Hilfesystem für den Message Passing Interface Standard MPI

Erzeugt drei Intrakommunikatoren und bildet einen Interkommunikator zwischen jeweils zweien. Dann werden ein paar Daten über Interkommunikator hin und her geschickt. Jeder Prozeß sendet seine ID aus MPI_COMM_WORLD an die Prozesse der anderen Intrakommunikatoren mit der gleichen lokalen ID.

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

#define GROUPS 3

int main(int argc, char *argv[]) {

    int           me, newid, numprocs, groupsize, color, msg, rbuf;
    int           local_leader, remote_leader;
    MPI_Status    stat;
    MPI_Comm      local_comm;
    MPI_Comm      myFirstComm, mySecondComm;

    if (MPI_Init(&argc, &argv)!=MPI_SUCCESS) {
	fprintf(stderr,"MPI_Init failed.\n");
	return -1;
    }
    MPI_Comm_rank(MPI_COMM_WORLD, &me);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    if ((numprocs%GROUPS)!=0) {
	if (me==0) {
	    fprintf(stderr,"Number of processes should be a multiple of %d\n", GROUPS);
	}
	MPI_Finalize();
	return -1;
    }

    color=me%GROUPS;
    MPI_Comm_split(MPI_COMM_WORLD, color, me, &local_comm);
    MPI_Comm_rank(local_comm, &newid);
    MPI_Comm_size(local_comm, &groupsize);
    fprintf(stderr,"Proc %d: I'm now number %d in group with color %d.\n",
	    me, newid, color);
    if (color==0) {
	MPI_Intercomm_create(local_comm, 0, MPI_COMM_WORLD, 1,
			     111, &myFirstComm);
	MPI_Intercomm_create(local_comm, 0, MPI_COMM_WORLD, 2,
			     222, &mySecondComm);
    }
    if (color==1) {
	MPI_Intercomm_create(local_comm, 0, MPI_COMM_WORLD, 0,
			     111, &myFirstComm);
	MPI_Intercomm_create(local_comm, 0, MPI_COMM_WORLD, 2,
			     999, &mySecondComm);
    }
    if (color==2) {
	MPI_Intercomm_create(local_comm, 0, MPI_COMM_WORLD, 0,
			     222, &myFirstComm);
	MPI_Intercomm_create(local_comm, 0, MPI_COMM_WORLD, 1,
			     999, &mySecondComm);
    }
    MPI_Barrier( MPI_COMM_WORLD);
    msg=me;
    if (color==0) {
	    MPI_Send(&msg, 1, MPI_INT, newid, 0, myFirstComm);
	    MPI_Send(&msg, 1, MPI_INT, newid, 0, mySecondComm);
	    fprintf(stderr,"Proc %d: Sending %d to partners.\n", me, msg);
	    MPI_Recv(&rbuf,1,MPI_INT,newid,MPI_ANY_TAG,myFirstComm,&stat);
	    fprintf(stderr,"Proc %d: Received %d from remote %d (tag %d)\n",
		    me, rbuf, stat.MPI_SOURCE, stat.MPI_TAG);
	    MPI_Recv(&rbuf,1,MPI_INT,newid,MPI_ANY_TAG,mySecondComm,&stat);
	    fprintf(stderr,"Proc %d: Received %d from remote %d (tag %d)\n",
		    me, rbuf, stat.MPI_SOURCE, stat.MPI_TAG);    
    }    
    if (color==1) {
	    MPI_Recv(&rbuf,1,MPI_INT,newid,MPI_ANY_TAG,myFirstComm,&stat);
	    fprintf(stderr,"Proc %d: Received %d from remote %d (tag %d)\n",
		    me, rbuf, stat.MPI_SOURCE, stat.MPI_TAG);
	    MPI_Send(&msg, 1, MPI_INT, newid, 0, myFirstComm);
	    MPI_Send(&msg, 1, MPI_INT, newid, 0, mySecondComm);
	    fprintf(stderr,"Proc %d: Sending %d to partners.\n", me, msg);

	    MPI_Recv(&rbuf,1,MPI_INT,newid,MPI_ANY_TAG,mySecondComm,&stat);
	    fprintf(stderr,"Proc %d: Received %d from remote %d (tag %d)\n",
		    me, rbuf, stat.MPI_SOURCE, stat.MPI_TAG);    
    }
    if (color==2) {
	    MPI_Recv(&rbuf,1,MPI_INT,newid,MPI_ANY_TAG,myFirstComm,&stat);
	    fprintf(stderr,"Proc %d: Received %d from remote %d (tag %d)\n",
		    me, rbuf, stat.MPI_SOURCE, stat.MPI_TAG);
	    MPI_Recv(&rbuf,1,MPI_INT,newid,MPI_ANY_TAG,mySecondComm,&stat);
	    fprintf(stderr,"Proc %d: Received %d from remote %d (tag %d)\n",
		    me, rbuf, stat.MPI_SOURCE, stat.MPI_TAG);   
	    MPI_Send(&msg, 1, MPI_INT, newid, 0, myFirstComm);
	    MPI_Send(&msg, 1, MPI_INT, newid, 0, mySecondComm);
	    fprintf(stderr,"Proc %d: Sending %d to partners.\n", me, msg);
    }
    MPI_Barrier(MPI_COMM_WORLD);	
    MPI_Comm_free(&myFirstComm);
    MPI_Comm_free(&mySecondComm);	
    MPI_Comm_free(&local_comm);
    MPI_Finalize();
}