_type, int src_type)
| dst_token | intent(in) An opaque pointer identifying the destination coarray. |
| dst_image_index | intent(in) The ID of the destination remote image; must be a positive number. |
| dst_refs | intent(in) The references on the remote array to store the data given by the source. Guaranteed to have at least one entry. |
| src_token | intent(in) An opaque pointer identifying the source coarray. |
| src_image_index | intent(in) The ID of the source remote image; must be a positive number. |
| src_refs | intent(in) The references to apply to the remote structure to get the data. |
| dst_kind | intent(in) Kind of the destination argument |
| src_kind | intent(in) Kind of the source argument |
| may_require_tmp | intent(in) The variable is false when
it is known at compile time that the dest and src either cannot
overlap or overlap (fully or partially) such that walking src and
dest in element wise element order (honoring the stride value) will not
lead to wrong results. Otherwise, the value is true. |
| dst_stat | intent(out) when non-NULL give the result of
the send-operation, i.e., zero on success and non-zero on error. When
NULL and an error occurs, then an error message is printed and the
program is terminated. |
| src_stat | intent(out) When non-NULL give the result of
the get-operation, i.e., zero on success and non-zero on error. When
NULL and an error occurs, then an error message is printed and the
program is terminated. |
| dst_type | intent(in) Give the type of the destination. When the destination is not an array, than the precise type, e.g. of a component in a derived type, is not known, but provided here. |
| src_type | intent(in) Give the type of the source. When the source is not an array, than the precise type, e.g. of a component in a derived type, is not known, but provided here. |
It is permitted to have the same image index for both src_image_index and
dst_image_index; the memory of the send-to and the send-from might
(partially) overlap in that case. The implementation has to take care that it
handles this case, e.g. using memmove which handles (partially)
overlapping memory. If may_require_tmp is true, the library
might additionally create a temporary variable, unless additional checks show
that this is not required (e.g. because walking backward is possible or because
both arrays are contiguous and memmove takes care of overlap issues).
Note that the assignment of a scalar to an array is permitted. In addition, the library has to handle numeric-type conversion and for strings, padding and different character kinds.
Because of the more complicated references possible some operations may be unsupported by certain libraries. The library is expected to issue a precise error message why the operation is not permitted.
Next: _gfortran_caf_lock — Unlocking a lock variable, Previous: _gfortran_caf_sendget_by_ref — Sending data between remote images using enhanced references on both sides, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_lock — Locking a lock variableAcquire a lock on the given image on a scalar locking variable or for the
given array element for an array-valued variable. If the acquired_lock
is NULL, the function returns after having obtained the lock. If it is
non-NULL, then acquired_lock is assigned the value true (one) when
the lock could be obtained and false (zero) otherwise. Locking a lock variable
which has already been locked by the same image is an error.
void _gfortran_caf_lock (caf_token_t token, size_t index, int image_index,
int *acquired_lock, int *stat, char *errmsg, size_t errmsg_len)
| token | intent(in) An opaque pointer identifying the coarray. |
| index | intent(in) Array index; first array index is 0. For scalars, it is always 0. |
| image_index | intent(in) The ID of the remote image; must be a positive number. |
| acquired_lock | intent(out) If not NULL, it returns whether lock could be obtained. |
| stat | intent(out) Stores the STAT=; may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg |
This function is also called for critical blocks; for those, the array index is always zero and the image index is one. Libraries are permitted to use other images for critical-block locking variables.
Next: _gfortran_caf_event_post — Post an event, Previous: _gfortran_caf_lock — Locking a lock variable, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_lock — Unlocking a lock variableRelease a lock on the given image on a scalar locking variable or for the given array element for an array-valued variable. Unlocking a lock variable which is unlocked or has been locked by a different image is an error.
void _gfortran_caf_unlock (caf_token_t token, size_t index, int image_index,
int *stat, char *errmsg, size_t errmsg_len)
| token | intent(in) An opaque pointer identifying the coarray. |
| index | intent(in) Array index; first array index is 0. For scalars, it is always 0. |
| image_index | intent(in) The ID of the remote image; must be a positive number. |
| stat | intent(out) For allocatable coarrays, stores the STAT=; may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg |
This function is also called for critical block; for those, the array index is always zero and the image index is one. Libraries are permitted to use other images for critical-block locking variables.
Next: _gfortran_caf_event_wait — Wait that an event occurred, Previous: _gfortran_caf_lock — Unlocking a lock variable, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_event_post — Post an eventIncrement the event count of the specified event variable.
void _gfortran_caf_event_post (caf_token_t token, size_t index,
int image_index, int *stat, char *errmsg, size_t errmsg_len)
| token | intent(in) An opaque pointer identifying the coarray. |
| index | intent(in) Array index; first array index is 0. For scalars, it is always 0. |
| image_index | intent(in) The ID of the remote image; must be a positive number; zero indicates the current image, when accessed noncoindexed. |
| stat | intent(out) Stores the STAT=; may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg |
This acts like an atomic add of one to the remote image’s event variable.
The statement is an image-control statement but does not imply sync memory.
Still, all preceeding push communications of this image to the specified
remote image have to be completed before event_wait on the remote
image returns.
Next: _gfortran_caf_event_query — Query event count, Previous: _gfortran_caf_event_post — Post an event, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_event_wait — Wait that an event occurredWait until the event count has reached at least the specified until_count; if so, atomically decrement the event variable by this amount and return.
void _gfortran_caf_event_wait (caf_token_t token, size_t index,
int until_count, int *stat, char *errmsg, size_t errmsg_len)
| token | intent(in) An opaque pointer identifying the coarray. |
| index | intent(in) Array index; first array index is 0. For scalars, it is always 0. |
| until_count | intent(in) The number of events which have to be available before the function returns. |
| stat | intent(out) Stores the STAT=; may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg |
This function only operates on a local coarray. It acts like a loop checking atomically the value of the event variable, breaking if the value is greater or equal the requested number of counts. Before the function returns, the event variable has to be decremented by the requested until_count value. A possible implementation would be a busy loop for a certain number of spins (possibly depending on the number of threads relative to the number of available cores) followed by another waiting strategy such as a sleeping wait (possibly with an increasing number of sleep time) or, if possible, a futex wait.
The statement is an image-control statement but does not imply sync memory.
Still, all preceeding push communications of this image to the specified
remote image have to be completed before event_wait on the remote
image returns.
Next: _gfortran_caf_sync_all — All-image barrier, Previous: _gfortran_caf_event_wait — Wait that an event occurred, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_event_query — Query event countReturn the event count of the specified event variable.
void _gfortran_caf_event_query (caf_token_t token, size_t index,
int image_index, int *count, int *stat)
| token | intent(in) An opaque pointer identifying the coarray. |
| index | intent(in) Array index; first array index is 0. For scalars, it is always 0. |
| image_index | intent(in) The ID of the remote image; must be a positive number; zero indicates the current image when accessed noncoindexed. |
| count | intent(out) The number of events currently posted to the event variable. |
| stat | intent(out) Stores the STAT=; may be NULL. |
The typical use is to check the local event variable to only call
event_wait when the data is available. However, a coindexed variable
is permitted; there is no ordering or synchronization implied. It acts like
an atomic fetch of the value of the event variable.
Next: _gfortran_caf_sync_images — Barrier for selected images, Previous: _gfortran_caf_event_query — Query event count, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_sync_all — All-image barrierSynchronization of all images in the current team; the program only continues on a given image after this function has been called on all images of the current team. Additionally, it ensures that all pending data transfers of previous segment have completed.
void _gfortran_caf_sync_all (int *stat, char *errmsg, size_t errmsg_len)
| stat | intent(out) Stores the status STAT= and may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg |
Next: _gfortran_caf_sync_memory — Wait for completion of segment-memory operations, Previous: _gfortran_caf_sync_all — All-image barrier, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_sync_images — Barrier for selected imagesSynchronization between the specified images; the program only continues on a
given image after this function has been called on all images specified for
that image. Note that one image can wait for all other images in the current
team (e.g. via sync images(*)) while those only wait for that specific
image. Additionally, sync images ensures that all pending data
transfers of previous segments have completed.
void _gfortran_caf_sync_images (int count, int images[], int *stat,
char *errmsg, size_t errmsg_len)
| count | intent(in) The number of images which are provided in
the next argument. For a zero-sized array, the value is zero. For
sync images (*), the value is -1. |
| images | intent(in) An array with the images provided by the user. If count is zero, a NULL pointer is passed. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg |
Next: _gfortran_caf_error_stop — Error termination with exit code, Previous: _gfortran_caf_sync_images — Barrier for selected images, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_sync_memory — Wait for completion of segment-memory operationsActs as optimization barrier between different segments. It also ensures that all pending memory operations of this image have been completed.
void _gfortran_caf_sync_memory (int *stat, char *errmsg, size_t errmsg_len)
| stat | intent(out) Stores the status STAT= and may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg |
__asm__ __volatile__ ("":::"memory") to prevent code movements.
Next: _gfortran_caf_error_stop_str — Error termination with string, Previous: _gfortran_caf_sync_memory — Wait for completion of segment-memory operations, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_error_stop — Error termination with exit codeInvoked for an ERROR STOP statement which has an integer argument. The
function should terminate the program with the specified exit code.
void _gfortran_caf_error_stop (int error)
| error | intent(in) The exit status to be used. |
Next: _gfortran_caf_fail_image — Mark the image failed and end its execution, Previous: _gfortran_caf_error_stop — Error termination with exit code, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_error_stop_str — Error termination with stringInvoked for an ERROR STOP statement which has a string as argument. The
function should terminate the program with a nonzero-exit code.
void _gfortran_caf_error_stop (const char *string, size_t len)
| string | intent(in) the error message (not zero terminated) |
| len | intent(in) the length of the string |
Next: _gfortran_caf_atomic_define — Atomic variable assignment, Previous: _gfortran_caf_error_stop_str — Error termination with string, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_fail_image — Mark the image failed and end its executionInvoked for an FAIL IMAGE statement. The function should terminate the
current image.
void _gfortran_caf_fail_image ()
This function follows TS18508.
Next: _gfortran_caf_atomic_ref — Atomic variable reference, Previous: _gfortran_caf_fail_image — Mark the image failed and end its execution, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_atomic_define — Atomic variable assignmentAssign atomically a value to an integer or logical variable.
void _gfortran_caf_atomic_define (caf_token_t token, size_t offset,
int image_index, void *value, int *stat, int type, int kind)
| token | intent(in) An opaque pointer identifying the coarray. |
| offset | intent(in) By which amount of bytes the actual data is shifted compared to the base address of the coarray. |
| image_index | intent(in) The ID of the remote image; must be a positive number; zero indicates the current image when used noncoindexed. |
| value | intent(in) the value to be assigned, passed by reference |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| type | intent(in) The data type, i.e. BT_INTEGER (1) or
BT_LOGICAL (2). |
| kind | intent(in) The kind value (only 4; always int) |
Next: _gfortran_caf_atomic_cas — Atomic compare and swap, Previous: _gfortran_caf_atomic_define — Atomic variable assignment, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_atomic_ref — Atomic variable referenceReference atomically a value of a kind-4 integer or logical variable.
void _gfortran_caf_atomic_ref (caf_token_t token, size_t offset,
int image_index, void *value, int *stat, int type, int kind)
| token | intent(in) An opaque pointer identifying the coarray. |
| offset | intent(in) By which amount of bytes the actual data is shifted compared to the base address of the coarray. |
| image_index | intent(in) The ID of the remote image; must be a positive number; zero indicates the current image when used noncoindexed. |
| value | intent(out) The variable assigned the atomically referenced variable. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| type | the data type, i.e. BT_INTEGER (1) or
BT_LOGICAL (2). |
| kind | The kind value (only 4; always int) |
Next: _gfortran_caf_atomic_op — Atomic operation, Previous: _gfortran_caf_atomic_ref — Atomic variable reference, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_atomic_cas — Atomic compare and swapAtomic compare and swap of a kind-4 integer or logical variable. Assigns atomically the specified value to the atomic variable, if the latter has the value specified by the passed condition value.
void _gfortran_caf_atomic_cas (caf_token_t token, size_t offset,
int image_index, void *old, void *compare, void *new_val, int *stat,
int type, int kind)
| token | intent(in) An opaque pointer identifying the coarray. |
| offset | intent(in) By which amount of bytes the actual data is shifted compared to the base address of the coarray. |
| image_index | intent(in) The ID of the remote image; must be a positive number; zero indicates the current image when used noncoindexed. |
| old | intent(out) The value which the atomic variable had just before the cas operation. |
| compare | intent(in) The value used for comparision. |
| new_val | intent(in) The new value for the atomic variable,
assigned to the atomic variable, if compare equals the value of the
atomic variable. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| type | intent(in) the data type, i.e. BT_INTEGER (1) or
BT_LOGICAL (2). |
| kind | intent(in) The kind value (only 4; always int) |
Next: _gfortran_caf_co_broadcast — Sending data to all images, Previous: _gfortran_caf_atomic_cas — Atomic compare and swap, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_atomic_op — Atomic operationApply an operation atomically to an atomic integer or logical variable.
After the operation, old contains the value just before the operation,
which, respectively, adds (GFC_CAF_ATOMIC_ADD) atomically the value to
the atomic integer variable or does a bitwise AND, OR or exclusive OR
between the atomic variable and value; the result is then stored in the
atomic variable.
void _gfortran_caf_atomic_op (int op, caf_token_t token, size_t offset,
int image_index, void *value, void *old, int *stat, int type, int kind)
| op | intent(in) the operation to be performed; possible values
GFC_CAF_ATOMIC_ADD (1), GFC_CAF_ATOMIC_AND (2),
GFC_CAF_ATOMIC_OR (3), GFC_CAF_ATOMIC_XOR (4). |
| token | intent(in) An opaque pointer identifying the coarray. |
| offset | intent(in) By which amount of bytes the actual data is shifted compared to the base address of the coarray. |
| image_index | intent(in) The ID of the remote image; must be a positive number; zero indicates the current image when used noncoindexed. |
| old | intent(out) The value which the atomic variable had just before the atomic operation. |
| val | intent(in) The new value for the atomic variable,
assigned to the atomic variable, if compare equals the value of the
atomic variable. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| type | intent(in) the data type, i.e. BT_INTEGER (1) or
BT_LOGICAL (2) |
| kind | intent(in) the kind value (only 4; always int) |
Next: _gfortran_caf_co_max — Collective maximum reduction, Previous: _gfortran_caf_atomic_op — Atomic operation, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_co_broadcast — Sending data to all imagesDistribute a value from a given image to all other images in the team. Has to be called collectively.
void _gfortran_caf_co_broadcast (gfc_descriptor_t *a,
int source_image, int *stat, char *errmsg, size_t errmsg_len)
| a | intent(inout) An array descriptor with the data to be broadcasted (on source_image) or to be received (other images). |
| source_image | intent(in) The ID of the image from which the data should be broadcasted. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg. |
Next: _gfortran_caf_co_min — Collective minimum reduction, Previous: _gfortran_caf_co_broadcast — Sending data to all images, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_co_max — Collective maximum reductionCalculates for each array element of the variable a the maximum value for that element in the current team; if result_image has the value 0, the result shall be stored on all images, otherwise, only on the specified image. This function operates on numeric values and character strings.
void _gfortran_caf_co_max (gfc_descriptor_t *a, int result_image,
int *stat, char *errmsg, int a_len, size_t errmsg_len)
| a | intent(inout) An array descriptor for the data to be processed. On the destination image(s) the result overwrites the old content. |
| result_image | intent(in) The ID of the image to which the reduced value should be copied to; if zero, it has to be copied to all images. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| a_len | intent(in) the string length of argument a |
| errmsg_len | intent(in) the buffer size of errmsg |
If result_image is nonzero, the data in the array descriptor a on all images except of the specified one become undefined; hence, the library may make use of this.
Next: _gfortran_caf_co_sum — Collective summing reduction, Previous: _gfortran_caf_co_max — Collective maximum reduction, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_co_min — Collective minimum reductionCalculates for each array element of the variable a the minimum value for that element in the current team; if result_image has the value 0, the result shall be stored on all images, otherwise, only on the specified image. This function operates on numeric values and character strings.
void _gfortran_caf_co_min (gfc_descriptor_t *a, int result_image,
int *stat, char *errmsg, int a_len, size_t errmsg_len)
| a | intent(inout) An array descriptor for the data to be processed. On the destination image(s) the result overwrites the old content. |
| result_image | intent(in) The ID of the image to which the reduced value should be copied to; if zero, it has to be copied to all images. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| a_len | intent(in) the string length of argument a |
| errmsg_len | intent(in) the buffer size of errmsg |
If result_image is nonzero, the data in the array descriptor a on all images except of the specified one become undefined; hence, the library may make use of this.
Next: _gfortran_caf_co_reduce — Generic collective reduction, Previous: _gfortran_caf_co_min — Collective minimum reduction, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_co_sum — Collective summing reductionCalculates for each array element of the variable a the sum of all values for that element in the current team; if result_image has the value 0, the result shall be stored on all images, otherwise, only on the specified image. This function operates on numeric values only.
void _gfortran_caf_co_sum (gfc_descriptor_t *a, int result_image,
int *stat, char *errmsg, size_t errmsg_len)
| a | intent(inout) An array descriptor with the data to be processed. On the destination image(s) the result overwrites the old content. |
| result_image | intent(in) The ID of the image to which the reduced value should be copied to; if zero, it has to be copied to all images. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| errmsg_len | intent(in) the buffer size of errmsg |
If result_image is nonzero, the data in the array descriptor a on all images except of the specified one become undefined; hence, the library may make use of this.
Previous: _gfortran_caf_co_sum — Collective summing reduction, Up: Function ABI Documentation [Contents][Index]
_gfortran_caf_co_reduce — Generic collective reductionCalculates for each array element of the variable a the reduction value for that element in the current team; if result_image has the value 0, the result shall be stored on all images, otherwise, only on the specified image. The opr is a pure function doing a mathematically commutative and associative operation.
The opr_flags denote the following; the values are bitwise ored.
GFC_CAF_BYREF (1) if the result should be returned
by reference; GFC_CAF_HIDDENLEN (2) whether the result and argument
string lengths shall be specified as hidden arguments;
GFC_CAF_ARG_VALUE (4) whether the arguments shall be passed by value,
GFC_CAF_ARG_DESC (8) whether the arguments shall be passed by descriptor.
void _gfortran_caf_co_reduce (gfc_descriptor_t *a,
void * (*opr) (void *, void *), int opr_flags, int result_image,
int *stat, char *errmsg, int a_len, size_t errmsg_len)
| a | intent(inout) An array descriptor with the data to be processed. On the destination image(s) the result overwrites the old content. |
| opr | intent(in) Function pointer to the reduction function |
| opr_flags | intent(in) Flags regarding the reduction function |
| result_image | intent(in) The ID of the image to which the reduced value should be copied to; if zero, it has to be copied to all images. |
| stat | intent(out) Stores the status STAT= and may be NULL. |
| errmsg | intent(out) When an error occurs, this will be set to an error message; may be NULL. |
| a_len | intent(in) the string length of argument a |
| errmsg_len | intent(in) the buffer size of errmsg |
If result_image is nonzero, the data in the array descriptor a on all images except of the specified one become undefined; hence, the library may make use of this.
For character arguments, the result is passed as first argument, followed by the result string length, next come the two string arguments, followed by the two hidden string length arguments. With C binding, there are no hidden arguments and by-reference passing and either only a single character is passed or an array descriptor.
Next: Intrinsic Modules, Previous: Coarray Programming, Up: Introduction [Contents][Index]
ABORT — Abort the programABS — Absolute valueACCESS — Checks file access modesACHAR — Character in ASCII collating sequenceACOS — Arccosine functionACOSD — Arccosine function, degreesACOSH — Inverse hyperbolic cosine functionADJUSTL — Left adjust a stringADJUSTR — Right adjust a stringAIMAG — Imaginary part of complex numberAINT — Truncate to a whole numberALARM — Execute a routine after a given delayALL — All values in MASK along DIM are trueALLOCATED — Status of an allocatable entityAND — Bitwise logical ANDANINT — Nearest whole numberANY — Any value in MASK along DIM is trueASIN — Arcsine functionASIND — Arcsine function, degreesASINH — Inverse hyperbolic sine functionASSOCIATED — Status of a pointer or pointer/target pairATAN — Arctangent functionATAND — Arctangent function, degreesATAN2 — Arctangent functionATAN2D — Arctangent function, degreesATANH — Inverse hyperbolic tangent functionATOMIC_ADD — Atomic ADD operationATOMIC_AND — Atomic bitwise AND operationATOMIC_CAS — Atomic compare and swapATOMIC_DEFINE — Setting a variable atomicallyATOMIC_FETCH_ADD — Atomic ADD operation with prior fetchATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetchATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetchATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetchATOMIC_OR — Atomic bitwise OR operationATOMIC_REF — Obtaining the value of a variable atomicallyATOMIC_XOR — Atomic bitwise OR operationBACKTRACE — Show a backtraceBESSEL_J0 — Bessel function of the first kind of order 0BESSEL_J1 — Bessel function of the first kind of order 1BESSEL_JN — Bessel function of the first kindBESSEL_Y0 — Bessel function of the second kind of order 0BESSEL_Y1 — Bessel function of the second kind of order 1BESSEL_YN — Bessel function of the second kindBGE — Bitwise greater than or equal toBGT — Bitwise greater thanBIT_SIZE — Bit size inquiry functionBLE — Bitwise less than or equal toBLT — Bitwise less thanBTEST — Bit test functionC_ASSOCIATED — Status of a C pointerC_F_POINTER — Convert C into Fortran pointerC_F_PROCPOINTER — Convert C into Fortran procedure pointerC_FUNLOC — Obtain the C address of a procedureC_LOC — Obtain the C address of an objectC_SIZEOF — Size in bytes of an expressionCEILING — Integer ceiling functionCHAR — Character conversion functionCHDIR — Change working directoryCHMOD — Change access permissions of filesCMPLX — Complex conversion functionCO_BROADCAST — Copy a value to all images the current set of imagesCO_MAX — Maximal value on the current set of imagesCO_MIN — Minimal value on the current set of imagesCO_REDUCE — Reduction of values on the current set of imagesCO_SUM — Sum of values on the current set of imagesCOMMAND_ARGUMENT_COUNT — Get number of command line argumentsCOMPILER_OPTIONS — Options passed to the compilerCOMPILER_VERSION — Compiler version stringCOMPLEX — Complex conversion functionCONJG — Complex conjugate functionCOS — Cosine functionCOSD — Cosine function, degreesCOSH — Hyperbolic cosine functionCOTAN — Cotangent functionCOTAND — Cotangent function, degreesCOUNT — Count functionCPU_TIME — CPU elapsed time in secondsCSHIFT — Circular shift elements of an arrayCTIME — Convert a time into a stringDATE_AND_TIME — Date and time subroutineDBLE — Double conversion functionDCMPLX — Double complex conversion functionDIGITS — Significant binary digits functionDIM — Positive differenceDOT_PRODUCT — Dot product functionDPROD — Double product functionDREAL — Double real part functionDSHIFTL — Combined left shiftDSHIFTR — Combined right shiftDTIME — Execution time subroutine (or function)EOSHIFT — End-off shift elements of an arrayEPSILON — Epsilon functionERF — Error functionERFC — Error functionERFC_SCALED — Error functionETIME — Execution time subroutine (or function)EVENT_QUERY — Query whether a coarray event has occurredEXECUTE_COMMAND_LINE — Execute a shell commandEXIT — Exit the program with status.EXP — Exponential functionEXPONENT — Exponent functionEXTENDS_TYPE_OF — Query dynamic type for extensionFDATE — Get the current time as a stringFGET — Read a single character in stream mode from stdinFGETC — Read a single character in stream modeFINDLOC — Search an array for a valueFLOOR — Integer floor functionFLUSH — Flush I/O unit(s)FNUM — File number functionFPUT — Write a single character in stream mode to stdoutFPUTC — Write a single character in stream modeFRACTION — Fractional part of the model representationFREE — Frees memoryFSEEK — Low level file positioning subroutineFSTAT — Get file statusFTELL — Current stream positionGAMMA — Gamma functionGERROR — Get last system error messageGETARG — Get command line argumentsGET_COMMAND — Get the entire command lineGET_COMMAND_ARGUMENT — Get command line argumentsGETCWD — Get current working directoryGETENV — Get an environmental variableGET_ENVIRONMENT_VARIABLE — Get an environmental variableGETGID — Group ID functionGETLOG — Get login nameGETPID — Process ID functionGETUID — User ID functionGMTIME — Convert time to GMT infoHOSTNM — Get system host nameHUGE — Largest number of a kindHYPOT — Euclidean distance functionIACHAR — Code in ASCII collating sequenceIALL — Bitwise AND of array elementsIAND — Bitwise logical andIANY — Bitwise OR of array elementsIARGC — Get the number of command line argumentsIBCLR — Clear bitIBITS — Bit extractionIBSET — Set bitICHAR — Character-to-integer conversion functionIDATE — Get current local time subroutine (day/month/year)IEOR — Bitwise logical exclusive orIERRNO — Get the last system error numberIMAGE_INDEX — Function that converts a cosubscript to an image indexINDEX — Position of a substring within a stringINT — Convert to integer typeINT2 — Convert to 16-bit integer typeINT8 — Convert to 64-bit integer typeIOR — Bitwise logical orIPARITY — Bitwise XOR of array elementsIRAND — Integer pseudo-random numberIS_CONTIGUOUS — Test whether an array is contiguousIS_IOSTAT_END — Test for end-of-file valueIS_IOSTAT_EOR — Test for end-of-record valueISATTY — Whether a unit is a terminal device.ISHFT — Shift bitsISHFTC — Shift bits circularlyISNAN — Test for a NaNITIME — Get current local time subroutine (hour/minutes/seconds)KILL — Send a signal to a processKIND — Kind of an entityLBOUND — Lower dimension bounds of an arrayLCOBOUND — Lower codimension bounds of an arrayLEADZ — Number of leading zero bits of an integerLEN — Length of a character entityLEN_TRIM — Length of a character entity without trailing blank charactersLGE — Lexical greater than or equalLGT — Lexical greater thanLINK — Create a hard linkLLE — Lexical less than or equalLLT — Lexical less thanLNBLNK — Index of the last non-blank character in a stringLOC — Returns the address of a variableLOG — Natural logarithm functionLOG10 — Base 10 logarithm functionLOG_GAMMA — Logarithm of the Gamma functionLOGICAL — Convert to logical typeLONG — Convert to integer typeLSHIFT — Left shift bitsLSTAT — Get file statusLTIME — Convert time to local time infoMALLOC — Allocate dynamic memoryMASKL — Left justified maskMASKR — Right justified maskMATMUL — matrix multiplicationMAX — Maximum value of an argument listMAXEXPONENT — Maximum exponent of a real kindMAXLOC — Location of the maximum value within an arrayMAXVAL — Maximum value of an arrayMCLOCK — Time functionMCLOCK8 — Time function (64-bit)MERGE — Merge variablesMERGE_BITS — Merge of bits under maskMIN — Minimum value of an argument listMINEXPONENT — Minimum exponent of a real kindMINLOC — Location of the minimum value within an arrayMINVAL — Minimum value of an arrayMOD — Remainder functionMODULO — Modulo functionMOVE_ALLOC — Move allocation from one object to anotherMVBITS — Move bits from one integer to anotherNEAREST — Nearest representable numberNEW_LINE — New line characterNINT — Nearest whole numberNORM2 — Euclidean vector normsNOT — Logical negationNULL — Function that returns an disassociated pointerNUM_IMAGES — Function that returns the number of imagesOR — Bitwise logical ORPACK — Pack an array into an array of rank onePARITY — Reduction with exclusive ORPERROR — Print system error messagePOPCNT — Number of bits setPOPPAR — Parity of the number of bits setPRECISION — Decimal precision of a real kindPRESENT — Determine whether an optional dummy argument is specifiedPRODUCT — Product of array elementsRADIX — Base of a model numberRAN — Real pseudo-random numberRAND — Real pseudo-random numberRANDOM_INIT — Initialize a pseudo-random number generatorRANDOM_NUMBER — Pseudo-random numberRANDOM_SEED — Initialize a pseudo-random number sequenceRANGE — Decimal exponent rangeRANK — Rank of a data objectREAL — Convert to real typeRENAME — Rename a fileREPEAT — Repeated string concatenationRESHAPE — Function to reshape an arrayRRSPACING — Reciprocal of the relative spacingRSHIFT — Right shift bitsSAME_TYPE_AS — Query dynamic types for equalitySCALE — Scale a real valueSCAN — Scan a string for the presence of a set of charactersSECNDS — Time functionSECOND — CPU time functionSELECTED_CHAR_KIND — Choose character kindSELECTED_INT_KIND — Choose integer kindSELECTED_REAL_KIND — Choose real kindSET_EXPONENT — Set the exponent of the modelSHAPE — Determine the shape of an arraySHIFTA — Right shift with fillSHIFTL — Left shiftSHIFTR — Right shiftSIGN — Sign copying functionSIGNAL — Signal handling subroutine (or function)SIN — Sine functionSIND — Sine function, degreesSINH — Hyperbolic sine functionSIZE — Determine the size of an arraySIZEOF — Size in bytes of an expressionSLEEP — Sleep for the specified number of secondsSPACING — Smallest distance between two numbers of a given typeSPREAD — Add a dimension to an arraySQRT — Square-root functionSRAND — Reinitialize the random number generatorSTAT — Get file statusSTORAGE_SIZE — Storage size in bitsSUM — Sum of array elementsSYMLNK — Create a symbolic linkSYSTEM — Execute a shell commandSYSTEM_CLOCK — Time functionTAN — Tangent functionTAND — Tangent function, degreesTANH — Hyperbolic tangent functionTHIS_IMAGE — Function that returns the cosubscript index of this imageTIME — Time functionTIME8 — Time function (64-bit)TINY — Smallest positive number of a real kindTRAILZ — Number of trailing zero bits of an integerTRANSFER — Transfer bit patternsTRANSPOSE — Transpose an array of rank twoTRIM — Remove trailing blank characters of a stringTTYNAM — Get the name of a terminal device.UBOUND — Upper dimension bounds of an arrayUCOBOUND — Upper codimension bounds of an arrayUMASK — Set the file creation maskUNLINK — Remove a file from the file systemUNPACK — Unpack an array of rank one into an arrayVERIFY — Scan a string for characters not a given setXOR — Bitwise logical exclusive OR
Next: ABORT — Abort the program, Up: Intrinsic Procedures [Contents][Index]
The intrinsic procedures provided by GNU Fortran include all of the intrinsic procedures required by the Fortran 95 standard, a set of intrinsic procedures for backwards compatibility with G77, and a selection of intrinsic procedures from the Fortran 2003 and Fortran 2008 standards. Any conflict between a description here and a description in either the Fortran 95 standard, the Fortran 2003 standard or the Fortran 2008 standard is unintentional, and the standard(s) should be considered authoritative.
