/* 

   example1: 

   fork parallel threads; each thread prints hello; when all threads
   are done, the master thread prints how many threads are in total.

 */ 


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



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

  int th_id, nthreads;
  
  
#pragma omp parallel private(th_id)
  /* 
     the block below is executed in parallel by as many threads as
     cores;

     th_id is declared above and is global to all threads, however is
     is specified as private; so each thread will have its own copy of
     th_id
  */
  {
    th_id = omp_get_thread_num();
    printf("Hello World from thread %d\n", th_id);

    //#pragma omp barrier
    /* 
       a barrier means that all threads wait until all teh otehr
       threads have reached this point */ 
    if ( th_id == 0 ) {
      nthreads = omp_get_num_threads();
      printf("There are %d threads\n",nthreads);
    }
  }

     
  // get_num_threads() is 1 outside a parallel section 
  nthreads = omp_get_num_threads();
  printf("\n\nThere are %d threads\n",nthreads);

  return EXIT_SUCCESS;
}