nagfor — NAG Fortran Compiler Release 7.1
nagfor [mode] [option]... file...
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 |
|=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 |
|=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).
A file ending in ‘
.f90’ or ‘
is taken to be a Fortran free-form source file, a file ending
.for’ or ‘
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 ‘
is taken to be a free-form file requiring preprocessing by fpp, and a file
ending in ‘
is taken to be a fixed-form file requiring preprocessing by fpp.
On Unix, a file
ending in ‘
.F90’ or ‘
is taken to be a free-form file requiring preprocessing by fpp, and a file
ending in ‘
is taken to be a fixed-form files requiring preprocessing by fpp.
(Note that on MacOS and Windows,
the file system is not case-sensitive so
uppercase and lowercase letters are equivalent in filenames including in
If a filename without a suffix is provided nagfor will look for a file with the
.f95’, and if that does not exist, the
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
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.
INCLUDE files and
#include files are
expected to exist in the current working directory or in a directory named
by an -I option.
|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.
|natural||(natural alignment for best performance;
this can alter the interpretation of |
|standard||(use standard-conforming alignment; this is the default).|
The whole program should be compiled with the same alignment option.
|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
See the Undefined Variable Detection section for further details.
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
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 -gline or -openmp. The -coarray=cosmp option may be specified with the -C=undefined option, but it will automatically disable the latter option.
Colours are: black, red, green, yellow, blue, magenta, cyan and white.
would be a rather garish colour scheme.
CONVERT=specifier in the
OPENstatement, 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):
| synonym for |
|big-endian with IEEE floating-point, quad precision is double-double|
|big-endian with IEEE floating-point, including quad precision|
|big-endian with native floating-point format|
| synonym for |
|little-endian with IEEE floating-point, quad precision is double-double|
|little-endian with IEEE floating-point, including quad precision|
|little-endian with native floating-point format|
|no conversion (the default)|
|Non-standard||Equivalent Standard Fortran Generic Intrinsic Function|
COMPLEX. Entities specified with explicit kind numbers or byte lengths are unaffected. If quadruple precision
REALis available, the size of
DOUBLE PRECISIONis also doubled.
.f95according to the suffix of the input file. This option is equivalent to -otype=Fortran.
SIGNintrinsic instead of the Fortran 95 one (they differ in the treatment of negative zero).
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 $main$
Aedit descriptor. This was superseded by the
CHARACTERdatatype in Fortran 77.
.mod) files and
INCLUDEfiles. 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).
LOGICALto 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
This has no effect on default
COMPLEX sizes, so the
compiler is not standard-conforming in this mode.
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.
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. This option is not available on IBM z9 Open Edition with hexadecimal floating point.
For -kind=byte, the kind numbers for
LOGICAL will match the number of bytes of storage (e.g.,
REAL is 4 and
DOUBLE PRECISION is 8).
COMPLEX kind numbers are the same as its
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
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).
.modfiles) only. This option is equivalent to -otype=mod.
PARAMETERto N MB (megabytes). N must be in the range 1 to 1048576 (1MB to 1TB); the default is 50 MB.
.mod) files to directory dir instead of the current working directory.
|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. The -mtrace=paranoia option is not available on IBM z9 Open Edition.
COMPLEXvariables 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
EQUIVALENCE. This option is not available on IBM z9 Open Edition with hexadecimal floating point.
.modfiles being out of date.
.mod) file production. Combining this with -M will produce no output (other than error and warning messages) at all, equivalent to -otype=none.
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
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.
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).
TARGETattribute; these are always accessed via the dope vector.
CHARACTER arrays are not affected by these options.
MATMULintrinsic. The default value (only for -O1 and above) is system and datatype dependent.
CHANGE TEAMconstruct is active.
|c||(C source file),|
|fortran||(Fortran source file),|
|mod||(module information file),|
|none||(no output file),|
The -c, -F and -M options are equivalent to -otype=obj, -otype=Fortran and -otype=mod respectively.
/usr/local/lib/NAG_Fortran’ or ‘
/opt/NAG_Fortran/lib’) This option is unnecessary on Windows as the installed location is automatically detected.
COMPLEX, and on machines for which quadruple-precision floating-point arithmetic is available, double the size of
DOUBLE PRECISION(and the non-standard
COMPLEXspecified with explicit
KINDnumbers or byte lengths are unaffected — but since the
KINDintrinsic returns the correct values,
COMPLEX(KIND(0d0))on a machine with quad-precision floating-point will correctly select quad-precision
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.
RECURSIVEby default. This option is implied by the -f2018 option.
This option affects compile-time evaluation as well as runtime evaluation.
SAVEstatement in all subprograms which are not pure, not declared
RECURSIVE, and not
RECURSIVEby 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.
CHARACTER*’ syntax. This message is not produced by default since many programs contain this syntax.
|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.