The enumeration of the KIND type parameter is processor defined in
the Fortran 95 standard. GNU Fortran defines the default integer type and
default real type by INTEGER(KIND=4) and REAL(KIND=4),
respectively. The standard mandates that both data types shall have
another kind, which have more precision. On typical target architectures
supported by gfortran, this kind type parameter is KIND=8.
Hence, REAL(KIND=8) and DOUBLE PRECISION are equivalent.
In the description of generic intrinsic procedures, the kind type parameter
will be specified by KIND=*, and in the description of specific
names for an intrinsic procedure the kind type parameter will be explicitly
given (e.g., REAL(KIND=4) or REAL(KIND=8)). Finally, for
brevity the optional KIND= syntax will be omitted.
Many of the intrinsic procedures take one or more optional arguments. This document follows the convention used in the Fortran 95 standard, and denotes such arguments by square brackets.
GNU Fortran offers the -std=f95 and -std=gnu options,
which can be used to restrict the set of intrinsic procedures to a
given standard. By default, gfortran sets the -std=gnu
option, and so all intrinsic procedures described here are accepted. There
is one caveat. For a select group of intrinsic procedures, g77
implemented both a function and a subroutine. Both classes
have been implemented in gfortran for backwards compatibility
with g77. It is noted here that these functions and subroutines
cannot be intermixed in a given subprogram. In the descriptions that follow,
the applicable standard for each intrinsic procedure is noted.
Next: ABS — Absolute value, Previous: Introduction to intrinsic procedures, Up: Intrinsic Procedures [Contents][Index]
ABORT — Abort the programABORT causes immediate termination of the program. On operating
systems that support a core dump, ABORT will produce a core dump.
It will also print a backtrace, unless -fno-backtrace is given.
GNU extension
Subroutine
CALL ABORT
Does not return.
program test_abort integer :: i = 1, j = 2 if (i /= j) call abort end program test_abort
EXIT — Exit the program with status.,
KILL — Send a signal to a process,
BACKTRACE — Show a backtrace
Next: ACCESS — Checks file access modes, Previous: ABORT — Abort the program, Up: Intrinsic Procedures [Contents][Index]
ABS — Absolute valueABS(A) computes the absolute value of A.
Fortran 77 and later, has overloads that are GNU extensions
Elemental function
RESULT = ABS(A)
| A | The type of the argument shall be an INTEGER,
REAL, or COMPLEX. |
The return value is of the same type and
kind as the argument except the return value is REAL for a
COMPLEX argument.
program test_abs integer :: i = -1 real :: x = -1.e0 complex :: z = (-1.e0,0.e0) i = abs(i) x = abs(x) x = abs(z) end program test_abs
| Name | Argument | Return type | Standard |
ABS(A) | REAL(4) A | REAL(4) | Fortran 77 and later |
CABS(A) | COMPLEX(4) A | REAL(4) | Fortran 77 and later |
DABS(A) | REAL(8) A | REAL(8) | Fortran 77 and later |
IABS(A) | INTEGER(4) A | INTEGER(4) | Fortran 77 and later |
BABS(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IIABS(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JIABS(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KIABS(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
ZABS(A) | COMPLEX(8) A | REAL(8) | GNU extension |
CDABS(A) | COMPLEX(8) A | REAL(8) | GNU extension |
Next: ACHAR — Character in ASCII collating sequence, Previous: ABS — Absolute value, Up: Intrinsic Procedures [Contents][Index]
ACCESS — Checks file access modesACCESS(NAME, MODE) checks whether the file NAME
exists, is readable, writable or executable. Except for the
executable check, ACCESS can be replaced by
Fortran 95’s INQUIRE.
GNU extension
Inquiry function
RESULT = ACCESS(NAME, MODE)
| NAME | Scalar CHARACTER of default kind with the
file name. Tailing blank are ignored unless the character achar(0)
is present, then all characters up to and excluding achar(0) are
used as file name. |
| MODE | Scalar CHARACTER of default kind with the
file access mode, may be any concatenation of "r" (readable),
"w" (writable) and "x" (executable), or " " to check
for existence. |
Returns a scalar INTEGER, which is 0 if the file is
accessible in the given mode; otherwise or if an invalid argument
has been given for MODE the value 1 is returned.
program access_test
implicit none
character(len=*), parameter :: file = 'test.dat'
character(len=*), parameter :: file2 = 'test.dat '//achar(0)
if(access(file,' ') == 0) print *, trim(file),' is exists'
if(access(file,'r') == 0) print *, trim(file),' is readable'
if(access(file,'w') == 0) print *, trim(file),' is writable'
if(access(file,'x') == 0) print *, trim(file),' is executable'
if(access(file2,'rwx') == 0) &
print *, trim(file2),' is readable, writable and executable'
end program access_test
Next: ACOS — Arccosine function, Previous: ACCESS — Checks file access modes, Up: Intrinsic Procedures [Contents][Index]
ACHAR — Character in ASCII collating sequenceACHAR(I) returns the character located at position I
in the ASCII collating sequence.
Fortran 77 and later, with KIND argument Fortran 2003 and later
Elemental function
RESULT = ACHAR(I [, KIND])
| I | The type shall be INTEGER. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type CHARACTER with a length of one.
If the KIND argument is present, the return value is of the
specified kind and of the default kind otherwise.
program test_achar character c c = achar(32) end program test_achar
See ICHAR — Character-to-integer conversion function for a discussion of converting between numerical values
and formatted string representations.
CHAR — Character conversion function,
IACHAR — Code in ASCII collating sequence,
ICHAR — Character-to-integer conversion function
Next: ACOSD — Arccosine function, degrees, Previous: ACHAR — Character in ASCII collating sequence, Up: Intrinsic Procedures [Contents][Index]
ACOS — Arccosine functionACOS(X) computes the arccosine of X (inverse of COS(X)).
Fortran 77 and later, for a complex argument Fortran 2008 or later
Elemental function
RESULT = ACOS(X)
| X | The type shall either be REAL with a magnitude that is
less than or equal to one - or the type shall be COMPLEX. |
The return value is of the same type and kind as X. The real part of the result is in radians and lies in the range 0 \leq \Re \acos(x) \leq \pi.
program test_acos real(8) :: x = 0.866_8 x = acos(x) end program test_acos
| Name | Argument | Return type | Standard |
ACOS(X) | REAL(4) X | REAL(4) | Fortran 77 and later |
DACOS(X) | REAL(8) X | REAL(8) | Fortran 77 and later |
Inverse function:
COS — Cosine function
Degrees function:
ACOSD — Arccosine function, degrees
Next: ACOSH — Inverse hyperbolic cosine function, Previous: ACOS — Arccosine function, Up: Intrinsic Procedures [Contents][Index]
ACOSD — Arccosine function, degreesACOSD(X) computes the arccosine of X in degrees (inverse of
COSD(X)).
This function is for compatibility only and should be avoided in favor of standard constructs wherever possible.
GNU extension, enabled with -fdec-math
Elemental function
RESULT = ACOSD(X)
| X | The type shall either be REAL with a magnitude that is
less than or equal to one - or the type shall be COMPLEX. |
The return value is of the same type and kind as X. The real part of the result is in degrees and lies in the range 0 \leq \Re \acos(x) \leq 180.
program test_acosd real(8) :: x = 0.866_8 x = acosd(x) end program test_acosd
| Name | Argument | Return type | Standard |
ACOSD(X) | REAL(4) X | REAL(4) | GNU extension |
DACOSD(X) | REAL(8) X | REAL(8) | GNU extension |
Inverse function:
COSD — Cosine function, degrees
Radians function:
ACOS — Arccosine function
Next: ADJUSTL — Left adjust a string, Previous: ACOSD — Arccosine function, degrees, Up: Intrinsic Procedures [Contents][Index]
ACOSH — Inverse hyperbolic cosine functionACOSH(X) computes the inverse hyperbolic cosine of X.
Fortran 2008 and later
Elemental function
RESULT = ACOSH(X)
| X | The type shall be REAL or COMPLEX. |
The return value has the same type and kind as X. If X is complex, the imaginary part of the result is in radians and lies between 0 \leq \Im \acosh(x) \leq \pi.
PROGRAM test_acosh REAL(8), DIMENSION(3) :: x = (/ 1.0, 2.0, 3.0 /) WRITE (*,*) ACOSH(x) END PROGRAM
| Name | Argument | Return type | Standard |
DACOSH(X) | REAL(8) X | REAL(8) | GNU extension |
Inverse function:
COSH — Hyperbolic cosine function
Next: ADJUSTR — Right adjust a string, Previous: ACOSH — Inverse hyperbolic cosine function, Up: Intrinsic Procedures [Contents][Index]
ADJUSTL — Left adjust a stringADJUSTL(STRING) will left adjust a string by removing leading spaces.
Spaces are inserted at the end of the string as needed.
Fortran 90 and later
Elemental function
RESULT = ADJUSTL(STRING)
| STRING | The type shall be CHARACTER. |
The return value is of type CHARACTER and of the same kind as
STRING where leading spaces are removed and the same number of
spaces are inserted on the end of STRING.
program test_adjustl character(len=20) :: str = ' gfortran' str = adjustl(str) print *, str end program test_adjustl
ADJUSTR — Right adjust a string,
TRIM — Remove trailing blank characters of a string
Next: AIMAG — Imaginary part of complex number, Previous: ADJUSTL — Left adjust a string, Up: Intrinsic Procedures [Contents][Index]
ADJUSTR — Right adjust a stringADJUSTR(STRING) will right adjust a string by removing trailing spaces.
Spaces are inserted at the start of the string as needed.
Fortran 90 and later
Elemental function
RESULT = ADJUSTR(STRING)
| STR | The type shall be CHARACTER. |
The return value is of type CHARACTER and of the same kind as
STRING where trailing spaces are removed and the same number of
spaces are inserted at the start of STRING.
program test_adjustr character(len=20) :: str = 'gfortran' str = adjustr(str) print *, str end program test_adjustr
ADJUSTL — Left adjust a string,
TRIM — Remove trailing blank characters of a string
Next: AINT — Truncate to a whole number, Previous: ADJUSTR — Right adjust a string, Up: Intrinsic Procedures [Contents][Index]
AIMAG — Imaginary part of complex numberAIMAG(Z) yields the imaginary part of complex argument Z.
The IMAG(Z) and IMAGPART(Z) intrinsic functions are provided
for compatibility with g77, and their use in new code is
strongly discouraged.
Fortran 77 and later, has overloads that are GNU extensions
Elemental function
RESULT = AIMAG(Z)
| Z | The type of the argument shall be COMPLEX. |
The return value is of type REAL with the
kind type parameter of the argument.
program test_aimag complex(4) z4 complex(8) z8 z4 = cmplx(1.e0_4, 0.e0_4) z8 = cmplx(0.e0_8, 1.e0_8) print *, aimag(z4), dimag(z8) end program test_aimag
| Name | Argument | Return type | Standard |
AIMAG(Z) | COMPLEX Z | REAL | Fortran 77 and later |
DIMAG(Z) | COMPLEX(8) Z | REAL(8) | GNU extension |
IMAG(Z) | COMPLEX Z | REAL | GNU extension |
IMAGPART(Z) | COMPLEX Z | REAL | GNU extension |
Next: ALARM — Execute a routine after a given delay, Previous: AIMAG — Imaginary part of complex number, Up: Intrinsic Procedures [Contents][Index]
AINT — Truncate to a whole numberAINT(A [, KIND]) truncates its argument to a whole number.
Fortran 77 and later
Elemental function
RESULT = AINT(A [, KIND])
| A | The type of the argument shall be REAL. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type REAL with the kind type parameter of the
argument if the optional KIND is absent; otherwise, the kind
type parameter will be given by KIND. If the magnitude of
X is less than one, AINT(X) returns zero. If the
magnitude is equal to or greater than one then it returns the largest
whole number that does not exceed its magnitude. The sign is the same
as the sign of X.
program test_aint real(4) x4 real(8) x8 x4 = 1.234E0_4 x8 = 4.321_8 print *, aint(x4), dint(x8) x8 = aint(x4,8) end program test_aint
| Name | Argument | Return type | Standard |
AINT(A) | REAL(4) A | REAL(4) | Fortran 77 and later |
DINT(A) | REAL(8) A | REAL(8) | Fortran 77 and later |
Next: ALL — All values in MASK along DIM are true, Previous: AINT — Truncate to a whole number, Up: Intrinsic Procedures [Contents][Index]
ALARM — Execute a routine after a given delayALARM(SECONDS, HANDLER [, STATUS]) causes external subroutine HANDLER
to be executed after a delay of SECONDS by using alarm(2) to
set up a signal and signal(2) to catch it. If STATUS is
supplied, it will be returned with the number of seconds remaining until
any previously scheduled alarm was due to be delivered, or zero if there
was no previously scheduled alarm.
GNU extension
Subroutine
CALL ALARM(SECONDS, HANDLER [, STATUS])
| SECONDS | The type of the argument shall be a scalar
INTEGER. It is INTENT(IN). |
| HANDLER | Signal handler (INTEGER FUNCTION or
SUBROUTINE) or dummy/global INTEGER scalar. The scalar
values may be either SIG_IGN=1 to ignore the alarm generated
or SIG_DFL=0 to set the default action. It is INTENT(IN). |
| STATUS | (Optional) STATUS shall be a scalar
variable of the default INTEGER kind. It is INTENT(OUT). |
program test_alarm external handler_print integer i call alarm (3, handler_print, i) print *, i call sleep(10) end program test_alarm
This will cause the external routine handler_print to be called after 3 seconds.
Next: ALLOCATED — Status of an allocatable entity, Previous: ALARM — Execute a routine after a given delay, Up: Intrinsic Procedures [Contents][Index]
ALL — All values in MASK along DIM are trueALL(MASK [, DIM]) determines if all the values are true in MASK
in the array along dimension DIM.
Fortran 90 and later
Transformational function
RESULT = ALL(MASK [, DIM])
| MASK | The type of the argument shall be LOGICAL and
it shall not be scalar. |
| DIM | (Optional) DIM shall be a scalar integer with a value that lies between one and the rank of MASK. |
ALL(MASK) returns a scalar value of type LOGICAL where
the kind type parameter is the same as the kind type parameter of
MASK. If DIM is present, then ALL(MASK, DIM) returns
an array with the rank of MASK minus 1. The shape is determined from
the shape of MASK where the DIM dimension is elided.
ALL(MASK) is true if all elements of MASK are true.
It also is true if MASK has zero size; otherwise, it is false.
If the rank of MASK is one, then ALL(MASK,DIM) is equivalent
to ALL(MASK). If the rank is greater than one, then ALL(MASK,DIM)
is determined by applying ALL to the array sections.
program test_all
logical l
l = all((/.true., .true., .true./))
print *, l
call section
contains
subroutine section
integer a(2,3), b(2,3)
a = 1
b = 1
b(2,2) = 2
print *, all(a .eq. b, 1)
print *, all(a .eq. b, 2)
end subroutine section
end program test_all
Next: AND — Bitwise logical AND, Previous: ALL — All values in MASK along DIM are true, Up: Intrinsic Procedures [Contents][Index]
ALLOCATED — Status of an allocatable entityALLOCATED(ARRAY) and ALLOCATED(SCALAR) check the allocation
status of ARRAY and SCALAR, respectively.
Fortran 90 and later. Note, the SCALAR= keyword and allocatable
scalar entities are available in Fortran 2003 and later.
Inquiry function
RESULT = ALLOCATED(ARRAY) |
RESULT = ALLOCATED(SCALAR) |
| ARRAY | The argument shall be an ALLOCATABLE array. |
| SCALAR | The argument shall be an ALLOCATABLE scalar. |
The return value is a scalar LOGICAL with the default logical
kind type parameter. If the argument is allocated, then the result is
.TRUE.; otherwise, it returns .FALSE.
program test_allocated integer :: i = 4 real(4), allocatable :: x(:) if (.not. allocated(x)) allocate(x(i)) end program test_allocated
Next: ANINT — Nearest whole number, Previous: ALLOCATED — Status of an allocatable entity, Up: Intrinsic Procedures [Contents][Index]
AND — Bitwise logical ANDBitwise logical AND.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. For integer arguments, programmers should consider
the use of the IAND — Bitwise logical and intrinsic defined by the Fortran standard.
GNU extension
Function
RESULT = AND(I, J)
| I | The type shall be either a scalar INTEGER
type or a scalar LOGICAL type or a boz-literal-constant. |
| J | The type shall be the same as the type of I or
a boz-literal-constant. I and J shall not both be
boz-literal-constants. If either I or J is a
boz-literal-constant, then the other argument must be a scalar INTEGER. |
The return type is either a scalar INTEGER or a scalar
LOGICAL. If the kind type parameters differ, then the
smaller kind type is implicitly converted to larger kind, and the
return has the larger kind. A boz-literal-constant is
converted to an INTEGER with the kind type parameter of
the other argument as-if a call to INT — Convert to integer type occurred.
PROGRAM test_and LOGICAL :: T = .TRUE., F = .FALSE. INTEGER :: a, b DATA a / Z'F' /, b / Z'3' / WRITE (*,*) AND(T, T), AND(T, F), AND(F, T), AND(F, F) WRITE (*,*) AND(a, b) END PROGRAM
Fortran 95 elemental function:
IAND — Bitwise logical and
Next: ANY — Any value in MASK along DIM is true, Previous: AND — Bitwise logical AND, Up: Intrinsic Procedures [Contents][Index]
ANINT — Nearest whole numberANINT(A [, KIND]) rounds its argument to the nearest whole number.
Fortran 77 and later
Elemental function
RESULT = ANINT(A [, KIND])
| A | The type of the argument shall be REAL. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type real with the kind type parameter of the
argument if the optional KIND is absent; otherwise, the kind
type parameter will be given by KIND. If A is greater than
zero, ANINT(A) returns AINT(X+0.5). If A is
less than or equal to zero then it returns AINT(X-0.5).
program test_anint real(4) x4 real(8) x8 x4 = 1.234E0_4 x8 = 4.321_8 print *, anint(x4), dnint(x8) x8 = anint(x4,8) end program test_anint
| Name | Argument | Return type | Standard |
ANINT(A) | REAL(4) A | REAL(4) | Fortran 77 and later |
DNINT(A) | REAL(8) A | REAL(8) | Fortran 77 and later |
Next: ASIN — Arcsine function, Previous: ANINT — Nearest whole number, Up: Intrinsic Procedures [Contents][Index]
ANY — Any value in MASK along DIM is trueANY(MASK [, DIM]) determines if any of the values in the logical array
MASK along dimension DIM are .TRUE..
Fortran 90 and later
Transformational function
RESULT = ANY(MASK [, DIM])
| MASK | The type of the argument shall be LOGICAL and
it shall not be scalar. |
| DIM | (Optional) DIM shall be a scalar integer with a value that lies between one and the rank of MASK. |
ANY(MASK) returns a scalar value of type LOGICAL where
the kind type parameter is the same as the kind type parameter of
MASK. If DIM is present, then ANY(MASK, DIM) returns
an array with the rank of MASK minus 1. The shape is determined from
the shape of MASK where the DIM dimension is elided.
ANY(MASK) is true if any element of MASK is true;
otherwise, it is false. It also is false if MASK has zero size.
If the rank of MASK is one, then ANY(MASK,DIM) is equivalent
to ANY(MASK). If the rank is greater than one, then ANY(MASK,DIM)
is determined by applying ANY to the array sections.
program test_any
logical l
l = any((/.true., .true., .true./))
print *, l
call section
contains
subroutine section
integer a(2,3), b(2,3)
a = 1
b = 1
b(2,2) = 2
print *, any(a .eq. b, 1)
print *, any(a .eq. b, 2)
end subroutine section
end program test_any
Next: ASIND — Arcsine function, degrees, Previous: ANY — Any value in MASK along DIM is true, Up: Intrinsic Procedures [Contents][Index]
ASIN — Arcsine functionASIN(X) computes the arcsine of its X (inverse of SIN(X)).
