NAG Fortran Compiler Release 7.2

Table of Contents

1 Name

nagfor — NAG Fortran Compiler Release 7.2

2 Usage

nagfor [mode] [option]... file...

3 Description

nagfor is the interface to the NAG Fortran Compiler system. The compiler translates programs written in Fortran into executable programs, relocatable binary modules, assembler source files or C source files.

The mode determines the action performed, and can be one of

=C Compile (and/or link) C source files, acting as the companion processor; this passes options to the C compiler that are suitable for the ABI and/or compatibility mode options specified, and differs from the =compiler mode in that it does not set NAG-specific macro definitions or alter the #include file search path to include the compiler library directory.
=compiler Compile (and/or link) the files; this is the default mode if none is specified.
=callgraph Produce a callgraph of the Fortran routines in the files (see the Producing a Call Graph section).
=depend Produce a dependency analysis of the Fortran files (see the Dependency Analysis section).
=epolish Pretty-print (polish) the Fortran files using the Enhanced Polisher (see the Enhanced Source File Polishing section).
=interfaces Produce a module or INCLUDE file containing procedure interfaces (see the Generating Interfaces section).
=polish Pretty-print (polish) the Fortran files (see the Source File Polishing section).
=unifyprecision Unify the precision of floating-point and complex entities in the files (see the Unifying Precision section).

Options that do not apply to the current mode of operation (e.g. polish options when the mode is for compilation) are ignored.

The mode can also be specified as -mode=mode; this may be useful if the user's command processor has a special meaning for equals signs (e.g. zsh).

4 File Types

A file ending in ‘.f90’ or ‘.f95’ is taken to be a Fortran free-form source file, a file ending in ‘.f’, ‘.for’ or ‘.ftn’ is taken to be a Fortran fixed-form source file; these assumptions can be overridden with the -fixed or -free option. A file ending in ‘.ff90’ or ‘.ff95’ is taken to be a free-form file requiring preprocessing by fpp, and a file ending in ‘.ff’ is taken to be a fixed-form file requiring preprocessing by fpp. A file ending in ‘.F90’ or ‘.F95’ is taken to be a free-form file requiring preprocessing by fpp, and a file ending in ‘.F’ is taken to be a fixed-form files requiring preprocessing by fpp.

If a filename without a suffix is provided nagfor will look for a file with the suffix ‘.f95’, and if that does not exist, the suffix ‘.f90’.

A file ending in ‘.c’ is taken to be a C source file. In the =compiler mode, this is assumed to be the output from the compiler with the -S option, and the C compiler is passed -D and -I options suitable for compiling such a file. In the =C mode, it is assumed to be a file for the companion processor; no -D is passed, and only -I options specified by the user. In both cases, options are passed to the C compiler according to the ABI and compatibility mode options.

Non-intrinsic modules, INCLUDE files and #include files are expected to exist in the current working directory or in a directory named by an -I option.

5 Compiler Options

-132
Increase the length of each fixed source form input line from 72 characters to 132 characters. This has no effect on free source form input.
-abi=abi
Specify the ABI to compile for, either 32 (the 32-bit ABI), or one of the 64-bit ABIs: 64c or 64t. The differences between the two 64-bit ABIs are as follows:

ABI Object size represented in Character length represented in
-abi=64t 64 bits 32 bits
-abi=64c 64 bits 64 bits

Programs compiled with -abi=32 will run on any x86 Linux system; those compiled with any 64-bit ABI will only run on a 64-bit kernel.

The default is -abi=64t. The -abi=64c option is compatible with the ABI used by Intel Fortran.

-Bbinding
Specify static or dynamic binding. This only has effect if specified during the link phase. The default is dynamic binding.
-c
Compile only (produce .o file for each source file), do not link the .o files to produce an executable file. This option is equivalent to -otype=obj.
-C
Compile with all but the most expensive runtime checks; this omits the -C=alias, -C=dangling, -C=intovf and -C=undefined options.
-C=check
Compile checking code according to the value of check, which must be one of:

alias (check for assignments to aliased dummy arguments),
all (perform all checks except for -C=undefined),
array (check array bounds),
bits (check bit intrinsic arguments),
calls (check procedure references),
dangling (check for dangling pointers),
do (check DO loops for zero step values and
illicit modification of the index variable via host association),
intovf (check for integer overflow),
none (do no checking: this is the default),
present (check OPTIONAL references),
pointer (check POINTER references),
recursion (check for invalid recursion) or
undefined (check for undefined variables).

The -C=alias option will produce a runtime error when it is detected that assignment to a dummy argument affects another dummy argument. At this release this is only detected for scalar dummy arguments.

The -C=dangling option will produce a runtime error when a dangling pointer is used; additionally, if the runtime option ‘show_dangling’ is set, a warning will be produced at the time the pointer becomes dangling (see Runtime Environment Variables for further information).

The -C=undefined option is subject to a number of limitations; in particular, it is not binary compatible with Fortran code compiled without that option, and is not compatible with calling C code via a BIND(C) interface. See the Undefined Variable Detection section for further details.

-coarray
This option is short for -coarray=cosmp.
-coarray=mode
Set the coarray operation mode to mode, which must be single for Single Image mode, or cosmp for Co-SMP mode; the option is not case-sensitive. The default is -coarray=single.

In Single Image mode (-coarray=single), all coarray syntax is accepted, but execution will not be in parallel: only a single image is supported.

In Co-SMP mode (-coarray=cosmp), parallel execution of multiple images on an SMP machine is supported. The maximum number of images in this mode is 1000. If the -num_images=N option is used, the default number of images to execute is N; with -num_images=auto, the default number of images is the number of hardware threads available on the processor. Note that the number of images may exceed the number of hardware threads, but doing so will only improve performance if images spend a lot of time waiting (e.g. for synchronisation or input/output). The -num_images= option may be overridden by the runtime environment variable NAGFORTRAN_NUM_IMAGES.

Code that uses any coarray features (coarray syntax or image control statements) or that has any common blocks or global (saved or initialised) variables, and that is compiled with -coarray=single, must never be executed in Co-SMP mode, as it will not work correctly. Code that avoids those features, and which is intended to work both in Co-SMP mode and single image mode, should be compiled with the -thread_safe option.

The -coarray=cosmp option cannot be used at the same time as the -openmp option. The -coarray=cosmp option may be specified with the -C=undefined option, but it will automatically disable the latter option.

-colour
Colour the message output from the compiler using ANSI escape sequences and the default foreground colouring scheme which is: red for error messages (including fatal errors), blue for warning messages and green for information messages.
-colour=scheme
Colour the message output from the compiler according to the specified scheme. This is a comma-separated list of colour specifications, each consisting of a message category name (“error”, “warn” or “info”) followed by a colon and the foreground colour name, optionally followed by a plus sign and the background colour name. The colouring for unspecified categories will be the default.

Colours are: black, red, green, yellow, blue, magenta, cyan and white.

E.g. -colour=error:red+blue,warn:cyan,info:magenta+yellow
would be a rather garish colour scheme.

-compatible
Make external linkages compatible with other compilers where possible; on Windows this is Microsoft Fortran (32-bit mode) or Intel Fortran (64-bit mode), on MacOS and Linux this is g77, g95 and gfortran, and on other systems this is the operating system vendor's compiler. This affects the naming convention and procedure calling convention (for example, on Windows it causes use of the “STDCALL” calling convention that is commonly used for most DLLs, and the names are in upper case with no added trailing underscore). On Windows in 64-bit mode, -compatible is always in effect.
-convert=format
Set the default conversion mode for unformatted files to format. This format may be overridden by an explicit CONVERT= specifier in the OPEN statement, or by the environment variable FORT_CONVERTn (where n is the unit number). The value of format must be one of the following (not case-sensitive):

Format Description
BIG_ENDIAN synonym for BIG_IEEE
BIG_IEEE_DD big-endian with IEEE floating-point, quad precision is double-double
BIG_IEEE big-endian with IEEE floating-point, including quad precision
BIG_NATIVE big-endian with native floating-point format
LITTLE_ENDIAN synonym for LITTLE_IEEE
LITTLE_IEEE_DD little-endian with IEEE floating-point, quad precision is double-double
LITTLE_IEEE little-endian with IEEE floating-point, including quad precision
LITTLE_NATIVE little-endian with native floating-point format
NATIVE no conversion (the default)
-Dname
Defines name to fpp as a preprocessor variable. This only affects files that are being preprocessed by fpp.
-d_lines
In fixed form only, accept lines beginning with “D” as normal Fortran statements, replacing the D with a space. Without this option, such lines are treated as comments.
-dcfuns
Enable recognition of non-standard double precision complex intrinsic functions. These act as specific versions of the standard generic intrinsics as follows:

Non-standard Equivalent Standard Fortran Generic Intrinsic Function
CDABS(A) ABS(A)
DCMPLX(X,Y) CMPLX(X,Y,KIND=KIND(0d0))
DCONJG(Z) CONJG(Z)
DIMAG(Z) AIMAG(Z)
DREAL(Z) REAL(Z) or DBLE(Z)
-double
Double the size of default INTEGER, LOGICAL, REAL and COMPLEX. Entities specified with explicit kind numbers or byte lengths are unaffected. If quadruple precision REAL is available, the size of DOUBLE PRECISION is also doubled.
-dryrun
Show but do not execute commands constructed by the compiler driver.
-dusty
Allows the compilation and execution of “legacy” software by downgrading the category of common errors found in such software from “Error” to “Warning” (which may then be suppressed entirely with the -w option). This option disables -C=calls, and also enables Hollerith i/o (see the -hollerith_io option).
-encoding=charset
Specifies that the encoding system of the Fortran source files is charset, which must be one of ISO_Latin_1, Shift_JIS or UTF_8. If this option is not specified, the default encoding is UTF-8 for Fortran source files that begin with a UTF-8 Byte Order Mark, and ISO Latin-1 (if the language setting is English) or Shift-JIS (if the language setting is Japanese) for other Fortran source files.
-english
Produce compiler messages in English (default).
-Error=class
Treat messages in class as being errors. The value of class must be one of the following (not case-sensitive):

Ancient use of an obsolete and non-standard FORTRAN 77 extension;
Deleted use of a feature that has been deleted from the Fortran standard;
Extension use of a feature that is an extension to the Fortran standard;
Obsolescent use of a feature that the Fortran standard says is obsolescent;
Questionable valid but questionable usage that may indicate a programming error;
Warning any warning-class message other than the above;
Any_Warning any of the above.

