#include "stdio.h"
#include "mpi.h"
void main(int argc, char *argv[])
{
	int Iam, p;
	int Neven, Nodd, members[6], even_rank, odd_rank;
	MPI_Group group_world, even_group, odd_group;

	/* Starts MPI processes ... */
	MPI_Init(&argc, &argv);				  /* starts MPI */
	MPI_Comm_rank(MPI_COMM_WORLD, &Iam);  /* get current process id */
	MPI_Comm_size(MPI_COMM_WORLD, &p);    /* get number of processes */
	Neven = (p + 1)/2;     /* All processes of MPI_COMM_WORLD are divided */
	Nodd = p - Neven;	/* into 2 groups, odd- and even-numbered groups */
	members[0] = 2;
	members[1] = 0;
	members[2] = 4;
	MPI_Comm_group(MPI_COMM_WORLD, &group_world);
	MPI_Group_incl(group_world, Neven, members, &even_group);
	MPI_Group_excl(group_world, Neven, members,  &odd_group);

	MPI_Barrier(MPI_COMM_WORLD);
	if(Iam == 0) {
		printf("MPI_Group_incl/excl Usage Example\n");
		printf("\n");
		printf("Number of processes is %d\n", p);
		printf("Number of odd processes is %d\n", Nodd);
		printf("Number of even processes is %d\n", Neven);
		printf("members[0] is assigned rank %d\n", members[0]);
		printf("members[1] is assigned rank %d\n", members[1]);
		printf("members[2] is assigned rank %d\n", members[2]);
		printf("\n");
		printf("MPI_UNDEFINED is set to     %d\n", MPI_UNDEFINED);
		printf("\n");
		printf("     Iam     even      odd\n");
	}
	MPI_Barrier(MPI_COMM_WORLD);

	MPI_Group_rank(even_group, &even_rank);
	MPI_Group_rank( odd_group,  &odd_rank);
	printf("%8d %8d %8d\n",Iam, even_rank, odd_rank);

	MPI_Finalize();			/* let MPI finish up ...  */
}