Fortran 77 and later, for a complex argument Fortran 2008 or later
Elemental function
RESULT = ASIN(X)
| X | The type shall be either REAL and a magnitude that is
less than or equal to one - or be COMPLEX. |
The return value is of the same type and kind as X. The real part of the result is in radians and lies in the range -\pi/2 \leq \Re \asin(x) \leq \pi/2.
program test_asin real(8) :: x = 0.866_8 x = asin(x) end program test_asin
| Name | Argument | Return type | Standard |
ASIN(X) | REAL(4) X | REAL(4) | Fortran 77 and later |
DASIN(X) | REAL(8) X | REAL(8) | Fortran 77 and later |
Inverse function:
SIN — Sine function
Degrees function:
ASIND — Arcsine function, degrees
Next: ASINH — Inverse hyperbolic sine function, Previous: ASIN — Arcsine function, Up: Intrinsic Procedures [Contents][Index]
ASIND — Arcsine function, degreesASIND(X) computes the arcsine of its X in degrees (inverse of
SIND(X)).
This function is for compatibility only and should be avoided in favor of standard constructs wherever possible.
GNU extension, enabled with -fdec-math.
Elemental function
RESULT = ASIND(X)
| X | The type shall be either REAL and a magnitude that is
less than or equal to one - or be COMPLEX. |
The return value is of the same type and kind as X. The real part of the result is in degrees and lies in the range -90 \leq \Re \asin(x) \leq 90.
program test_asind real(8) :: x = 0.866_8 x = asind(x) end program test_asind
| Name | Argument | Return type | Standard |
ASIND(X) | REAL(4) X | REAL(4) | GNU extension |
DASIND(X) | REAL(8) X | REAL(8) | GNU extension |
Inverse function:
SIND — Sine function, degrees
Radians function:
ASIN — Arcsine function
Next: ASSOCIATED — Status of a pointer or pointer/target pair, Previous: ASIND — Arcsine function, degrees, Up: Intrinsic Procedures [Contents][Index]
ASINH — Inverse hyperbolic sine functionASINH(X) computes the inverse hyperbolic sine of X.
Fortran 2008 and later
Elemental function
RESULT = ASINH(X)
| X | The type shall be REAL or COMPLEX. |
The return value is of the same type and kind as X. If X is complex, the imaginary part of the result is in radians and lies between -\pi/2 \leq \Im \asinh(x) \leq \pi/2.
PROGRAM test_asinh REAL(8), DIMENSION(3) :: x = (/ -1.0, 0.0, 1.0 /) WRITE (*,*) ASINH(x) END PROGRAM
| Name | Argument | Return type | Standard |
DASINH(X) | REAL(8) X | REAL(8) | GNU extension. |
Inverse function:
SINH — Hyperbolic sine function
Next: ATAN — Arctangent function, Previous: ASINH — Inverse hyperbolic sine function, Up: Intrinsic Procedures [Contents][Index]
ASSOCIATED — Status of a pointer or pointer/target pairASSOCIATED(POINTER [, TARGET]) determines the status of the pointer
POINTER or if POINTER is associated with the target TARGET.
Fortran 90 and later
Inquiry function
RESULT = ASSOCIATED(POINTER [, TARGET])
| POINTER | POINTER shall have the POINTER attribute
and it can be of any type. |
| TARGET | (Optional) TARGET shall be a pointer or a target. It must have the same type, kind type parameter, and array rank as POINTER. |
The association status of neither POINTER nor TARGET shall be undefined.
ASSOCIATED(POINTER) returns a scalar value of type LOGICAL(4).
There are several cases:
ASSOCIATED(POINTER) is true if POINTER is associated with a target; otherwise, it returns false.
TARGET is not a zero-sized storage sequence and the target associated with POINTER occupies the same storage units. If POINTER is disassociated, the result is false.
TARGET and POINTER have the same shape, are not zero-sized arrays, are arrays whose elements are not zero-sized storage sequences, and TARGET and POINTER occupy the same storage units in array element order. As in case(B), the result is false, if POINTER is disassociated.
if TARGET is associated with POINTER, the target associated with TARGET are not zero-sized storage sequences and occupy the same storage units. The result is false, if either TARGET or POINTER is disassociated.
target associated with POINTER and the target associated with TARGET have the same shape, are not zero-sized arrays, are arrays whose elements are not zero-sized storage sequences, and TARGET and POINTER occupy the same storage units in array element order. The result is false, if either TARGET or POINTER is disassociated.
program test_associated implicit none real, target :: tgt(2) = (/1., 2./) real, pointer :: ptr(:) ptr => tgt if (associated(ptr) .eqv. .false.) call abort if (associated(ptr,tgt) .eqv. .false.) call abort end program test_associated
Next: ATAND — Arctangent function, degrees, Previous: ASSOCIATED — Status of a pointer or pointer/target pair, Up: Intrinsic Procedures [Contents][Index]
ATAN — Arctangent functionATAN(X) computes the arctangent of X.
Fortran 77 and later, for a complex argument and for two arguments Fortran 2008 or later
Elemental function
RESULT = ATAN(X) |
RESULT = ATAN(Y, X) |
| X | The type shall be REAL or COMPLEX;
if Y is present, X shall be REAL. |
| Y | The type and kind type parameter shall be the same as X. |
The return value is of the same type and kind as X.
If Y is present, the result is identical to ATAN2(Y,X).
Otherwise, it the arcus tangent of X, where the real part of
the result is in radians and lies in the range
-\pi/2 \leq \Re \atan(x) \leq \pi/2.
program test_atan real(8) :: x = 2.866_8 x = atan(x) end program test_atan
| Name | Argument | Return type | Standard |
ATAN(X) | REAL(4) X | REAL(4) | Fortran 77 and later |
DATAN(X) | REAL(8) X | REAL(8) | Fortran 77 and later |
Inverse function:
TAN — Tangent function
Degrees function:
ATAND — Arctangent function, degrees
Next: ATAN2 — Arctangent function, Previous: ATAN — Arctangent function, Up: Intrinsic Procedures [Contents][Index]
ATAND — Arctangent function, degreesATAND(X) computes the arctangent of X in degrees (inverse of
TAND — Tangent function, degrees).
This function is for compatibility only and should be avoided in favor of standard constructs wherever possible.
GNU extension, enabled with -fdec-math.
Elemental function
RESULT = ATAND(X) |
RESULT = ATAND(Y, X) |
| X | The type shall be REAL or COMPLEX;
if Y is present, X shall be REAL. |
| Y | The type and kind type parameter shall be the same as X. |
The return value is of the same type and kind as X.
If Y is present, the result is identical to ATAND2(Y,X).
Otherwise, it is the arcus tangent of X, where the real part of
the result is in degrees and lies in the range
-90 \leq \Re \atand(x) \leq 90.
program test_atand real(8) :: x = 2.866_8 x = atand(x) end program test_atand
| Name | Argument | Return type | Standard |
ATAND(X) | REAL(4) X | REAL(4) | GNU extension |
DATAND(X) | REAL(8) X | REAL(8) | GNU extension |
Inverse function:
TAND — Tangent function, degrees
Radians function:
ATAN — Arctangent function
Next: ATAN2D — Arctangent function, degrees, Previous: ATAND — Arctangent function, degrees, Up: Intrinsic Procedures [Contents][Index]
ATAN2 — Arctangent functionATAN2(Y, X) computes the principal value of the argument
function of the complex number X + i Y. This function can
be used to transform from Cartesian into polar coordinates and
allows to determine the angle in the correct quadrant.
Fortran 77 and later
Elemental function
RESULT = ATAN2(Y, X)
| Y | The type shall be REAL. |
| X | The type and kind type parameter shall be the same as Y. If Y is zero, then X must be nonzero. |
The return value has the same type and kind type parameter as Y. It is the principal value of the complex number X + i Y. If X is nonzero, then it lies in the range -\pi \le \atan (x) \leq \pi. The sign is positive if Y is positive. If Y is zero, then the return value is zero if X is strictly positive, \pi if X is negative and Y is positive zero (or the processor does not handle signed zeros), and -\pi if X is negative and Y is negative zero. Finally, if X is zero, then the magnitude of the result is \pi/2.
program test_atan2 real(4) :: x = 1.e0_4, y = 0.5e0_4 x = atan2(y,x) end program test_atan2
| Name | Argument | Return type | Standard |
ATAN2(X, Y) | REAL(4) X, Y | REAL(4) | Fortran 77 and later |
DATAN2(X, Y) | REAL(8) X, Y | REAL(8) | Fortran 77 and later |
Alias:
ATAN — Arctangent function
Degrees function:
ATAN2D — Arctangent function, degrees
Next: ATANH — Inverse hyperbolic tangent function, Previous: ATAN2 — Arctangent function, Up: Intrinsic Procedures [Contents][Index]
ATAN2D — Arctangent function, degreesATAN2D(Y, X) computes the principal value of the argument
function of the complex number X + i Y in degrees. This function can
be used to transform from Cartesian into polar coordinates and
allows to determine the angle in the correct quadrant.
This function is for compatibility only and should be avoided in favor of standard constructs wherever possible.
GNU extension, enabled with -fdec-math.
Elemental function
RESULT = ATAN2D(Y, X)
| Y | The type shall be REAL. |
| X | The type and kind type parameter shall be the same as Y. If Y is zero, then X must be nonzero. |
The return value has the same type and kind type parameter as Y. It is the principal value of the complex number X + i Y. If X is nonzero, then it lies in the range -180 \le \atan (x) \leq 180. The sign is positive if Y is positive. If Y is zero, then the return value is zero if X is strictly positive, 180 if X is negative and Y is positive zero (or the processor does not handle signed zeros), and -180 if X is negative and Y is negative zero. Finally, if X is zero, then the magnitude of the result is 90.
program test_atan2d real(4) :: x = 1.e0_4, y = 0.5e0_4 x = atan2d(y,x) end program test_atan2d
| Name | Argument | Return type | Standard |
ATAN2D(X, Y) | REAL(4) X, Y | REAL(4) | GNU extension |
DATAN2D(X, Y) | REAL(8) X, Y | REAL(8) | GNU extension |
Alias:
ATAND — Arctangent function, degrees
Radians function:
ATAN2 — Arctangent function
Next: ATOMIC_ADD — Atomic ADD operation, Previous: ATAN2D — Arctangent function, degrees, Up: Intrinsic Procedures [Contents][Index]
ATANH — Inverse hyperbolic tangent functionATANH(X) computes the inverse hyperbolic tangent of X.
Fortran 2008 and later
Elemental function
RESULT = ATANH(X)
| X | The type shall be REAL or COMPLEX. |
The return value has same type and kind as X. If X is complex, the imaginary part of the result is in radians and lies between -\pi/2 \leq \Im \atanh(x) \leq \pi/2.
PROGRAM test_atanh REAL, DIMENSION(3) :: x = (/ -1.0, 0.0, 1.0 /) WRITE (*,*) ATANH(x) END PROGRAM
| Name | Argument | Return type | Standard |
DATANH(X) | REAL(8) X | REAL(8) | GNU extension |
Inverse function:
TANH — Hyperbolic tangent function
Next: ATOMIC_AND — Atomic bitwise AND operation, Previous: ATANH — Inverse hyperbolic tangent function, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_ADD — Atomic ADD operationATOMIC_ADD(ATOM, VALUE) atomically adds the value of VALUE to the
variable ATOM. When STAT is present and the invocation was
successful, it is assigned the value 0. If it is present and the invocation
has failed, it is assigned a positive value; in particular, for a coindexed
ATOM, if the remote image has stopped, it is assigned the value of
ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image has
failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_ADD (ATOM, VALUE [, STAT])
| ATOM | Scalar coarray or coindexed variable of integer
type with ATOMIC_INT_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*] call atomic_add (atom[1], this_image()) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_FETCH_ADD — Atomic ADD operation with prior fetch,
ISO_FORTRAN_ENV,
ATOMIC_AND — Atomic bitwise AND operation,
ATOMIC_OR — Atomic bitwise OR operation,
ATOMIC_XOR — Atomic bitwise OR operation
Next: ATOMIC_CAS — Atomic compare and swap, Previous: ATOMIC_ADD — Atomic ADD operation, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_AND — Atomic bitwise AND operationATOMIC_AND(ATOM, VALUE) atomically defines ATOM with the bitwise
AND between the values of ATOM and VALUE. When STAT is present
and the invocation was successful, it is assigned the value 0. If it is present
and the invocation has failed, it is assigned a positive value; in particular,
for a coindexed ATOM, if the remote image has stopped, it is assigned the
value of ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote
image has failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_AND (ATOM, VALUE [, STAT])
| ATOM | Scalar coarray or coindexed variable of integer
type with ATOMIC_INT_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*] call atomic_and (atom[1], int(b'10100011101')) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetch,
ISO_FORTRAN_ENV,
ATOMIC_ADD — Atomic ADD operation,
ATOMIC_OR — Atomic bitwise OR operation,
ATOMIC_XOR — Atomic bitwise OR operation
Next: ATOMIC_DEFINE — Setting a variable atomically, Previous: ATOMIC_AND — Atomic bitwise AND operation, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_CAS — Atomic compare and swapATOMIC_CAS compares the variable ATOM with the value of
COMPARE; if the value is the same, ATOM is set to the value
of NEW. Additionally, OLD is set to the value of ATOM
that was used for the comparison. When STAT is present and the invocation
was successful, it is assigned the value 0. If it is present and the invocation
has failed, it is assigned a positive value; in particular, for a coindexed
ATOM, if the remote image has stopped, it is assigned the value of
ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image has
failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_CAS (ATOM, OLD, COMPARE, NEW [, STAT])
| ATOM | Scalar coarray or coindexed variable of either integer
type with ATOMIC_INT_KIND kind or logical type with
ATOMIC_LOGICAL_KIND kind. |
| OLD | Scalar of the same type and kind as ATOM. |
| COMPARE | Scalar variable of the same type and kind as ATOM. |
| NEW | Scalar variable of the same type as ATOM. If kind is different, the value is converted to the kind of ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env logical(atomic_logical_kind) :: atom[*], prev call atomic_cas (atom[1], prev, .false., .true.)) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_REF — Obtaining the value of a variable atomically,
ISO_FORTRAN_ENV
Next: ATOMIC_FETCH_ADD — Atomic ADD operation with prior fetch, Previous: ATOMIC_CAS — Atomic compare and swap, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_DEFINE — Setting a variable atomicallyATOMIC_DEFINE(ATOM, VALUE) defines the variable ATOM with the value
VALUE atomically. When STAT is present and the invocation was
successful, it is assigned the value 0. If it is present and the invocation
has failed, it is assigned a positive value; in particular, for a coindexed
ATOM, if the remote image has stopped, it is assigned the value of
ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image has
failed, the value STAT_FAILED_IMAGE.
Fortran 2008 and later; with STAT, TS 18508 or later
Atomic subroutine
CALL ATOMIC_DEFINE (ATOM, VALUE [, STAT])
| ATOM | Scalar coarray or coindexed variable of either integer
type with ATOMIC_INT_KIND kind or logical type with
ATOMIC_LOGICAL_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*] call atomic_define (atom[1], this_image()) end program atomic
ATOMIC_REF — Obtaining the value of a variable atomically,
ATOMIC_CAS — Atomic compare and swap,
ISO_FORTRAN_ENV,
ATOMIC_ADD — Atomic ADD operation,
ATOMIC_AND — Atomic bitwise AND operation,
ATOMIC_OR — Atomic bitwise OR operation,
ATOMIC_XOR — Atomic bitwise OR operation
Next: ATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetch, Previous: ATOMIC_DEFINE — Setting a variable atomically, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_FETCH_ADD — Atomic ADD operation with prior fetchATOMIC_FETCH_ADD(ATOM, VALUE, OLD) atomically stores the value of
ATOM in OLD and adds the value of VALUE to the
variable ATOM. When STAT is present and the invocation was
successful, it is assigned the value 0. If it is present and the invocation
has failed, it is assigned a positive value; in particular, for a coindexed
ATOM, if the remote image has stopped, it is assigned the value of
ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image has
failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_FETCH_ADD (ATOM, VALUE, old [, STAT])
| ATOM | Scalar coarray or coindexed variable of integer
type with ATOMIC_INT_KIND kind.
ATOMIC_LOGICAL_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| OLD | Scalar of the same type and kind as ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*], old call atomic_add (atom[1], this_image(), old) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_ADD — Atomic ADD operation,
ISO_FORTRAN_ENV,
ATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetch,
ATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetch,
ATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetch
Next: ATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetch, Previous: ATOMIC_FETCH_ADD — Atomic ADD operation with prior fetch, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetchATOMIC_AND(ATOM, VALUE) atomically stores the value of ATOM in
OLD and defines ATOM with the bitwise AND between the values of
ATOM and VALUE. When STAT is present and the invocation was
successful, it is assigned the value 0. If it is present and the invocation has
failed, it is assigned a positive value; in particular, for a coindexed
ATOM, if the remote image has stopped, it is assigned the value of
ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image has
failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_FETCH_AND (ATOM, VALUE, OLD [, STAT])
| ATOM | Scalar coarray or coindexed variable of integer
type with ATOMIC_INT_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| OLD | Scalar of the same type and kind as ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*], old call atomic_fetch_and (atom[1], int(b'10100011101'), old) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_AND — Atomic bitwise AND operation,
ISO_FORTRAN_ENV,
ATOMIC_FETCH_ADD — Atomic ADD operation with prior fetch,
ATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetch,
ATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetch
Next: ATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetch, Previous: ATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetch, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetchATOMIC_OR(ATOM, VALUE) atomically stores the value of ATOM in
OLD and defines ATOM with the bitwise OR between the values of
ATOM and VALUE. When STAT is present and the invocation was
successful, it is assigned the value 0. If it is present and the invocation has
failed, it is assigned a positive value; in particular, for a coindexed
ATOM, if the remote image has stopped, it is assigned the value of
ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image has
failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_FETCH_OR (ATOM, VALUE, OLD [, STAT])
| ATOM | Scalar coarray or coindexed variable of integer
type with ATOMIC_INT_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| OLD | Scalar of the same type and kind as ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*], old call atomic_fetch_or (atom[1], int(b'10100011101'), old) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_OR — Atomic bitwise OR operation,
ISO_FORTRAN_ENV,
ATOMIC_FETCH_ADD — Atomic ADD operation with prior fetch,
ATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetch,
ATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetch
Next: ATOMIC_OR — Atomic bitwise OR operation, Previous: ATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetch, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetchATOMIC_XOR(ATOM, VALUE) atomically stores the value of ATOM in
OLD and defines ATOM with the bitwise XOR between the values of
ATOM and VALUE. When STAT is present and the invocation was
successful, it is assigned the value 0. If it is present and the invocation has
failed, it is assigned a positive value; in particular, for a coindexed
ATOM, if the remote image has stopped, it is assigned the value of
ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image has
failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_FETCH_XOR (ATOM, VALUE, OLD [, STAT])
| ATOM | Scalar coarray or coindexed variable of integer
type with ATOMIC_INT_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| OLD | Scalar of the same type and kind as ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*], old call atomic_fetch_xor (atom[1], int(b'10100011101'), old) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_XOR — Atomic bitwise OR operation,
ISO_FORTRAN_ENV,
ATOMIC_FETCH_ADD — Atomic ADD operation with prior fetch,
ATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetch,
ATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetch
Next: ATOMIC_REF — Obtaining the value of a variable atomically, Previous: ATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetch, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_OR — Atomic bitwise OR operationATOMIC_OR(ATOM, VALUE) atomically defines ATOM with the bitwise
AND between the values of ATOM and VALUE. When STAT is present
and the invocation was successful, it is assigned the value 0. If it is present
and the invocation has failed, it is assigned a positive value; in particular,
for a coindexed ATOM, if the remote image has stopped, it is assigned the
value of ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote
image has failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_OR (ATOM, VALUE [, STAT])
| ATOM | Scalar coarray or coindexed variable of integer
type with ATOMIC_INT_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*] call atomic_or (atom[1], int(b'10100011101')) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetch,
ISO_FORTRAN_ENV,
ATOMIC_ADD — Atomic ADD operation,
ATOMIC_OR — Atomic bitwise OR operation,
ATOMIC_XOR — Atomic bitwise OR operation
Next: ATOMIC_XOR — Atomic bitwise OR operation, Previous: ATOMIC_OR — Atomic bitwise OR operation, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_REF — Obtaining the value of a variable atomicallyATOMIC_DEFINE(ATOM, VALUE) atomically assigns the value of the
variable ATOM to VALUE. When STAT is present and the
invocation was successful, it is assigned the value 0. If it is present and the
invocation has failed, it is assigned a positive value; in particular, for a
coindexed ATOM, if the remote image has stopped, it is assigned the value
of ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote image
has failed, the value STAT_FAILED_IMAGE.
Fortran 2008 and later; with STAT, TS 18508 or later
Atomic subroutine
CALL ATOMIC_REF(VALUE, ATOM [, STAT])
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| ATOM | Scalar coarray or coindexed variable of either integer
type with ATOMIC_INT_KIND kind or logical type with
ATOMIC_LOGICAL_KIND kind. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic
use iso_fortran_env
logical(atomic_logical_kind) :: atom[*]
logical :: val
call atomic_ref (atom, .false.)
! ...
call atomic_ref (atom, val)
if (val) then
print *, "Obtained"
end if
end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_CAS — Atomic compare and swap,
ISO_FORTRAN_ENV,
ATOMIC_FETCH_ADD — Atomic ADD operation with prior fetch,
ATOMIC_FETCH_AND — Atomic bitwise AND operation with prior fetch,
ATOMIC_FETCH_OR — Atomic bitwise OR operation with prior fetch,
ATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetch
Next: BACKTRACE — Show a backtrace, Previous: ATOMIC_REF — Obtaining the value of a variable atomically, Up: Intrinsic Procedures [Contents][Index]
ATOMIC_XOR — Atomic bitwise OR operationATOMIC_AND(ATOM, VALUE) atomically defines ATOM with the bitwise
XOR between the values of ATOM and VALUE. When STAT is present
and the invocation was successful, it is assigned the value 0. If it is present
and the invocation has failed, it is assigned a positive value; in particular,
for a coindexed ATOM, if the remote image has stopped, it is assigned the
value of ISO_FORTRAN_ENV’s STAT_STOPPED_IMAGE and if the remote
image has failed, the value STAT_FAILED_IMAGE.
TS 18508 or later
Atomic subroutine
CALL ATOMIC_XOR (ATOM, VALUE [, STAT])
| ATOM | Scalar coarray or coindexed variable of integer
type with ATOMIC_INT_KIND kind. |
| VALUE | Scalar of the same type as ATOM. If the kind is different, the value is converted to the kind of ATOM. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic use iso_fortran_env integer(atomic_int_kind) :: atom[*] call atomic_xor (atom[1], int(b'10100011101')) end program atomic
ATOMIC_DEFINE — Setting a variable atomically,
ATOMIC_FETCH_XOR — Atomic bitwise XOR operation with prior fetch,
ISO_FORTRAN_ENV,
ATOMIC_ADD — Atomic ADD operation,
ATOMIC_OR — Atomic bitwise OR operation,
ATOMIC_XOR — Atomic bitwise OR operation
Next: BESSEL_J0 — Bessel function of the first kind of order 0, Previous: ATOMIC_XOR — Atomic bitwise OR operation, Up: Intrinsic Procedures [Contents][Index]
BACKTRACE — Show a backtraceBACKTRACE shows a backtrace at an arbitrary place in user code. Program
execution continues normally afterwards. The backtrace information is printed
to the unit corresponding to ERROR_UNIT in ISO_FORTRAN_ENV.
GNU extension
Subroutine
CALL BACKTRACE
None
Next: BESSEL_J1 — Bessel function of the first kind of order 1, Previous: BACKTRACE — Show a backtrace, Up: Intrinsic Procedures [Contents][Index]
BESSEL_J0 — Bessel function of the first kind of order 0BESSEL_J0(X) computes the Bessel function of the first kind of
order 0 of X. This function is available under the name
BESJ0 as a GNU extension.
Fortran 2008 and later
Elemental function
RESULT = BESSEL_J0(X)
| X | The type shall be REAL. |
The return value is of type REAL and lies in the
range - 0.4027... \leq Bessel (0,x) \leq 1. It has the same
kind as X.
program test_besj0 real(8) :: x = 0.0_8 x = bessel_j0(x) end program test_besj0
| Name | Argument | Return type | Standard |
DBESJ0(X) | REAL(8) X | REAL(8) | GNU extension |
Next: BESSEL_JN — Bessel function of the first kind, Previous: BESSEL_J0 — Bessel function of the first kind of order 0, Up: Intrinsic Procedures [Contents][Index]
BESSEL_J1 — Bessel function of the first kind of order 1BESSEL_J1(X) computes the Bessel function of the first kind of
order 1 of X. This function is available under the name
BESJ1 as a GNU extension.
Fortran 2008
Elemental function
RESULT = BESSEL_J1(X)
| X | The type shall be REAL. |
The return value is of type REAL and lies in the
range - 0.5818... \leq Bessel (0,x) \leq 0.5818 . It has the same
kind as X.
program test_besj1 real(8) :: x = 1.0_8 x = bessel_j1(x) end program test_besj1
| Name | Argument | Return type | Standard |
DBESJ1(X) | REAL(8) X | REAL(8) | GNU extension |
Next: BESSEL_Y0 — Bessel function of the second kind of order 0, Previous: BESSEL_J1 — Bessel function of the first kind of order 1, Up: Intrinsic Procedures [Contents][Index]
BESSEL_JN — Bessel function of the first kindBESSEL_JN(N, X) computes the Bessel function of the first kind of
order N of X. This function is available under the name
BESJN as a GNU extension. If N and X are arrays,
their ranks and shapes shall conform.
