/*
// The root node sends out a message process 1. Process 1 send back to Process 0.
*/

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

#define BUFSIZE 64	//The size of the messege being passed

main( int argc, char** argv)
{
	int my_rank;		//the rank of this process
	int n_processes;	//the total number of processes
	char buf[BUFSIZE];	//a buffer for the messege
	int tag=0;			//not important here
	int count;
	MPI_Status status;	//not important here

	MPI_Init(&argc, &argv);						//Initializing mpi
	MPI_Comm_size(MPI_COMM_WORLD, &n_processes);//Getting # of processes
	MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);	//Getting my rank

	if( my_rank == 0 )
	{ 
		//send to the next node */
		printf("Hello world! I am %d of %d, sending to Proc %d\n", my_rank, n_processes, my_rank+1);
		MPI_Send(buf, BUFSIZE, MPI_CHAR, my_rank+1, tag, MPI_COMM_WORLD);

		//recieve from the last node */
		MPI_Recv(buf, BUFSIZE, MPI_CHAR, n_processes-1, tag, MPI_COMM_WORLD, &status);

		MPI_Get_count(&status, MPI_CHAR, &count);
		printf("Hello world! I am %d of %d, recv %d entries from proc 1\n", my_rank, n_processes, count);
	}
	else
	{
		//recieve from proc 0
		MPI_Recv(buf, BUFSIZE, MPI_CHAR, 0, tag, MPI_COMM_WORLD, &status);

		MPI_Get_count(&status, MPI_CHAR, &count);
		printf("Hello world! I am %d of %d, recv %d entries from Proc 0\n", my_rank, n_processes, count);

		//send to the next node
		printf("Hello world! I am %d of %d, sending to Proc 0\n", my_rank, n_processes);
		MPI_Send(buf, BUFSIZE, MPI_CHAR, 0, tag, MPI_COMM_WORLD);
	}
	MPI_Finalize();		//Finalize MPI

	return 0;
}