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C | Fortran-90
omp_get_num_threads returns the number of threads in the current OpenMP region. If this function is called outside a parallel region, only the master thread is present hence the value returned is 1. Although spellings are close, do not confuse this function with omp_get_thread_num.
int omp_get_num_threads();The number of threads contained in the current region.
#include <stdio.h>
#include <stdlib.h>
#include <omp.h>
/**
* @brief Illustrates how to get the number of threads.
* @details This code prints the number of threads at two specific locations:
* 1) Outside an OpenMP parallel region
* 2) Inside an OpenMP parallel region
**/
int main(int argc, char* argv[])
{
// Tell OpenMP to use 4 threads in parallel regions
omp_set_num_threads(4);
// 1) Outside the OpenMP parallel region
printf("Outside the OpenMP parallel region, we are %d threads.\n", omp_get_num_threads());
// Create the OpenMP parallel region, which will contain 4 threads
#pragma omp parallel
{
// 2) Inside the OpenMP parallel region
printf("Inside the OpenMP parallel region, we are %d threads.\n", omp_get_num_threads());
}
return EXIT_SUCCESS;
}