Note that -Error=Obsolescent implies -Error=Deleted, as all deleted features were previously obsolescent. Also, -Error=Extension implies -Error=Ancient, as ancient obsolete extensions are extensions.

Also note that messages do not have their prefix changed, e.g. a warning message will still begin ‘Warning:’, but if the -colour option is used, the message colour will be coloured as an error.

-F
Preprocess only, do not compile. Each file that is preprocessed will produce an output file of the same name with the suffix replaced by .f, .f90 or .f95 according to the suffix of the input file. This option is equivalent to -otype=Fortran.
-f90_sign
Use the Fortran 77/90 version of the SIGN intrinsic instead of the Fortran 95 one (they differ in the treatment of negative zero).
-f95
Specify that the base language is Fortran 95. This only affects extension message generation (Fortran 2003 and 2008 features will be reported as extensions).
-f2003
Specify that the base language is Fortran 2003. This only affects extension message generation (Fortran 2008 features will be reported as extensions).
-f2008
Specify that the base language is Fortran 2008. This is the default.
-f2018
Specify that the base language is Fortran 2018. This implies the -recursive option.
-fixed
Interpret all Fortran source files according to fixed-form rules.
-float-store
Do not store floating-point variables in registers on machines with floating-point registers wider than 64 bits. This can avoid problems with excess precision.
-fpp
Preprocess the source files using fpp even if the suffix would normally indicate an ordinary Fortran file.
-fpplonglines
This option directs the fpp preprocessor not to break output lines that are longer than 132 characters in free source form. (If broken, such lines may have #line directives in the middle of a continued token, and that may cause difficulty with other software tools.)
-free
Interpret all Fortran source files according to free-form rules.
-g
Produce information for interactive debugging by the host system debugger.
-g90
Produce debugging information for dbx90, a Fortran 90 aware front-end to the host system debugger. This produces a debug information (.g90) file for each Fortran source file. This option must be specified for both compilation and linking.
-gc
Enables automatic garbage collection of the executable program. This option must be specified for both compilation and linking, and is unavailable on IBM z9 OpenEdition, MacOS, and Windows. It is incompatible with the -thread_safe and -mtrace options. For more details see the Automatic Garbage Collection section.
-gline
Compile code to produce a traceback when a runtime error message is generated. Only routines compiled with this option will appear in such a traceback. This option increases both executable file size and execution time.

For example: 

   Runtime Error: Invalid input for real editing
   Program terminated by I/O error on unit 5 (Input_Unit,Formatted,Sequential)
   main.f90, line 28: Error occurred in READ_DATA
   main.f90, line 57: Called by READ_COORDS
   main.f90, line 40: Called by INITIAL
   main.f90, line 13: Called by $main$
-help
Display a one-line summary of the options available for the current mode (=compiler, =callgraph, =depend, =epolish, =interfaces, =polish or =unifyprecision).
-hollerith_io
Enable Fortran-66 compatible input/output of character data stored in numeric variables using the A edit descriptor. This was superseded by the CHARACTER datatype in Fortran 77.
-I pathname
Add pathname to the list of directories which are to be searched for module information (.mod) files and INCLUDE files. The current working directory is always searched first, then any directories named in -I options, then the compiler's library directory (see the -Qpath option).
-i8
Set the size of default INTEGER and LOGICAL to 64 bits. This can be useful for switching between libraries that have 32-bit integer arguments (on one platform) and 64-bit integer arguments (on another platform), but which do not provide a named constant with the necessary KIND value.

This has no effect on default REAL and COMPLEX sizes, so the compiler is not standard-conforming in this mode.

-indirect file
Read the contents of file as additional arguments to the compiler driver. This option may also be given by “@file”; note in this case there is no space between the ‘@’ and the file name.

In an indirect file, arguments may be given on separate lines; on a single line, multiple arguments may be separated by blanks. A blank can be included in an option or file name by putting the whole option or file name in quotes ("); this is the only quoting mechanism. An indirect file may reference other indirect files.

-ieee=mode
Set the mode of IEEE arithmetic operation according to mode, which must be one of full, nonstd or stop.
full
enables all IEEE arithmetic facilities including non-stop arithmetic.
nonstd
Disables non-stop arithmetic, terminating execution on floating overflow, division by zero or invalid operand. If the hardware supports it, this also disables IEEE gradual underflow, producing zero instead of a denormalised number; this can improve performance on some systems.
stop
enables all IEEE arithmetic facilities except for non-stop arithmetic; execution will be terminated on floating overflow, division by zero or invalid operand.

The -ieee option must be specified when compiling the main program unit, and its effect is global. The default mode is -ieee=stop. For more details see the IEEE 754 Arithmetic Support section.

-info
Request output of information messages, both “Info” and “Remark” (the least important). The default is to suppress these messages.
-kind=option
Specify the kind numbering system to be used; option must be one of byte, sequential or unique.

For -kind=byte, the kind numbers for INTEGER, REAL and LOGICAL will match the number of bytes of storage (e.g., default REAL is 4 and DOUBLE PRECISION is 8). Note that COMPLEX kind numbers are the same as its REAL components, and thus half of the total byte length in the entity.

For -kind=sequential (the default), the kind numbers for all datatypes are numbered sequentially from 1, increasing with precision (e.g., default REAL is 1 and DOUBLE PRECISION is 2).

For -kind=unique, the kind numbers are unique across all data types, so that a kind number for one data type cannot be accidentally used for another data type (except that COMPLEX and REAL are still the same). These kind numbers are all greater than 100 so do not match byte sizes either.

This option does not affect the interpretation of byte-length specifiers (an extension to Fortran 77).

-lx
Link with library libx.a. The linker will search for this library in the directories specified by -Ldir options followed by the normal system directories (see the ld(1) command).
-Ldir
Add dir to the list of directories for library files (see the ld(1) command).
-M
Produce module information files (.mod files) only. This option is equivalent to -otype=mod.
-max_internal_proc_instances=N
Set the maximum number of simultaneously active host instances of an internal procedure that is being passed as an actual argument, or assigned to a procedure pointer, to N. The default maximum is normally 30, and increased to 160 if either the -openmp or -thread_safe options are used.
-max_parameter_size=N
Set the maximum size of a PARAMETER to N MB (megabytes). N must be in the range 1 to 1048576 (1MB to 1TB); the default is 50 MB.
-maxcontin=N
Increase the limit on the number of continuation lines from 255 to N. This option will not decrease the limit below the standard number.
-mdir dir
Write any module information (.mod) files to directory dir instead of the current working directory.
-message_encoding=charset
Set the encoding scheme for compiler messages to charset, which must be one of ISO_Latin_1, Shift_JIS or UTF_8 (not case-sensitive). The -message_encoding=ISO_Latin_1 option is incompatible with the -nihongo option. The default message encoding is Shift_JIS on Windows and UTF_8 on other systems.
-mismatch
Downgrade consistency checking of procedure argument lists so that mismatches produce warning messages instead of error messages. This only affects calls to a routine which is not in the current file; calls to a routine in the file being compiled must still be correct. This option disables -C=calls.
-mismatch_all
Further downgrade consistency checking of procedure argument lists so that calls to routines in the same file which are incorrect will produce warnings instead of error messages. This option disables -C=calls.
-mtrace
Trace memory allocation and deallocation. This option is a synonym for -mtrace=on.
-mtrace=trace_opt_list
Trace memory allocation and deallocation according to the value of trace_opt_list, which must be a comma separated list of one or more of:
address (display addresses),
all (all options except for off),
line (display file/line info if known),
off (disable tracing output),
on (enable tracing output),
paranoia (protect memory allocator data structures against the user program),
size (display size in bytes) or
verbose (all options except for off and paranoia ).

This option should be specified during both compilation and linking, and is incompatible with the -gc option. For more details see the Memory Tracing section.

-nan
Initialise REAL and COMPLEX variables to IEEE Signalling NaN, causing a runtime crash if the values are used before being set. This affects local variables, module variables, and INTENT(OUT) dummy arguments only; it does not affect variables in COMMON or EQUIVALENCE.
-nihongo
Produce compiler messages in Japanese (if necessary, the encoding can be changed by the -message_encoding= option).
-no_underflow_warning
Suppress the warning message that normally appears if a floating-point underflow occurred during execution. This option is only effective if specified when compiling the main program.
-nocheck_modtime
Do not check for .mod files being out of date.
-nomod
Suppress module information (.mod) file production. Combining this with -M will produce no output (other than error and warning messages) at all, equivalent to -otype=none.
-nonstrict
Do not check for strict conformance to the Fortran standard, specifically:
  • do not produce obsolescence warning messages for use of ‘CHARACTER*’ syntax;
  • do not produce extension messages when the declared type of a value for a polymorphic allocatable component is an extension of the declared type of the component (this was a wording error in Fortran 2003, not corrected until Fortran 2018).
-noqueue
If no licence for the compiler is immediately available, exit with an error instead of queueing for it.
-not_openmp
Suppress the usual warning message if an OpenMP directive appears in a program when it is being compiled without the -openmp option. That is, it is deliberately being compiled without -openmp.
-num_images=N
Set the expected number of images the program will run with to N, which should be a number in the range 1 to 1000, ‘auto’, or ‘unknown’.

In Single Image mode (-coarray=single), the only affect is on analysis of constant cosubscripts: if N is numeric, and they evaluate to an image index greater than N, an error will be produced. The effect of -num_images=unknown (or -num_images=auto) is to suppress such analysis.

In CoSMP mode (-coarray=cosmp), the effect is to specify the default number of images at execution time; this may be overridden by the runtime environment variable NAGFORTRAN_NUM_IMAGES. The effect of -num_images=auto (or -num_images=unknown) is to set the default number of images to the number of hardware threads on the processor. This option takes effect when compiling the main program.

The default in -coarray=single mode is -num_images=1, and the default in -coarray=smp mode is -num_images=auto.

