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3.1.7 omp_set_dynamic Function

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The omp_set_dynamic function enables or disables dynamic adjustment of the number of threads available for execution of parallel regions. The format is as follows:

#include <omp.h>
void omp_set_dynamic(int dynamic_threads);

If dynamic_threads evaluates to a nonzero value, the number of threads that are used for executing subsequent parallel regions may be adjusted automatically by the run-time environment to best utilize system resources. As a consequence, the number of threads specified by the user is the maximum thread count. The number of threads in the team executing a parallel region remains fixed for the duration of that parallel region and is reported by the omp_get_num_threads function.

If dynamic_threads evaluates to 0, dynamic adjustment is disabled.

This function has the effects described above when called from a portion of the program where the omp_in_parallel function returns zero. If it is called from a portion of the program where the omp_in_parallel function returns a nonzero value, the behavior of this function is undefined.

A call to omp_set_dynamic has precedence over the OMP_DYNAMIC environment variable.

The default for the dynamic adjustment of threads is implementation-defined. As a result, user codes that depend on a specific number of threads for correct execution should explicitly disable dynamic threads. Implementations are not required to provide the ability to dynamically adjust the number of threads, but they are required to provide the interface in order to support portability across all platforms.

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