/*									tab:4
 *
 * msample.c - Sample MPI program
 *
 */

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

#define Tag 100

/* All processes start executing in main */
int main(int argc, char **argv) {
  MPI_Status status;
  int NPROCS = -1;				/* Number of Processes */
  int MyProc = -1;				/* Process address */
  int msg[128];					/* Message buffer area for send and recv */
  int nodes = 0;
  int reports[1024];			/* Record of reports */
  int i;
  
  /* Initialize MPI environment */
  MPI_Init(&argc, &argv);		        
  MPI_Comm_size(MPI_COMM_WORLD, &NPROCS); /* Number of Procs */
  MPI_Comm_rank(MPI_COMM_WORLD, &MyProc);	  /* Local address */

  if (MyProc == 0) printf ("Process %d: initialized\n", MyProc);  

  /* Everybody sends to node 0. It receives them in any order */
  if (MyProc == 0) {
	  reports[0] = 0;
	  nodes = 1;
	  while (nodes < NPROCS) {
		  MPI_Recv(msg, 128, MPI_INT, MPI_ANY_SOURCE, MPI_ANY_TAG, 
				   MPI_COMM_WORLD, &status);
		  reports[nodes] = msg[0]; /* Record source node */
		  nodes++;
	  }
	  printf ("Process %d: all report in\n", MyProc);  
	  for (i = 0; i < NPROCS; i++) {
		  printf ("%d->%d.\n", i, reports[i]);  
	  }
  }
  else							/* Everyone sends to zero */
  {
	  msg[0] = MyProc;
	  MPI_Send(msg, 1, MPI_INT, 0, Tag, MPI_COMM_WORLD);
  }
  
  /* Everybody gets a specific message back from node zero */

  if (MyProc == 0)				/* Node 0 to serve as master */
  {
	  for (nodes =1; nodes < NPROCS; nodes++) 
	  {
		  msg[0] = nodes;
		  MPI_Send(msg, 16, MPI_INT, nodes, Tag, MPI_COMM_WORLD);
	  }
	  printf ("Process %d: done\n", MyProc);  
  }
  else
  {
	  MPI_Recv(msg, 16, MPI_INT, 0, Tag, MPI_COMM_WORLD, &status);
	  printf ("Process %d: done\n", MyProc);  
  }
  MPI_Finalize();				/* Cleanup MPI environment */
}