-o output
Name the output file output instead of the default. If an executable is being produced the default is a.out; otherwise it is file.o with the -c option, file.c with the -S option, and file.f, file.f90 or file.f95 with the -F option, where file is the base part of the source file (i.e. with the suffix removed).
-O
Normal optimisation, equivalent to -O2.
-ON
Set the optimisation level to N. The optimisation levels are:
-O0 No optimisation. This is the default, and is recommended when debugging.
-O1 Minimal quick optimisation.
-O2 Normal optimisation.
-O3 Further optimisation.
-O4 Maximal optimisation.
-Oassumed
This is a synonym for -Oassumed=contig.
-Oassumed=shape
Optimises assumed-shape array dummy arguments according to the value of shape, which must be one of
always_contig
Optimised for contiguous actual arguments. If the actual argument is not contiguous a runtime error will occur (the compiler is not standard-conforming under this option).
contig
Optimised for contiguous actual arguments; if the actual argument is not contiguous (i.e. it is an array section) a contiguous local copy is made. This may speed up array section accessing if a sufficiently large number of array element or array operations is performed (i.e. if the cost of making the local copy is less than the overhead of discontiguous array accesses), but usually makes such accesses slower. Note that this option does not affect dummy arguments with the TARGET attribute; these are always accessed via the dope vector.
section
Optimised for low-moderate accesses to array section (discontiguous) actual arguments. This is the default.

Note that CHARACTER arrays are not affected by these options.

-Oblock=N
Specify the dimension of the blocks used for evaluating the MATMUL intrinsic. The default value (only for -O1 and above) is system and datatype dependent.
-Onopropagate
Disable the optimisation of constant propagation. This is the default for -O1 and lower.
-Onoteams
Generate coarray access code assuming that teams are not being used. This will produce incorrect results if executed while a CHANGE TEAM construct is active.
-Opropagate
Enable the optimisation of constant propagation. This is the default for -O2 and higher.
-Orounding
Specify that the program does not alter the default rounding mode. This enables the use of faster code for the ANINT intrinsic.
-Ounroll=N
Specify the depth to which simple loops and array operations should be unrolled. The default is no unrolling (i.e. a depth of 1) for -O0 and -O1, and a depth of 2 for -O and higher optimisation levels. It can be advantageous to disable the Fortran compiler's loop unrolling if the C compiler normally does a very good job itself — this can be accomplished with -Ounroll=1.
-Ounsafe
Perform possibly unsafe optimisations that may depend on the numerical stability of the program.
-odir dir
Specifies, for the dependency analyser only (nagfor =depend), when generating Makefile dependencies using the -otype=make option, that the object files which depend on the source files are located in directory dir. For example, the object file that depends on “file.f90” will be considered to be “dir/file.o” instead of simply “file.o”.
-openmp
Enable OpenMP, producing extension messages for use of OpenMP features more recent than the currently fully-supported OpenMP version. In nagfor 7.1, this is equivalent to -openmp=3.1.
-openmp=version
Recognise OpenMP directives and link with the OpenMP support library. Produce extension messages for the use of OpenMP features more recent than OpenMP version, which must be equal to 3.0, 3.1, 4.0, 4.5, 5.0 or 5.1. For more details see the OpenMP Support section. This option is incompatible with the -coarray=smp option.
-otype=filetype
Specify the type of output file required to filetype, which must be one of

c (C source file),
exe (executable file),
fortran (Fortran source file),
mod (module information file),
none (no output file),
obj (object file).

The -c, -F and -M options are equivalent to -otype=obj, -otype=Fortran and -otype=mod respectively.

-pg
Compile code to generate profiling information which is written at run-time to an implementation-dependent file (usually gmon.out or mon.out). An execution profile may then be generated using gprof. This option must be specified for compilation and linking and may be unavailable on some implementations.
-pic
Produce position-independent code (small model), for use in a shared library. If the shared library is too big for the small model, use -PIC.
-PIC
Produce position-independent code (large model), for use in a shared library.
-quiet
Suppress the compiler banner and the summary line, so that only diagnostic messages will appear.
-Qpath pathname
Change the compiler library pathname from its default location to pathname. (The default location on Unix is usually ‘/usr/local/lib/NAG_Fortran’.)
-r8
Double the size of default REAL and COMPLEX, and on machines for which quadruple-precision floating-point arithmetic is available, double the size of DOUBLE PRECISION (and the non-standard DOUBLE COMPLEX). REAL or COMPLEX specified with explicit KIND numbers or byte lengths are unaffected — but since the KIND intrinsic returns the correct values, COMPLEX(KIND(0d0)) on a machine with quad-precision floating-point will correctly select quad-precision COMPLEX.

This has no effect on INTEGER sizes, and so the compiler is not standard-conforming in this mode.

Note: This option has been superseded by the -double option which doubles the size of all numeric data types.

-random=version
This option controls which pseudo-random-number generator will be used in calls to RANDOM_NUMBER in the file being compiled. If version is 7.2, the generator used will provide complete entropy even for the lowest-order bits of the random numbers. If version is 5.2, the previous version of the generator is used; this does not provide as much entropy in each individual number, but is significantly faster for double and quad precision. Other values for version are not allowed. The default is -random=7.2.
-recursive
Specifies that procedures are RECURSIVE by default. This is the default unless the -f95, -f2003 or -f2008 option is specified.
-round_hreal
Round all half precision operations to half precision. Without this option, half precision expressions are evaluated in single precision and only rounded to half precision when being assigned to a variable or passed as an actual argument to a non-intrinsic or non-mathematical procedure.

This option affects compile-time evaluation as well as runtime evaluation.

-s
Strip symbol table information from the executable file. This option is only effective if specified during the link phase.
-S
Produce assembler (actually C source code). The resulting .c file should be compiled with the NAG Fortran compiler, not with the C compiler directly. This option is equivalent to -otype=c.
-save
This is equivalent to inserting the SAVE statement in all subprograms which are not pure, not declared RECURSIVE, and not RECURSIVE by default (see the -recursive option). It thus causes all non-automatic local variables in such subprograms to be statically allocated. It has no effect on variables in BLOCK constructs.
-target=machine
Specify the machine for which code should be generated and optimised. For x86-32 (x86-compatible 32-bit mode compilation on Linux and Windows), machine may be one of
i486, i586, i686, pentium2, pentium3, pentium4, prescott the specified Intel processor,
k6, k6-2, k6-3, k6-4, athlon, athlon-4, athlon-xp, athlon-mp the specified AMD processor,
pentium (equivalent to i586) or
pentiumpro (equivalent to i686).

The default is to compile for pentium4 on Linux, and prescott on Windows.

For x86-64 (x86-compatible 64-bit mode compilation on Linux, MacOS and Windows), machine may be athlon64, nocona, or core2. On Linux and Windows, machine may also be nehalem, westmere, sandybridge, ivybridge, haswell, broadwell, skylake, zen, or native (which targets the current machine).

-tempdir directory
Set the directory used for the compiler's temporary files to directory. The default is to use the directory named by the TMPDIR environment variable, or if that is not set, /tmp on Unix-like systems and the Windows temporary folder on Windows.
-thread_safe
Compile code for safe execution in a multi-threaded environment. This must be specified when compiling and also during the link phase. It is incompatible with the -gc option.
-time
Report execution times for the various compilation phases.
-u
This is an abbreviation for -u=type.
-u=noimplicit-list
Control implicit and default settings according to the value of noimplicit-list, which must be a comma separated list of one or more of:
all equivalent to specifying all of the other sub-options;
external specifies IMPLICIT NONE (EXTERNAL), which requires all external and dummy procedures to either have an explicit interface, or to be explicitly given the EXTERNAL attribute;
locality specifies default locality of NONE in DO CONCURRENT constructs, as if DEFAULT(NONE) were explicitly specified;
sharing specifies default sharing of NONE in OpenMP PARALLEL and TASK constructs that do not have an explicit DEFAULT(…) clause (including in combined constructs such as PARALLELDO);
type specifies that IMPLICIT NONE (TYPE) is in effect by default (which disables implicit typing), unless overridden by explicit IMPLICIT statements.

The items in noimplicit-list may appear in any order, and are not case-sensitive.

-unsharedrts
Bind with the unshared (static) version of the Fortran runtime system; this allows a dynamically linked executable to be run on systems where the NAG Fortran Compiler is not installed. This option is only effective if specified during the link phase.
-v
Verbose. Print the name of each file as it is compiled.
-V
Print version information about the compiler.
-w
Suppress all warning messages. This option is a synonym for -w=all.
-w=class
Suppress the warning messages specified by class, which must be one of all, alloctr, longlines, note, obs, ques, uda, uei, uep, uip, ulv, unreffed, unused, uparam, usf, usy, x77 or x95.
-w=all
suppresses all warning messages;
-w=alloctr
suppresses warning messages about the use of allocatable components, dummy arguments and functions;
-w=longlines
suppresses warning messages about Fortran free source form lines being longer than permitted by the Fortran standard (132 characters up to Fortran 2018, 10000 characters from Fortran 2023) — the NAG Fortran Compiler accepts free source form lines of any length;
-w=note
Suppress informational Notes;
-w=obs
suppresses warning messages about the use of obsolescent features;
-w=ques
suppresses warning messages about questionable usage;
-w=uda
suppresses warning messages about unused dummy arguments;
-w=uei
suppresses warning messages about unused explicit imports;
-w=uep
suppresses warning messages about unused external procedures;
-w=uip
suppresses warning messages about unused intrinsic procedures;
-w=ulv
suppresses warning messages about unused local variables;
-w=unreffed
suppresses warning messages about variables set but never referenced;
-w=unused
suppresses warning messages about unused entities — this is equivalent to ‘-w=uda -w=uei -w=uep -w=uip -w=ulv -w=uparam -w=usf -w=usy’;
-w=uparam
suppresses warning messages about unused PARAMETERs;
-w=usf
suppresses warning messages about unused statement functions;
-w=usy
suppresses warning messages about unused symbols;
-w=x77
suppresses extension warnings for obsolete but common extensions to Fortran 77 — these are TAB format, byte-length specifiers, Hollerith constants and D lines;
-w=x95
suppresses extension warnings for extensions to modern Fortran (not just Fortran 95) that are not part of any Fortran standard.
-Woptions
The -W option can be used to specify the path to use for a compilation component or to pass an option directly to such a component. The possible combinations are:
-W0=path
Specify the path used for the Fortran Compiler front-end. Note that this does not affect the library directory; the -Qpath option should be used to specify that.
-Wc=path
Specify the path to use for invoking the C compiler; this is used both for the final stage of compilation and for linking.
-Wc,option
Pass option directly to the host C compiler when compiling (producing the .o file). Multiple options may be specified in a single -Wc, option by separating them with commas.
-Wl=path
Specify the path to use for invoking the linker (producing the executable).
-Wl,option
Pass option directly to the host C compiler when linking (producing the executable). Multiple options may be specified in a single -Wl, option by separating them with commas. A comma may be included in an option by repeating it, e.g. -Wl,-filelist=file1,,file2,,file3 becomes the linker option -filelist=file1,file2,file3. Note that options specified with -Wl, are appended to the linking command; for options that need to be in a specific place, the -xldarg option can be used.
-Wp=path
Specify the path to use for invoking the fpp preprocessor.
-Wp,option
Pass option directly to fpp when preprocessing.
-Warn=class
Produce additional warning messages specified by class, which must be one of:

allocation
warn if an intrinsic assignment might cause allocation of the variable (or a subcomponent thereof) being assigned to;
constant_coindexing
warn if an image selector has constant cosubscripts;
default_double_literals
note, and warn if inexact, default double precision literal constants;
reallocation
warn if an intrinsic assignment might cause reallocation of an already-allocated variable (or a subcomponent thereof) being assigned to;
subnormal
warn if an intrinsic operation or function with normal operands produces a subnormal result (reduced precision, less than TINY(...));
unkind_real_literals
note, and warn if inexact, default real literal constants with no kind specifier.

