Compiling with OpenMP, Directive Format, and Diagnostics

To run the Intel® compiler in OpenMP mode, invoke the compiler with the -openmp (Linux*) or /Qopenmp (Windows*) option using a command structured similar to the following:

Before you run the multithreaded code, you can set the number of desired threads in the OpenMP environment variable, OMP_NUM_THREADS. For more information, see the OpenMP Environment Variablessection. The Intel Extension Routines topic describes the OpenMP extensions to the specification that have been added by Intel to the Intel® compiler.

OpenMP Option

The -openmp (Linux*) or /Qopenmp (Windows*) option enables the parallelizer to generate multithreaded code based on the OpenMP directives. The code can be executed in parallel on both uniprocessor and multiprocessor systems.

The -openmp (Linux) or /Qopenmp (Windows) option works with both -O0 (Linux) and /Od (Windows), or with any optimization level of -O1, -O2 and -O3. (Linux) or /O1, /O2 and /O3 (Windows). Specifying -O0 (Linux) or /Od (Windows) with the OpenMP option helps to debug OpenMP applications.

When you use the openmp option, the compiler sets the -auto (Linux) or /Qauto (Windows) option, which causes all variables to be allocated on the stack, rather than in local static storage.

OpenMP Directive Format and Syntax

The OpenMP directives use the following format:

where:

• #pragma omp - Required for all OpenMP directives.

• directive-name - A valid OpenMP directive. Must appear after the pragma and before any clauses.

• clause - Optional. Clauses can be in any order, and repeated as necessary unless otherwise restricted.

• newline - Required. Proceeds the structured block which is enclosed by this directive.

OpenMP Diagnostic Reports

The -openmp-report (Linux) or /Qopenmp-report (Windows) option controls the OpenMP* parallelizer's diagnostic levels 0, 1, or 2 as follows:

For more information about the option behaviors listed above, see the following topic in Compiler Options:

• -openmp-report