Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

  • 0.9
  • 09/09/2020
  • Public Content
Contents

mkl_set_num_threads

Specifies the number of OpenMP* threads to use.

Syntax

void mkl_set_num_threads
(
int
nt
)
;
Include Files
  • mkl.h
Input Parameters
Name
Type
Description
nt
int
nt
 > 0 - The number of threads suggested by the user.
nt
≤
 0 - Invalid value, which is ignored.
Description
This function enables you to specify how many OpenMP threads
Intel® oneAPI Math Kernel Library
 should use for internal parallel regions. If this number is not set (default),
Intel® oneAPI Math Kernel Library
 functions use the default number of threads for the OpenMP run-time library. The specified number of threads applies:
  • To all
    Intel® oneAPI Math Kernel Library
     functions except the functions from the domains where the number of threads is set withmkl_domain_set_num_threads
  • To all execution threads except the threads where the number of threads is set with mkl_set_num_threads_local
The number specified is a hint, and
Intel® oneAPI Math Kernel Library
 may actually use a smaller number.
This function takes precedence over the
MKL_NUM_THREADS
 environment variable.

Example

#include "mkl.h"
…
mkl_set_num_threads(4);
my_compute_using_mkl();	// Intel MKL uses up to 4 OpenMP threads

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804