The default is to compile for SPARC V7.
Note that programs compiled for later versions of the architecture may not run, or may run much more slowly, on an earlier machine. The -target=native option is not available with gcc.
TMPDIRenvironment variable, or if that is not set, /tmp on Unix-like systems and the Windows temporary folder on Windows.
IMPLICIT NONEis in effect by default, unless overridden by explicit
TASKconstructs (including in combined constructs such as
PARALLELDO). This has the same effect as the
DEFAULT(NONE)clause, unless overridden by an explicit
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.
|/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 7.1\nagfor\lib||Default NAG Fortran Compiler library directory on 32-bit Windows.|
|C:\Program Files (x86)\NAG\EFBuilder 7.1\nagfor\lib||Default NAG Fortran Compiler library directory on 64-bit Windows.|
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 according to the -f95, -f2003 and -f2008 options). 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.|
|Maximum number of ||2047|
|Maximum number of dummy arguments||32767|
|Maximum number of arguments to ||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|
|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
/tmp’ on Unix and the Windows temporary directory on Windows.
This default may be overridden with the
TMPDIR environment variable.
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
The following table lists the OpenMP environment variables with their default values and, if applicable, their limits.
|number of cores||1-32768|
|False||true or false|
|False||true or false|
|0||<1GB (32-bit) or 16GB (64-bit)|
|None||active or passive|
|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 and -gline options.
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
WRITE without an explicit
By default the specific filename for unit n is
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
whereas the default filename is ‘
fort.1’ (unless the
prefix has been changed, see the description of module
A file preconnected in this manner is opened with
If the initial
WRITE is an unformatted i/o statement, it
is opened with
FORM='UNFORMATTED' otherwise it is opened
By default a formatted connection is opened with
Automatic preconnection applies only to the initial use of a logical unit; once
CLOSEd the unit will not be reconnected automatically but must be
Note that this facility means that it is possible for a
IOSTAT= clause to receive an i/o error code
associated with the implicit
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;
REAL variables may take on the values +Infinity, −Infinity and NaN
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; that is, it affects the entire executable program.
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.
Half precision (16-bit) floating-point is supported for values and variables of
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
The largest finite half-precision value is
65504.0, the smallest normal half-precision value is
0.00006103515625, and the smallest subnormal value is
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
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.
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
and therefore it is
strongly recommended that the
RANDOM_SEED routine only be used with
PUT argument that is the
value returned by a previous call with
GET; i.e., only to repeat a
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).
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
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.
is provided; it contains functions and variables that can control the behaviour
of the garbage collector.
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).
suboptions may be overridden at run time by the
environment variable, which should be set to the required trace_opt_list
The memory tracing file may be specified at run time by the
NAGFORTRAN_MTRACE_FILE environment variable.
NAGFORTRAN_MTRACE_OPTIONS variable can also contain an option to
limit the total amount of memory that may be allocated.
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
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.
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.
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.
ISO_C_BINDINGmodule can only be used with all-Fortran programs as the option makes changes to the ABI.
CHARACTERarray requires the entire specified array subobject to be “defined”, even those elements corresponding to records not actually read.
CHARACTERarray is considered to define the entire specified array subobject, even those elements corresponding to records not actually written.
RESHAPEwhen no padding is actually required, and elements of the
PACKthat correspond to false elements of the
CLASS(*)variables are allocated using the
SOURCE=expression is a
CLASS(*)dummy and the actual argument is a constant.
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|
|1||4||301|| ||Single precision floating-point|
|2||8||302|| ||Double precision floating-point|
|3||16||303|| ||Quad precision floating-point|
|16||2||304|| ||Half precision floating-point|
|1||4||301|| ||Single precision complex|
|2||8||302|| ||Double precision complex|
|3||16||303|| ||Quadruple precision complex|
|16||2||304|| ||Half precision complex|
|1||1||201|| ||Single byte logical|
|2||2||202|| ||Double byte logical|
|3||4||203|| ||Default logical|
|4||8||204|| ||Eight byte logical|
|1||1||101|| ||8-bit integer|
|2||2||102|| ||16-bit integer|
|3||4||103|| ||32-bit (default) integer|
|4||8||104|| ||64-bit integer|
|1||1||646|| ||ASCII or ISO 8859-1 character|
|2||2||213|| ||JIS X 0213 character|
|3||3||5323|| ||Unicode (UCS-2) character|
|4||4||10646|| ||ISO 10646 (UCS-4) character|
The Name column of the table indicates the name provided by the intrinsic
F90_KIND; the ones marked
are also provided by the
standard intrinsic module
Using these names avoids the portability problems that arise if the kind numbers
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.
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.