Reallocation only occurs when the shape of an array, the value of a deferred type parameter, or the dynamic type (if polymorphic), differs between the variable (or subcomponent) and the expression (or the corresponding subcomponent). Allocation can occur also when the variable (or subcomponent) is not allocated prior to execution of the assignment (except for broadcast assignment). Note that -Warn=allocation thus subsumes -Warn=reallocation.

-wmismatch=proc-name-list
Specify a list of external procedures for which to suppress argument data type and arrayness consistency checking. The procedure names should be separated by commas, e.g. -wmismatch=p_one,p2. Unlike the -mismatch option, this only affects data type and arrayness checking, and no warning messages are produced.
-xldarg arg
Pass arg to the linking phase. Unlike the -Wl, option, arg is in the position where the option occurs, as if it were a .o file. Also, multiple linking arguments cannot be combined in a single option with commas; each needs to be specified as a separate -xldarg option.
-xlicinfo
Report on the availability of licences for the compiler instead of compiling anything. Also report the exact version of Kusari being used.

6 Files

file.a Library of object files.
file.c C source file.
file.f Fortran source file in fixed source form (obsolete).
file.f90 Fortran source file in free source form.
file.f95 Fortran source file in free source form.
file.F Preprocessor source file for fixed-form Fortran (obsolete).
file.ff90 Preprocessor source file for free-form Fortran.
file.F90 Preprocessor source file for free-form Fortran.
file.ff95 Preprocessor source file for free-form Fortran.
file.F95 Preprocessor source file for free-form Fortran.
name.mod Compiled module information file; name is the name of the module in lower case.
file.o Object file
/opt/NAG_Fortran/lib Default NAG Fortran Compiler library directory on Sun Solaris (see -Qpath); referred to as library hereafter.
/usr/local/lib/NAG_Fortran Default NAG Fortran Compiler library directory on other Unix-based operating systems.
C:\Program Files\NAG\EFBuilder 7.2\nagfor\lib Default NAG Fortran Compiler library directory on 32-bit Windows.
C:\Program Files (x86)\NAG\EFBuilder 7.2\nagfor\lib Default NAG Fortran Compiler library directory on 64-bit Windows.
library/f90_iostat.f90 Source code for the f90_iostat module.
library/f90_kind.f90 Source code for the f90_kind module.
library/f90_stat.f90 Source code for the f90_stat module.
library/f90_util.f90 A sample Fortran 90 program that displays implementation-specific information
library/iso_fortran_env.f90 Source code for the iso_fortran_env module.
library/nagfmcheck.f90 Source code for the nagfmcheck program, see the Memory Tracing section.

7 Compilation Messages

The messages produced by the NAG Fortran Compiler itself during compilation are intended to be self-explanatory. The linker, or more rarely the host C compiler, may produce occasional messages.

Messages produced by the compiler are classified by severity level; these levels are:

Remark
a comment about the source code (this is the least important class of informational message).
Info
informational message, noting an aspect of the source code in which the user may be interested.
Note
an informational message of greater import than “Info”.
Warning
the source code appears likely to be in error.
Questionable
some questionable usage has been found in the source code which may indicate a programming error. This has the same severity as “warning”.
Extension
some non-standard-conforming source code has been detected but has successfully been compiled as an extension to the language. This has the same severity as “warning”.
Obsolescent
some archaic source code has been detected which although standard-conforming was classified as obsolescent by the Fortran standard (selected by a -fN option). This has the same severity as “warning”.
Deleted feature used
a feature that was present in an older Fortran standard but deleted from the Fortran standard (selected by a -fN option) was used. This has the same severity as “warning”.
Error
the source code does not conform to the Fortran standard or does not make sense. Compilation continues after recovery.
Fatal
a serious error in the user's program from which the compiler cannot recover, the compilation is immediately terminated.
Panic
an internal inconsistency is found by one of the compiler's self-checks; this is a bug in the compiler itself and NAG should be notified.

8 Compiler Limits

Item Limit
Maximum INCLUDE file nesting 20
Maximum number of INCLUDE file references per compilation 2047
Maximum DATA-implied-DO loop nesting 99
Maximum array-constructor-implied-DO loop nesting 99
Maximum number of dummy arguments 32767
Maximum number of arguments to MIN and MAX 100
Maximum character length (except as below) 2147483647
Maximum character length (64-bit Windows and -abi=64c Linux) 1099511627775 (240-1)
Maximum array size (32-bit systems) 2147483647 bytes
Maximum array size (64-bit systems) 1 TiB
Maximum unit number 2147483647
Maximum input/output record length 2147483647 bytes

9 Input/Output Information

Item Value
Standard error (stderr) unit number 0
Standard input (stdin) unit number 5
Standard output (stdout) unit number 6
Default maximum record length for formatted output 1024 characters
Default maximum record length for unformatted output 2147483647 bytes

The default directory used for files opened with STATUS='SCRATCH' is ‘/tmp’ on Unix and the Windows temporary directory on Windows. This default may be overridden with the TMPDIR environment variable.

10 OpenMP Support

OpenMP 3.1 is fully supported. Some features from more recent OpenMP specifications are also supported; check the Release Notes for details.

When using the IEEE arithmetic support modules, the IEEE modes (rounding, halting and underflow) are propagated into spawned OpenMP threads at the beginning of a PARALLEL construct, and any IEEE flag that are set by an OpenMP thread is passed back to the parent thread at the end of the PARALLEL construct.

The following table lists the OpenMP environment variables with their default values and, if applicable, their limits.

Environment Variable Default Limits
OMP_NUM_THREADS number of cores 1-32768
OMP_DYNAMIC False true or false
OMP_NESTED False true or false
OMP_STACKSIZE 0 <1GB (32-bit) or 16GB (64-bit)
OMP_WAIT_POLICY None active or passive
OMP_MAX_ACTIVE_LEVELS 1 1-64
OMP_THREAD_LIMIT 32768 1-32768
OMP_CANCELLATION False true or false

Note that although the NAG runtime supports up to 32768 threads, operating system limits may prevent usage of so many.

OpenMP is not compatible with the -coarray=cosmp option.

11 Automatic File Preconnection

All logical unit numbers are automatically preconnected to specific files. These files need not exist and will only be opened or created if they are accessed with READ or WRITE without an explicit OPEN. By default the specific filename for unit n is fort.n; however if the environment variable FORTnn exists its value is used as the filename. Note that there are two digits in this variable name, e.g. the variable controlling unit 1 is FORT01 whereas the default filename is ‘fort.1’ (unless the prefix has been changed, see the description of module F90_PRECONN_IO).

A file preconnected in this manner is opened with ACCESS='SEQUENTIAL'. If the initial READ or WRITE is an unformatted i/o statement, it is opened with FORM='UNFORMATTED' otherwise it is opened with FORM='FORMATTED'. By default a formatted connection is opened with BLANK='NULL' and POSITION='REWIND' (see module F90_PRECONN_IO).

Automatic preconnection applies only to the initial use of a logical unit; once CLOSEd the unit will not be reconnected automatically but must be explicitly OPENed.

Note that this facility means that it is possible for a READ or WRITE statement with an IOSTAT= clause to receive an i/o error code associated with the implicit OPEN.

12 IEEE 754 Arithmetic Support

If no floating-point option is specified, any floating divide-by-zero, overflow or invalid operand exception will cause the execution of the program to be terminated (with an informative message and usually a core dump). Occurrence of floating underflow may be reported on normal termination of the program. On hardware supporting IEEE 754 standard arithmetic gradual underflow with denormalised numbers will be enabled. Note that this mode of operation is the only one available on hardware which does not support IEEE 754.

If the -ieee=full option is specified, non-stop arithmetic is enabled; thus REAL variables may take on the values +Infinity, −Infinity and NaN (Not-a-Number). If any of the floating exceptions listed above are detected by the hardware during execution, this fact will be reported on normal termination. The -ieee=full option must be specified when compiling the main program and has global effect.

If the -ieee=nonstd option is specified, floating-point exceptions are handled in the default manner (i.e. execution is terminated). However, gradual underflow is not enabled, so results which would have produced a denormalised number produce zero instead. This option can only be used on hardware for which this mode of operation is faster. Like -ieee=full, the -ieee=nonstd option must be specified when compiling the main program and has global effect.

13 Half precision floating-point

Half precision (16-bit) floating-point is supported for values and variables of type REAL and COMPLEX. This floating-point kind conforms to the IEEE arithmetic standard (ISO/IEC/IEEE 60559:2011).

The intrinsic function SELECTED_REAL_KIND(3) and intrinsic module function IEEE_SELECTED_REAL_KIND(3) return the kind value for half precision. In -kind=byte mode, the value will be two; in -kind=sequential mode, it will be 16 (this unusual value was chosen to maintain upward compatibility of kind numbers).

The largest finite half-precision value is 65504.0, the smallest normal half-precision value is 0.00006103515625, and the smallest subnormal value is 0.000000059604644775390625.

Scalar half-precision operations are evaluated in single precision, and only rounded to half precision when assigned to a variable or passed as an actual argument to a non-intrinsic or non-mathematical procedure (e.g. SQRT is mathematical, but NEAREST is not). This can be controlled by the -round_hreal option; if used, all half-precision operations will be rounded to half precision, both at compile time and run time.

