XL Fortran Enterprise Edition for AIX : User's Guide - IBM

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(for example, loops for which you specified the PARALLEL DO directive). OpenMP Environment Variables The following environment variables, which are included in the OpenMP standard, allow you to control the execution of parallel code. Note: If you specify both the XLSMPOPTS environment variable and an OpenMP environment variable, the OpenMP environment variable takes precedence. OMP_DYNAMIC Environment Variable The OMP_DYNAMIC environment variable enables or disables dynamic adjustment of the number of threads available for the execution of parallel regions. The syntax is as follows: ►► OMP_DYNAMIC= TRUE FALSE ►◄ If you set this environment variable to TRUE, the run-time environment can adjust the number of threads it uses for executing parallel regions so that it makes the most efficient use of system resources. If you set this environment variable to FALSE, dynamic adjustment is disabled. The default value for OMP_DYNAMIC is TRUE. Therefore, if your code needs to use a specific number of threads to run correctly, you should disable dynamic thread adjustment. The omp_set_dynamic subroutine takes precedence over the OMP_DYNAMIC environment variable. OMP_NESTED Environment Variable The OMP_NESTED environment variable enables or disables nested parallelism. The syntax is as follows: ►► OMP_NESTED= TRUE FALSE ►◄ If you set this environment variable to TRUE, nested parallelism is enabled. This means that the run-time environment might deploy extra threads to form the team of threads for the nested parallel region. If you set this environment variable to FALSE, nested parallelism is disabled. The default value for OMP_NESTED is FALSE. The omp_set_nested subroutine takes precedence over the OMP_NESTED environment variable. OMP_NUM_THREADS Environment Variable The OMP_NUM_THREADS environment variable sets the number of threads that a program will use when it runs. The syntax is as follows: ►► OMP_NUM_THREADS= num ►◄ 64 XL Fortran Enterprise Edition for AIX : User’s Guide
num the maximum number of threads that can be used if dynamic adjustment of the number of threads is enabled. If dynamic adjustment of the number of threads is not enabled, the value of OMP_NUM_THREADS is the exact number of threads that can be used. It must be a positive, scalar integer. The default number of threads that a program uses when it runs is the number of online processors on the machine. If you specify the number of threads with both the PARTHDS suboption of the XLSMPOPTS environment variable and the OMP_NUM_THREADS environment variable, the OMP_NUM_THREADS environment variable takes precedence. The omp_set_num_threads subroutine takes precedence over the OMP_NUM_THREADS environment variable. The following example shows how you can set the OMP_NUM_THREADS environment variable: export OMP_NUM_THREADS=16 OMP_SCHEDULE Environment Variable The OMP_SCHEDULE environment variable applies to PARALLEL DO and work-sharing DO directives that have a schedule type of RUNTIME. The syntax is as follows: ►► OMP_SCHEDULE= sched_type , chunk_size ►◄ sched_type is either DYNAMIC, GUIDED, or STATIC. chunk_size is a positive, scalar integer that represents the chunk size. This environment variable is ignored for PARALLEL DO and work-sharing DO directives that have a schedule type other than RUNTIME. If you have not specified a schedule type either at compile time (through a directive) or at run time (through the OMP_SCHEDULE environment variable or the SCHEDULE option of the XLSMPOPTS environment variable), the default schedule type is STATIC, and the default chunk size is set to the following for the first N - 1 threads: chunk_size = ceiling(Iters/N) It is set to the following for the Nth thread, where N is the total number of threads and Iters is the total number of iterations in the DO loop: chunk_size = Iters - ((N - 1) * ceiling(Iters/N)) If you specify both the SCHEDULE option of the XLSMPOPTS environment variable and the OMP_SCHEDULE environment variable, the OMP_SCHEDULE environment variable takes precedence. The following examples show how you can set the OMP_SCHEDULE environment variable: export OMP_SCHEDULE="GUIDED,4" export OMP_SCHEDULE="DYNAMIC" Editing, Compiling, Linking, and Running XL Fortran Programs 65
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XL Fortran Enterprise Edition for A
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Note! Before using this information
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Options That Control Listings and M
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How XLF I/O Interacts with Pipes, S
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viii XL Fortran Enterprise Edition
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x XL Fortran Enterprise Edition for
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The following performance-related d
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How to Read the Syntax Diagrams and
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v Optionally, enter the value of at
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6 XL Fortran Enterprise Edition for
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Migration Support The XL Fortran co
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These items are located, or accesse
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v /usr/share/man/info/en_US/xlf/pos
Page 28 and 29: Notes: 1. Specifying the LC_ALL env
Page 30 and 31: 3. Installing a compiler program te
Page 32 and 33: fsuffix cppsuffix osuffix ssuffix l
Page 34 and 35: mcrt = /lib/mcrt0_r.o gcrt = /lib/g
Page 36 and 37: options include -L/usr/lpp/xlf/lib,
Page 38 and 39: Related Information: You can use th
Page 40 and 41: Table 1. Potential Problems Migrati
Page 42 and 43: Table 1. Potential Problems Migrati
Page 44 and 45: ►► xlf90 xlf90_r xlf90_r7 xlf95
Page 46 and 47: xlf90, xlf90_r, and xlf90_r7 comman
Page 48 and 49: Related Information: The ssuffix at
Page 50 and 51: Related Information: See “-qpdf O
Page 52 and 53: The @PROCESS compiler directive mus
Page 54 and 55: Passing Fortran Files through the C
Page 56 and 57: the trigraph sequence. XL Fortran u
Page 58 and 59: The configuration file /etc/xlf.cfg
Page 60 and 61: esulting program work as you expect
Page 62 and 63: v v Do not use names that are the s
Page 64 and 65: v v Build the application by using
Page 66 and 67: If you have applications in which F
Page 68 and 69: total_usertime Returns the total us
Page 70 and 71: To obtain support for items that ar
Page 72 and 73: Note: You may need the old setting
Page 74 and 75: These partitions are then assigned
Page 76 and 77: During the busy-wait search for wor
Page 80 and 81: Other Environment Variables That Af
Page 82 and 83: Options That Control Input to the C
Page 84 and 85: Table 3. Options That Control Input
Page 86 and 87: Table 5. Options for Performance Op
Page 88 and 89: Table 5. Options for Performance Op
Page 90 and 91: Table 6. Options for Debugging and
Page 92 and 93: Table 7. Options That Control Listi
Page 94 and 95: Table 8. Options for Compatibility
Page 102 and 103: v v Determine names and options for
Page 104 and 105: Detailed Descriptions of the XL For
Page 106 and 107: -1 Option Syntax -1 ONETRIP | NOONE