BESSEL_JN(N1, N2, X) returns an array with the Bessel functions
of the first kind of the orders N1 to N2.
Fortran 2008 and later, negative N is allowed as GNU extension
Elemental function, except for the transformational function
BESSEL_JN(N1, N2, X)
RESULT = BESSEL_JN(N, X) |
RESULT = BESSEL_JN(N1, N2, X) |
| N | Shall be a scalar or an array of type INTEGER. |
| N1 | Shall be a non-negative scalar of type INTEGER. |
| N2 | Shall be a non-negative scalar of type INTEGER. |
| X | Shall be a scalar or an array of type REAL;
for BESSEL_JN(N1, N2, X) it shall be scalar. |
The return value is a scalar of type REAL. It has the same
kind as X.
The transformational function uses a recurrence algorithm which might, for some values of X, lead to different results than calls to the elemental function.
program test_besjn real(8) :: x = 1.0_8 x = bessel_jn(5,x) end program test_besjn
| Name | Argument | Return type | Standard |
DBESJN(N, X) | INTEGER N | REAL(8) | GNU extension |
REAL(8) X |
Next: BESSEL_Y1 — Bessel function of the second kind of order 1, Previous: BESSEL_JN — Bessel function of the first kind, Up: Intrinsic Procedures [Contents][Index]
BESSEL_Y0 — Bessel function of the second kind of order 0BESSEL_Y0(X) computes the Bessel function of the second kind of
order 0 of X. This function is available under the name
BESY0 as a GNU extension.
Fortran 2008 and later
Elemental function
RESULT = BESSEL_Y0(X)
| X | The type shall be REAL. |
The return value is of type REAL. It has the same kind as X.
program test_besy0 real(8) :: x = 0.0_8 x = bessel_y0(x) end program test_besy0
| Name | Argument | Return type | Standard |
DBESY0(X) | REAL(8) X | REAL(8) | GNU extension |
Next: BESSEL_YN — Bessel function of the second kind, Previous: BESSEL_Y0 — Bessel function of the second kind of order 0, Up: Intrinsic Procedures [Contents][Index]
BESSEL_Y1 — Bessel function of the second kind of order 1BESSEL_Y1(X) computes the Bessel function of the second kind of
order 1 of X. This function is available under the name
BESY1 as a GNU extension.
Fortran 2008 and later
Elemental function
RESULT = BESSEL_Y1(X)
| X | The type shall be REAL. |
The return value is of type REAL. It has the same kind as X.
program test_besy1 real(8) :: x = 1.0_8 x = bessel_y1(x) end program test_besy1
| Name | Argument | Return type | Standard |
DBESY1(X) | REAL(8) X | REAL(8) | GNU extension |
Next: BGE — Bitwise greater than or equal to, Previous: BESSEL_Y1 — Bessel function of the second kind of order 1, Up: Intrinsic Procedures [Contents][Index]
BESSEL_YN — Bessel function of the second kindBESSEL_YN(N, X) computes the Bessel function of the second kind of
order N of X. This function is available under the name
BESYN as a GNU extension. If N and X are arrays,
their ranks and shapes shall conform.
BESSEL_YN(N1, N2, X) returns an array with the Bessel functions
of the first kind of the orders N1 to N2.
Fortran 2008 and later, negative N is allowed as GNU extension
Elemental function, except for the transformational function
BESSEL_YN(N1, N2, X)
RESULT = BESSEL_YN(N, X) |
RESULT = BESSEL_YN(N1, N2, X) |
| N | Shall be a scalar or an array of type INTEGER . |
| N1 | Shall be a non-negative scalar of type INTEGER. |
| N2 | Shall be a non-negative scalar of type INTEGER. |
| X | Shall be a scalar or an array of type REAL;
for BESSEL_YN(N1, N2, X) it shall be scalar. |
The return value is a scalar of type REAL. It has the same
kind as X.
The transformational function uses a recurrence algorithm which might, for some values of X, lead to different results than calls to the elemental function.
program test_besyn real(8) :: x = 1.0_8 x = bessel_yn(5,x) end program test_besyn
| Name | Argument | Return type | Standard |
DBESYN(N,X) | INTEGER N | REAL(8) | GNU extension |
REAL(8) X |
Next: BGT — Bitwise greater than, Previous: BESSEL_YN — Bessel function of the second kind, Up: Intrinsic Procedures [Contents][Index]
BGE — Bitwise greater than or equal toDetermines whether an integral is a bitwise greater than or equal to another.
Fortran 2008 and later
Elemental function
RESULT = BGE(I, J)
| I | Shall be of INTEGER type. |
| J | Shall be of INTEGER type, and of the same kind
as I. |
The return value is of type LOGICAL and of the default kind.
BGT — Bitwise greater than,
BLE — Bitwise less than or equal to,
BLT — Bitwise less than
Next: BIT_SIZE — Bit size inquiry function, Previous: BGE — Bitwise greater than or equal to, Up: Intrinsic Procedures [Contents][Index]
BGT — Bitwise greater thanDetermines whether an integral is a bitwise greater than another.
Fortran 2008 and later
Elemental function
RESULT = BGT(I, J)
| I | Shall be of INTEGER type. |
| J | Shall be of INTEGER type, and of the same kind
as I. |
The return value is of type LOGICAL and of the default kind.
BGE — Bitwise greater than or equal to,
BLE — Bitwise less than or equal to,
BLT — Bitwise less than
Next: BLE — Bitwise less than or equal to, Previous: BGT — Bitwise greater than, Up: Intrinsic Procedures [Contents][Index]
BIT_SIZE — Bit size inquiry functionBIT_SIZE(I) returns the number of bits (integer precision plus sign bit)
represented by the type of I. The result of BIT_SIZE(I) is
independent of the actual value of I.
Fortran 90 and later
Inquiry function
RESULT = BIT_SIZE(I)
| I | The type shall be INTEGER. |
The return value is of type INTEGER
program test_bit_size
integer :: i = 123
integer :: size
size = bit_size(i)
print *, size
end program test_bit_size
Next: BLT — Bitwise less than, Previous: BIT_SIZE — Bit size inquiry function, Up: Intrinsic Procedures [Contents][Index]
BLE — Bitwise less than or equal toDetermines whether an integral is a bitwise less than or equal to another.
Fortran 2008 and later
Elemental function
RESULT = BLE(I, J)
| I | Shall be of INTEGER type. |
| J | Shall be of INTEGER type, and of the same kind
as I. |
The return value is of type LOGICAL and of the default kind.
BGT — Bitwise greater than,
BGE — Bitwise greater than or equal to,
BLT — Bitwise less than
Next: BTEST — Bit test function, Previous: BLE — Bitwise less than or equal to, Up: Intrinsic Procedures [Contents][Index]
BLT — Bitwise less thanDetermines whether an integral is a bitwise less than another.
Fortran 2008 and later
Elemental function
RESULT = BLT(I, J)
| I | Shall be of INTEGER type. |
| J | Shall be of INTEGER type, and of the same kind
as I. |
The return value is of type LOGICAL and of the default kind.
BGE — Bitwise greater than or equal to,
BGT — Bitwise greater than,
BLE — Bitwise less than or equal to
Next: C_ASSOCIATED — Status of a C pointer, Previous: BLT — Bitwise less than, Up: Intrinsic Procedures [Contents][Index]
BTEST — Bit test functionBTEST(I,POS) returns logical .TRUE. if the bit at POS
in I is set. The counting of the bits starts at 0.
Fortran 90 and later, has overloads that are GNU extensions
Elemental function
RESULT = BTEST(I, POS)
| I | The type shall be INTEGER. |
| POS | The type shall be INTEGER. |
The return value is of type LOGICAL
program test_btest
integer :: i = 32768 + 1024 + 64
integer :: pos
logical :: bool
do pos=0,16
bool = btest(i, pos)
print *, pos, bool
end do
end program test_btest
| Name | Argument | Return type | Standard |
BTEST(I,POS) | INTEGER I,POS | LOGICAL | Fortran 95 and later |
BBTEST(I,POS) | INTEGER(1) I,POS | LOGICAL(1) | GNU extension |
BITEST(I,POS) | INTEGER(2) I,POS | LOGICAL(2) | GNU extension |
BJTEST(I,POS) | INTEGER(4) I,POS | LOGICAL(4) | GNU extension |
BKTEST(I,POS) | INTEGER(8) I,POS | LOGICAL(8) | GNU extension |
Next: C_F_POINTER — Convert C into Fortran pointer, Previous: BTEST — Bit test function, Up: Intrinsic Procedures [Contents][Index]
C_ASSOCIATED — Status of a C pointerC_ASSOCIATED(c_ptr_1[, c_ptr_2]) determines the status of the C pointer
c_ptr_1 or if c_ptr_1 is associated with the target c_ptr_2.
Fortran 2003 and later
Inquiry function
RESULT = C_ASSOCIATED(c_ptr_1[, c_ptr_2])
| c_ptr_1 | Scalar of the type C_PTR or C_FUNPTR. |
| c_ptr_2 | (Optional) Scalar of the same type as c_ptr_1. |
The return value is of type LOGICAL; it is .false. if either
c_ptr_1 is a C NULL pointer or if c_ptr1 and c_ptr_2
point to different addresses.
subroutine association_test(a,b)
use iso_c_binding, only: c_associated, c_loc, c_ptr
implicit none
real, pointer :: a
type(c_ptr) :: b
if(c_associated(b, c_loc(a))) &
stop 'b and a do not point to same target'
end subroutine association_test
C_LOC — Obtain the C address of an object,
C_FUNLOC — Obtain the C address of a procedure
Next: C_F_PROCPOINTER — Convert C into Fortran procedure pointer, Previous: C_ASSOCIATED — Status of a C pointer, Up: Intrinsic Procedures [Contents][Index]
C_F_POINTER — Convert C into Fortran pointerC_F_POINTER(CPTR, FPTR[, SHAPE]) assigns the target of the C pointer
CPTR to the Fortran pointer FPTR and specifies its shape.
Fortran 2003 and later
Subroutine
CALL C_F_POINTER(CPTR, FPTR[, SHAPE])
| CPTR | scalar of the type C_PTR. It is
INTENT(IN). |
| FPTR | pointer interoperable with cptr. It is
INTENT(OUT). |
| SHAPE | (Optional) Rank-one array of type INTEGER
with INTENT(IN). It shall be present
if and only if fptr is an array. The size
must be equal to the rank of fptr. |
program main
use iso_c_binding
implicit none
interface
subroutine my_routine(p) bind(c,name='myC_func')
import :: c_ptr
type(c_ptr), intent(out) :: p
end subroutine
end interface
type(c_ptr) :: cptr
real,pointer :: a(:)
call my_routine(cptr)
call c_f_pointer(cptr, a, [12])
end program main
C_LOC — Obtain the C address of an object,
C_F_PROCPOINTER — Convert C into Fortran procedure pointer
Next: C_FUNLOC — Obtain the C address of a procedure, Previous: C_F_POINTER — Convert C into Fortran pointer, Up: Intrinsic Procedures [Contents][Index]
C_F_PROCPOINTER — Convert C into Fortran procedure pointerC_F_PROCPOINTER(CPTR, FPTR) Assign the target of the C function pointer
CPTR to the Fortran procedure pointer FPTR.
Fortran 2003 and later
Subroutine
CALL C_F_PROCPOINTER(cptr, fptr)
| CPTR | scalar of the type C_FUNPTR. It is
INTENT(IN). |
| FPTR | procedure pointer interoperable with cptr. It is
INTENT(OUT). |
program main
use iso_c_binding
implicit none
abstract interface
function func(a)
import :: c_float
real(c_float), intent(in) :: a
real(c_float) :: func
end function
end interface
interface
function getIterFunc() bind(c,name="getIterFunc")
import :: c_funptr
type(c_funptr) :: getIterFunc
end function
end interface
type(c_funptr) :: cfunptr
procedure(func), pointer :: myFunc
cfunptr = getIterFunc()
call c_f_procpointer(cfunptr, myFunc)
end program main
C_LOC — Obtain the C address of an object,
C_F_POINTER — Convert C into Fortran pointer
Next: C_LOC — Obtain the C address of an object, Previous: C_F_PROCPOINTER — Convert C into Fortran procedure pointer, Up: Intrinsic Procedures [Contents][Index]
C_FUNLOC — Obtain the C address of a procedureC_FUNLOC(x) determines the C address of the argument.
Fortran 2003 and later
Inquiry function
RESULT = C_FUNLOC(x)
| x | Interoperable function or pointer to such function. |
The return value is of type C_FUNPTR and contains the C address
of the argument.
module x
use iso_c_binding
implicit none
contains
subroutine sub(a) bind(c)
real(c_float) :: a
a = sqrt(a)+5.0
end subroutine sub
end module x
program main
use iso_c_binding
use x
implicit none
interface
subroutine my_routine(p) bind(c,name='myC_func')
import :: c_funptr
type(c_funptr), intent(in) :: p
end subroutine
end interface
call my_routine(c_funloc(sub))
end program main
C_ASSOCIATED — Status of a C pointer,
C_LOC — Obtain the C address of an object,
C_F_POINTER — Convert C into Fortran pointer,
C_F_PROCPOINTER — Convert C into Fortran procedure pointer
Next: C_SIZEOF — Size in bytes of an expression, Previous: C_FUNLOC — Obtain the C address of a procedure, Up: Intrinsic Procedures [Contents][Index]
C_LOC — Obtain the C address of an objectC_LOC(X) determines the C address of the argument.
Fortran 2003 and later
Inquiry function
RESULT = C_LOC(X)
| X | Shall have either the POINTER or TARGET attribute. It shall not be a coindexed object. It shall either be a variable with interoperable type and kind type parameters, or be a scalar, nonpolymorphic variable with no length type parameters. |
The return value is of type C_PTR and contains the C address
of the argument.
subroutine association_test(a,b)
use iso_c_binding, only: c_associated, c_loc, c_ptr
implicit none
real, pointer :: a
type(c_ptr) :: b
if(c_associated(b, c_loc(a))) &
stop 'b and a do not point to same target'
end subroutine association_test
C_ASSOCIATED — Status of a C pointer,
C_FUNLOC — Obtain the C address of a procedure,
C_F_POINTER — Convert C into Fortran pointer,
C_F_PROCPOINTER — Convert C into Fortran procedure pointer
Next: CEILING — Integer ceiling function, Previous: C_LOC — Obtain the C address of an object, Up: Intrinsic Procedures [Contents][Index]
C_SIZEOF — Size in bytes of an expressionC_SIZEOF(X) calculates the number of bytes of storage the
expression X occupies.
Fortran 2008
Inquiry function of the module ISO_C_BINDING
N = C_SIZEOF(X)
| X | The argument shall be an interoperable data entity. |
The return value is of type integer and of the system-dependent kind
C_SIZE_T (from the ISO_C_BINDING module). Its value is the
number of bytes occupied by the argument. If the argument has the
POINTER attribute, the number of bytes of the storage area pointed
to is returned. If the argument is of a derived type with POINTER
or ALLOCATABLE components, the return value does not account for
the sizes of the data pointed to by these components.
use iso_c_binding integer(c_int) :: i real(c_float) :: r, s(5) print *, (c_sizeof(s)/c_sizeof(r) == 5) end
The example will print T unless you are using a platform
where default REAL variables are unusually padded.
SIZEOF — Size in bytes of an expression,
STORAGE_SIZE — Storage size in bits
Next: CHAR — Character conversion function, Previous: C_SIZEOF — Size in bytes of an expression, Up: Intrinsic Procedures [Contents][Index]
CEILING — Integer ceiling functionCEILING(A) returns the least integer greater than or equal to A.
Fortran 95 and later
Elemental function
RESULT = CEILING(A [, KIND])
| A | The type shall be REAL. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type INTEGER(KIND) if KIND is present
and a default-kind INTEGER otherwise.
program test_ceiling
real :: x = 63.29
real :: y = -63.59
print *, ceiling(x) ! returns 64
print *, ceiling(y) ! returns -63
end program test_ceiling
Next: CHDIR — Change working directory, Previous: CEILING — Integer ceiling function, Up: Intrinsic Procedures [Contents][Index]
CHAR — Character conversion functionCHAR(I [, KIND]) returns the character represented by the integer I.
Fortran 77 and later
Elemental function
RESULT = CHAR(I [, KIND])
| I | The type shall be INTEGER. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type CHARACTER(1)
program test_char
integer :: i = 74
character(1) :: c
c = char(i)
print *, i, c ! returns 'J'
end program test_char
| Name | Argument | Return type | Standard |
CHAR(I) | INTEGER I | CHARACTER(LEN=1) | Fortran 77 and later |
See ICHAR — Character-to-integer conversion function for a discussion of converting between numerical values
and formatted string representations.
ACHAR — Character in ASCII collating sequence,
IACHAR — Code in ASCII collating sequence,
ICHAR — Character-to-integer conversion function
Next: CHMOD — Change access permissions of files, Previous: CHAR — Character conversion function, Up: Intrinsic Procedures [Contents][Index]
CHDIR — Change working directoryChange current working directory to a specified path.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
Subroutine, function
CALL CHDIR(NAME [, STATUS]) |
STATUS = CHDIR(NAME) |
| NAME | The type shall be CHARACTER of default
kind and shall specify a valid path within the file system. |
| STATUS | (Optional) INTEGER status flag of the default
kind. Returns 0 on success, and a system specific and nonzero error code
otherwise. |
PROGRAM test_chdir
CHARACTER(len=255) :: path
CALL getcwd(path)
WRITE(*,*) TRIM(path)
CALL chdir("/tmp")
CALL getcwd(path)
WRITE(*,*) TRIM(path)
END PROGRAM
Next: CMPLX — Complex conversion function, Previous: CHDIR — Change working directory, Up: Intrinsic Procedures [Contents][Index]
CHMOD — Change access permissions of filesCHMOD changes the permissions of a file.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
Subroutine, function
CALL CHMOD(NAME, MODE[, STATUS]) |
STATUS = CHMOD(NAME, MODE) |
| NAME | Scalar CHARACTER of default kind with the
file name. Trailing blanks are ignored unless the character
achar(0) is present, then all characters up to and excluding
achar(0) are used as the file name. |
| MODE | Scalar CHARACTER of default kind giving the
file permission. MODE uses the same syntax as the chmod utility
as defined by the POSIX standard. The argument shall either be a string of
a nonnegative octal number or a symbolic mode. |
| STATUS | (optional) scalar INTEGER, which is
0 on success and nonzero otherwise. |
In either syntax, STATUS is set to 0 on success and nonzero
otherwise.
CHMOD as subroutine
program chmod_test
implicit none
integer :: status
call chmod('test.dat','u+x',status)
print *, 'Status: ', status
end program chmod_test
CHMOD as function:
program chmod_test
implicit none
integer :: status
status = chmod('test.dat','u+x')
print *, 'Status: ', status
end program chmod_test
Next: CO_BROADCAST — Copy a value to all images the current set of images, Previous: CHMOD — Change access permissions of files, Up: Intrinsic Procedures [Contents][Index]
CMPLX — Complex conversion functionCMPLX(X [, Y [, KIND]]) returns a complex number where X is converted to
the real component. If Y is present it is converted to the imaginary
component. If Y is not present then the imaginary component is set to
0.0. If X is complex then Y must not be present.
Fortran 77 and later
Elemental function
RESULT = CMPLX(X [, Y [, KIND]])
| X | The type may be INTEGER, REAL,
or COMPLEX. |
| Y | (Optional; only allowed if X is not
COMPLEX.) May be INTEGER or REAL. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of COMPLEX type, with a kind equal to
KIND if it is specified. If KIND is not specified, the
result is of the default COMPLEX kind, regardless of the kinds of
X and Y.
program test_cmplx
integer :: i = 42
real :: x = 3.14
complex :: z
z = cmplx(i, x)
print *, z, cmplx(x)
end program test_cmplx
Next: CO_MAX — Maximal value on the current set of images, Previous: CMPLX — Complex conversion function, Up: Intrinsic Procedures [Contents][Index]
CO_BROADCAST — Copy a value to all images the current set of imagesCO_BROADCAST copies the value of argument A on the image with
image index SOURCE_IMAGE to all images in the current team. A
becomes defined as if by intrinsic assignment. If the execution was
successful and STAT is present, it is assigned the value zero. If the
execution failed, STAT gets assigned a nonzero value and, if present,
ERRMSG gets assigned a value describing the occurred error.
Technical Specification (TS) 18508 or later
Collective subroutine
CALL CO_BROADCAST(A, SOURCE_IMAGE [, STAT, ERRMSG])
| A | INTENT(INOUT) argument; shall have the same dynamic type and type parameters on all images of the current team. If it is an array, it shall have the same shape on all images. |
| SOURCE_IMAGE | a scalar integer expression. It shall have the same value on all images and refer to an image of the current team. |
| STAT | (optional) a scalar integer variable |
| ERRMSG | (optional) a scalar character variable |
program test
integer :: val(3)
if (this_image() == 1) then
val = [1, 5, 3]
end if
call co_broadcast (val, source_image=1)
print *, this_image, ":", val
end program test
CO_MAX — Maximal value on the current set of images,
CO_MIN — Minimal value on the current set of images,
CO_SUM — Sum of values on the current set of images,
CO_REDUCE — Reduction of values on the current set of images
Next: CO_MIN — Minimal value on the current set of images, Previous: CO_BROADCAST — Copy a value to all images the current set of images, Up: Intrinsic Procedures [Contents][Index]
CO_MAX — Maximal value on the current set of imagesCO_MAX determines element-wise the maximal value of A on all
images of the current team. If RESULT_IMAGE is present, the maximum
values are returned in A on the specified image only and the value
of A on the other images become undefined. If RESULT_IMAGE is
not present, the value is returned on all images. If the execution was
successful and STAT is present, it is assigned the value zero. If the
execution failed, STAT gets assigned a nonzero value and, if present,
ERRMSG gets assigned a value describing the occurred error.
Technical Specification (TS) 18508 or later
Collective subroutine
CALL CO_MAX(A [, RESULT_IMAGE, STAT, ERRMSG])
| A | shall be an integer, real or character variable, which has the same type and type parameters on all images of the team. |
| RESULT_IMAGE | (optional) a scalar integer expression; if present, it shall have the same value on all images and refer to an image of the current team. |
| STAT | (optional) a scalar integer variable |
| ERRMSG | (optional) a scalar character variable |
program test
integer :: val
val = this_image ()
call co_max (val, result_image=1)
if (this_image() == 1) then
write(*,*) "Maximal value", val ! prints num_images()
end if
end program test
CO_MIN — Minimal value on the current set of images,
CO_SUM — Sum of values on the current set of images,
CO_REDUCE — Reduction of values on the current set of images,
CO_BROADCAST — Copy a value to all images the current set of images
Next: CO_REDUCE — Reduction of values on the current set of images, Previous: CO_MAX — Maximal value on the current set of images, Up: Intrinsic Procedures [Contents][Index]
CO_MIN — Minimal value on the current set of imagesCO_MIN determines element-wise the minimal value of A on all
images of the current team. If RESULT_IMAGE is present, the minimal
values are returned in A on the specified image only and the value
of A on the other images become undefined. If RESULT_IMAGE is
not present, the value is returned on all images. If the execution was
successful and STAT is present, it is assigned the value zero. If the
execution failed, STAT gets assigned a nonzero value and, if present,
ERRMSG gets assigned a value describing the occurred error.
Technical Specification (TS) 18508 or later
Collective subroutine
CALL CO_MIN(A [, RESULT_IMAGE, STAT, ERRMSG])
| A | shall be an integer, real or character variable, which has the same type and type parameters on all images of the team. |
| RESULT_IMAGE | (optional) a scalar integer expression; if present, it shall have the same value on all images and refer to an image of the current team. |
| STAT | (optional) a scalar integer variable |
| ERRMSG | (optional) a scalar character variable |
program test
integer :: val
val = this_image ()
call co_min (val, result_image=1)
if (this_image() == 1) then
write(*,*) "Minimal value", val ! prints 1
end if
end program test
CO_MAX — Maximal value on the current set of images,
CO_SUM — Sum of values on the current set of images,
CO_REDUCE — Reduction of values on the current set of images,
CO_BROADCAST — Copy a value to all images the current set of images
Next: CO_SUM — Sum of values on the current set of images, Previous: CO_MIN — Minimal value on the current set of images, Up: Intrinsic Procedures [Contents][Index]
CO_REDUCE — Reduction of values on the current set of imagesCO_REDUCE determines element-wise the reduction of the value of A
on all images of the current team. The pure function passed as OPERATOR
is used to pairwise reduce the values of A by passing either the value
of A of different images or the result values of such a reduction as
argument. If A is an array, the deduction is done element wise. If
RESULT_IMAGE is present, the result values are returned in A on
the specified image only and the value of A on the other images become
undefined. If RESULT_IMAGE is not present, the value is returned on all
images. If the execution was successful and STAT is present, it is
assigned the value zero. If the execution failed, STAT gets assigned
a nonzero value and, if present, ERRMSG gets assigned a value describing
the occurred error.