Because of all the conversions needed, half precision is slower than single precision; its sole benefit is halving the memory and file storage requirements.

14 Random Number Algorithm

The random number generator supplied as the intrinsic subroutine RANDOM_NUMBER is the “Mersenne Twister”.

Note that this generator has a large state (630 32-bit integers) and an extremely long period (approx 106000), and therefore it is strongly recommended that the RANDOM_SEED routine only be used with a PUT argument that is the value returned by a previous call with GET; i.e., only to repeat a previous sequence. This is because if a user-specified seed has low entropy (likely since there are 630 values to be supplied), it is highly likely to set the generator to an apparently-low-entropy part of the sequence.

If you do want to provide your own seed (and thus entropy), you should store your values in the initial elements of the seed array and set all the remaining elements to zero — trailing zero elements will be ignored and not used to initialise the generator. Note that the seed is a random bitstream, and is therefore expected to have approximately half of its bits nonzero (thus providing many small integer values will likely result in a low-entropy part of the Mersenne Twister sequence being reached).

With the -random=7.2 option (default), two 32-bit elements of the Mersenne Twister sequence are used for each double precision number, and four for each quad precision number. With the -random=5.2 option, only one element is used for a double precision number, and two for a quad precision number; this provides increased performance, but with reduced entropy in the low-order bits of each value.

15 Automatic Garbage Collection

The -gc option enables use of the runtime garbage collector. It is necessary to use this option during the link phase for it to have effect; specifying it additionally during the compilation phase can result in improved performance.

The supplied Technical Information note (TECHINFO) lists whether garbage collection is available for your system. If it is available, there will be a file ‘gc.o’ in the compiler's library directory.

The collector used is based on version 5.3 of the publicly available general purpose garbage collecting storage allocator of Hans-J Boehm, Alan J Demers and Xerox Corporation, described in “Garbage Collection in an Uncooperative Environment” (H Boehm and M Weiser, Software Practice and Experience, September 1988, pp 807-820).

The copyright notice attached to their latest version is as follows: 

Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved.
Copyright 1996-1999 by Silicon Graphics.  All rights reserved.
Copyright 1999 by Hewlett-Packard Company.  All rights reserved.


THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.

Permission is hereby granted to use or copy this program
for any purpose,  provided the above notices are retained on all copies.
Permission to modify the code and to distribute modified code is granted,
provided the above notices are retained, and a notice that the code was
modified is included with the above copyright notice.

Note that the “NO WARRANTY” disclaimer refers to the original copyright holders Boehm, Demers, Xerox Corporation, Silicon Graphics and Hewlett-Packard Company. The modified collector distributed in binary form with the NAG Fortran Compiler is subject to the same warranty and conditions as the rest of the NAG Fortran compilation system.

The module F90_GC is provided; it contains functions and variables that can control the behaviour of the garbage collector.

16 Memory Tracing

Tracing of memory allocation and deallocation is provided by the -mtrace option. Control is provided over whether the address, size, and line number of each allocation is displayed, or the tracing output can be suppressed entirely. A “paranoia” mode is provided where the memory allocator protects its data structures against inadvertent modification by the user program.

Runtime environment variables may be used to override the tracing options a program was built with, and to specify where to write the tracing output. These are only operative if the program was built with some tracing option; -mtrace=off will build a program with the tracing-capable memory allocator.

If -mtrace=off is not specified, use of any -mtrace option will implicitly do a -mtrace=on.

Basic tracing produces a message to the memory tracing file (normally standard error) for each allocation and deallocation, including those for automatic variables, i/o buffers and compiler-generated temporaries. Each allocation is numbered sequentially; the first three items are the i/o buffers for units 0, 5 and 6 (standard error, standard input and standard output).

All -mtrace= suboptions may be overridden at run time by the NAGFORTRAN_MTRACE_OPTIONS environment variable, which should be set to the required trace_opt_list (e.g. ‘on,size’). The memory tracing file may be specified at run time by the NAGFORTRAN_MTRACE_FILE environment variable.

The NAGFORTRAN_MTRACE_OPTIONS variable can also contain an option to limit the total amount of memory that may be allocated. The ‘limit=N’ option limits the maximum memory allocated to N MiB (mebibytes), but only if the program was built with a tracing option (minimally, -mtrace=off). Exceeding the memory limit will result in a normal “out of memory” condition, which if it occurs in an ALLOCATE statement, can be captured by a STAT= clause. Note that the memory limit applies to the overall memory usage including automatic variables and compiler-generated array temporaries.

The -mtrace option must be specified when linking, and is incompatible with -gc. Additionally, line number information is only available for those files compiled with -mtrace=line.

The nagfmcheck program can be used to check the output from the -mtrace option. It is designed to be used as a filter. Any lines that do not look like memory tracing output are ignored. It reports to standard output any errors it detects such as deallocating something twice, deallocating something that was never allocated, or deallocating something with a size different from that with which it was allocated. It also reports any apparent memory leaks, though this is less useful if the program terminated prematurely.

17 Undefined Variable Detection

Use of undefined variables can be detected with the -C=undefined option. Program units compiled with this option use a different ABI, which means that they are incompatible with program units compiled without this option, and not interoperable with C; thus the whole program must be Fortran code and compiled the same way. For this reason, -C=undefined is not part of -C or -C=all.

Currently, there are a number of other limitations on the use of -C=undefined.

  1. It is incompatible with pointers in an initialised COMMON.
  2. All intrinsic modules are available, but the ISO_C_BINDING module can only be used with all-Fortran programs as the option makes changes to the ABI.
  3. Internal READ from a CHARACTER array requires the entire specified array subobject to be “defined”, even those elements corresponding to records not actually read.
  4. Internal WRITE to a CHARACTER array is considered to define the entire specified array subobject, even those elements corresponding to records not actually written.
  5. Certain intrinsic functions require the entirety of their arguments to be defined, even if some portions are not actually required for the value of the function. For example, the PAD argument to RESHAPE when no padding is actually required, and elements of the ARRAY argument to PACK that correspond to false elements of the MASK.
  6. It is incompatible with the use of coarrays.
  7. It cannot be used on types with length type parameters.
  8. It cannot be used when CLASS(*) variables are allocated using the MOLD= specifier.
  9. It cannot be used with ALLOCATE when the SOURCE= expression is a CLASS(*) dummy and the actual argument is a constant.

18 Data Types

The table below lists the intrinsic data types provided by the NAG Fortran Compiler together with their kind numbers. There are three possible schemes for the intrinsic kind type parameters: the default mode of operation (which may be specified explicitly by the -kind=sequential option), the “byte” numbering scheme (specified by the -kind=byte option) and the “unique” numbering scheme (specified by the -kind=unique).

Type KIND Number KIND Number KIND Number Name Description
Name (sequential) (byte) (unique)
REAL 1 4 301 REAL32* Single precision floating-point
REAL 2 8 302 REAL64* Double precision floating-point
REAL 3 16 303 REAL128* Quad precision floating-point
REAL 16 2 304 REAL16* Half precision floating-point
COMPLEX 1 4 301 REAL32* Single precision complex
COMPLEX 2 8 302 REAL64* Double precision complex
COMPLEX 3 16 303 REAL128* Quadruple precision complex
COMPLEX 16 2 304 REAL16* Half precision complex
LOGICAL 1 1 201 BYTE Single byte logical
LOGICAL 2 2 202 TWOBYTE Double byte logical
LOGICAL 3 4 203 WORD Default logical
LOGICAL 4 8 204 LOGICAL64 Eight byte logical
INTEGER 1 1 101 INT8* 8-bit integer
INTEGER 2 2 102 INT16* 16-bit integer
INTEGER 3 4 103 INT32* 32-bit (default) integer
INTEGER 4 8 104 INT64* 64-bit integer
CHARACTER 1 1 646 ASCII ASCII or ISO 8859-1 character
CHARACTER 2 2 213 JIS JIS X 0213 character
CHARACTER 3 3 5323 UCS2 Unicode (UCS-2) character
CHARACTER 4 4 10646 UCS4 ISO 10646 (UCS-4) character

The Name column of the table indicates the name provided by the intrinsic module F90_KIND; the ones marked * are also provided by the standard intrinsic module ISO_FORTRAN_ENV. Using these names avoids the portability problems that arise if the kind numbers are hard-coded.

Note that on all machines except Sun Solaris with the SunPro C compiler, quadruple precision is actually “double double” precision; this provides nearly twice the precision of Double precision but with a reduced exponent range.

19 Modules

To use a module it must be an intrinsic module, previously compiled, or defined in the file prior to its use. When separately compiling a module the -c option should be specified.

Compiling a module creates a ‘.mod’ file and a ‘.o’ file. The ‘.mod’ file is used by the compiler at compile time to provide information about module contents, the ‘.o’ file (if generated) contains the code of any module procedures and must be specified when creating an executable file.

Note that the name of the ‘.mod’ file will be the name of the module, the ‘.o’ file will be named after the original source file.

When a previously compiled module is USEd the NAG Fortran Compiler attempts to find its source file and, if that is successful, checks the modification times producing a warning message if the ‘.mod’ file is out of date.

20 Runtime Environment Variables

The following variables control the runtime environment for programs compiled with the NAG Fortran Compiler.

NAGFORTRAN_MTRACE_FILE
Programs compiled using any -mtrace= option will write the memory trace to this file. The default is standard error.
NAGFORTRAN_MTRACE_OPTIONS
Changes the memory tracing options for programs compiled using any -mtrace= option.
NAGFORTRAN_NUM_IMAGES
Sets the number of images with which to execute a program in Co-SMP mode (it has no effect if the main program was compiled with -coarray=single). If the value of the variable is not an integer value, or is less than one or greater than 1000, it is ignored. In the absence of this variable, the number of images for a Co-SMP mode program is taken from the -num_images= option, or from the number of hardware threads.
NAGFORTRAN_RUNTIME_ERROR_FILE
Runtime error messages will be written to this file. The default is standard error.
NAGFORTRAN_RUNTIME_LANGUAGE
Controls the language used for runtime error messages. This may be ‘English’ or ‘Japanese’ (not case-sensitive); the default is English.
NAGFORTRAN_RUNTIME_OPTIONS
Controls runtime optional behaviour excluding memory tracing. This is a comma-separated list of options from the following list.

