/* From: "COMPUTATIONAL PHYSICS, 2nd Ed" 
   by RH Landau, MJ Paez, and CC Bordeianu 
   Copyright Wiley-VCH 2007.
   Electronic Materials copyright: R Landau, Oregon State Univ, 2007;
   MJ Paez, Univ Antioquia, 2007; & CC Bordeianu, Univ Bucharest, 2007
   Support by National Science Foundation                              
*/  
//  MPImessage3.c: guests send rank to the host, who prints them

#include "mpi.h"
#include <stdio.h>

int main(int argc,char *argv[])  {   
	
  int rank, size;
  int msg_size = 6;
  MPI_Status status;
  int tag = 10;
  int host = 0;
  MPI_Init(&argc,&argv);                            // Initialize MPI
  MPI_Comm_rank(MPI_COMM_WORLD,&rank);              // Get CPU's rank
  MPI_Comm_size(MPI_COMM_WORLD,&size);          // Get number of CPUs
  if (rank != host) { 
    int n[1];                                   // Array of 1 integer
    n[0] = rank;
    printf("node %d about to send message\n", rank);         
    MPI_Send(&n, 1, MPI_INTEGER, host, tag, MPI_COMM_WORLD);   
  }
  else  { 
    int r[1];
    int i;
    for(i=1; i < size; i++)  { 
      MPI_Recv(&r, 1, MPI_INTEGER, MPI_ANY_SOURCE, tag,
                                            MPI_COMM_WORLD, &status);
      printf("Message recieved:  %d\n", r[0]);     
    }  
  }
  MPI_Finalize();                                     // Finalize MPI
  return 0;
}