// use MPI_Bsend to send a single message in buffered mode
// note that a buffered mode send operation can be started
// whether or not a matching receive has been posted
// in this case, the MPI_Bsend completes before a matching receive is posted

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

#define BUFSIZE 2048			//The size of the messege being passed

main( int argc, char** argv)
{
	int rank;					//the rank of this process
	int tag = 0;
	int bufsize, abufsize;
	float *buf, *abuf, *message;
	MPI_Status status;			//not important here

	bufsize = (BUFSIZE * sizeof(float) + MPI_BSEND_OVERHEAD);
	buf = (float *)malloc(bufsize);
	message = (float *)malloc(sizeof(float) * BUFSIZE);

	MPI_Init(&argc, &argv);		//Initializing mpi
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);	//Getting my rank

	if( rank == 0 )
	{
		printf("Hello world! I am proc 0, sending to proc 1..\n");
		MPI_Buffer_attach(buf, bufsize); 
		/* a buffer can now be used by MPI_Bsend */ 
		//send to the proc 1
		MPI_Bsend(message, BUFSIZE, MPI_FLOAT, 1, tag, MPI_COMM_WORLD);
		MPI_Buffer_detach(&abuf, &abufsize); 
		/* Buffer size reduced to zero */ 
		free(abuf);
	}
	else if( rank == 1)
	{
		//sleep for 3 sec
		sleep(3);
		printf("Hello world! I am proc 1, just wake up!!\n");
		//recieve from the proc 0
		MPI_Recv(message, BUFSIZE, MPI_FLOAT, 0, tag, MPI_COMM_WORLD, &status);
		printf("Hello world! Received 1 message from proc 1!!\n");
	}
	printf("Proc %d finished!!\n", rank);
	MPI_Finalize();
	return 0;
}