/* Send a message from all processes with rank != 0 to process 0. Process 0 prints the messages received.
 */
#include <stdio.h>
#include <string.h>
#include "mpi.h"

int main(int argc, char* argv[])
{
  int         my_rank;       /* rank of process      */
  int         p;             /* number of processes  */
  int         source;        /* rank of sender       */
  int         dest;          /* rank of receiver     */
  int         tag = 0;       /* tag for messages     */
  char        message[100];  /* storage for message  */
  MPI_Status  status;        /* status for receive   */
  
  /* Initialize MPI */
  MPI_Init(&argc, &argv);
  
  /* Find out process rank  */
  MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
  
  /* Find out number of processes */
  MPI_Comm_size(MPI_COMM_WORLD, &p);

  if (my_rank != 0) {
    printf("PE %d sends    to   PE 0: Hello from process %d \n", my_rank, my_rank);
    /* Create message */
    sprintf(message,"Hello from process %d", my_rank);
    dest = 0;
    /* Use strlen+1 so that '\0' gets transmitted */
    MPI_Send(message, strlen(message)+1, MPI_CHAR, 
	     dest, tag, MPI_COMM_WORLD);
  } 
  else { /* my_rank == 0 */
    for (source = 1; source < p; source++) 
      {
	MPI_Recv(message, 100, MPI_CHAR, source, tag, 
		 MPI_COMM_WORLD, &status);
	printf("PE 0 receives from PE %d: %s\n", source, message);
      }
  }
  
  /* Shut down MPI */
  MPI_Finalize();

  return 0;
}