Technical Specification (TS) 18508 or later
Collective subroutine
CALL CO_REDUCE(A, OPERATOR, [, RESULT_IMAGE, STAT, ERRMSG])
| A | is an INTENT(INOUT) argument and shall be
nonpolymorphic. If it is allocatable, it shall be allocated; if it is a pointer,
it shall be associated. A shall have the same type and type parameters on
all images of the team; if it is an array, it shall have the same shape on all
images. |
| OPERATOR | pure function with two scalar nonallocatable arguments, which shall be nonpolymorphic and have the same type and type parameters as A. The function shall return a nonallocatable scalar of the same type and type parameters as A. The function shall be the same on all images and with regards to the arguments mathematically commutative and associative. Note that OPERATOR may not be an elemental function, unless it is an intrisic function. |
| RESULT_IMAGE | (optional) a scalar integer expression; if present, it shall have the same value on all images and refer to an image of the current team. |
| STAT | (optional) a scalar integer variable |
| ERRMSG | (optional) a scalar character variable |
program test
integer :: val
val = this_image ()
call co_reduce (val, result_image=1, operator=myprod)
if (this_image() == 1) then
write(*,*) "Product value", val ! prints num_images() factorial
end if
contains
pure function myprod(a, b)
integer, value :: a, b
integer :: myprod
myprod = a * b
end function myprod
end program test
While the rules permit in principle an intrinsic function, none of the intrinsics in the standard fulfill the criteria of having a specific function, which takes two arguments of the same type and returning that type as result.
CO_MIN — Minimal value on the current set of images,
CO_MAX — Maximal value on the current set of images,
CO_SUM — Sum of values on the current set of images,
CO_BROADCAST — Copy a value to all images the current set of images
Next: COMMAND_ARGUMENT_COUNT — Get number of command line arguments, Previous: CO_REDUCE — Reduction of values on the current set of images, Up: Intrinsic Procedures [Contents][Index]
CO_SUM — Sum of values on the current set of imagesCO_SUM sums up the values of each element of A on all
images of the current team. If RESULT_IMAGE is present, the summed-up
values are returned in A on the specified image only and the value
of A on the other images become undefined. If RESULT_IMAGE is
not present, the value is returned on all images. If the execution was
successful and STAT is present, it is assigned the value zero. If the
execution failed, STAT gets assigned a nonzero value and, if present,
ERRMSG gets assigned a value describing the occurred error.
Technical Specification (TS) 18508 or later
Collective subroutine
CALL CO_SUM(A [, RESULT_IMAGE, STAT, ERRMSG])
| A | shall be an integer, real or complex variable, which has the same type and type parameters on all images of the team. |
| RESULT_IMAGE | (optional) a scalar integer expression; if present, it shall have the same value on all images and refer to an image of the current team. |
| STAT | (optional) a scalar integer variable |
| ERRMSG | (optional) a scalar character variable |
program test
integer :: val
val = this_image ()
call co_sum (val, result_image=1)
if (this_image() == 1) then
write(*,*) "The sum is ", val ! prints (n**2 + n)/2,
! with n = num_images()
end if
end program test
CO_MAX — Maximal value on the current set of images,
CO_MIN — Minimal value on the current set of images,
CO_REDUCE — Reduction of values on the current set of images,
CO_BROADCAST — Copy a value to all images the current set of images
Next: COMPILER_OPTIONS — Options passed to the compiler, Previous: CO_SUM — Sum of values on the current set of images, Up: Intrinsic Procedures [Contents][Index]
COMMAND_ARGUMENT_COUNT — Get number of command line argumentsCOMMAND_ARGUMENT_COUNT returns the number of arguments passed on the
command line when the containing program was invoked.
Fortran 2003 and later
Inquiry function
RESULT = COMMAND_ARGUMENT_COUNT()
| None |
The return value is an INTEGER of default kind.
program test_command_argument_count
integer :: count
count = command_argument_count()
print *, count
end program test_command_argument_count
GET_COMMAND — Get the entire command line,
GET_COMMAND_ARGUMENT — Get command line arguments
Next: COMPILER_VERSION — Compiler version string, Previous: COMMAND_ARGUMENT_COUNT — Get number of command line arguments, Up: Intrinsic Procedures [Contents][Index]
COMPILER_OPTIONS — Options passed to the compilerCOMPILER_OPTIONS returns a string with the options used for
compiling.
Fortran 2008
Inquiry function of the module ISO_FORTRAN_ENV
STR = COMPILER_OPTIONS()
None
The return value is a default-kind string with system-dependent length.
It contains the compiler flags used to compile the file, which called
the COMPILER_OPTIONS intrinsic.
use iso_fortran_env
print '(4a)', 'This file was compiled by ', &
compiler_version(), ' using the options ', &
compiler_options()
end
Next: COMPLEX — Complex conversion function, Previous: COMPILER_OPTIONS — Options passed to the compiler, Up: Intrinsic Procedures [Contents][Index]
COMPILER_VERSION — Compiler version stringCOMPILER_VERSION returns a string with the name and the
version of the compiler.
Fortran 2008
Inquiry function of the module ISO_FORTRAN_ENV
STR = COMPILER_VERSION()
None
The return value is a default-kind string with system-dependent length. It contains the name of the compiler and its version number.
use iso_fortran_env
print '(4a)', 'This file was compiled by ', &
compiler_version(), ' using the options ', &
compiler_options()
end
COMPILER_OPTIONS — Options passed to the compiler,
ISO_FORTRAN_ENV
Next: CONJG — Complex conjugate function, Previous: COMPILER_VERSION — Compiler version string, Up: Intrinsic Procedures [Contents][Index]
COMPLEX — Complex conversion functionCOMPLEX(X, Y) returns a complex number where X is converted
to the real component and Y is converted to the imaginary
component.
GNU extension
Elemental function
RESULT = COMPLEX(X, Y)
| X | The type may be INTEGER or REAL. |
| Y | The type may be INTEGER or REAL. |
If X and Y are both of INTEGER type, then the return
value is of default COMPLEX type.
If X and Y are of REAL type, or one is of REAL
type and one is of INTEGER type, then the return value is of
COMPLEX type with a kind equal to that of the REAL
argument with the highest precision.
program test_complex
integer :: i = 42
real :: x = 3.14
print *, complex(i, x)
end program test_complex
Next: COS — Cosine function, Previous: COMPLEX — Complex conversion function, Up: Intrinsic Procedures [Contents][Index]
CONJG — Complex conjugate functionCONJG(Z) returns the conjugate of Z. If Z is (x, y)
then the result is (x, -y)
Fortran 77 and later, has an overload that is a GNU extension
Elemental function
Z = CONJG(Z)
| Z | The type shall be COMPLEX. |
The return value is of type COMPLEX.
program test_conjg
complex :: z = (2.0, 3.0)
complex(8) :: dz = (2.71_8, -3.14_8)
z= conjg(z)
print *, z
dz = dconjg(dz)
print *, dz
end program test_conjg
| Name | Argument | Return type | Standard |
DCONJG(Z) | COMPLEX(8) Z | COMPLEX(8) | GNU extension |
Next: COSD — Cosine function, degrees, Previous: CONJG — Complex conjugate function, Up: Intrinsic Procedures [Contents][Index]
COS — Cosine functionCOS(X) computes the cosine of X.
Fortran 77 and later, has overloads that are GNU extensions
Elemental function
RESULT = COS(X)
| X | The type shall be REAL or
COMPLEX. |
The return value is of the same type and kind as X. The real part
of the result is in radians. If X is of the type REAL,
the return value lies in the range -1 \leq \cos (x) \leq 1.
program test_cos real :: x = 0.0 x = cos(x) end program test_cos
| Name | Argument | Return type | Standard |
COS(X) | REAL(4) X | REAL(4) | Fortran 77 and later |
DCOS(X) | REAL(8) X | REAL(8) | Fortran 77 and later |
CCOS(X) | COMPLEX(4) X | COMPLEX(4) | Fortran 77 and later |
ZCOS(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension |
CDCOS(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension |
Inverse function:
ACOS — Arccosine function
Degrees function:
COSD — Cosine function, degrees
Next: COSH — Hyperbolic cosine function, Previous: COS — Cosine function, Up: Intrinsic Procedures [Contents][Index]
COSD — Cosine function, degreesCOSD(X) computes the cosine of X in degrees.
This function is for compatibility only and should be avoided in favor of standard constructs wherever possible.
GNU extension, enabled with -fdec-math.
Elemental function
RESULT = COSD(X)
| X | The type shall be REAL or
COMPLEX. |
The return value is of the same type and kind as X. The real part
of the result is in degrees. If X is of the type REAL,
the return value lies in the range -1 \leq \cosd (x) \leq 1.
program test_cosd real :: x = 0.0 x = cosd(x) end program test_cosd
| Name | Argument | Return type | Standard |
COSD(X) | REAL(4) X | REAL(4) | GNU extension |
DCOSD(X) | REAL(8) X | REAL(8) | GNU extension |
CCOSD(X) | COMPLEX(4) X | COMPLEX(4) | GNU extension |
ZCOSD(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension |
CDCOSD(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension |
Inverse function:
ACOSD — Arccosine function, degrees
Radians function:
COS — Cosine function
Next: COTAN — Cotangent function, Previous: COSD — Cosine function, degrees, Up: Intrinsic Procedures [Contents][Index]
COSH — Hyperbolic cosine functionCOSH(X) computes the hyperbolic cosine of X.
Fortran 77 and later, for a complex argument Fortran 2008 or later
Elemental function
X = COSH(X)
| X | The type shall be REAL or COMPLEX. |
The return value has same type and kind as X. If X is
complex, the imaginary part of the result is in radians. If X
is REAL, the return value has a lower bound of one,
\cosh (x) \geq 1.
program test_cosh real(8) :: x = 1.0_8 x = cosh(x) end program test_cosh
| Name | Argument | Return type | Standard |
COSH(X) | REAL(4) X | REAL(4) | Fortran 77 and later |
DCOSH(X) | REAL(8) X | REAL(8) | Fortran 77 and later |
Inverse function:
ACOSH — Inverse hyperbolic cosine function
Next: COTAND — Cotangent function, degrees, Previous: COSH — Hyperbolic cosine function, Up: Intrinsic Procedures [Contents][Index]
COTAN — Cotangent functionCOTAN(X) computes the cotangent of X. Equivalent to COS(x)
divided by SIN(x), or 1 / TAN(x).
This function is for compatibility only and should be avoided in favor of standard constructs wherever possible.
GNU extension, enabled with -fdec-math.
Elemental function
RESULT = COTAN(X)
| X | The type shall be REAL or COMPLEX. |
The return value has same type and kind as X, and its value is in radians.
program test_cotan real(8) :: x = 0.165_8 x = cotan(x) end program test_cotan
| Name | Argument | Return type | Standard |
COTAN(X) | REAL(4) X | REAL(4) | GNU extension |
DCOTAN(X) | REAL(8) X | REAL(8) | GNU extension |
Converse function:
TAN — Tangent function
Degrees function:
COTAND — Cotangent function, degrees
Next: COUNT — Count function, Previous: COTAN — Cotangent function, Up: Intrinsic Procedures [Contents][Index]
COTAND — Cotangent function, degreesCOTAND(X) computes the cotangent of X in degrees. Equivalent to
COSD(x) divided by SIND(x), or 1 / TAND(x).
GNU extension, enabled with -fdec-math.
This function is for compatibility only and should be avoided in favor of standard constructs wherever possible.
Elemental function
RESULT = COTAND(X)
| X | The type shall be REAL or COMPLEX. |
The return value has same type and kind as X, and its value is in degrees.
program test_cotand real(8) :: x = 0.165_8 x = cotand(x) end program test_cotand
| Name | Argument | Return type | Standard |
COTAND(X) | REAL(4) X | REAL(4) | GNU extension |
DCOTAND(X) | REAL(8) X | REAL(8) | GNU extension |
Converse function:
TAND — Tangent function, degrees
Radians function:
COTAN — Cotangent function
Next: CPU_TIME — CPU elapsed time in seconds, Previous: COTAND — Cotangent function, degrees, Up: Intrinsic Procedures [Contents][Index]
COUNT — Count functionCounts the number of .TRUE. elements in a logical MASK,
or, if the DIM argument is supplied, counts the number of
elements along each row of the array in the DIM direction.
If the array has zero size, or all of the elements of MASK are
.FALSE., then the result is 0.
Fortran 90 and later, with KIND argument Fortran 2003 and later
Transformational function
RESULT = COUNT(MASK [, DIM, KIND])
| MASK | The type shall be LOGICAL. |
| DIM | (Optional) The type shall be INTEGER. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
If DIM is present, the result is an array with a rank one less
than the rank of ARRAY, and a size corresponding to the shape
of ARRAY with the DIM dimension removed.
program test_count
integer, dimension(2,3) :: a, b
logical, dimension(2,3) :: mask
a = reshape( (/ 1, 2, 3, 4, 5, 6 /), (/ 2, 3 /))
b = reshape( (/ 0, 7, 3, 4, 5, 8 /), (/ 2, 3 /))
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print *
print '(3i3)', b(1,:)
print '(3i3)', b(2,:)
print *
mask = a.ne.b
print '(3l3)', mask(1,:)
print '(3l3)', mask(2,:)
print *
print '(3i3)', count(mask)
print *
print '(3i3)', count(mask, 1)
print *
print '(3i3)', count(mask, 2)
end program test_count
Next: CSHIFT — Circular shift elements of an array, Previous: COUNT — Count function, Up: Intrinsic Procedures [Contents][Index]
CPU_TIME — CPU elapsed time in secondsReturns a REAL value representing the elapsed CPU time in
seconds. This is useful for testing segments of code to determine
execution time.
If a time source is available, time will be reported with microsecond
resolution. If no time source is available, TIME is set to
-1.0.
Note that TIME may contain a, system dependent, arbitrary offset
and may not start with 0.0. For CPU_TIME, the absolute
value is meaningless, only differences between subsequent calls to
this subroutine, as shown in the example below, should be used.
Fortran 95 and later
Subroutine
CALL CPU_TIME(TIME)
| TIME | The type shall be REAL with INTENT(OUT). |
None
program test_cpu_time
real :: start, finish
call cpu_time(start)
! put code to test here
call cpu_time(finish)
print '("Time = ",f6.3," seconds.")',finish-start
end program test_cpu_time
SYSTEM_CLOCK — Time function,
DATE_AND_TIME — Date and time subroutine
Next: CTIME — Convert a time into a string, Previous: CPU_TIME — CPU elapsed time in seconds, Up: Intrinsic Procedures [Contents][Index]
CSHIFT — Circular shift elements of an arrayCSHIFT(ARRAY, SHIFT [, DIM]) performs a circular shift on elements of
ARRAY along the dimension of DIM. If DIM is omitted it is
taken to be 1. DIM is a scalar of type INTEGER in the
range of 1 \leq DIM \leq n) where n is the rank of ARRAY.
If the rank of ARRAY is one, then all elements of ARRAY are shifted
by SHIFT places. If rank is greater than one, then all complete rank one
sections of ARRAY along the given dimension are shifted. Elements
shifted out one end of each rank one section are shifted back in the other end.
Fortran 90 and later
Transformational function
RESULT = CSHIFT(ARRAY, SHIFT [, DIM])
| ARRAY | Shall be an array of any type. |
| SHIFT | The type shall be INTEGER. |
| DIM | The type shall be INTEGER. |
Returns an array of same type and rank as the ARRAY argument.
program test_cshift
integer, dimension(3,3) :: a
a = reshape( (/ 1, 2, 3, 4, 5, 6, 7, 8, 9 /), (/ 3, 3 /))
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print '(3i3)', a(3,:)
a = cshift(a, SHIFT=(/1, 2, -1/), DIM=2)
print *
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print '(3i3)', a(3,:)
end program test_cshift
Next: DATE_AND_TIME — Date and time subroutine, Previous: CSHIFT — Circular shift elements of an array, Up: Intrinsic Procedures [Contents][Index]
CTIME — Convert a time into a stringCTIME converts a system time value, such as returned by
TIME8 — Time function (64-bit), to a string. The output will be of the form ‘Sat
Aug 19 18:13:14 1995’.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
Subroutine, function
CALL CTIME(TIME, RESULT). |
RESULT = CTIME(TIME). |
| TIME | The type shall be of type INTEGER. |
| RESULT | The type shall be of type CHARACTER and
of default kind. It is an INTENT(OUT) argument. If the length
of this variable is too short for the time and date string to fit
completely, it will be blank on procedure return. |
The converted date and time as a string.
program test_ctime
integer(8) :: i
character(len=30) :: date
i = time8()
! Do something, main part of the program
call ctime(i,date)
print *, 'Program was started on ', date
end program test_ctime
DATE_AND_TIME — Date and time subroutine,
GMTIME — Convert time to GMT info,
LTIME — Convert time to local time info,
TIME — Time function,
TIME8 — Time function (64-bit)
Next: DBLE — Double conversion function, Previous: CTIME — Convert a time into a string, Up: Intrinsic Procedures [Contents][Index]
DATE_AND_TIME — Date and time subroutineDATE_AND_TIME(DATE, TIME, ZONE, VALUES) gets the corresponding date and
time information from the real-time system clock. DATE is
INTENT(OUT) and has form ccyymmdd. TIME is INTENT(OUT) and
has form hhmmss.sss. ZONE is INTENT(OUT) and has form (+-)hhmm,
representing the difference with respect to Coordinated Universal Time (UTC).
Unavailable time and date parameters return blanks.
VALUES is INTENT(OUT) and provides the following:
VALUE(1): | The year |
VALUE(2): | The month |
VALUE(3): | The day of the month |
VALUE(4): | Time difference with UTC in minutes |
VALUE(5): | The hour of the day |
VALUE(6): | The minutes of the hour |
VALUE(7): | The seconds of the minute |
VALUE(8): | The milliseconds of the second |
Fortran 90 and later
Subroutine
CALL DATE_AND_TIME([DATE, TIME, ZONE, VALUES])
| DATE | (Optional) The type shall be CHARACTER(LEN=8)
or larger, and of default kind. |
| TIME | (Optional) The type shall be CHARACTER(LEN=10)
or larger, and of default kind. |
| ZONE | (Optional) The type shall be CHARACTER(LEN=5)
or larger, and of default kind. |
| VALUES | (Optional) The type shall be INTEGER(8). |
None
program test_time_and_date
character(8) :: date
character(10) :: time
character(5) :: zone
integer,dimension(8) :: values
! using keyword arguments
call date_and_time(date,time,zone,values)
call date_and_time(DATE=date,ZONE=zone)
call date_and_time(TIME=time)
call date_and_time(VALUES=values)
print '(a,2x,a,2x,a)', date, time, zone
print '(8i5)', values
end program test_time_and_date
CPU_TIME — CPU elapsed time in seconds,
SYSTEM_CLOCK — Time function
Next: DCMPLX — Double complex conversion function, Previous: DATE_AND_TIME — Date and time subroutine, Up: Intrinsic Procedures [Contents][Index]
DBLE — Double conversion functionDBLE(A) Converts A to double precision real type.
Fortran 77 and later
Elemental function
RESULT = DBLE(A)
| A | The type shall be INTEGER, REAL,
or COMPLEX. |
The return value is of type double precision real.
program test_dble
real :: x = 2.18
integer :: i = 5
complex :: z = (2.3,1.14)
print *, dble(x), dble(i), dble(z)
end program test_dble
Next: DIGITS — Significant binary digits function, Previous: DBLE — Double conversion function, Up: Intrinsic Procedures [Contents][Index]
DCMPLX — Double complex conversion functionDCMPLX(X [,Y]) returns a double complex number where X is
converted to the real component. If Y is present it is converted to the
imaginary component. If Y is not present then the imaginary component is
set to 0.0. If X is complex then Y must not be present.
GNU extension
Elemental function
RESULT = DCMPLX(X [, Y])
| X | The type may be INTEGER, REAL,
or COMPLEX. |
| Y | (Optional if X is not COMPLEX.) May be
INTEGER or REAL. |
The return value is of type COMPLEX(8)
program test_dcmplx
integer :: i = 42
real :: x = 3.14
complex :: z
z = cmplx(i, x)
print *, dcmplx(i)
print *, dcmplx(x)
print *, dcmplx(z)
print *, dcmplx(x,i)
end program test_dcmplx
Next: DIM — Positive difference, Previous: DCMPLX — Double complex conversion function, Up: Intrinsic Procedures [Contents][Index]
DIGITS — Significant binary digits functionDIGITS(X) returns the number of significant binary digits of the internal
model representation of X. For example, on a system using a 32-bit
floating point representation, a default real number would likely return 24.
Fortran 90 and later
Inquiry function
RESULT = DIGITS(X)
| X | The type may be INTEGER or REAL. |
The return value is of type INTEGER.
program test_digits
integer :: i = 12345
real :: x = 3.143
real(8) :: y = 2.33
print *, digits(i)
print *, digits(x)
print *, digits(y)
end program test_digits
Next: DOT_PRODUCT — Dot product function, Previous: DIGITS — Significant binary digits function, Up: Intrinsic Procedures [Contents][Index]
DIM — Positive differenceDIM(X,Y) returns the difference X-Y if the result is positive;
otherwise returns zero.
Fortran 77 and later
Elemental function
RESULT = DIM(X, Y)
| X | The type shall be INTEGER or REAL |
| Y | The type shall be the same type and kind as X. (As a GNU extension, arguments of different kinds are permitted.) |
The return value is of type INTEGER or REAL. (As a GNU
extension, kind is the largest kind of the actual arguments.)
program test_dim
integer :: i
real(8) :: x
i = dim(4, 15)
x = dim(4.345_8, 2.111_8)
print *, i
print *, x
end program test_dim
| Name | Argument | Return type | Standard |
DIM(X,Y) | REAL(4) X, Y | REAL(4) | Fortran 77 and later |
IDIM(X,Y) | INTEGER(4) X, Y | INTEGER(4) | Fortran 77 and later |
DDIM(X,Y) | REAL(8) X, Y | REAL(8) | Fortran 77 and later |
Next: DPROD — Double product function, Previous: DIM — Positive difference, Up: Intrinsic Procedures [Contents][Index]
DOT_PRODUCT — Dot product functionDOT_PRODUCT(VECTOR_A, VECTOR_B) computes the dot product multiplication
of two vectors VECTOR_A and VECTOR_B. The two vectors may be
either numeric or logical and must be arrays of rank one and of equal size. If
the vectors are INTEGER or REAL, the result is
SUM(VECTOR_A*VECTOR_B). If the vectors are COMPLEX, the result
is SUM(CONJG(VECTOR_A)*VECTOR_B). If the vectors are LOGICAL,
the result is ANY(VECTOR_A .AND. VECTOR_B).
Fortran 90 and later
Transformational function
RESULT = DOT_PRODUCT(VECTOR_A, VECTOR_B)
| VECTOR_A | The type shall be numeric or LOGICAL, rank 1. |
| VECTOR_B | The type shall be numeric if VECTOR_A is of numeric type or LOGICAL if VECTOR_A is of type LOGICAL. VECTOR_B shall be a rank-one array. |
If the arguments are numeric, the return value is a scalar of numeric type,
INTEGER, REAL, or COMPLEX. If the arguments are
LOGICAL, the return value is .TRUE. or .FALSE..
program test_dot_prod
integer, dimension(3) :: a, b
a = (/ 1, 2, 3 /)
b = (/ 4, 5, 6 /)
print '(3i3)', a
print *
print '(3i3)', b
print *
print *, dot_product(a,b)
end program test_dot_prod
Next: DREAL — Double real part function, Previous: DOT_PRODUCT — Dot product function, Up: Intrinsic Procedures [Contents][Index]
DPROD — Double product functionDPROD(X,Y) returns the product X*Y.
Fortran 77 and later
Elemental function
RESULT = DPROD(X, Y)
| X | The type shall be REAL. |
| Y | The type shall be REAL. |
The return value is of type REAL(8).
program test_dprod
real :: x = 5.2
real :: y = 2.3
real(8) :: d
d = dprod(x,y)
print *, d
end program test_dprod
| Name | Argument | Return type | Standard |
DPROD(X,Y) | REAL(4) X, Y | REAL(8) | Fortran 77 and later |
Next: DSHIFTL — Combined left shift, Previous: DPROD — Double product function, Up: Intrinsic Procedures [Contents][Index]
DREAL — Double real part functionDREAL(Z) returns the real part of complex variable Z.
GNU extension
Elemental function
RESULT = DREAL(A)
| A | The type shall be COMPLEX(8). |
The return value is of type REAL(8).
program test_dreal
complex(8) :: z = (1.3_8,7.2_8)
print *, dreal(z)
end program test_dreal
Next: DSHIFTR — Combined right shift, Previous: DREAL — Double real part function, Up: Intrinsic Procedures [Contents][Index]
DSHIFTL — Combined left shiftDSHIFTL(I, J, SHIFT) combines bits of I and J. The
rightmost SHIFT bits of the result are the leftmost SHIFT
bits of J, and the remaining bits are the rightmost bits of
I.
Fortran 2008 and later
Elemental function
RESULT = DSHIFTL(I, J, SHIFT)
| I | Shall be of type INTEGER or a BOZ constant. |
| J | Shall be of type INTEGER or a BOZ constant.
If both I and J have integer type, then they shall have
the same kind type parameter. I and J shall not both be
BOZ constants. |
| SHIFT | Shall be of type INTEGER. It shall
be nonnegative. If I is not a BOZ constant, then SHIFT
shall be less than or equal to BIT_SIZE(I); otherwise,
SHIFT shall be less than or equal to BIT_SIZE(J). |
If either I or J is a BOZ constant, it is first converted
as if by the intrinsic function INT to an integer type with the
kind type parameter of the other.
Next: DTIME — Execution time subroutine (or function), Previous: DSHIFTL — Combined left shift, Up: Intrinsic Procedures [Contents][Index]
DSHIFTR — Combined right shiftDSHIFTR(I, J, SHIFT) combines bits of I and J. The
leftmost SHIFT bits of the result are the rightmost SHIFT
bits of I, and the remaining bits are the leftmost bits of
J.
