Parallel programming with XL Fortran

Parallel programming with XL Fortran involves a combination of compiling, setting of runtime options, and optimization of your code, by incorporating SMP directives and by using the pthreads library module.

XL Fortran supports the OpenMP specification, as understood and interpreted by IBM as well as the POSIX 1003.1-1996 standard, and the Draft 7 POSIX pthreads API on AIX®.

Note: IBM implementation of OpenMP in XL Fortran is an extension to the standard Fortran language.

See the following topics for further information:

Compiling your parallelized code
To compile parallelized code, you must specify the -qsmp compiler option. When compiling with -qsmp, the driver links the libraries found on the smplibraries line in the active stanza of your configuration file.
Setting runtime options
When you write parallel code, set the necessary XLSMPOPTS environment variables, and the environment variables for OpenMP.
Optimizing your SMP code
Most IBM processors are capable of shared-memory parallel processing. Compile with -qsmp to generate the threaded code needed to exploit this capability. The option implies a -O2 optimization level. The default behavior for the option without suboptions is to do automatic parallelization with optimization.
An introduction to parallelization directives
These directives allow you to exert control over parallelization. For example, the PARALLEL DO directive specifies that the loop immediately following the directive should be run in parallel. All parallelization directives are comment form directives.
Detailed descriptions of parallelization directives
This section lists, in alphabetical order, all parallelization directives supported by XL Fortran.
Data sharing attribute rules
The rules of data sharing attributes determine the attributes of variables that are referenced in PARALLEL and TASK directives, and work-sharing regions.
Directive clauses
You can use directive clauses to specify additional information to directives.
Routines for OpenMP
The OpenMP specification provides a number of routines that you can use to control and query the parallel execution environment, timing, and lock.
Pthreads Library Module
The Pthreads Library Module (f_pthread) is a Fortran 90 module that defines data types and routines to make it easier to interface with the AIX pthreads library. The AIX pthreads library is used to parallelize and to make your code thread-safe.

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