/* 
 * hello.ex1.c 
 * Parallel version using MPI calls
 * Modified from basic version so that workers send back 
 * a message to the master, who prints out a message 
 * for each worker 
 * RLF 10/11/95 
*/

#include <stddef.h>
#include <stdlib.h>
#include "mpi.h"
main(int argc, char **argv )
{
	char message[20];
	int i,rank, size, type=99;
	MPI_Status status;

	MPI_Init(&argc, &argv);
	MPI_Comm_size(MPI_COMM_WORLD,&size);
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
	if(rank == 0) {
	   strcpy(message, "Hello, world");
	   for (i=1; i<size; i++) 
	   MPI_Send(message, 13, MPI_CHAR, i, 
               type, MPI_COMM_WORLD);
           printf("node %d : %.13s\n", rank, message);
           for (i=1; i<size; i++) {
           MPI_Recv(&rank, 1, MPI_INT,MPI_ANY_SOURCE,type, 
               MPI_COMM_WORLD, &status);                 
           printf("node %d : Hello back\n", rank);
           }
	} 
  	else {
	  MPI_Recv(message, 20, MPI_CHAR, 0,
	       type, MPI_COMM_WORLD, &status);
          MPI_Send(&rank, 1, MPI_INT, 0, type,
               MPI_COMM_WORLD);
          }
      	MPI_Finalize();
}