Fortran 2008 and later
Elemental function
RESULT = DSHIFTR(I, J, SHIFT)
| I | Shall be of type INTEGER or a BOZ constant. |
| J | Shall be of type INTEGER or a BOZ constant.
If both I and J have integer type, then they shall have
the same kind type parameter. I and J shall not both be
BOZ constants. |
| SHIFT | Shall be of type INTEGER. It shall
be nonnegative. If I is not a BOZ constant, then SHIFT
shall be less than or equal to BIT_SIZE(I); otherwise,
SHIFT shall be less than or equal to BIT_SIZE(J). |
If either I or J is a BOZ constant, it is first converted
as if by the intrinsic function INT to an integer type with the
kind type parameter of the other.
Next: EOSHIFT — End-off shift elements of an array, Previous: DSHIFTR — Combined right shift, Up: Intrinsic Procedures [Contents][Index]
DTIME — Execution time subroutine (or function)DTIME(VALUES, TIME) initially returns the number of seconds of runtime
since the start of the process’s execution in TIME. VALUES
returns the user and system components of this time in VALUES(1) and
VALUES(2) respectively. TIME is equal to VALUES(1) +
VALUES(2).
Subsequent invocations of DTIME return values accumulated since the
previous invocation.
On some systems, the underlying timings are represented using types with sufficiently small limits that overflows (wrap around) are possible, such as 32-bit types. Therefore, the values returned by this intrinsic might be, or become, negative, or numerically less than previous values, during a single run of the compiled program.
Please note, that this implementation is thread safe if used within OpenMP
directives, i.e., its state will be consistent while called from multiple
threads. However, if DTIME is called from multiple threads, the result
is still the time since the last invocation. This may not give the intended
results. If possible, use CPU_TIME instead.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
VALUES and TIME are INTENT(OUT) and provide the following:
VALUES(1): | User time in seconds. |
VALUES(2): | System time in seconds. |
TIME: | Run time since start in seconds. |
GNU extension
Subroutine, function
CALL DTIME(VALUES, TIME). |
TIME = DTIME(VALUES), (not recommended). |
| VALUES | The type shall be REAL(4), DIMENSION(2). |
| TIME | The type shall be REAL(4). |
Elapsed time in seconds since the last invocation or since the start of program execution if not called before.
program test_dtime
integer(8) :: i, j
real, dimension(2) :: tarray
real :: result
call dtime(tarray, result)
print *, result
print *, tarray(1)
print *, tarray(2)
do i=1,100000000 ! Just a delay
j = i * i - i
end do
call dtime(tarray, result)
print *, result
print *, tarray(1)
print *, tarray(2)
end program test_dtime
Next: EPSILON — Epsilon function, Previous: DTIME — Execution time subroutine (or function), Up: Intrinsic Procedures [Contents][Index]
EOSHIFT — End-off shift elements of an arrayEOSHIFT(ARRAY, SHIFT[, BOUNDARY, DIM]) performs an end-off shift on
elements of ARRAY along the dimension of DIM. If DIM is
omitted it is taken to be 1. DIM is a scalar of type
INTEGER in the range of 1 \leq DIM \leq n) where n is the
rank of ARRAY. If the rank of ARRAY is one, then all elements of
ARRAY are shifted by SHIFT places. If rank is greater than one,
then all complete rank one sections of ARRAY along the given dimension are
shifted. Elements shifted out one end of each rank one section are dropped. If
BOUNDARY is present then the corresponding value of from BOUNDARY
is copied back in the other end. If BOUNDARY is not present then the
following are copied in depending on the type of ARRAY.
| Array Type | Boundary Value |
| Numeric | 0 of the type and kind of ARRAY. |
| Logical | .FALSE.. |
| Character(len) | len blanks. |
Fortran 90 and later
Transformational function
RESULT = EOSHIFT(ARRAY, SHIFT [, BOUNDARY, DIM])
| ARRAY | May be any type, not scalar. |
| SHIFT | The type shall be INTEGER. |
| BOUNDARY | Same type as ARRAY. |
| DIM | The type shall be INTEGER. |
Returns an array of same type and rank as the ARRAY argument.
program test_eoshift
integer, dimension(3,3) :: a
a = reshape( (/ 1, 2, 3, 4, 5, 6, 7, 8, 9 /), (/ 3, 3 /))
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print '(3i3)', a(3,:)
a = EOSHIFT(a, SHIFT=(/1, 2, 1/), BOUNDARY=-5, DIM=2)
print *
print '(3i3)', a(1,:)
print '(3i3)', a(2,:)
print '(3i3)', a(3,:)
end program test_eoshift
Next: ERF — Error function, Previous: EOSHIFT — End-off shift elements of an array, Up: Intrinsic Procedures [Contents][Index]
EPSILON — Epsilon functionEPSILON(X) returns the smallest number E of the same kind
as X such that 1 + E > 1.
Fortran 90 and later
Inquiry function
RESULT = EPSILON(X)
| X | The type shall be REAL. |
The return value is of same type as the argument.
program test_epsilon
real :: x = 3.143
real(8) :: y = 2.33
print *, EPSILON(x)
print *, EPSILON(y)
end program test_epsilon
Next: ERFC — Error function, Previous: EPSILON — Epsilon function, Up: Intrinsic Procedures [Contents][Index]
ERF — Error functionERF(X) computes the error function of X.
Fortran 2008 and later
Elemental function
RESULT = ERF(X)
| X | The type shall be REAL. |
The return value is of type REAL, of the same kind as
X and lies in the range -1 \leq erf (x) \leq 1 .
program test_erf real(8) :: x = 0.17_8 x = erf(x) end program test_erf
| Name | Argument | Return type | Standard |
DERF(X) | REAL(8) X | REAL(8) | GNU extension |
Next: ERFC_SCALED — Error function, Previous: ERF — Error function, Up: Intrinsic Procedures [Contents][Index]
ERFC — Error functionERFC(X) computes the complementary error function of X.
Fortran 2008 and later
Elemental function
RESULT = ERFC(X)
| X | The type shall be REAL. |
The return value is of type REAL and of the same kind as X.
It lies in the range 0 \leq erfc (x) \leq 2 .
program test_erfc real(8) :: x = 0.17_8 x = erfc(x) end program test_erfc
| Name | Argument | Return type | Standard |
DERFC(X) | REAL(8) X | REAL(8) | GNU extension |
Next: ETIME — Execution time subroutine (or function), Previous: ERFC — Error function, Up: Intrinsic Procedures [Contents][Index]
ERFC_SCALED — Error functionERFC_SCALED(X) computes the exponentially-scaled complementary
error function of X.
Fortran 2008 and later
Elemental function
RESULT = ERFC_SCALED(X)
| X | The type shall be REAL. |
The return value is of type REAL and of the same kind as X.
program test_erfc_scaled real(8) :: x = 0.17_8 x = erfc_scaled(x) end program test_erfc_scaled
Next: EVENT_QUERY — Query whether a coarray event has occurred, Previous: ERFC_SCALED — Error function, Up: Intrinsic Procedures [Contents][Index]
ETIME — Execution time subroutine (or function)ETIME(VALUES, TIME) returns the number of seconds of runtime
since the start of the process’s execution in TIME. VALUES
returns the user and system components of this time in VALUES(1) and
VALUES(2) respectively. TIME is equal to VALUES(1) + VALUES(2).
On some systems, the underlying timings are represented using types with sufficiently small limits that overflows (wrap around) are possible, such as 32-bit types. Therefore, the values returned by this intrinsic might be, or become, negative, or numerically less than previous values, during a single run of the compiled program.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
VALUES and TIME are INTENT(OUT) and provide the following:
VALUES(1): | User time in seconds. |
VALUES(2): | System time in seconds. |
TIME: | Run time since start in seconds. |
GNU extension
Subroutine, function
CALL ETIME(VALUES, TIME). |
TIME = ETIME(VALUES), (not recommended). |
| VALUES | The type shall be REAL(4), DIMENSION(2). |
| TIME | The type shall be REAL(4). |
Elapsed time in seconds since the start of program execution.
program test_etime
integer(8) :: i, j
real, dimension(2) :: tarray
real :: result
call ETIME(tarray, result)
print *, result
print *, tarray(1)
print *, tarray(2)
do i=1,100000000 ! Just a delay
j = i * i - i
end do
call ETIME(tarray, result)
print *, result
print *, tarray(1)
print *, tarray(2)
end program test_etime
Next: EXECUTE_COMMAND_LINE — Execute a shell command, Previous: ETIME — Execution time subroutine (or function), Up: Intrinsic Procedures [Contents][Index]
EVENT_QUERY — Query whether a coarray event has occurredEVENT_QUERY assignes the number of events to COUNT which have been
posted to the EVENT variable and not yet been removed by calling
EVENT WAIT. When STAT is present and the invocation was successful,
it is assigned the value 0. If it is present and the invocation has failed,
it is assigned a positive value and COUNT is assigned the value -1.
TS 18508 or later
subroutine
CALL EVENT_QUERY (EVENT, COUNT [, STAT])
| EVENT | (intent(IN)) Scalar of type EVENT_TYPE,
defined in ISO_FORTRAN_ENV; shall not be coindexed. |
| COUNT | (intent(out))Scalar integer with at least the precision of default integer. |
| STAT | (optional) Scalar default-kind integer variable. |
program atomic
use iso_fortran_env
implicit none
type(event_type) :: event_value_has_been_set[*]
integer :: cnt
if (this_image() == 1) then
call event_query (event_value_has_been_set, cnt)
if (cnt > 0) write(*,*) "Value has been set"
elseif (this_image() == 2) then
event post (event_value_has_been_set[1])
end if
end program atomic
Next: EXIT — Exit the program with status., Previous: EVENT_QUERY — Query whether a coarray event has occurred, Up: Intrinsic Procedures [Contents][Index]
EXECUTE_COMMAND_LINE — Execute a shell commandEXECUTE_COMMAND_LINE runs a shell command, synchronously or
asynchronously.
The COMMAND argument is passed to the shell and executed (The
shell is sh on Unix systems, and cmd.exe on Windows.).
If WAIT is present and has the value false, the execution of
the command is asynchronous if the system supports it; otherwise, the
command is executed synchronously using the C library’s system
call.
The three last arguments allow the user to get status information. After
synchronous execution, EXITSTAT contains the integer exit code of
the command, as returned by system. CMDSTAT is set to zero
if the command line was executed (whatever its exit status was).
CMDMSG is assigned an error message if an error has occurred.
Note that the system function need not be thread-safe. It is
the responsibility of the user to ensure that system is not
called concurrently.
For asynchronous execution on supported targets, the POSIX
posix_spawn or fork functions are used. Also, a signal
handler for the SIGCHLD signal is installed.
Fortran 2008 and later
Subroutine
CALL EXECUTE_COMMAND_LINE(COMMAND [, WAIT, EXITSTAT, CMDSTAT, CMDMSG ])
| COMMAND | Shall be a default CHARACTER scalar. |
| WAIT | (Optional) Shall be a default LOGICAL scalar. |
| EXITSTAT | (Optional) Shall be an INTEGER of the
default kind. |
| CMDSTAT | (Optional) Shall be an INTEGER of the
default kind. |
| CMDMSG | (Optional) Shall be an CHARACTER scalar of the
default kind. |
program test_exec
integer :: i
call execute_command_line ("external_prog.exe", exitstat=i)
print *, "Exit status of external_prog.exe was ", i
call execute_command_line ("reindex_files.exe", wait=.false.)
print *, "Now reindexing files in the background"
end program test_exec
Because this intrinsic is implemented in terms of the system
function call, its behavior with respect to signaling is processor
dependent. In particular, on POSIX-compliant systems, the SIGINT and
SIGQUIT signals will be ignored, and the SIGCHLD will be blocked. As
such, if the parent process is terminated, the child process might not be
terminated alongside.
Next: EXP — Exponential function, Previous: EXECUTE_COMMAND_LINE — Execute a shell command, Up: Intrinsic Procedures [Contents][Index]
EXIT — Exit the program with status.EXIT causes immediate termination of the program with status. If status
is omitted it returns the canonical success for the system. All Fortran
I/O units are closed.
GNU extension
Subroutine
CALL EXIT([STATUS])
| STATUS | Shall be an INTEGER of the default kind. |
STATUS is passed to the parent process on exit.
program test_exit integer :: STATUS = 0 print *, 'This program is going to exit.' call EXIT(STATUS) end program test_exit
ABORT — Abort the program,
KILL — Send a signal to a process
Next: EXPONENT — Exponent function, Previous: EXIT — Exit the program with status., Up: Intrinsic Procedures [Contents][Index]
EXP — Exponential functionEXP(X) computes the base e exponential of X.
Fortran 77 and later, has overloads that are GNU extensions
Elemental function
RESULT = EXP(X)
| X | The type shall be REAL or
COMPLEX. |
The return value has same type and kind as X.
program test_exp real :: x = 1.0 x = exp(x) end program test_exp
| Name | Argument | Return type | Standard |
EXP(X) | REAL(4) X | REAL(4) | Fortran 77 and later |
DEXP(X) | REAL(8) X | REAL(8) | Fortran 77 and later |
CEXP(X) | COMPLEX(4) X | COMPLEX(4) | Fortran 77 and later |
ZEXP(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension |
CDEXP(X) | COMPLEX(8) X | COMPLEX(8) | GNU extension |
Next: EXTENDS_TYPE_OF — Query dynamic type for extension, Previous: EXP — Exponential function, Up: Intrinsic Procedures [Contents][Index]
EXPONENT — Exponent functionEXPONENT(X) returns the value of the exponent part of X. If X
is zero the value returned is zero.
Fortran 90 and later
Elemental function
RESULT = EXPONENT(X)
| X | The type shall be REAL. |
The return value is of type default INTEGER.
program test_exponent real :: x = 1.0 integer :: i i = exponent(x) print *, i print *, exponent(0.0) end program test_exponent
Next: FDATE — Get the current time as a string, Previous: EXPONENT — Exponent function, Up: Intrinsic Procedures [Contents][Index]
EXTENDS_TYPE_OF — Query dynamic type for extensionQuery dynamic type for extension.
Fortran 2003 and later
Inquiry function
RESULT = EXTENDS_TYPE_OF(A, MOLD)
| A | Shall be an object of extensible declared type or unlimited polymorphic. |
| MOLD | Shall be an object of extensible declared type or unlimited polymorphic. |
The return value is a scalar of type default logical. It is true if and only if the dynamic type of A is an extension type of the dynamic type of MOLD.
Next: FGET — Read a single character in stream mode from stdin, Previous: EXTENDS_TYPE_OF — Query dynamic type for extension, Up: Intrinsic Procedures [Contents][Index]
FDATE — Get the current time as a stringFDATE(DATE) returns the current date (using the same format as
CTIME — Convert a time into a string) in DATE. It is equivalent to CALL CTIME(DATE,
TIME()).
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
Subroutine, function
CALL FDATE(DATE). |
DATE = FDATE(). |
| DATE | The type shall be of type CHARACTER of the
default kind. It is an INTENT(OUT) argument. If the length of
this variable is too short for the date and time string to fit
completely, it will be blank on procedure return. |
The current date and time as a string.
program test_fdate
integer(8) :: i, j
character(len=30) :: date
call fdate(date)
print *, 'Program started on ', date
do i = 1, 100000000 ! Just a delay
j = i * i - i
end do
call fdate(date)
print *, 'Program ended on ', date
end program test_fdate
DATE_AND_TIME — Date and time subroutine,
CTIME — Convert a time into a string
Next: FGETC — Read a single character in stream mode, Previous: FDATE — Get the current time as a string, Up: Intrinsic Procedures [Contents][Index]
FGET — Read a single character in stream mode from stdinRead a single character in stream mode from stdin by bypassing normal formatted output. Stream I/O should not be mixed with normal record-oriented (formatted or unformatted) I/O on the same unit; the results are unpredictable.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
Note that the FGET intrinsic is provided for backwards compatibility with
g77. GNU Fortran provides the Fortran 2003 Stream facility.
Programmers should consider the use of new stream IO feature in new code
for future portability. See also Fortran 2003 status.
GNU extension
Subroutine, function
CALL FGET(C [, STATUS]) |
STATUS = FGET(C) |
| C | The type shall be CHARACTER and of default
kind. |
| STATUS | (Optional) status flag of type INTEGER.
Returns 0 on success, -1 on end-of-file, and a system specific positive
error code otherwise. |
PROGRAM test_fget
INTEGER, PARAMETER :: strlen = 100
INTEGER :: status, i = 1
CHARACTER(len=strlen) :: str = ""
WRITE (*,*) 'Enter text:'
DO
CALL fget(str(i:i), status)
if (status /= 0 .OR. i > strlen) exit
i = i + 1
END DO
WRITE (*,*) TRIM(str)
END PROGRAM
FGETC — Read a single character in stream mode,
FPUT — Write a single character in stream mode to stdout,
FPUTC — Write a single character in stream mode
Next: FINDLOC — Search an array for a value, Previous: FGET — Read a single character in stream mode from stdin, Up: Intrinsic Procedures [Contents][Index]
FGETC — Read a single character in stream modeRead a single character in stream mode by bypassing normal formatted output. Stream I/O should not be mixed with normal record-oriented (formatted or unformatted) I/O on the same unit; the results are unpredictable.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
Note that the FGET intrinsic is provided for backwards compatibility
with g77. GNU Fortran provides the Fortran 2003 Stream facility.
Programmers should consider the use of new stream IO feature in new code
for future portability. See also Fortran 2003 status.
GNU extension
Subroutine, function
CALL FGETC(UNIT, C [, STATUS]) |
STATUS = FGETC(UNIT, C) |
| UNIT | The type shall be INTEGER. |
| C | The type shall be CHARACTER and of default
kind. |
| STATUS | (Optional) status flag of type INTEGER.
Returns 0 on success, -1 on end-of-file and a system specific positive
error code otherwise. |
PROGRAM test_fgetc
INTEGER :: fd = 42, status
CHARACTER :: c
OPEN(UNIT=fd, FILE="/etc/passwd", ACTION="READ", STATUS = "OLD")
DO
CALL fgetc(fd, c, status)
IF (status /= 0) EXIT
call fput(c)
END DO
CLOSE(UNIT=fd)
END PROGRAM
FGET — Read a single character in stream mode from stdin,
FPUT — Write a single character in stream mode to stdout,
FPUTC — Write a single character in stream mode
Next: FLOOR — Integer floor function, Previous: FGETC — Read a single character in stream mode, Up: Intrinsic Procedures [Contents][Index]
FINDLOC — Search an array for a valueDetermines the location of the element in the array with the value
given in the VALUE argument, or, if the DIM argument is
supplied, determines the locations of the elements equal to the
VALUE argument element along each
row of the array in the DIM direction. If MASK is
present, only the elements for which MASK is .TRUE. are
considered. If more than one element in the array has the value
VALUE, the location returned is that of the first such element
in array element order if the BACK is not present or if it is
.FALSE.. If BACK is true, the location returned is that
of the last such element. If the array has zero size, or all of the
elements of MASK are .FALSE., then the result is an array
of zeroes. Similarly, if DIM is supplied and all of the
elements of MASK along a given row are zero, the result value
for that row is zero.
Fortran 2008 and later.
Transformational function
RESULT = FINDLOC(ARRAY, VALUE, DIM [, MASK] [,KIND] [,BACK]) |
RESULT = FINDLOC(ARRAY, VALUE, [, MASK] [,KIND] [,BACK]) |
| ARRAY | Shall be an array of intrinsic type. |
| VALUE | A scalar of intrinsic type which is in type conformance with ARRAY. |
| DIM | (Optional) Shall be a scalar of type
INTEGER, with a value between one and the rank of ARRAY,
inclusive. It may not be an optional dummy argument. |
| MASK | (Optional) Shall be of type LOGICAL,
and conformable with ARRAY. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
| BACK | (Optional) A scalar of type LOGICAL. |
If DIM is absent, the result is a rank-one array with a length equal to the rank of ARRAY. If DIM is present, the result is an array with a rank one less than the rank of ARRAY, and a size corresponding to the size of ARRAY with the DIM dimension removed. If DIM is present and ARRAY has a rank of one, the result is a scalar. If the optional argument KIND is present, the result is an integer of kind KIND, otherwise it is of default kind.
MAXLOC — Location of the maximum value within an array,
MINLOC — Location of the minimum value within an array
Next: FLUSH — Flush I/O unit(s), Previous: FINDLOC — Search an array for a value, Up: Intrinsic Procedures [Contents][Index]
FLOOR — Integer floor functionFLOOR(A) returns the greatest integer less than or equal to X.
Fortran 95 and later
Elemental function
RESULT = FLOOR(A [, KIND])
| A | The type shall be REAL. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type INTEGER(KIND) if KIND is present
and of default-kind INTEGER otherwise.
program test_floor
real :: x = 63.29
real :: y = -63.59
print *, floor(x) ! returns 63
print *, floor(y) ! returns -64
end program test_floor
CEILING — Integer ceiling function,
NINT — Nearest whole number
Next: FNUM — File number function, Previous: FLOOR — Integer floor function, Up: Intrinsic Procedures [Contents][Index]
FLUSH — Flush I/O unit(s)Flushes Fortran unit(s) currently open for output. Without the optional argument, all units are flushed, otherwise just the unit specified.
GNU extension
Subroutine
CALL FLUSH(UNIT)
| UNIT | (Optional) The type shall be INTEGER. |
Beginning with the Fortran 2003 standard, there is a FLUSH
statement that should be preferred over the FLUSH intrinsic.
The FLUSH intrinsic and the Fortran 2003 FLUSH statement
have identical effect: they flush the runtime library’s I/O buffer so
that the data becomes visible to other processes. This does not guarantee
that the data is committed to disk.
On POSIX systems, you can request that all data is transferred to the
storage device by calling the fsync function, with the POSIX file
descriptor of the I/O unit as argument (retrieved with GNU intrinsic
FNUM). The following example shows how:
! Declare the interface for POSIX fsync function
interface
function fsync (fd) bind(c,name="fsync")
use iso_c_binding, only: c_int
integer(c_int), value :: fd
integer(c_int) :: fsync
end function fsync
end interface
! Variable declaration
integer :: ret
! Opening unit 10
open (10,file="foo")
! ...
! Perform I/O on unit 10
! ...
! Flush and sync
flush(10)
ret = fsync(fnum(10))
! Handle possible error
if (ret /= 0) stop "Error calling FSYNC"
Next: FPUT — Write a single character in stream mode to stdout, Previous: FLUSH — Flush I/O unit(s), Up: Intrinsic Procedures [Contents][Index]
FNUM — File number functionFNUM(UNIT) returns the POSIX file descriptor number corresponding to the
open Fortran I/O unit UNIT.
GNU extension
Function
RESULT = FNUM(UNIT)
| UNIT | The type shall be INTEGER. |
The return value is of type INTEGER
program test_fnum integer :: i open (unit=10, status = "scratch") i = fnum(10) print *, i close (10) end program test_fnum
Next: FPUTC — Write a single character in stream mode, Previous: FNUM — File number function, Up: Intrinsic Procedures [Contents][Index]
FPUT — Write a single character in stream mode to stdoutWrite a single character in stream mode to stdout by bypassing normal formatted output. Stream I/O should not be mixed with normal record-oriented (formatted or unformatted) I/O on the same unit; the results are unpredictable.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
Note that the FGET intrinsic is provided for backwards compatibility with
g77. GNU Fortran provides the Fortran 2003 Stream facility.
Programmers should consider the use of new stream IO feature in new code
for future portability. See also Fortran 2003 status.
GNU extension
Subroutine, function
CALL FPUT(C [, STATUS]) |
STATUS = FPUT(C) |
| C | The type shall be CHARACTER and of default
kind. |
| STATUS | (Optional) status flag of type INTEGER.
Returns 0 on success, -1 on end-of-file and a system specific positive
error code otherwise. |
PROGRAM test_fput
CHARACTER(len=10) :: str = "gfortran"
INTEGER :: i
DO i = 1, len_trim(str)
CALL fput(str(i:i))
END DO
END PROGRAM
FPUTC — Write a single character in stream mode,
FGET — Read a single character in stream mode from stdin,
FGETC — Read a single character in stream mode
Next: FRACTION — Fractional part of the model representation, Previous: FPUT — Write a single character in stream mode to stdout, Up: Intrinsic Procedures [Contents][Index]
FPUTC — Write a single character in stream modeWrite a single character in stream mode by bypassing normal formatted output. Stream I/O should not be mixed with normal record-oriented (formatted or unformatted) I/O on the same unit; the results are unpredictable.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
Note that the FGET intrinsic is provided for backwards compatibility with
g77. GNU Fortran provides the Fortran 2003 Stream facility.
Programmers should consider the use of new stream IO feature in new code
for future portability. See also Fortran 2003 status.
GNU extension
Subroutine, function
CALL FPUTC(UNIT, C [, STATUS]) |
STATUS = FPUTC(UNIT, C) |
| UNIT | The type shall be INTEGER. |
| C | The type shall be CHARACTER and of default
kind. |
| STATUS | (Optional) status flag of type INTEGER.
Returns 0 on success, -1 on end-of-file and a system specific positive
error code otherwise. |
PROGRAM test_fputc
CHARACTER(len=10) :: str = "gfortran"
INTEGER :: fd = 42, i
OPEN(UNIT = fd, FILE = "out", ACTION = "WRITE", STATUS="NEW")
DO i = 1, len_trim(str)
CALL fputc(fd, str(i:i))
END DO
CLOSE(fd)
END PROGRAM
FPUT — Write a single character in stream mode to stdout,
FGET — Read a single character in stream mode from stdin,
FGETC — Read a single character in stream mode
Next: FREE — Frees memory, Previous: FPUTC — Write a single character in stream mode, Up: Intrinsic Procedures [Contents][Index]
FRACTION — Fractional part of the model representationFRACTION(X) returns the fractional part of the model
representation of X.