Page 108 and 109: -b64 Option Syntax -b64 The AIX ope
Page 110 and 111: Examples xlf95 f.f -brtl -bshared -
Page 112 and 113: -bloadmap Option Syntax -bloadmap:n
Page 114 and 115: -brtl Option Syntax -brtl | -bnortl
Page 116 and 117: -bstatic Option Related Information
Page 118 and 119: -c Option Syntax -c Prevents the co
Page 120 and 121: -d Option Syntax -d Causes preproce
Page 122 and 123: -g Option Syntax -g DBG | NODBG Gen
Page 124 and 125: -k Option Syntax -k FREE(F90) Speci
Page 126 and 127: -l Option Syntax -lkey Searches the
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-O Option Syntax -O[level] OPTimize
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-o Option Syntax -o name Specifies
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-p Option Syntax -p[g] Sets up the
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-q32 Option Related Information See
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-qalias Option Syntax -qalias={[no]
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equivalence (a, b(3)) t = b; a = t
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a derived type are stored with suff
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pwr2s p2sc You can run the executab
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v v If your primary concern is exec
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-qassert Option Syntax -qassert={de
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-qautodbl Option Syntax -qautodbl=s
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Related Information For background
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2 Level-2 cache or the table lookas
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-qcheck Option Syntax -qcheck | -qn
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-qcompact Option Syntax -qcompact |
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-qctyplss Option Syntax -qctyplss[(
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-qdbg Option Syntax -qdbg | -qnodbg
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-qdirective Option Syntax -qdirecti
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-qdirectstorage Option Syntax -qdir
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-qdpc Option Syntax -qdpc[=e] | -qn
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-qescape Option Syntax -qescape | -
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-qextchk Option Syntax -qextchk | -
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-qextname Option Syntax -qextname[=
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-qfdpr Option Syntax -qfdpr | -qnof
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-qflag Option Syntax -qflag=listing
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the reciprocal of the divisor. It a
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export SQRT_EXCEPTION=3.1 166 XL Fo
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-qfree Option Syntax -qfree[={f90|i
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-qhalt Option Syntax -qhalt=severit
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If you specify -qhot=novector, the
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-qhssngl Option Syntax -qhssngl | -
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-qinit Option Syntax -qinit=f90ptr
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v You can specify alphabetic digits
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-qintsize Option Syntax -qintsize=b
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-qipa Option Syntax -qipa[=suboptio
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If you specify short, the Object Fi
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Table 15. Regular expression syntax
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-qkeepparm Option Syntax -qkeepparm
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Restrictions The -qflag option can
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-qlibansi Option Related Informatio
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-qlibposix Option Related Informati
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-qlistopt Option Syntax -qlistopt |
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-qlog4 Option Syntax -qlog4 | -qnol
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Restrictions Depending on the sourc
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-qmixed Option Syntax -qmixed | -qn
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-qmodule Option Syntax -qmodule=man
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-qnullterm Option Syntax -qnullterm
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-qonetrip Option Syntax -qonetrip |
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-qpdf Option Syntax -qpdf{1|2} Tune
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mergepdf Generates a single pdf rec
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-qphsinfo Option Syntax -qphsinfo |
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-qpic Option Syntax -qpic[=suboptio
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sce | nosce } else if (a == 3) *res
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-qprefetch Option Syntax -qprefetch
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-qrealsize Option Syntax -qrealsize
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-qrecur Option Syntax -qrecur | -qn
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To produce a listing file that you
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-qsave Option Syntax -qsave[={all|d
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-qsclk Option Syntax -qsclk[=centi
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-qsigtrap Option Syntax -qsigtrap[=
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-qsmp Option Syntax -qsmp[=suboptio
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threshold=n The work in a partition
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xlf90 -qsmp=noopt -O3... is equival
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-qspillsize Option Syntax -qspillsi
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-qstrictieeemod Option Syntax -qstr
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-qsuffix Option Syntax -qsuffix=opt
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Examples @process nullterm i = 1; j
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Related Information See the OpenMP
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-qthreaded Option Syntax -qthreaded
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If you do not specify -qtune, its s
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-qundef Option Syntax -qundef | -qn
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-qunwind Option Syntax -qunwind |-q
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-qwarn64 Option See “-qwarn64 Opt
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-qxflag=xalias Option Syntax -qxfla
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intxor | nointxor Treats .XOR. as a
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Examples Consider the following pro
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In this example, conditional compil
