/*
* Illustrate the usage of MPI_SEND_RECV
* All the proc send message to the next proc simultaneously,
* and then receive message from the previous proc
*/

#include<stdio.h>	//for input/output
#include<mpi.h>		//for mpi routines

main( int argc, char** argv)
{
	int rank;			//the rank of this process
	int tag=0;			//not important here
	int nproc;
	int sendbuf[1], recvbuf[1];
	int dest;			//store the destination
	MPI_Status status;	//not important here

	MPI_Init(&argc, &argv);						//Initializing mpi
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);	//Getting my rank
	MPI_Comm_size(MPI_COMM_WORLD, &nproc);	//Getting total no of proc

	dest = (rank + 1) % nproc;
	printf("Proc %d: Sending message to %d...\n", rank, dest);
	if( rank == 0 )
	{
		MPI_Sendrecv(sendbuf, 1, MPI_INT, dest, tag, recvbuf, 1, MPI_INT, nproc - 1, tag, MPI_COMM_WORLD, &status);
	}
	else
	{
		MPI_Sendrecv(sendbuf, 1, MPI_INT, dest, tag, recvbuf, 1, MPI_INT, rank - 1, tag, MPI_COMM_WORLD, &status);
	}
	printf("Proc %d: Receive message from %d...\n", rank, status.MPI_SOURCE);

	MPI_Finalize();		//Finalize MPI
	return 0;
}