/*
 * example for MPI_Sendrecv_replace
*/

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

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

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

  	a = (double)myid;

  	printf("Before communication: Process %d: a=%.2f\n", myid, a); 

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

  	MPI_Sendrecv_replace(&a, 1, MPI_DOUBLE, dest, 111, 
                       src, 111, MPI_COMM_WORLD, &status);
  
  	printf("After communication: Process %d: a=%.2f\n", myid, a);

  	MPI_Finalize();
  	return 0;
}