Compiling with OpenMP, Directive Format, and Diagnostics

To run the Intel® C++ Compiler in OpenMP* mode, invoke the compiler with the -openmp option:

prompt>icpc -openmp file.cpp

Before you run the multithreaded code, you can set the number of desired threads in the OpenMP environment variable, OMP_NUM_THREADS. See OpenMP Environment Variables for further information.

-openmp Option

The -openmp 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 option works with both -O0 (no optimization) and any optimization level of -O1, -O2 (default) and -O3. Specifying -O0 with -openmp helps to debug OpenMP applications.

OpenMP Directive Format and Syntax

An OpenMP directive has the form:

#pragma omp directive-name [clause, ...] newline

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 Diagnostics

The -openmp_report{0|1|2} option controls the OpenMP parallelizer's diagnostic levels 0, 1, or 2 as follows:

• -openmp_report0 = no diagnostic information is displayed.
• -openmp_report1 = display diagnostics indicating loops, regions, and sections successfully parallelized.
• -openmp_report2 = same as -openmp_report1 plus diagnostics indicating MASTER constructs, SINGLE constructs, CRITICAL constructs, ORDERED constructs, ATOMIC directives, etc. are successfully handled.

The default is -openmp_report1.