The following variables control the runtime environment for programs compiled with the NAG Fortran Compiler.
|autoskip_namelist||Enables auto-skipping namelist input.|
|blank_common_size=N|| Sets the default size of blank |
|executing in Co-SMP mode.|
|log_autoskip_namelist||Enables auto-skipping namelist input, with logging.|
|show_dangling||Enables tracing of dangling pointers; this only|
|affects code compiled with -C=dangling.|
|suppress_underflow_warning||Do not produce the usual warning on program termination|
|when the floating-point underflow flag is set.|
|underflow_warning||Do produce the usual warning on program termination|
|when the floating-point underflow flag is set.|
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 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. 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_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.
On Windows debugging is built-in to the Fortran Builder. 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.
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, -noqueue, -o, -openmp, -Qpath, -r8, -strict95, -thread_safe, -u, -u=sharing, -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.
ENTRYpoint names in the call graph; without this option, calls to an
ENTRYpoint are shown as calls to the containing subprogram.
USEstatement, show the renaming.
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:
|blist||(the filenames as an ordered build list),|
|dfile|| (the dependencies in Makefile format, written to separate file|
|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.
INCLUDEfiles that are relative specifications will be prefixed by the current working directory.
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
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
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, -noqueue, -o, -openmp, -Qpath, -r8, -strict95, -tempdir, -thread_safe, -u, -u=sharing, -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:
INTERFACEstatement, giving the date and time that the file was generated. This is the default.
FUNCTIONstatement) indicating the source of the procedure.
|module||(Fortran module in a new source file).|
The default is -otype=module.
The polisher takes a set of Fortran source files, which may be in fixed or free form, and produces a free 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:
/)’) or Square (use square brackets, i.e. ‘
]’). The default is -array_constructor_brackets=Asis.
CHARACTERtype 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 |
|Kind_Keyword_Only|| (use |
|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
When both the length and kind appear in the input statement, the length will
appear first in the output statement.
FORMATstatements; X must be one of Asis (use the same comma scheme as the input), Insert or Remove. The default is -commas_in_formats=Insert.
::’ 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.
::’ 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.
FORMATstatements in a separate sequence, the first
FORMATstatement will be N; the default is -format_start=90000.
FORMATstatements 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).
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.
Double Precision’ and ‘
Non_recursive’; with -kwcase=Camel, the latter is produced as ‘
FORMATstatements in the same position as they are in the input file; this is the opposite of -move_formats_to_end, and is the default.
FORMATstatements to the end of the subprogram or program unit, immediately before the
END TYPEstatement 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 INTERFACEstatement. The default is -name_scopes=Keywords.
::’ in declarations. This is the default, and is equivalent to specifying alignment at column zero via -dcolon_column=0.
FORMATstatements; this is the default.
DOloop terminating statements.
.LE., etc.) or F90+ (use
<=, etc.); the default is -relational=F90+.
FORMATstatements in a separate sequence from non-
DOloops so that each loop ends with an
ENDDOstatement; this is the default.
&’) 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 1024, however values higher than 130 will produce output that does not conform to the Fortran standard.
The enhanced polisher takes a set of Fortran source files, which may be in fixed or free form, and produces a free 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, -noqueue, -o, -openmp, -Qpath, -r8, -strict95, -tempdir, -thread_safe, -u, -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.
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.
|all||(all classes of procedure),|
|bound||(object-bound and type-bound 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.
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).
MIN functions use the number of actual
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.
Camel_Case), and kind is one of the categories listed below:
| ||Construct name|
| ||Intrinsic procedure|
| ||Type-bound procedure|
| ||Derived type parameter|
| ||Derived type|
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;
proc all fall back to
intr will fall back to
tbp will fall back to
If there is no rule or fall-back rule, the -idcase= option setting (or default) is used.
INTRINSICstatements, and that if all the names in an
INTRINSICstatement are removed in this way, the
INTRINSICstatement itself should be removed. Any comments associated with the
INTRINSICstatement will remain.
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
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:
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || || || |
| || || |
(See also the description of -dcfuns.)
DBLE is converted to
REAL. Following that, the
KIND= argument is added to calls to
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.
EQUIVALENCEstatements or in references to the
DPRODintrinsic (perhaps as a means of performing higher- (double-) precision computations in a single-precision program unit).
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, -noqueue, -o, -openmp, -Qpath, -r8, -strict95, -tempdir, -thread_safe, -u, -u=sharing, -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:
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.
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
REAL (and possibly default
specifying -double or -r8 will likewise modify
the meaning of this -precision= option too.
Please check the web page https://www.nag.com/doc/inun/np71/supplementary.html for details of any new information related to the applicability or usage of this product.
Please report any bugs found to ‘firstname.lastname@example.org’ or ‘email@example.com’, along with any suggestions for improvements.
Malcolm Cohen, Nihon Numerical Algorithms Group KK, Tokyo, Japan.