Option Effect
abort_on_error Signal abort on runtime error (default except on Windows).
autoskip_namelist Enable auto-skipping namelist input.
blank_common_size=N Set default size of blank COMMON blocks in Co-SMP mode.
floating_exception_warnings Display exception warnings on program termination (default).
log_autoskip_namelist Enable auto-skipping namelist input, with logging.
no_abort_on_error Non-zero exit on runtime error, without signalling abort.
show_dangling Enable tracing of dangling pointers (only with -C=dangling).
suppress_floating_exception_warnings Suppress all exception warnings on program termination.
suppress_underflow_warning Suppress floating underflow warning on program termination.
underflow_warning Display underflow warning on program termination.

The abort_on_error option causes the SIGABRT signal to be raised on error termination, via the abort() function. This is the default except on Windows.

The autoskip_namelist option enables autoskipping namelist input. In this mode, when the name after the ampersand in the input record does not match the namelist group name in the READ statement, instead of raising an i/o error condition it skips records until it finds one that begins with an ampersand and the correct name.

The blank_common_size=N option sets the default size of blank COMMON blocks to N bytes when executing in Co-SMP mode with multiple images; it has no effect otherwise. If not specified, the default size is one mebibyte (1048576 bytes). This option is only needed if blank COMMON blocks in different program units have different sizes, and the largest one is not encountered first.

The floating_exception_warnings option enables display, on normal termination, of any IEEE floating exception flags that are set, except for IEEE_INEXACT (that flag is nearly always set). This is the default.

The log_autoskip_namelist option enables autoskipping namelist input (as above), with logging. In this mode, when an autoskip occurs, the location of the READ statement and the action being taken are logged to standard error, for example: 

       [example.f90, line 5: Looking for namelist group NAME, skipping WRONG]

The show_dangling option causes messages to be produced on the runtime error file when a dangling pointer is created, reassociated with something else, nullified, or ceases to exist. The source code manipulating the dangling pointer needs to be compiled with the -C=dangling option for this to be effective. For example, 

[a.f90, line 20: Dangling pointer P detected (number 1), associated at b.f90, line 18]
[c.f90, line 7: Dangling pointer P (number 1) has been reassociated]
[c.f90, line 9: Dangling pointer Q (number 2) has been nullified]
[file.f90, line 21: Dangling pointer R (number 3) no longer exists]
The dangling pointer number is incremented every time a dangling pointer is detected. If an array with dangling pointer components ceases to exist, a message will be produced for each dangling pointer component of each element; however, the element subscripts will not be shown, instead ‘(...)’ will be produced to indicate that it is an array element, e.g. 
[file.f90, line 44: Dangling pointer X(...)%A (number 8) no longer exists]

The suppress_floating_exception_warnings option suppresses the warnings, on program termination, if the floating-point division-by-zero, invalid-operation or overflow flags are set.

The suppress_underflow_warning runtime option has the same effect as the -no_underflow_warning compilation option; that is, it suppresses the usual warning message on program termination when the floating-point underflow flag is set.

The underflow_warning runtime option requests that if the floating-point underflow flag is set on program termination, a warning message should be produced. This is the default behaviour, but the runtime option will override the -no_underflow_warning compilation option.

TMPDIR
Controls the directory used for scratch files (the default is system-dependent).

21 Debugging

For operating systems other than Windows a Modern Fortran-aware debugger might be available as dbx90; see TECHINFO.txt for details.

In general, host system debuggers, such as dbx or gdb, may be used successfully on Fortran code as the names of the original source files, plus line numbers, are passed through to the intermediate C files. In using such debuggers it should be noted that most local variables have an underscore appended to their names. It may be useful to look at the intermediate C code when debugging; this is produced by the -S option.

22 Producing a Call Graph

The call graph generator takes a set of Fortran source files and produces a call graph with optional index and called-by tables. C files and fpp-processed files are not handled.

The call graph generator understands the following compiler options with the same meaning: -132, -dcfuns, -double, -dryrun, -dusty, -encoding, -english, -f2003, -f2008, -f95, -fixed, -free, -help, -I, -i8, -indirect, -info, -kind, -max_parameter_size, -maxcontin, -mismatch, -mismatch_all, -nihongo, -nocheck_modtime, -nomod, -nonstrict, -noqueue, -o, -openmp, -Qpath, -r8, -thread_safe, -u, -u=, -v, -V, -w and -xlicinfo.

The “@filename” syntax may also be used, with the same effect as the “-indirect filename” option.

The call graph is written to the file specified by the -o option, or to standard output if no -o option is specified.

The following additional options control the output produced.

-calledby
Produce a “called-by” table showing, for each routine, the routines that call it directly or indirectly. This is produced at the end of the output.
-indent=N
Indent by N for each level in the graph, up to the maximum. The default is -indent=4.
-indent_max=N
The maximum indentation is N. The default is -indent_max=70.
-index
Produce an alphabetic index listing, for each routine, the line of the call graph where the routine first appears. This follows the call graph itself and precedes the called-by table (when the -calledby option is used).
-show_entry
Show ENTRY point names in the call graph; without this option, calls to an ENTRY point are shown as calls to the containing subprogram.
-show_generic
If a call is via a generic identifier, show the generic identifier in the call graph.
-show_host
Show the host scope names for calls to internal and module procedures.
-show_pclass
Show the class of each procedure (e.g. ‘module’, ‘internal’, ...).
-show_rename
If a called procedure was renamed on a USE statement, show the renaming.

23 Dependency Analysis

The dependency analyser takes a set of Fortran source files and produces dependency information in the form specified. C files and fpp-processed files are not handled.

The dependency analyser understands the following compiler options with the same meaning: -132, -dryrun, -english, -fixed, -free, -help, -I, -indirect, -maxcontin, -nihongo, -o, -Qpath, -tempdir, -v and -V. The “@filename” syntax may also be used with the same effect as the “-indirect filename” option.

The following additional options control the operation of the dependency analyser:

-otype=type
This option controls the output form, type must be one of:

blist (the filenames as an ordered build list),
dfile (the dependencies in Makefile format, written to separate file.d files),
info (the dependencies as English descriptions) or
make (the dependencies in Makefile format).

The default is -otype=info. If -otype=dfile is specified, no -o option is permitted; otherwise, the result is written to the file specified by the -o option or to standard output if no -o option is specified.

-paths=pathtype
Specifes the form to use for dependency paths; pathtype must be either absolute or relative. With -paths=absolute, paths for INCLUDE files that are relative specifications will be prefixed by the current working directory.

24 Generating Interfaces

The interface generator takes a set of Fortran source files and produces interfaces for the procedures therein. The output is either a module (in a new source file), or an INCLUDE file.

The interfaces are written either to the file specified by the -o option, or if module output is being produced to the file with the same name as the module and extension ‘.f90’, or otherwise (an INCLUDE file is being produced) to ‘interfaces.inc’. In each case the interfaces are all within a single INTERFACE block.

The interface generator understands the following compiler options with the same meaning: -132, -dcfuns, -double, -dryrun, -dusty, -encoding, -english, -f2003, -f2008, -f95, -fixed, -free, -help, -I, -i8, -indirect, -info, -kind, -max_parameter_size, -maxcontin, -mismatch, -mismatch_all, -nihongo, -nocheck_modtime, -nonstrict, -noqueue, -o, -openmp, -Qpath, -r8, -tempdir, -thread_safe, -u, -u=, -v, -V, -w and -xlicinfo.

The interface generator understands all the enhanced polish options with the same meaning.

The following additional options control the operation of the interface generator:

-cmt_generation
Add a comment before the INTERFACE statement, giving the date and time that the file was generated. This is the default.
-cmt_provenance
Add a comment after each procedure heading (SUBROUTINE or FUNCTION statement) indicating the source of the procedure.
-module=X
Specifies the name of the module to generate containing procedure interfaces. The default is ‘interfaces’.
-otype=type
Specify the type of output file required to type, which must be one of

include (INCLUDE file),
module (Fortran module in a new source file).

The default is -otype=module.

-nocmt_generation
Do not add any comment before the INTERFACE statement.
-nocmt_provenance
Do not add any comment after each procedure heading. This is the default.

25 Source File Polishing

The polisher takes a set of Fortran source files, which may be in fixed or free form, and produces a free source form “polished” version of each file. C files and fpp-processed files are not handled.

The polisher understands the following compiler options with the same meaning: -132, -encoding, -english, -f2003, -f2008, -f95, -fixed, -free, -help, -I, -indirect, -info, -maxcontin, -nihongo, -noqueue, -o, -openmp, -Qpath, -tempdir, -v, -V, -w and -xlicinfo.

The polished output is written to the file specified by the -o option, or to the same filename with the extension replaced by ‘.f90_pol’ if no -o option is specified. The output file cannot have the same name as the input file.

The following additional options control the operation of the polisher:

-align_right_continuation
Align the continuation markers (ampersands) at the end of a continued line to column N+2, where N is the normal line width (specified by the -width= option). This only affects lines that do not end with an inline comment.
-alter_comments
Enable options to alter comments; without this option, any options that would otherwise alter the comments are ignored.
-array_constructor_brackets=X
Specify the form to use for array constructor delimiters; X must be one of Asis (same as the input file), ParenSlash (use parentheses+slash pairs, i.e. ‘(/ ... /)’) or Square (use square brackets, i.e. ‘[ ... ]’). The default is -array_constructor_brackets=Asis.
-blank_cmt_to_blank_line
Turn comment lines that have no text (other than the comment-initiating character) into plain blank lines; this is the default if the -alter_comments option is set.
-blank_line_after_decls
Ensure that there is a blank line after the declarations and before the first executable statement; this is the default.
-bom=X
Specify whether to write a Unicode Byte-Order Mark at the beginning of the output file; X must be one of Asis (same as the input file), Insert (insert a byte-order mark) or Remove (remove any byte-order mark). This option only has effect if the input file is known to be in UTF-8 encoding, either because it begins with a byte-order mark or the -encoding=UTF8 option was used. The default is -bom=Asis.
-break_long_comment_word
If a comment line will be split into two lines, the comment may be broken in the middle of a long word.
-canonicalise_floating_literals
Specifies canonicalisation of floating-point literal constants. The canonical form of a floating-point literal always has a decimal point, with at least one digit before it and after it. If it has an exponent letter of E, the exponent is always non-zero. If there is an exponent, the exponent letter is always followed by a sign, and the exponent value has no leading zero.
-character_decl=style
Specify the style to be used for CHARACTER type declaration statements; style must be one of the following (not case-sensitive):

Asis (same as the input statement, but obey any -kind_keyword= option),
Keywords (use LEN= and KIND=),
Kind_Keyword_Only (use KIND= but not LEN=) or
No_Keywords (use modern style with no keywords).

