You are doing blocking

Carlos_Alexandre_T_ · ‎03-07-2014

So.. the code above is something I think it should've worked but it's bugging (by bugging i mean that rank 0 is expecting the messages

and the other ranks are waiting for them to be received but that never happens).

What I tried to do was something like this:

if(rank == 0){
	for (a = 0; a < 100; a++){
		MPI_Recv(&buff, 1, MPI_INT, MPI_ANY_SOURCE, a+100; MPI_COMM_WORLD, &status);
		MPI_Recv(&buff2, 1, MPI_INT, MPI_ANY_SOURCE, a+100; MPI_COMM_WORLD, &status);
		MPI_Recv(&buff3, 1, MPI_INT, MPI_ANY_SOURCE, a+100; MPI_COMM_WORLD, &status);
	}
}else{

	// Receive id that goes from 0 to 99. line 2.
	MPI_Recv(&id, 1, MPI_INT, 1, RECEIVEID, MPI_COMM_WORLD, &status);

	MPI_Request requestNull;

	MPI_Isend(&buff4, 1, MPI_INT, 0, id+100, MPI_COMM_WORLD, &requestNull);
	MPI_Isend(&buff5, 1, MPI_INT, 0, id+100, MPI_COMM_WORLD, &requestNull);
	MPI_Isend(&buff6, 1, MPI_INT, 0, id+100, MPI_COMM_WORLD, &requestNull);
}

I already did something like this as well and it didn't work..

MPI_Request request[3];
MPI_Status status[3];

MPI_Isend(&buff4, 1, MPI_INT, 0, id+100, MPI_COMM_WORLD, &request[0]]);
MPI_Isend(&buff5, 1, MPI_INT, 0, id+100, MPI_COMM_WORLD, &request[1]);
MPI_Isend(&buff6, 1, MPI_INT, 0, id+100, MPI_COMM_WORLD, &request[2]);

MPI_Waitall(3, request, status);

So.. any help?

Thanks in advance!

Santak_D_ · ‎03-20-2014

You are doing blocking receives on all nodes. SO unless they receive something the next instruction won't proceed.

Many ranks MPI_Isend to one rank