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-qzerosize Option Syntax -qzerosize
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-t Option Syntax -tcomponents Appli
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-u Option Syntax -u UNDEF | NOUNDEF
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-V Option Syntax -V This option is
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$ ./a.out 1 2 3 4 276 XL Fortran En
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-y Option Syntax -y{n | m | p | z}
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64-Bit Thread Support On AIX Versio
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-q64 Option Syntax -q64[=largetype]
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-qwarn64 Option Syntax -qwarn64 | -
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286 XL Fortran Enterprise Edition f
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v v If the data or program code con
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v Comparisons involving NaN values
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How XL Fortran Rounds Floating-Poin
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2. For thread-safety and reentrancy
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v The fltint suboption speeds up fl
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There are other related operating s
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Another method is to use the ieee_s
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call fpgets(fpstat) fpstat(fpox) =
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The following example shows the dif
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v Code that might cause an exceptio
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Optimization levels Option -qnoopt/
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v -qcache=auto Optimization level -
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v v v Reducing the costs of memory
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Loop unrolling also increases code
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2. Run the application using a typi
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# Let the compiler decide (relative
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can also use the SNAPSHOT directive
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-qipa=list cross-file type checking
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Stream-access formatted files: A re
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I/O Redirection The important thing
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Default Record Lengths File Permiss
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XLFRTEOPTS="unit_vars=yes" # Allow
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Logical Volume I/O To use a logical
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READ(unit_number,ID=idvar) a .... W
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450 end do close(20) end Performanc
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Table 22. Table for Binding an Appl
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v The result of an application does
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Sometimes an application can guaran
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v v The XL compilers generate code
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#include template class junk { pri
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Notes: 1. In interlanguage communic
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Table 25. Escape Sequences for Char
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You can use this built-in function
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The system linkage convention passe
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Run-time Stack for 32-bit Environme
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processing, and the fifth doublewor
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v v v v v v v In a 32-bit Environme
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Will Be Passed In: R3 0 Storage Map
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Function Values Functions return th
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Example The control structure has t
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technique can reduce the amount of
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Note: When you run an XL Fortran pr
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Duplicating Extensions from Other S
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Input/Output Errors If the error de
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-> xlf95 -qddim -g testprog.f -o te
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7. The next step is to research why
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Note that you cannot use the -qextn
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v v Memory leak reporting that indi
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HD_FILL HD_STACK=n called a certain
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Source Section The source section c
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Attribute and Cross-Reference Secti
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Automating Large, Complex Compilati
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For fixed source form code, in addi
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Common Industry Extensions That XL
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Example 2 - Valid C Routine Source
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close(10) open(10, file="fun10.out"
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!**********************************
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operating system require the same o
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Examples of Storage Relationships f
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0 4 8 16 32 64 COMPLEX (16) COMPLEX
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! Data values between r8 and x16 ar
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end function sqrt real*8 function r
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Table 34. MASS Vector Library Funct
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IBM may use or distribute any of th
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ind. To relate an identifier to ano
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expression. A sequence of operands,
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name. A lexical token consisting of
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labels can be used to transfer cont
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.profile file 12 .s files 33, 34 .X
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fdate_ service and utility subprogr
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nonested_par suboption of -qsmp 234
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vi text editor 29 W W error severit
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