/********************************************************************
 Sharon Chambers
 username:  chambers
 program:  hello2.c
 11/04/1999
********************************************************************/
#include <stdio.h>
#include <string.h>
#include <mpi.h>

#define TAG MPI_ANY_TAG                 /* tag for messages */
#define ROOT 0
#define COMM MPI_COMM_WORLD     /* define handle for communication */
#define MAX 20                          /* max msg size */

void
main(int argc, char **argv)
{
  int i, rank, size, worker[1];
  char buff[MAX], *msg="Hello World!";
  MPI_Status status;

  MPI_Init(&argc, &argv);                       /* initialize mpi */
  MPI_Comm_rank(COMM, &rank);                   /* get rank */
  worker[0] = rank;

  if(rank == 0)                                 /* master */
  {
    MPI_Comm_size(COMM, &size); /* get size,send broadcast msg*/
    for(i=1; i<size; i++)
    {                   /* send-receive msg to-from all workers */
        MPI_Send(msg,strlen(msg),MPI_CHAR,i,10,COMM);
        MPI_Recv(worker,1,MPI_INT,i,TAG,COMM,&status);
        printf("Answer received from %d\n", worker[0]);
    }
  }
  else                          /* receive message from master */
  {
    MPI_Recv(buff,MAX,MPI_CHAR,0,TAG,COMM,&status);
    printf("%s\n", buff);       /* send rank to master */
    MPI_Send(worker,1,MPI_INT,0,11,COMM);
  }

  MPI_Finalize();                               /* finalize mpi */
}