Fortran 90 and later
Elemental function
Y = FRACTION(X)
| X | The type of the argument shall be a REAL. |
The return value is of the same type and kind as the argument.
The fractional part of the model representation of X is returned;
it is X * RADIX(X)**(-EXPONENT(X)).
program test_fraction real :: x x = 178.1387e-4 print *, fraction(x), x * radix(x)**(-exponent(x)) end program test_fraction
Next: FSEEK — Low level file positioning subroutine, Previous: FRACTION — Fractional part of the model representation, Up: Intrinsic Procedures [Contents][Index]
FREE — Frees memoryFrees memory previously allocated by MALLOC. The FREE
intrinsic is an extension intended to be used with Cray pointers, and is
provided in GNU Fortran to allow user to compile legacy code. For
new code using Fortran 95 pointers, the memory de-allocation intrinsic is
DEALLOCATE.
GNU extension
Subroutine
CALL FREE(PTR)
| PTR | The type shall be INTEGER. It represents the
location of the memory that should be de-allocated. |
None
See MALLOC for an example.
Next: FSTAT — Get file status, Previous: FREE — Frees memory, Up: Intrinsic Procedures [Contents][Index]
FSEEK — Low level file positioning subroutineMoves UNIT to the specified OFFSET. If WHENCE
is set to 0, the OFFSET is taken as an absolute value SEEK_SET,
if set to 1, OFFSET is taken to be relative to the current position
SEEK_CUR, and if set to 2 relative to the end of the file SEEK_END.
On error, STATUS is set to a nonzero value. If STATUS the seek
fails silently.
This intrinsic routine is not fully backwards compatible with g77.
In g77, the FSEEK takes a statement label instead of a
STATUS variable. If FSEEK is used in old code, change
CALL FSEEK(UNIT, OFFSET, WHENCE, *label)
to
INTEGER :: status CALL FSEEK(UNIT, OFFSET, WHENCE, status) IF (status /= 0) GOTO label
Please note that GNU Fortran provides the Fortran 2003 Stream facility. Programmers should consider the use of new stream IO feature in new code for future portability. See also Fortran 2003 status.
GNU extension
Subroutine
CALL FSEEK(UNIT, OFFSET, WHENCE[, STATUS])
| UNIT | Shall be a scalar of type INTEGER. |
| OFFSET | Shall be a scalar of type INTEGER. |
| WHENCE | Shall be a scalar of type INTEGER.
Its value shall be either 0, 1 or 2. |
| STATUS | (Optional) shall be a scalar of type
INTEGER(4). |
PROGRAM test_fseek INTEGER, PARAMETER :: SEEK_SET = 0, SEEK_CUR = 1, SEEK_END = 2 INTEGER :: fd, offset, ierr ierr = 0 offset = 5 fd = 10 OPEN(UNIT=fd, FILE="fseek.test") CALL FSEEK(fd, offset, SEEK_SET, ierr) ! move to OFFSET print *, FTELL(fd), ierr CALL FSEEK(fd, 0, SEEK_END, ierr) ! move to end print *, FTELL(fd), ierr CALL FSEEK(fd, 0, SEEK_SET, ierr) ! move to beginning print *, FTELL(fd), ierr CLOSE(UNIT=fd) END PROGRAM
Next: FTELL — Current stream position, Previous: FSEEK — Low level file positioning subroutine, Up: Intrinsic Procedures [Contents][Index]
FSTAT — Get file statusFSTAT is identical to STAT — Get file status, except that information about an
already opened file is obtained.
The elements in VALUES are the same as described by STAT — Get file status.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
Subroutine, function
CALL FSTAT(UNIT, VALUES [, STATUS]) |
STATUS = FSTAT(UNIT, VALUES) |
| UNIT | An open I/O unit number of type INTEGER. |
| VALUES | The type shall be INTEGER(4), DIMENSION(13). |
| STATUS | (Optional) status flag of type INTEGER(4). Returns 0
on success and a system specific error code otherwise. |
See STAT — Get file status for an example.
To stat a link:
LSTAT — Get file status
To stat a file:
STAT — Get file status
Next: GAMMA — Gamma function, Previous: FSTAT — Get file status, Up: Intrinsic Procedures [Contents][Index]
FTELL — Current stream positionRetrieves the current position within an open file.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
Subroutine, function
CALL FTELL(UNIT, OFFSET) |
OFFSET = FTELL(UNIT) |
| OFFSET | Shall of type INTEGER. |
| UNIT | Shall of type INTEGER. |
In either syntax, OFFSET is set to the current offset of unit number UNIT, or to -1 if the unit is not currently open.
PROGRAM test_ftell INTEGER :: i OPEN(10, FILE="temp.dat") CALL ftell(10,i) WRITE(*,*) i END PROGRAM
Next: GERROR — Get last system error message, Previous: FTELL — Current stream position, Up: Intrinsic Procedures [Contents][Index]
GAMMA — Gamma functionGAMMA(X) computes Gamma (\Gamma) of X. For positive,
integer values of X the Gamma function simplifies to the factorial
function \Gamma(x)=(x-1)!.
Fortran 2008 and later
Elemental function
X = GAMMA(X)
| X | Shall be of type REAL and neither zero
nor a negative integer. |
The return value is of type REAL of the same kind as X.
program test_gamma real :: x = 1.0 x = gamma(x) ! returns 1.0 end program test_gamma
| Name | Argument | Return type | Standard |
DGAMMA(X) | REAL(8) X | REAL(8) | GNU extension |
Logarithm of the Gamma function:
LOG_GAMMA — Logarithm of the Gamma function
Next: GETARG — Get command line arguments, Previous: GAMMA — Gamma function, Up: Intrinsic Procedures [Contents][Index]
GERROR — Get last system error messageReturns the system error message corresponding to the last system error.
This resembles the functionality of strerror(3) in C.
GNU extension
Subroutine
CALL GERROR(RESULT)
| RESULT | Shall be of type CHARACTER and of default kind. |
PROGRAM test_gerror CHARACTER(len=100) :: msg CALL gerror(msg) WRITE(*,*) msg END PROGRAM
IERRNO — Get the last system error number,
PERROR — Print system error message
Next: GET_COMMAND — Get the entire command line, Previous: GERROR — Get last system error message, Up: Intrinsic Procedures [Contents][Index]
GETARG — Get command line argumentsRetrieve the POS-th argument that was passed on the command line when the containing program was invoked.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use of
the GET_COMMAND_ARGUMENT — Get command line arguments intrinsic defined by the Fortran 2003
standard.
GNU extension
Subroutine
CALL GETARG(POS, VALUE)
| POS | Shall be of type INTEGER and not wider than
the default integer kind; POS \geq 0 |
| VALUE | Shall be of type CHARACTER and of default
kind. |
After GETARG returns, the VALUE argument holds the
POSth command line argument. If VALUE cannot hold the
argument, it is truncated to fit the length of VALUE. If there are
less than POS arguments specified at the command line, VALUE
will be filled with blanks. If POS = 0, VALUE is set
to the name of the program (on systems that support this feature).
PROGRAM test_getarg
INTEGER :: i
CHARACTER(len=32) :: arg
DO i = 1, iargc()
CALL getarg(i, arg)
WRITE (*,*) arg
END DO
END PROGRAM
GNU Fortran 77 compatibility function:
IARGC — Get the number of command line arguments
Fortran 2003 functions and subroutines:
GET_COMMAND — Get the entire command line,
GET_COMMAND_ARGUMENT — Get command line arguments,
COMMAND_ARGUMENT_COUNT — Get number of command line arguments
Next: GET_COMMAND_ARGUMENT — Get command line arguments, Previous: GETARG — Get command line arguments, Up: Intrinsic Procedures [Contents][Index]
GET_COMMAND — Get the entire command lineRetrieve the entire command line that was used to invoke the program.
Fortran 2003 and later
Subroutine
CALL GET_COMMAND([COMMAND, LENGTH, STATUS])
| COMMAND | (Optional) shall be of type CHARACTER and
of default kind. |
| LENGTH | (Optional) Shall be of type INTEGER and of
default kind. |
| STATUS | (Optional) Shall be of type INTEGER and of
default kind. |
If COMMAND is present, stores the entire command line that was used to invoke the program in COMMAND. If LENGTH is present, it is assigned the length of the command line. If STATUS is present, it is assigned 0 upon success of the command, -1 if COMMAND is too short to store the command line, or a positive value in case of an error.
PROGRAM test_get_command CHARACTER(len=255) :: cmd CALL get_command(cmd) WRITE (*,*) TRIM(cmd) END PROGRAM
GET_COMMAND_ARGUMENT — Get command line arguments,
COMMAND_ARGUMENT_COUNT — Get number of command line arguments
Next: GETCWD — Get current working directory, Previous: GET_COMMAND — Get the entire command line, Up: Intrinsic Procedures [Contents][Index]
GET_COMMAND_ARGUMENT — Get command line argumentsRetrieve the NUMBER-th argument that was passed on the command line when the containing program was invoked.
Fortran 2003 and later
Subroutine
CALL GET_COMMAND_ARGUMENT(NUMBER [, VALUE, LENGTH, STATUS])
| NUMBER | Shall be a scalar of type INTEGER and of
default kind, NUMBER \geq 0 |
| VALUE | (Optional) Shall be a scalar of type CHARACTER
and of default kind. |
| LENGTH | (Optional) Shall be a scalar of type INTEGER
and of default kind. |
| STATUS | (Optional) Shall be a scalar of type INTEGER
and of default kind. |
After GET_COMMAND_ARGUMENT returns, the VALUE argument holds the
NUMBER-th command line argument. If VALUE cannot hold the argument, it is
truncated to fit the length of VALUE. If there are less than NUMBER
arguments specified at the command line, VALUE will be filled with blanks.
If NUMBER = 0, VALUE is set to the name of the program (on
systems that support this feature). The LENGTH argument contains the
length of the NUMBER-th command line argument. If the argument retrieval
fails, STATUS is a positive number; if VALUE contains a truncated
command line argument, STATUS is -1; and otherwise the STATUS is
zero.
PROGRAM test_get_command_argument
INTEGER :: i
CHARACTER(len=32) :: arg
i = 0
DO
CALL get_command_argument(i, arg)
IF (LEN_TRIM(arg) == 0) EXIT
WRITE (*,*) TRIM(arg)
i = i+1
END DO
END PROGRAM
GET_COMMAND — Get the entire command line,
COMMAND_ARGUMENT_COUNT — Get number of command line arguments
Next: GETENV — Get an environmental variable, Previous: GET_COMMAND_ARGUMENT — Get command line arguments, Up: Intrinsic Procedures [Contents][Index]
GETCWD — Get current working directoryGet current working directory.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
Subroutine, function
CALL GETCWD(C [, STATUS]) |
STATUS = GETCWD(C) |
| C | The type shall be CHARACTER and of default kind. |
| STATUS | (Optional) status flag. Returns 0 on success, a system specific and nonzero error code otherwise. |
PROGRAM test_getcwd CHARACTER(len=255) :: cwd CALL getcwd(cwd) WRITE(*,*) TRIM(cwd) END PROGRAM
Next: GET_ENVIRONMENT_VARIABLE — Get an environmental variable, Previous: GETCWD — Get current working directory, Up: Intrinsic Procedures [Contents][Index]
GETENV — Get an environmental variableGet the VALUE of the environmental variable NAME.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use of
the GET_ENVIRONMENT_VARIABLE — Get an environmental variable intrinsic defined by the Fortran
2003 standard.
Note that GETENV need not be thread-safe. It is the
responsibility of the user to ensure that the environment is not being
updated concurrently with a call to the GETENV intrinsic.
GNU extension
Subroutine
CALL GETENV(NAME, VALUE)
| NAME | Shall be of type CHARACTER and of default kind. |
| VALUE | Shall be of type CHARACTER and of default kind. |
Stores the value of NAME in VALUE. If VALUE is not large enough to hold the data, it is truncated. If NAME is not set, VALUE will be filled with blanks.
PROGRAM test_getenv
CHARACTER(len=255) :: homedir
CALL getenv("HOME", homedir)
WRITE (*,*) TRIM(homedir)
END PROGRAM
Next: GETGID — Group ID function, Previous: GETENV — Get an environmental variable, Up: Intrinsic Procedures [Contents][Index]
GET_ENVIRONMENT_VARIABLE — Get an environmental variableGet the VALUE of the environmental variable NAME.
Note that GET_ENVIRONMENT_VARIABLE need not be thread-safe. It
is the responsibility of the user to ensure that the environment is
not being updated concurrently with a call to the
GET_ENVIRONMENT_VARIABLE intrinsic.
Fortran 2003 and later
Subroutine
CALL GET_ENVIRONMENT_VARIABLE(NAME[, VALUE, LENGTH, STATUS, TRIM_NAME)
| NAME | Shall be a scalar of type CHARACTER
and of default kind. |
| VALUE | (Optional) Shall be a scalar of type CHARACTER
and of default kind. |
| LENGTH | (Optional) Shall be a scalar of type INTEGER
and of default kind. |
| STATUS | (Optional) Shall be a scalar of type INTEGER
and of default kind. |
| TRIM_NAME | (Optional) Shall be a scalar of type LOGICAL
and of default kind. |
Stores the value of NAME in VALUE. If VALUE is
not large enough to hold the data, it is truncated. If NAME
is not set, VALUE will be filled with blanks. Argument LENGTH
contains the length needed for storing the environment variable NAME
or zero if it is not present. STATUS is -1 if VALUE is present
but too short for the environment variable; it is 1 if the environment
variable does not exist and 2 if the processor does not support environment
variables; in all other cases STATUS is zero. If TRIM_NAME is
present with the value .FALSE., the trailing blanks in NAME
are significant; otherwise they are not part of the environment variable
name.
PROGRAM test_getenv
CHARACTER(len=255) :: homedir
CALL get_environment_variable("HOME", homedir)
WRITE (*,*) TRIM(homedir)
END PROGRAM
Next: GETLOG — Get login name, Previous: GET_ENVIRONMENT_VARIABLE — Get an environmental variable, Up: Intrinsic Procedures [Contents][Index]
GETGID — Group ID functionReturns the numerical group ID of the current process.
GNU extension
Function
RESULT = GETGID()
The return value of GETGID is an INTEGER of the default
kind.
See GETPID for an example.
Next: GETPID — Process ID function, Previous: GETGID — Group ID function, Up: Intrinsic Procedures [Contents][Index]
GETLOG — Get login nameGets the username under which the program is running.
GNU extension
Subroutine
CALL GETLOG(C)
| C | Shall be of type CHARACTER and of default kind. |
Stores the current user name in C. (On systems where POSIX
functions geteuid and getpwuid are not available, and
the getlogin function is not implemented either, this will
return a blank string.)
PROGRAM TEST_GETLOG CHARACTER(32) :: login CALL GETLOG(login) WRITE(*,*) login END PROGRAM
Next: GETUID — User ID function, Previous: GETLOG — Get login name, Up: Intrinsic Procedures [Contents][Index]
GETPID — Process ID functionReturns the numerical process identifier of the current process.
GNU extension
Function
RESULT = GETPID()
The return value of GETPID is an INTEGER of the default
kind.
program info print *, "The current process ID is ", getpid() print *, "Your numerical user ID is ", getuid() print *, "Your numerical group ID is ", getgid() end program info
Next: GMTIME — Convert time to GMT info, Previous: GETPID — Process ID function, Up: Intrinsic Procedures [Contents][Index]
GETUID — User ID functionReturns the numerical user ID of the current process.
GNU extension
Function
RESULT = GETUID()
The return value of GETUID is an INTEGER of the default
kind.
See GETPID for an example.
Next: HOSTNM — Get system host name, Previous: GETUID — User ID function, Up: Intrinsic Procedures [Contents][Index]
GMTIME — Convert time to GMT infoGiven a system time value TIME (as provided by the TIME — Time function
intrinsic), fills VALUES with values extracted from it appropriate
to the UTC time zone (Universal Coordinated Time, also known in some
countries as GMT, Greenwich Mean Time), using gmtime(3).
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use of
the DATE_AND_TIME — Date and time subroutine intrinsic defined by the Fortran 95
standard.
GNU extension
Subroutine
CALL GMTIME(TIME, VALUES)
| TIME | An INTEGER scalar expression
corresponding to a system time, with INTENT(IN). |
| VALUES | A default INTEGER array with 9 elements,
with INTENT(OUT). |
The elements of VALUES are assigned as follows:
DATE_AND_TIME — Date and time subroutine,
CTIME — Convert a time into a string,
LTIME — Convert time to local time info,
TIME — Time function,
TIME8 — Time function (64-bit)
Next: HUGE — Largest number of a kind, Previous: GMTIME — Convert time to GMT info, Up: Intrinsic Procedures [Contents][Index]
HOSTNM — Get system host nameRetrieves the host name of the system on which the program is running.
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
Subroutine, function
CALL HOSTNM(C [, STATUS]) |
STATUS = HOSTNM(NAME) |
| C | Shall of type CHARACTER and of default kind. |
| STATUS | (Optional) status flag of type INTEGER.
Returns 0 on success, or a system specific error code otherwise. |
In either syntax, NAME is set to the current hostname if it can be obtained, or to a blank string otherwise.
Next: HYPOT — Euclidean distance function, Previous: HOSTNM — Get system host name, Up: Intrinsic Procedures [Contents][Index]
HUGE — Largest number of a kindHUGE(X) returns the largest number that is not an infinity in
the model of the type of X.
Fortran 90 and later
Inquiry function
RESULT = HUGE(X)
| X | Shall be of type REAL or INTEGER. |
The return value is of the same type and kind as X
program test_huge_tiny print *, huge(0), huge(0.0), huge(0.0d0) print *, tiny(0.0), tiny(0.0d0) end program test_huge_tiny
Next: IACHAR — Code in ASCII collating sequence, Previous: HUGE — Largest number of a kind, Up: Intrinsic Procedures [Contents][Index]
HYPOT — Euclidean distance functionHYPOT(X,Y) is the Euclidean distance function. It is equal to
\sqrt{X^2 + Y^2}, without undue underflow or overflow.
Fortran 2008 and later
Elemental function
RESULT = HYPOT(X, Y)
| X | The type shall be REAL. |
| Y | The type and kind type parameter shall be the same as X. |
The return value has the same type and kind type parameter as X.
program test_hypot real(4) :: x = 1.e0_4, y = 0.5e0_4 x = hypot(x,y) end program test_hypot
Next: IALL — Bitwise AND of array elements, Previous: HYPOT — Euclidean distance function, Up: Intrinsic Procedures [Contents][Index]
IACHAR — Code in ASCII collating sequenceIACHAR(C) returns the code for the ASCII character
in the first character position of C.
Fortran 95 and later, with KIND argument Fortran 2003 and later
Elemental function
RESULT = IACHAR(C [, KIND])
| C | Shall be a scalar CHARACTER, with INTENT(IN) |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
program test_iachar
integer i
i = iachar(' ')
end program test_iachar
See ICHAR — Character-to-integer conversion function for a discussion of converting between numerical values
and formatted string representations.
ACHAR — Character in ASCII collating sequence,
CHAR — Character conversion function,
ICHAR — Character-to-integer conversion function
Next: IAND — Bitwise logical and, Previous: IACHAR — Code in ASCII collating sequence, Up: Intrinsic Procedures [Contents][Index]
IALL — Bitwise AND of array elementsReduces with bitwise AND the elements of ARRAY along dimension DIM
if the corresponding element in MASK is TRUE.
Fortran 2008 and later
Transformational function
RESULT = IALL(ARRAY[, MASK]) |
RESULT = IALL(ARRAY, DIM[, MASK]) |
| ARRAY | Shall be an array of type INTEGER |
| DIM | (Optional) shall be a scalar of type
INTEGER with a value in the range from 1 to n, where n
equals the rank of ARRAY. |
| MASK | (Optional) shall be of type LOGICAL
and either be a scalar or an array of the same shape as ARRAY. |
The result is of the same type as ARRAY.
If DIM is absent, a scalar with the bitwise ALL of all elements in ARRAY is returned. Otherwise, an array of rank n-1, where n equals the rank of ARRAY, and a shape similar to that of ARRAY with dimension DIM dropped is returned.
PROGRAM test_iall INTEGER(1) :: a(2) a(1) = b'00100100' a(2) = b'01101010' ! prints 00100000 PRINT '(b8.8)', IALL(a) END PROGRAM
IANY — Bitwise OR of array elements,
IPARITY — Bitwise XOR of array elements,
IAND — Bitwise logical and
Next: IANY — Bitwise OR of array elements, Previous: IALL — Bitwise AND of array elements, Up: Intrinsic Procedures [Contents][Index]
IAND — Bitwise logical andBitwise logical AND.
Fortran 90 and later, with boz-literal-constant Fortran 2008 and later, has overloads that are GNU extensions
Elemental function
RESULT = IAND(I, J)
| I | The type shall be INTEGER or a boz-literal-constant. |
| J | The type shall be INTEGER with the same
kind type parameter as I or a boz-literal-constant.
I and J shall not both be boz-literal-constants. |
The return type is INTEGER with the kind type parameter of the
arguments.
A boz-literal-constant is converted to an INTEGER with the kind
type parameter of the other argument as-if a call to INT — Convert to integer type occurred.
PROGRAM test_iand INTEGER :: a, b DATA a / Z'F' /, b / Z'3' / WRITE (*,*) IAND(a, b) END PROGRAM
| Name | Argument | Return type | Standard |
IAND(A) | INTEGER A | INTEGER | Fortran 90 and later |
BIAND(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IIAND(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JIAND(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KIAND(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
IOR — Bitwise logical or,
IEOR — Bitwise logical exclusive or,
IBITS — Bit extraction,
IBSET — Set bit,
IBCLR — Clear bit,
NOT — Logical negation
Next: IARGC — Get the number of command line arguments, Previous: IAND — Bitwise logical and, Up: Intrinsic Procedures [Contents][Index]
IANY — Bitwise OR of array elementsReduces with bitwise OR (inclusive or) the elements of ARRAY along
dimension DIM if the corresponding element in MASK is TRUE.
Fortran 2008 and later
Transformational function
RESULT = IANY(ARRAY[, MASK]) |
RESULT = IANY(ARRAY, DIM[, MASK]) |
| ARRAY | Shall be an array of type INTEGER |
| DIM | (Optional) shall be a scalar of type
INTEGER with a value in the range from 1 to n, where n
equals the rank of ARRAY. |
| MASK | (Optional) shall be of type LOGICAL
and either be a scalar or an array of the same shape as ARRAY. |
The result is of the same type as ARRAY.
If DIM is absent, a scalar with the bitwise OR of all elements in ARRAY is returned. Otherwise, an array of rank n-1, where n equals the rank of ARRAY, and a shape similar to that of ARRAY with dimension DIM dropped is returned.
PROGRAM test_iany INTEGER(1) :: a(2) a(1) = b'00100100' a(2) = b'01101010' ! prints 01101110 PRINT '(b8.8)', IANY(a) END PROGRAM
IPARITY — Bitwise XOR of array elements,
IALL — Bitwise AND of array elements,
IOR — Bitwise logical or
Next: IBCLR — Clear bit, Previous: IANY — Bitwise OR of array elements, Up: Intrinsic Procedures [Contents][Index]
IARGC — Get the number of command line argumentsIARGC returns the number of arguments passed on the
command line when the containing program was invoked.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use of
the COMMAND_ARGUMENT_COUNT — Get number of command line arguments intrinsic defined by the Fortran 2003
standard.
GNU extension
Function
RESULT = IARGC()
None
The number of command line arguments, type INTEGER(4).
GNU Fortran 77 compatibility subroutine:
GETARG — Get command line arguments
Fortran 2003 functions and subroutines:
GET_COMMAND — Get the entire command line,
GET_COMMAND_ARGUMENT — Get command line arguments,
COMMAND_ARGUMENT_COUNT — Get number of command line arguments
Next: IBITS — Bit extraction, Previous: IARGC — Get the number of command line arguments, Up: Intrinsic Procedures [Contents][Index]
IBCLR — Clear bitIBCLR returns the value of I with the bit at position
POS set to zero.
Fortran 90 and later, has overloads that are GNU extensions
Elemental function
RESULT = IBCLR(I, POS)
| I | The type shall be INTEGER. |
| POS | The type shall be INTEGER. |
The return value is of type INTEGER and of the same kind as
I.
| Name | Argument | Return type | Standard |
IBCLR(A) | INTEGER A | INTEGER | Fortran 90 and later |
BBCLR(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IIBCLR(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JIBCLR(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KIBCLR(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
IBITS — Bit extraction,
IBSET — Set bit,
IAND — Bitwise logical and,
IOR — Bitwise logical or,
IEOR — Bitwise logical exclusive or,
MVBITS — Move bits from one integer to another
Next: IBSET — Set bit, Previous: IBCLR — Clear bit, Up: Intrinsic Procedures [Contents][Index]
IBITS — Bit extractionIBITS extracts a field of length LEN from I,
starting from bit position POS and extending left for LEN
bits. The result is right-justified and the remaining bits are
zeroed. The value of POS+LEN must be less than or equal to the
value BIT_SIZE(I).
