Listing 1. ompdemo.c

#include <stdio.h>
#include <omp.h>

int main (int argc, char **argv)  {

  int nthreads, tid, i;

  /* Get the number of processors */
  printf("Number of processors available:: %d\n",omp_get_num_procs());

  /* Set the number of threads to the number of processors */
  omp_set_num_threads(omp_get_num_procs());

  /* Fork a team of threads with each thread having a
     private tid variable * */
#pragma omp parallel  private(tid)
  {
    /* Obtain and print thread id */
    tid = omp_get_thread_num();
    printf("Hello World from thread = %d\n", tid);

    /* Only master thread does this */
    if (tid == 0)
      {
        nthreads = omp_get_num_threads();
        printf("Number of threads = %d\n", nthreads);
      }
  }  /* All threads join master thread and terminate */

  return 0;
}