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

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

    MPI_Comm GlobalComm;
	MPI_Group GlobalGroup, Group0, Group1;
    int i, numproc, numproc0, numproc1, id;
	int *ranks, *ranks0, *ranks1;

    MPI_Init(&argc, &argv);
    MPI_Comm_dup(MPI_COMM_WORLD,&GlobalComm);
    MPI_Comm_size(GlobalComm, &numproc);
    MPI_Comm_rank(GlobalComm, &id);

	ranks=malloc(numproc*sizeof((int)1));
	ranks0=malloc(numproc*sizeof((int)1));
	ranks1=malloc(numproc*sizeof((int)1));
	for ( i = 0; i < numproc; i++ ) {
	   ranks[i] = ranks0[i] = ranks1[i] = 0;
	}
	
	/* Group of default communicator */
	MPI_Comm_group(GlobalComm,&GlobalGroup);
	
    /* Divide processes in 2 groups */
    numproc0 = numproc/2;
	for ( i = 0; i < numproc0; i++ ) {
	   ranks0[i] = i;
	}
    MPI_Group_incl(GlobalGroup, numproc0, ranks0, &Group0);
    MPI_Group_excl(GlobalGroup, numproc0, ranks0, &Group1);
    MPI_Group_size(Group1, &numproc1);

	for ( i = 0; i < numproc; i++ ) {
	   ranks[i] = i;
	}
    MPI_Group_translate_ranks(GlobalGroup, numproc, ranks, Group0, ranks0);
    MPI_Group_translate_ranks(GlobalGroup, numproc, ranks, Group1, ranks1);
    if ( id == 0 ) {
       fprintf(stdout,"Translating table: GlobalGroup, Group0, Group1\n");
	   	for ( i = 0; i < numproc; i++ ) {
			fprintf(stdout,"              %10d, %10d, %10d\n",ranks[i], ranks0[i],ranks1[i]);
		}
    }
	
    MPI_Barrier(GlobalComm);
    MPI_Group_free(&GlobalGroup);
    MPI_Group_free(&Group0);
    MPI_Group_free(&Group1);

    MPI_Finalize();

    return(0);
}