Fortran 90 and later, has overloads that are GNU extensions
Elemental function
RESULT = IBITS(I, POS, LEN)
| I | The type shall be INTEGER. |
| POS | The type shall be INTEGER. |
| LEN | The type shall be INTEGER. |
The return value is of type INTEGER and of the same kind as
I.
| Name | Argument | Return type | Standard |
IBITS(A) | INTEGER A | INTEGER | Fortran 90 and later |
BBITS(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IIBITS(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JIBITS(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KIBITS(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
BIT_SIZE — Bit size inquiry function,
IBCLR — Clear bit,
IBSET — Set bit,
IAND — Bitwise logical and,
IOR — Bitwise logical or,
IEOR — Bitwise logical exclusive or
Next: ICHAR — Character-to-integer conversion function, Previous: IBITS — Bit extraction, Up: Intrinsic Procedures [Contents][Index]
IBSET — Set bitIBSET returns the value of I with the bit at position
POS set to one.
Fortran 90 and later, has overloads that are GNU extensions
Elemental function
RESULT = IBSET(I, POS)
| I | The type shall be INTEGER. |
| POS | The type shall be INTEGER. |
The return value is of type INTEGER and of the same kind as
I.
| Name | Argument | Return type | Standard |
IBSET(A) | INTEGER A | INTEGER | Fortran 90 and later |
BBSET(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IIBSET(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JIBSET(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KIBSET(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
IBCLR — Clear bit,
IBITS — Bit extraction,
IAND — Bitwise logical and,
IOR — Bitwise logical or,
IEOR — Bitwise logical exclusive or,
MVBITS — Move bits from one integer to another
Next: IDATE — Get current local time subroutine (day/month/year), Previous: IBSET — Set bit, Up: Intrinsic Procedures [Contents][Index]
ICHAR — Character-to-integer conversion functionICHAR(C) returns the code for the character in the first character
position of C in the system’s native character set.
The correspondence between characters and their codes is not necessarily
the same across different GNU Fortran implementations.
Fortran 77 and later, with KIND argument Fortran 2003 and later
Elemental function
RESULT = ICHAR(C [, KIND])
| C | Shall be a scalar CHARACTER, with INTENT(IN) |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
program test_ichar
integer i
i = ichar(' ')
end program test_ichar
| Name | Argument | Return type | Standard |
ICHAR(C) | CHARACTER C | INTEGER(4) | Fortran 77 and later |
No intrinsic exists to convert between a numeric value and a formatted
character string representation – for instance, given the
CHARACTER value '154', obtaining an INTEGER or
REAL value with the value 154, or vice versa. Instead, this
functionality is provided by internal-file I/O, as in the following
example:
program read_val integer value character(len=10) string, string2 string = '154' ! Convert a string to a numeric value read (string,'(I10)') value print *, value ! Convert a value to a formatted string write (string2,'(I10)') value print *, string2 end program read_val
ACHAR — Character in ASCII collating sequence,
CHAR — Character conversion function,
IACHAR — Code in ASCII collating sequence
Next: IEOR — Bitwise logical exclusive or, Previous: ICHAR — Character-to-integer conversion function, Up: Intrinsic Procedures [Contents][Index]
IDATE — Get current local time subroutine (day/month/year)IDATE(VALUES) Fills VALUES with the numerical values at the
current local time. The day (in the range 1-31), month (in the range 1-12),
and year appear in elements 1, 2, and 3 of VALUES, respectively.
The year has four significant digits.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use of
the DATE_AND_TIME — Date and time subroutine intrinsic defined by the Fortran 95
standard.
GNU extension
Subroutine
CALL IDATE(VALUES)
| VALUES | The type shall be INTEGER, DIMENSION(3) and
the kind shall be the default integer kind. |
Does not return anything.
program test_idate integer, dimension(3) :: tarray call idate(tarray) print *, tarray(1) print *, tarray(2) print *, tarray(3) end program test_idate
Next: IERRNO — Get the last system error number, Previous: IDATE — Get current local time subroutine (day/month/year), Up: Intrinsic Procedures [Contents][Index]
IEOR — Bitwise logical exclusive orIEOR returns the bitwise Boolean exclusive-OR of I and
J.
Fortran 90 and later, with boz-literal-constant Fortran 2008 and later, has overloads that are GNU extensions
Elemental function
RESULT = IEOR(I, J)
| I | The type shall be INTEGER or a boz-literal-constant. |
| J | The type shall be INTEGER with the same
kind type parameter as I or a boz-literal-constant.
I and J shall not both be boz-literal-constants. |
The return type is INTEGER with the kind type parameter of the
arguments.
A boz-literal-constant is converted to an INTEGER with the kind
type parameter of the other argument as-if a call to INT — Convert to integer type occurred.
| Name | Argument | Return type | Standard |
IEOR(A) | INTEGER A | INTEGER | Fortran 90 and later |
BIEOR(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IIEOR(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JIEOR(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KIEOR(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
IOR — Bitwise logical or,
IAND — Bitwise logical and,
IBITS — Bit extraction,
IBSET — Set bit,
IBCLR — Clear bit,
NOT — Logical negation
Next: IMAGE_INDEX — Function that converts a cosubscript to an image index, Previous: IEOR — Bitwise logical exclusive or, Up: Intrinsic Procedures [Contents][Index]
IERRNO — Get the last system error numberReturns the last system error number, as given by the C errno
variable.
GNU extension
Function
RESULT = IERRNO()
None
The return value is of type INTEGER and of the default integer
kind.
Next: INDEX — Position of a substring within a string, Previous: IERRNO — Get the last system error number, Up: Intrinsic Procedures [Contents][Index]
IMAGE_INDEX — Function that converts a cosubscript to an image indexReturns the image index belonging to a cosubscript.
Fortran 2008 and later
Inquiry function.
RESULT = IMAGE_INDEX(COARRAY, SUB)
| COARRAY | Coarray of any type. |
| SUB | default integer rank-1 array of a size equal to the corank of COARRAY. |
Scalar default integer with the value of the image index which corresponds to the cosubscripts. For invalid cosubscripts the result is zero.
INTEGER :: array[2,-1:4,8,*] ! Writes 28 (or 0 if there are fewer than 28 images) WRITE (*,*) IMAGE_INDEX (array, [2,0,3,1])
THIS_IMAGE — Function that returns the cosubscript index of this image,
NUM_IMAGES — Function that returns the number of images
Next: INT — Convert to integer type, Previous: IMAGE_INDEX — Function that converts a cosubscript to an image index, Up: Intrinsic Procedures [Contents][Index]
INDEX — Position of a substring within a stringReturns the position of the start of the first occurrence of string SUBSTRING as a substring in STRING, counting from one. If SUBSTRING is not present in STRING, zero is returned. If the BACK argument is present and true, the return value is the start of the last occurrence rather than the first.
Fortran 77 and later, with KIND argument Fortran 2003 and later
Elemental function
RESULT = INDEX(STRING, SUBSTRING [, BACK [, KIND]])
| STRING | Shall be a scalar CHARACTER, with
INTENT(IN) |
| SUBSTRING | Shall be a scalar CHARACTER, with
INTENT(IN) |
| BACK | (Optional) Shall be a scalar LOGICAL, with
INTENT(IN) |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
| Name | Argument | Return type | Standard |
INDEX(STRING, SUBSTRING) | CHARACTER | INTEGER(4) | Fortran 77 and later |
SCAN — Scan a string for the presence of a set of characters,
VERIFY — Scan a string for characters not a given set
Next: INT2 — Convert to 16-bit integer type, Previous: INDEX — Position of a substring within a string, Up: Intrinsic Procedures [Contents][Index]
INT — Convert to integer typeConvert to integer type
Fortran 77 and later, with boz-literal-constant Fortran 2008 and later.
Elemental function
RESULT = INT(A [, KIND))
| A | Shall be of type INTEGER,
REAL, or COMPLEX or a boz-literal-constant. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
These functions return a INTEGER variable or array under
the following rules:
If A is of type INTEGER, INT(A) = A
If A is of type REAL and |A| < 1, INT(A)
equals 0. If |A| \geq 1, then INT(A) is the integer
whose magnitude is the largest integer that does not exceed the magnitude
of A and whose sign is the same as the sign of A.
If A is of type COMPLEX, rule B is applied to the real part of A.
program test_int integer :: i = 42 complex :: z = (-3.7, 1.0) print *, int(i) print *, int(z), int(z,8) end program
| Name | Argument | Return type | Standard |
INT(A) | REAL(4) A | INTEGER | Fortran 77 and later |
IFIX(A) | REAL(4) A | INTEGER | Fortran 77 and later |
IDINT(A) | REAL(8) A | INTEGER | Fortran 77 and later |
Next: INT8 — Convert to 64-bit integer type, Previous: INT — Convert to integer type, Up: Intrinsic Procedures [Contents][Index]
INT2 — Convert to 16-bit integer typeConvert to a KIND=2 integer type. This is equivalent to the
standard INT intrinsic with an optional argument of
KIND=2, and is only included for backwards compatibility.
The SHORT intrinsic is equivalent to INT2.
GNU extension
Elemental function
RESULT = INT2(A)
| A | Shall be of type INTEGER,
REAL, or COMPLEX. |
The return value is a INTEGER(2) variable.
INT — Convert to integer type,
INT8 — Convert to 64-bit integer type,
LONG — Convert to integer type
Next: IOR — Bitwise logical or, Previous: INT2 — Convert to 16-bit integer type, Up: Intrinsic Procedures [Contents][Index]
INT8 — Convert to 64-bit integer typeConvert to a KIND=8 integer type. This is equivalent to the
standard INT intrinsic with an optional argument of
KIND=8, and is only included for backwards compatibility.
GNU extension
Elemental function
RESULT = INT8(A)
| A | Shall be of type INTEGER,
REAL, or COMPLEX. |
The return value is a INTEGER(8) variable.
INT — Convert to integer type,
INT2 — Convert to 16-bit integer type,
LONG — Convert to integer type
Next: IPARITY — Bitwise XOR of array elements, Previous: INT8 — Convert to 64-bit integer type, Up: Intrinsic Procedures [Contents][Index]
IOR — Bitwise logical orIOR returns the bitwise Boolean inclusive-OR of I and
J.
Fortran 90 and later, with boz-literal-constant Fortran 2008 and later, has overloads that are GNU extensions
Elemental function
RESULT = IOR(I, J)
| I | The type shall be INTEGER or a boz-literal-constant. |
| J | The type shall be INTEGER with the same
kind type parameter as I or a boz-literal-constant.
I and J shall not both be boz-literal-constants. |
The return type is INTEGER with the kind type parameter of the
arguments.
A boz-literal-constant is converted to an INTEGER with the kind
type parameter of the other argument as-if a call to INT — Convert to integer type occurred.
| Name | Argument | Return type | Standard |
IOR(A) | INTEGER A | INTEGER | Fortran 90 and later |
BIOR(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IIOR(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JIOR(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KIOR(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
IEOR — Bitwise logical exclusive or,
IAND — Bitwise logical and,
IBITS — Bit extraction,
IBSET — Set bit,
IBCLR — Clear bit,
NOT — Logical negation
Next: IRAND — Integer pseudo-random number, Previous: IOR — Bitwise logical or, Up: Intrinsic Procedures [Contents][Index]
IPARITY — Bitwise XOR of array elementsReduces with bitwise XOR (exclusive or) the elements of ARRAY along
dimension DIM if the corresponding element in MASK is TRUE.
Fortran 2008 and later
Transformational function
RESULT = IPARITY(ARRAY[, MASK]) |
RESULT = IPARITY(ARRAY, DIM[, MASK]) |
| ARRAY | Shall be an array of type INTEGER |
| DIM | (Optional) shall be a scalar of type
INTEGER with a value in the range from 1 to n, where n
equals the rank of ARRAY. |
| MASK | (Optional) shall be of type LOGICAL
and either be a scalar or an array of the same shape as ARRAY. |
The result is of the same type as ARRAY.
If DIM is absent, a scalar with the bitwise XOR of all elements in ARRAY is returned. Otherwise, an array of rank n-1, where n equals the rank of ARRAY, and a shape similar to that of ARRAY with dimension DIM dropped is returned.
PROGRAM test_iparity INTEGER(1) :: a(2) a(1) = int(b'00100100', 1) a(2) = int(b'01101010', 1) ! prints 01001110 PRINT '(b8.8)', IPARITY(a) END PROGRAM
IANY — Bitwise OR of array elements,
IALL — Bitwise AND of array elements,
IEOR — Bitwise logical exclusive or,
PARITY — Reduction with exclusive OR
Next: IS_CONTIGUOUS — Test whether an array is contiguous, Previous: IPARITY — Bitwise XOR of array elements, Up: Intrinsic Procedures [Contents][Index]
IRAND — Integer pseudo-random numberIRAND(FLAG) returns a pseudo-random number from a uniform
distribution between 0 and a system-dependent limit (which is in most
cases 2147483647). If FLAG is 0, the next number
in the current sequence is returned; if FLAG is 1, the generator
is restarted by CALL SRAND(0); if FLAG has any other value,
it is used as a new seed with SRAND.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. It implements a simple modulo generator as provided
by g77. For new code, one should consider the use of
RANDOM_NUMBER — Pseudo-random number as it implements a superior algorithm.
GNU extension
Function
RESULT = IRAND(I)
| I | Shall be a scalar INTEGER of kind 4. |
The return value is of INTEGER(kind=4) type.
program test_irand integer,parameter :: seed = 86456 call srand(seed) print *, irand(), irand(), irand(), irand() print *, irand(seed), irand(), irand(), irand() end program test_irand
Next: IS_IOSTAT_END — Test for end-of-file value, Previous: IRAND — Integer pseudo-random number, Up: Intrinsic Procedures [Contents][Index]
IS_CONTIGUOUS — Test whether an array is contiguousIS_CONTIGUOUS tests whether an array is contiguous.
Fortran 2008 and later
Inquiry function
RESULT = IS_CONTIGUOUS(ARRAY)
| ARRAY | Shall be an array of any type. |
Returns a LOGICAL of the default kind, which .TRUE. if
ARRAY is contiguous and false otherwise.
program test
integer :: a(10)
a = [1,2,3,4,5,6,7,8,9,10]
call sub (a) ! every element, is contiguous
call sub (a(::2)) ! every other element, is noncontiguous
contains
subroutine sub (x)
integer :: x(:)
if (is_contiguous (x)) then
write (*,*) 'X is contiguous'
else
write (*,*) 'X is not contiguous'
end if
end subroutine sub
end program test
Next: IS_IOSTAT_EOR — Test for end-of-record value, Previous: IS_CONTIGUOUS — Test whether an array is contiguous, Up: Intrinsic Procedures [Contents][Index]
IS_IOSTAT_END — Test for end-of-file valueIS_IOSTAT_END tests whether an variable has the value of the I/O
status “end of file”. The function is equivalent to comparing the variable
with the IOSTAT_END parameter of the intrinsic module
ISO_FORTRAN_ENV.
Fortran 2003 and later
Elemental function
RESULT = IS_IOSTAT_END(I)
| I | Shall be of the type INTEGER. |
Returns a LOGICAL of the default kind, which .TRUE. if
I has the value which indicates an end of file condition for
IOSTAT= specifiers, and is .FALSE. otherwise.
PROGRAM iostat IMPLICIT NONE INTEGER :: stat, i OPEN(88, FILE='test.dat') READ(88, *, IOSTAT=stat) i IF(IS_IOSTAT_END(stat)) STOP 'END OF FILE' END PROGRAM
Next: ISATTY — Whether a unit is a terminal device., Previous: IS_IOSTAT_END — Test for end-of-file value, Up: Intrinsic Procedures [Contents][Index]
IS_IOSTAT_EOR — Test for end-of-record valueIS_IOSTAT_EOR tests whether an variable has the value of the I/O
status “end of record”. The function is equivalent to comparing the
variable with the IOSTAT_EOR parameter of the intrinsic module
ISO_FORTRAN_ENV.
Fortran 2003 and later
Elemental function
RESULT = IS_IOSTAT_EOR(I)
| I | Shall be of the type INTEGER. |
Returns a LOGICAL of the default kind, which .TRUE. if
I has the value which indicates an end of file condition for
IOSTAT= specifiers, and is .FALSE. otherwise.
PROGRAM iostat IMPLICIT NONE INTEGER :: stat, i(50) OPEN(88, FILE='test.dat', FORM='UNFORMATTED') READ(88, IOSTAT=stat) i IF(IS_IOSTAT_EOR(stat)) STOP 'END OF RECORD' END PROGRAM
Next: ISHFT — Shift bits, Previous: IS_IOSTAT_EOR — Test for end-of-record value, Up: Intrinsic Procedures [Contents][Index]
ISATTY — Whether a unit is a terminal device.Determine whether a unit is connected to a terminal device.
GNU extension
Function
RESULT = ISATTY(UNIT)
| UNIT | Shall be a scalar INTEGER. |
Returns .TRUE. if the UNIT is connected to a terminal
device, .FALSE. otherwise.
PROGRAM test_isatty
INTEGER(kind=1) :: unit
DO unit = 1, 10
write(*,*) isatty(unit=unit)
END DO
END PROGRAM
Next: ISHFTC — Shift bits circularly, Previous: ISATTY — Whether a unit is a terminal device., Up: Intrinsic Procedures [Contents][Index]
ISHFT — Shift bitsISHFT returns a value corresponding to I with all of the
bits shifted SHIFT places. A value of SHIFT greater than
zero corresponds to a left shift, a value of zero corresponds to no
shift, and a value less than zero corresponds to a right shift. If the
absolute value of SHIFT is greater than BIT_SIZE(I), the
value is undefined. Bits shifted out from the left end or right end are
lost; zeros are shifted in from the opposite end.
Fortran 90 and later, has overloads that are GNU extensions
Elemental function
RESULT = ISHFT(I, SHIFT)
| I | The type shall be INTEGER. |
| SHIFT | The type shall be INTEGER. |
The return value is of type INTEGER and of the same kind as
I.
| Name | Argument | Return type | Standard |
ISHFT(A) | INTEGER A | INTEGER | Fortran 90 and later |
BSHFT(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IISHFT(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JISHFT(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KISHFT(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
Next: ISNAN — Test for a NaN, Previous: ISHFT — Shift bits, Up: Intrinsic Procedures [Contents][Index]
ISHFTC — Shift bits circularlyISHFTC returns a value corresponding to I with the
rightmost SIZE bits shifted circularly SHIFT places; that
is, bits shifted out one end are shifted into the opposite end. A value
of SHIFT greater than zero corresponds to a left shift, a value of
zero corresponds to no shift, and a value less than zero corresponds to
a right shift. The absolute value of SHIFT must be less than
SIZE. If the SIZE argument is omitted, it is taken to be
equivalent to BIT_SIZE(I).
Fortran 90 and later, has overloads that are GNU extensions
Elemental function
RESULT = ISHFTC(I, SHIFT [, SIZE])
| I | The type shall be INTEGER. |
| SHIFT | The type shall be INTEGER. |
| SIZE | (Optional) The type shall be INTEGER;
the value must be greater than zero and less than or equal to
BIT_SIZE(I). |
The return value is of type INTEGER and of the same kind as
I.
| Name | Argument | Return type | Standard |
ISHFTC(A) | INTEGER A | INTEGER | Fortran 90 and later |
BSHFTC(A) | INTEGER(1) A | INTEGER(1) | GNU extension |
IISHFTC(A) | INTEGER(2) A | INTEGER(2) | GNU extension |
JISHFTC(A) | INTEGER(4) A | INTEGER(4) | GNU extension |
KISHFTC(A) | INTEGER(8) A | INTEGER(8) | GNU extension |
Next: ITIME — Get current local time subroutine (hour/minutes/seconds), Previous: ISHFTC — Shift bits circularly, Up: Intrinsic Procedures [Contents][Index]
ISNAN — Test for a NaNISNAN tests whether a floating-point value is an IEEE
Not-a-Number (NaN).
GNU extension
Elemental function
ISNAN(X)
| X | Variable of the type REAL. |
Returns a default-kind LOGICAL. The returned value is TRUE
if X is a NaN and FALSE otherwise.
program test_nan implicit none real :: x x = -1.0 x = sqrt(x) if (isnan(x)) stop '"x" is a NaN' end program test_nan
Next: KILL — Send a signal to a process, Previous: ISNAN — Test for a NaN, Up: Intrinsic Procedures [Contents][Index]
ITIME — Get current local time subroutine (hour/minutes/seconds)ITIME(VALUES) Fills VALUES with the numerical values at the
current local time. The hour (in the range 1-24), minute (in the range 1-60),
and seconds (in the range 1-60) appear in elements 1, 2, and 3 of VALUES,
respectively.
This intrinsic routine is provided for backwards compatibility with
GNU Fortran 77. In new code, programmers should consider the use of
the DATE_AND_TIME — Date and time subroutine intrinsic defined by the Fortran 95
standard.
GNU extension
Subroutine
CALL ITIME(VALUES)
| VALUES | The type shall be INTEGER, DIMENSION(3)
and the kind shall be the default integer kind. |
Does not return anything.
program test_itime integer, dimension(3) :: tarray call itime(tarray) print *, tarray(1) print *, tarray(2) print *, tarray(3) end program test_itime
Next: KIND — Kind of an entity, Previous: ITIME — Get current local time subroutine (hour/minutes/seconds), Up: Intrinsic Procedures [Contents][Index]
KILL — Send a signal to a processSends the signal specified by SIG to the process PID.
See kill(2).
This intrinsic is provided in both subroutine and function forms; however, only one form can be used in any given program unit.
GNU extension
GNU extension
Subroutine, function
CALL KILL(PID, SIG [, STATUS]) |
STATUS = KILL(PID, SIG) |
| PID | Shall be a scalar INTEGER with INTENT(IN). |
| SIG | Shall be a scalar INTEGER with INTENT(IN). |
| STATUS | [Subroutine](Optional)
Shall be a scalar INTEGER.
Returns 0 on success; otherwise a system-specific error code is returned. |
| STATUS | [Function] The kind type parameter is that of
pid.
Returns 0 on success; otherwise a system-specific error code is returned. |
ABORT — Abort the program,
EXIT — Exit the program with status.
Next: LBOUND — Lower dimension bounds of an array, Previous: KILL — Send a signal to a process, Up: Intrinsic Procedures [Contents][Index]
KIND — Kind of an entityKIND(X) returns the kind value of the entity X.
Fortran 95 and later
Inquiry function
K = KIND(X)
| X | Shall be of type LOGICAL, INTEGER,
REAL, COMPLEX or CHARACTER. It may be scalar or
array valued. |
The return value is a scalar of type INTEGER and of the default
integer kind.
program test_kind
integer,parameter :: kc = kind(' ')
integer,parameter :: kl = kind(.true.)
print *, "The default character kind is ", kc
print *, "The default logical kind is ", kl
end program test_kind
Next: LCOBOUND — Lower codimension bounds of an array, Previous: KIND — Kind of an entity, Up: Intrinsic Procedures [Contents][Index]
LBOUND — Lower dimension bounds of an arrayReturns the lower bounds of an array, or a single lower bound along the DIM dimension.
Fortran 90 and later, with KIND argument Fortran 2003 and later
Inquiry function
RESULT = LBOUND(ARRAY [, DIM [, KIND]])
| ARRAY | Shall be an array, of any type. |
| DIM | (Optional) Shall be a scalar INTEGER. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
If DIM is absent, the result is an array of the lower bounds of
ARRAY. If DIM is present, the result is a scalar
corresponding to the lower bound of the array along that dimension. If
ARRAY is an expression rather than a whole array or array
structure component, or if it has a zero extent along the relevant
dimension, the lower bound is taken to be 1.
UBOUND — Upper dimension bounds of an array,
LCOBOUND — Lower codimension bounds of an array
Next: LEADZ — Number of leading zero bits of an integer, Previous: LBOUND — Lower dimension bounds of an array, Up: Intrinsic Procedures [Contents][Index]
LCOBOUND — Lower codimension bounds of an arrayReturns the lower bounds of a coarray, or a single lower cobound along the DIM codimension.
Fortran 2008 and later
Inquiry function
RESULT = LCOBOUND(COARRAY [, DIM [, KIND]])
| ARRAY | Shall be an coarray, of any type. |
| DIM | (Optional) Shall be a scalar INTEGER. |
| KIND | (Optional) An INTEGER initialization
expression indicating the kind parameter of the result. |
The return value is of type INTEGER and of kind KIND. If
KIND is absent, the return value is of default integer kind.
If DIM is absent, the result is an array of the lower cobounds of
COARRAY. If DIM is present, the result is a scalar
corresponding to the lower cobound of the array along that codimension.
UCOBOUND — Upper codimension bounds of an array,
LBOUND — Lower dimension bounds of an array
Next: LEN — Length of a character entity, Previous: LCOBOUND — Lower codimension bounds of an array, Up: Intrinsic Procedures [Contents][Index]
LEADZ — Number of leading zero bits of an integerLEADZ returns the number of leading zero bits of an integer.
Fortran 2008 and later
Elemental function
RESULT = LEADZ(I)
| I | Shall be of type INTEGER. |
The type of the return value is the default INTEGER.
If all the bits of I are zero, the result value is BIT_SIZE(I).
PROGRAM test_leadz WRITE (*,*) BIT_SIZE(1) ! prints 32 WRITE (*,*) LEADZ(1) ! prints 31 END PROGRAM
BIT_SIZE — Bit size inquiry function,
TRAILZ — Number of trailing zero bits of an integer,
POPCNT — Number of bits set,
POPPAR — Parity of the number of bits set
Next: LEN_TRIM — Length of a character entity without trailing blank characters, Previous: LEADZ — Number of leading zero bits of an integer, Up: Intrinsic Procedures [Contents][Index]
LEN — Length of a character entityReturns the length of a character string. If STRING is an array, the length of an element of STRING is returned. Note that STRING need no