/*
 * example for send and recv
*/

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

int main(int argc, char *argv[])
{
  	int myid, np, src, dest;
  	int a, b;
  	MPI_Status status;

  	MPI_Init(&argc, &argv);
  	MPI_Comm_rank(MPI_COMM_WORLD, &myid);
  	MPI_Comm_size(MPI_COMM_WORLD, &np);

  	a = myid;

  	printf("Before communication: Process %d: a=%d\n", myid, a);
  	MPI_Barrier(MPI_COMM_WORLD);

  	src = myid-1;  if (src==-1) src=np-1;
  	dest = myid+1; if (dest==np) dest=0;

  	if(myid==0)
  	{
    	MPI_Send(&a, 1, MPI_INT, dest, 111, MPI_COMM_WORLD);
    	MPI_Recv(&b, 1, MPI_INT, src, 111, MPI_COMM_WORLD, &status);
  	}  
  	else
  	{
    	MPI_Recv(&b, 1, MPI_INT, src, 111, MPI_COMM_WORLD, &status);
    	MPI_Send(&a, 1, MPI_INT, dest, 111, MPI_COMM_WORLD);
  	}  
  
  	printf("After communication: Process %d: b=%d\n", myid, b);

  	MPI_Finalize();
  	return 0;
}