/* file: bcast.c
   compile: cc -64 bcast.c -lmpi
   run: mpirun -np 4 ./a.out
*/

#include <mpi.h>
#include <stdio.h>
#define N 5
main(int argc, char *argv[])
{
  int num_procs;
  int my_proc;
  int a[N];
  int i, j;
  int root=0;  /* rank=0 */

  /* initialize an array 'a' with -11 in all processes */
  for(i = 0; i < N; i++) a[i] = -11; 

  MPI_Init(&argc, &argv);
  MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
  MPI_Comm_rank(MPI_COMM_WORLD, &my_proc);

  /* update the array 'a' with -20 in the root process */
  if (my_proc == root) {
    for(i=0;i<N;i++)
      a[i] = -20;
  }

  /* then broadcast this array to the rest processors */
  MPI_Bcast ((void *) a, N, MPI_INT, root, MPI_COMM_WORLD);

  /*------- output ----------
  rank=0: -20 -20 -20 -20 -20 
  rank=1: -20 -20 -20 -20 -20 
  rank=2: -20 -20 -20 -20 -20 
  rank=3: -20 -20 -20 -20 -20 
   -------------------------*/

  printf("rank=%d: ", my_proc);
  for (j = 0; j < N; j++)  printf("%d ",a[j]);
  printf("\n");
  MPI_Finalize();
}