The default is Asis; with any other style, the obsolescent “CHARACTER*length” form will be changed to the modern “CHARACTER(length)” form. When both the length and kind appear in the input statement, the length will appear first in the output statement.

-commas_in_formats=X
Specify whether to add optional commas in FORMAT statements; X must be one of Asis (use the same comma scheme as the input), Insert or Remove. The default is -commas_in_formats=Insert.
-dcolon_column=N
Align double colon ‘::’ in declarations at column N and align any subsequent continuation lines to match. The default is for no special alignment, which is equivalent to -dcolon_column=0.
-dcolon_in_decls=X
Specifies how to handle the optional double colon ‘::’ in declarations; X must be one of Asis (preserve the input status), Insert (insert ‘::’ if not present), or Remove (remove ‘::’ if present and optional); the default is -dcolon_in_decls=Asis.
-delete_all_comments
Delete all comments (if the -alter_comments option is set).
-delete_blank_lines
Delete blank lines and comment lines that have no text (other than the comment-initiating character), if the -alter_comments option is set.
-delete_unused_labels
Delete labels that are never referenced; this is the default.
-elcase=X
Set the case to use for exponent letters (E or D): X must be one of Asis, lowercase, UPPERCASE, or an abbreviation thereof; the default is -elcase=UPPERCASE. The interpretation of X is not case-sensitive (e.g. -elcase=u is the same as -elcase=U). Note that -elcase=Asis is only available for basic polishing (=polish), not in Enhanced Polish (=epolish) or any other tool (e.g. =unifyprecision).
-format_start=N
If renumbering FORMAT statements in a separate sequence, the first FORMAT statement will be N; the default is -format_start=90000.
-format_step=N
If renumbering FORMAT statements in a separate sequence, the step from one label to the next will be N; the default is -format_step=10. Note that this may be negative (but not zero).
-idcase=X
Set the case to use for identifiers; X must be one of Asis, Capitalised, lowercase, UPPERCASE, Camel_Case, or an abbreviation thereof (both C and Ca are treated as Capitalised, not Camel_Case); the default is -idcase=lowercase. The interpretation of X is not case-sensitive (e.g. -idcase=u is the same as -idcase=U). Note that -idcase=Asis is only available for basic polishing (=polish), not in Enhanced Polish (=epolish) or any other tool (e.g. =unifyprecision).
-indent=N
Indent statements within a construct by N spaces from the current indentation level; the default is -indent=2.
-indent_comment_marker
When indenting comments, the comment-initiating character should be indented to the indentation level; this is the default.
-indent_comments
Indent comments; this is the default if the -alter_comments option is set. The result is also affected by the -indent_comment_marker option.
-indent_continuation=N
Indent continuation lines by an additional N spaces; the default is -indent_continuation=2.
-indent_max=N
Set the maximum indentation level to N spaces; the default is -indent_max=60. The value must be at least 10 less than the output line length (-width=).
-inline_comment_indent=N
Set the indentation level for inline comments to column N; the default is -inline_comment_index=35.
-keep_blank_lines
Do not delete blank lines or comment lines with no text; this is the opposite of -delete_blank_lines and is the default.
-keep_comments
Do not delete non-blank comment lines; this is the opposite of -delete_comments and is the default.
-keep_unused_labels
Do not delete unused (unreferenced) labels; this is the opposite of -delete_unused_labels.
-kind_keyword=X
Specifies how to handle the KIND= specifier in declarations; X must be one of Asis (take no action but preserve the input status), Insert (insert KIND= if not present), or Remove (remove KIND= if present); the default is -kind_keyword=Asis.
-kwcase=X
Set the case to use for language keywords; X must be one of Capitalised, lowercase, UPPERCASE, Camel_Case, or an abbreviation thereof (both C and Ca are treated as Capitalised, not Camel_Case); the default is -kwcase=Capitalised. The interpretation of X is not case-sensitive (e.g. -kwcase=u is the same as -kwcase=U). The -kwcase=C produces ‘Double Precision’ and ‘Non_recursive’; with -kwcase=Camel, the latter is produced as ‘Non_Recursive’.
-label_after_indent
Indent labels; this is the opposite to -label_before_indent.
-label_before_indent
Output the statement label, if any, before indenting the statement; this is the default.
-leave_formats_in_place
Leave FORMAT statements in the same position as they are in the input file; this is the opposite of -move_formats_to_end, and is the default.
-margin=N
Set the left margin (initial indent) to N. The value must be at least 10 less than the output line length (-width=). The default value for the left margin is 4.
-move_formats_to_end
Move FORMAT statements to the end of the subprogram or program unit, immediately before the CONTAINS or END statement.
-name_scopes=X
Specify whether to add optional keywords and scope names to the END or END TYPE statement for a scope; X must be one of Asis (leave as is), Insert (insert keywords and/or names), Keywords (insert keywords but remove names) or Remove (remove optional keywords and names). This option also applies to the END INTERFACE statement. The default is -name_scopes=Keywords.
-noalign_right_continuation
Do not align the continuation markers (ampersands) at the end of continued lines; this is the default.
-noalter_comments
Do not alter comments in any way; this is the default.
-noblank_cmt_to_blank_line
Do not turn blank comments to blank lines.
-noblank_line_after_decls
Do not insert a blank line between the last declaration and the first executable statement.
-nobreak_long_comment_word
If a comment line will be split into two lines, do not break the comment in the middle of a long word; this is the default.
-nodcolon_column
Do not align double colon ‘::’ in declarations. This is the default, and is equivalent to specifying alignment at column zero via -dcolon_column=0.
-noindent_comment_marker
Place the comment-initiating character for a comment line in column 1.
-noindent_comments
Do not indent the text of a comment line.
-norenumber
Do not renumber statement labels.
-noseparate_format_numbering
When renumbering statement labels, use a single sequence for both FORMAT and non-FORMAT statements; this is the default.
-noterminate_do_with_enddo
Do not change DO loop terminating statements.
-nowrap_comments
Do not wrap long comment lines (they will still be indented if comments are being indented).
-relational=X
Specifies the form to use for relational operators, X must be either F77- (use .EQ., .LE., etc.) or F90+ (use ==, <=, etc.); the default is -relational=F90+.
-renumber
Renumber statement labels; this is the default.
-renumber_start=N
When renumbering statement labels, the first label will be N; the default is -renumber_start=100.
-renumber_step=N
When renumbering statement labels, the step from one label to the next will be N; the default value is -renumber_step=10.
-separate_format_numbering
When renumbering statement labels, renumber FORMAT statements in a separate sequence from non-FORMAT statements.
-terminate_do_with_enddo
Change the terminating statements of all DO loops so that each loop ends with an ENDDO statement; this is the default.
-width=N
Set the maximum length of the text on each output line to N; the default is -width=78. Note that in the case of continuation lines, an additional two characters (‘ &’) will be produced after the last text on a line and this may take the line length over the limit. The width must be at least 10 more than the left margin (-margin=) and the maximum indent (-indent_max=). The maximum width setting is 10204, however values higher than 9998 may produce output that does not conform to the Fortran 2018 standard, and values higher than 130 may procedure output that does not conform to older Fortran standards.
-wrap_comments
Wrap long comment lines that would otherwise exceed the maximum line length. This is the default.

26 Enhanced Source File Polishing

The enhanced polisher takes a set of Fortran source files, which may be in fixed or free source form, and produces a free source form “polished” version of each file. C files and fpp-processed files are not handled. Unlike the simple polisher, the Fortran source files must be compilable without error; this is because the information needed for enhanced polishing requires successful semantic analysis of the files.

The enhanced polisher understands the following compiler options with the same meaning: -132, -abi, -dcfuns, -double, -dryrun, -dusty, -encoding, -english, -f2003, -f2008, -f95, -fixed, -free, -help, -I, -i8, -indirect, -info, -kind, -max_parameter_size, -maxcontin, -mismatch, -mismatch_all, -nihongo, -nocheck_modtime, -nomod, -nonstrict, -noqueue, -o, -openmp, -Qpath, -r8, -tempdir, -thread_safe, -u, -u=external, -u=locality, -u=sharing, -v, -V, -w and -xlicinfo.

The enhanced polisher includes all the simple polish options, which are not repeated here, except for -idcase=Asis.

Note that unlike nagfor =polish, -name_scopes=Asis acts as if it were -name_scopes=Keywords, which is the default. Similarly, -array_constructor_brackets=Asis acts as if it were -array_constructor_brackets=ParenSlash, and is the default, and -dcolon_in_decls=Asis acts as if it were -dcolon_in_decls=Insert, and is the default.

The default filename extension for the output file is ‘.f90_epo’, used when no -o option is specified.

The following additional options control the operation of this tool.

-add_arg_keywords
Add keywords to actual arguments in references to user-defined procedures with an explicit interface and at least two dummy arguments, and in references to intrinsic procedures and intrinsic module procedures with at least three dummy arguments (except for MAX and MIN, where it is at least three actual arguments).

Keywords are not added to arguments that precede a label argument. The order of the arguments is unchanged.

This option is equivalent to -add_arg_keywords=all2,intrinsic3.

-add_arg_keywords=proc_class_list
Add keywords to actual arguments in procedure references, when the procedure has an explicit interface, for the classes of procedure listed in proc_class_list, which is a comma-separated list that may contain the following suboptions:

all (all classes of procedure),
bound (object-bound and type-bound procedures),
dummy (dummy procedures),
external (external procedures),
internal (internal procedures),
intrinsic (intrinsic procedures and intrinsic module procedures),
module (non-intrinsic module procedures),
user (procedures other than intrinsic procedures and intrinsic module procedures).

Keywords are not added to arguments that precede a label argument. The order of the arguments is unchanged. Procedure pointer components are also known as “object-bound procedures”, and thus included in -add_arg_keywords=bound; named procedure pointers are treated as external procedures and thus included in -add_arg_keywords=external.

A suboption name may be followed by a single nonzero digit (e.g. “intrinsic3”); this specifies that for procedures covered by that suboption, keywords are only to be added if the procedure has at least that many dummy arguments. For type-bound and object-bound procedures, the passed-object dummy argument does not count towards the limit (as it never appears in the argument list). The intrinsic MAX and MIN functions use the number of actual arguments instead.

