#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <math.h>

#define size 16000
#define TAG 1

void send (int sendto)
{
  int myid,numprocs;
  double *data = (double *) malloc (size * sizeof (double));
  assert (NULL != data);
  MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
  MPI_Comm_rank(MPI_COMM_WORLD,&myid);
  printf ("myid = %d numprocs = %d\n", myid, numprocs);
  printf ("myid = %d: Sending to %d size = %d\n", myid, sendto, size);
  MPI_Send (data, size, MPI_DOUBLE, sendto, TAG, MPI_COMM_WORLD);
}

void receive (void)
{
  MPI_Status status;
  int myid,numprocs;
  double *data = (double *) malloc (size * sizeof (double));
  assert (NULL != data);
  MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
  MPI_Comm_rank(MPI_COMM_WORLD,&myid);
  printf ("myid = %d numprocs = %d\n", myid, numprocs);
  printf ("myid = %d: Receiving from 0 size = %d\n", myid, size);
  MPI_Recv (data, size, MPI_DOUBLE, 0, TAG, MPI_COMM_WORLD, &status);
}

int main(int argc, char *argv[])
{
    int ierr = 0;
    int myid, numprocs;
    int i = 0;
    ierr = MPI_Init(&argc,&argv);
    printf ("MPI_Init returned %d\n",ierr);
    MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD,&myid);
    if (myid==0) {
      for (i=1; i< numprocs; i++) {
       	printf ("myid = %d i = %d\n", myid, i);
	send (i);
      }
    }
    else
      receive ();
    MPI_Finalize();
    return 0;
}