Developer Reference for Intel® oneAPI Math Kernel Library for C

ID 766684
Date 12/16/2022
Public

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Document Table of Contents

mkl_set_dynamic

Enables Intel® oneAPI Math Kernel Library to dynamically change the number of OpenMP* threads.

Syntax

void mkl_set_dynamic (int flag);

Include Files
  • mkl.h
Input Parameters

Name

Type

Description

flag

int

flag = 0 - Requests disabling dynamic adjustment of the number of threads.

flag 0 - Requests enabling dynamic adjustment of the number of threads.

Description

This function indicates whether Intel® oneAPI Math Kernel Library can dynamically change the number of OpenMP threads or should avoid doing this. The setting applies to all Intel® oneAPI Math Kernel Library functions on all execution threads. This function takes precedence over theMKL_DYNAMIC environment variable.

Dynamic adjustment of the number of threads is enabled by default. Specifically, Intel® oneAPI Math Kernel Library may use fewer threads in parallel regions than the number returned by themkl_get_max_threadsfunction. Disabling dynamic adjustment of the number of threads does not ensure that Intel® oneAPI Math Kernel Library actually uses the specified number of threads, although the library attempts to use that number.

TIP:

If you call Intel® oneAPI Math Kernel Library from within an OpenMP parallel region and want to create internal parallel regions, either disable dynamic adjustment of the number of threads or set the thread-local number of threads (seemkl_set_num_threads_local for how to do it).

Example
#include "mkl.h"
…
mkl_set_num_threads( 8 );
#pragma omp parallel
{
	my_compute_with_mkl();	// Intel MKL uses 1 thread, being called from OpenMP parallel region
	mkl_set_dynamic( 0 );	// disable adjustment of the number of threads
	my_compute_with_mkl();	// Intel MKL uses 8 threads
}