A suboption name followed by a digit may be further followed by the letter ‘a’ (e.g. “intrinsic3a”; this specifies that the argument limit applies to the number of actual arguments in a reference to the procedure, not the number of dummy arguments (the number of actual arguments will be less than the number of dummy arguments when an optional argument is omitted).

Note that suboptions are parsed from left to right, and later suboptions override earlier ones.

-case:kind=case-list
Specifies case rules for specific kinds of name; this option overrides other case options except for -casex. The colon is followed by a comma-separated list of “kind=case”, where case is a case specification (UPPERCASE, lowercase, Capitalised, Camel_Case), and kind is one of the categories listed below:

comp Component
constr Construct name
intr Intrinsic procedure
param PARAMETER
proc Procedure
tbp Type-bound procedure
tparam Derived type parameter
type Derived type
var Variable

For example, -case:var=lower,proc=u specifies lowercase for variables and UPPERCASE for procedures. If there is no setting for a particular kind of name, it will fall back to an appropriate category; param, type, comp, tparam and proc all fall back to var, intr will fall back to proc, and tbp will fall back to comp or proc. If there is no rule or fall-back rule, the -idcase= option setting (or default) is used.

-casex:name-list
Specifies exceptions to the case rules. The colon is followed by a comma-separated list of names in the exact case required. For example, -casex:MaxVal,XYz will result in every occurence of a name equivalent to maxval or xyz appearing as MaxVal or XYz respectively.
-intrinsic_case=analogy
Specifies whether the case of an intrinsic procedure name should be the same as other names (as_names), or the same as language keywords (as_keywords). The default is -intrinsic_case=as_names.
-remove_intrinsic_stmts
Specifies that intrinsic procedure names that were not passed as actual arguments should be removed from INTRINSIC statements, and that if all the names in an INTRINSIC statement are removed in this way, the INTRINSIC statement itself should be removed. Any comments associated with the INTRINSIC statement will remain.
-subroutine_parens
Specifies that empty parentheses should appear on argumentless SUBROUTINE and CALL statements. By default, these optional parentheses are omitted (except for a SUBROUTINE statement with a BIND(C) clause).

27 Unifying Precision

The precision unifier standardises floating-point and complex variable declarations, floating-point and complex literal constants, and some specific (non-generic) intrinsic procedures in a set of Fortran source files in order to unify the precision of these entities.

Standardisation to quadruple precision is only available on machines for which quadruple-precision floating-point arithmetic is available.

The tool attempts to make a standardising precision parameter accessible in program units (and interface blocks) via a use statement. You can control the form of this statement: the -pp_name= option controls the name of the precision parameter, and the -pp_module= option supplies the name of its host module (which is known as the ‘precision module’). The default form for the use statement (when no options are specified) is USE WORKING_PRECISION, ONLY: WP.

The -precision= option (whose default value is Double) can be supplied to set the desired unifying precision. The tool will use this setting when performing a number of checks of the validity of the standardisation process on the input files.

The precision module can be created by the tool, but otherwise does not itself undergo precision unification. A warning is issued if the tool encounters this module. A message is also emitted if no definition for the precision parameter is found in the module, or otherwise if the defined precision parameter specifies a different kind to the desired precision as provided or implied by the -precision= option.

The tool searches each program unit and interface block in the input source and determines whether the precision parameter is already accessible. If it is not, then a use statement, in the form given above, is inserted in the last allowable position for its statement type. For an internal or module procedure this statement is placed in the host. If the precision parameter is already declared in the form INTEGER, PARAMETER :: wp = constant_expression, then this declaration is deleted and a new use statement added, as previously described. (This PARAMETER form of statement is only recognised as declaring the precision parameter if it precedes all declarations of floating-point or complex entities in the scoping unit.) Any other form of definition or import of the precision parameter will not be modified, and the tool issues a warning that the standardised use statement could not be inserted.

Type declarations for floating-point and complex entities are standardised to include the precision parameter as kind parameter. Entities that are implicitly typed to be floating-point or complex are explicitly declared, in the same form. In the case when a function is defined with a floating-point or complex type specification on the function statement, this specification is deleted and a distinct type declaration statement for the function result is inserted into the function's declaration section.

Floating-point and complex literal constants are standardised to use the precision parameter as their kind.

The option -pu_floats= controls the extent of precision conversions that are applied. The default behaviour described above for floating-point and complex entities corresponds to -pu_floats=On. The value -pu_floats=Default_Kinds may be supplied in order to limit the precision unification only to entities having default kind; i.e., kind specifiers already given in type declarations or for literals will be preserved, even if they differ from the desired unifying precision. Modification of all floating-point and complex entities may be suppressed altogether via -pu_floats=Off.

The following specific procedure references are standardised to the generic replacement listed below:

Specific Generic Specific Generic Specific Generic
ALOG10 LOG10 DATAN ATAN DSINH SINH
ALOG LOG DBLE REAL DSIN SIN
AMAX0(...) REAL(MAX(...)) DCMPLX CMPLX DSQRT SQRT
AMAX1 MAX DCONJG CONJG DTANH TANH
AMIN0(...) REAL(MIN(...)) DCOS COS DTAN TAN
AMIN1 MIN DCOSH COSH FLOAT REAL
AMOD MOD DDIM DIM IABS ABS
CABS ABS DEXP EXP IDIM DIM
CCOS COS DIMAG AIMAG IDINT INT
CDABS ABS DINT AINT IDNINT NINT
CEXP EXP DLOG10 LOG10 IFIX INT
CLOG LOG DLOG LOG ISIGN SIGN
CSIN SIN DMAX1 MAX MAX0 MAX
CSQRT SQRT DMIN1 MIN MAX1(...) INT(MAX(...))
DABS ABS DMOD MOD MIN0 MIN
DACOS ACOS DNINT ANINT MIN1(...) INT(MIN(...))
DASIN ASIN DREAL REAL SNGL REAL
DATAN2 ATAN2 DSIGN SIGN

(See also the description of -dcfuns.)

Furthermore, DBLE is converted to REAL. Following that, the KIND= argument is added to calls to REAL and CMPLX, when appropriate.

In cases where unifying the precision of the input source may lead in the generated output to undesirable side effects, or even invalid Fortran, the tool will attempt to issue a warning alerting you to the possibility. Here is a non-exhaustive list of situations where it may be inappropriate to apply this tool.

  1. Your source intentionally uses a mix of floating-point and complex precisions and you are running the tool in (the default) mode -pu_floats=On.
  2. You are employing Fortran language features for generic programming (such as generic interface blocks or parameterised derived types).
  3. You have floating-point or complex data in EQUIVALENCE statements or in references to the TRANSFER intrinsic.
  4. You have explicitly-typed intrinsic functions, or are passing intrinsic functions as procedure arguments.
  5. You are using the DPROD intrinsic (perhaps as a means of performing higher- (double-) precision computations in a single-precision program unit).
  6. You are mixing Fortran and non-Fortran code.

For procedures spread across several files clearly it is desirable to make sure this tool is applied to all files consistently. This will ensure, for example, that procedure references and the corresponding procedure definitions do not become inconsistent with respect to the type standardisation.

The precision unifier understands the following compiler options with the same meaning: -132, -abi, -dcfuns, -double, -dryrun, -dusty, -encoding, -english, -f2003, -f2008, -f95, -fixed, -free, -help, -I, -i8, -indirect, -info, -kind, -max_parameter_size, -maxcontin, -mismatch, -mismatch_all, -nihongo, -nocheck_modtime, -nomod, -nonstrict, -noqueue, -o, -openmp, -Qpath, -r8, -tempdir, -thread_safe, -u, -u=, -v, -V, -w and -xlicinfo.

Note that using the -double or -r8 option affects the meaning of the -precision= option; see the description of the latter, below.

The standardised output is written to the file specified by the -o option, or to the same filename with the extension replaced by ‘.f90_prs’ if no -o option is specified. The output file cannot have the same name as the input file.

The precision unifier understands all the enhanced polish options with the same meaning.

The following additional options control the operation of this tool:

-nocmt_generation
If creating the precision module, do not add a comment saying when it was generated.
-pp_create_module
Automatically create the precision module, in the file whose name is the name of the module, converted to lower case, with file type ‘.f90’; thus the default filename is working_precision.f90. If the file already exists it will not be overwritten by this option.

The created module will contain only the definition of the precision parameter, and unless the -nocmt_generation option is given, a comment identifying when the module was created.

-pp_name=X
Specifies the name of the precision parameter to use in the standardised output, which must be a legal identifier that does not conflict with existing names in the input source. The default is ‘WP’.
-pp_module=X
Specifies the name of the precision module from which the precision parameter is to be imported. This module name must be a legal identifier that does not conflict with existing names in the input source. The default is ‘WORKING_PRECISION’.
-pp_nocreate_module
Do not create the precision module. This is the default.
-precision=X
Specifies the desired target unifying precision in the output; X must be one of Half, Single (i.e., same precision as default REAL), Double (i.e., same precision as default DOUBLE PRECISION) or Quadruple. The default is -precision=Double.

Note that, since -double and -r8 double the size of default REAL (and possibly default DOUBLE PRECISION), specifying -double or -r8 will likewise modify the meaning of this -precision= option too.

-pu_floats=X
Controls the precision-unification mode for floating-point and complex entities; X must be one of Off, On or Default_Kinds. In the latter mode of operation already-kinded entities will not be modified. The default is -pu_floats=On.

28 See Also

f90_gc(3), f90_iostat(3), f90_kind(3), f90_preconn_io(3), f90_stat(3), f90_unix_dir(3), f90_unix_dirent(3), f90_unix_env(3), f90_unix_errno(3), f90_unix_file(3), f90_unix_proc(3), ieee_arithmetic(3), ieee_exceptions(3), ieee_features(3), iso_c_binding(3), iso_fortran_env(3), nag_modules(3), nagfmcheck(1).

29 Supplementary Information

Please check the web page https://support.nag.com/doc/inun/np72/supplementary.html for details of any new information related to the applicability or usage of this product.

30 Bugs

Please report any bugs found to ‘support@nag.co.uk’ or ‘support@nag.com’, along with any suggestions for improvements.

31 Author

Malcolm Cohen, Nihon Numerical Algorithms Group KK, Tokyo, Japan.