#include "stdio.h"
#include "mpi.h"
void main(int argc, char *argv[])
{
	int nrow, mcol, root, Iam, ndim, p, rank;
	int dims[2], coords[2], cyclic[2], reorder;
	MPI_Comm comm2D, comm2Dp;
	/* 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 */

	nrow = 3; mcol = 2; ndim = 2;
	root = 0; cyclic[0] = 0; cyclic[1] = 0; reorder = 1;

	if(Iam == root) {
		printf("\n");
		printf("There are six (6) processes\n");
		printf("use all 6 to create 3x2 cartesian topology\n");
		printf("    Cart. Coords.     Cart\n");
		printf("       i        j     rank      Iam\n");
	}
	MPI_Barrier(MPI_COMM_WORLD);
	/* first, create 3x2 cartesian topology for processes */
	dims[0] = nrow;	/* rows */
	dims[1] = mcol;	/* columns */
	/* <em> */
	MPI_Cart_create(MPI_COMM_WORLD, ndim, dims, cyclic, reorder, &comm2D);
	/* </em> */

	if (comm2D != MPI_COMM_NULL) {
		MPI_Cart_coords(comm2D, Iam, ndim, coords);
		MPI_Cart_rank(comm2D, coords, &rank);
		printf("%8d %8d %8d %8d\n",coords[0], coords[1], rank, Iam);
	}
	MPI_Barrier(MPI_COMM_WORLD);
	/* next, create 2x2 cartesian topology for processes */
	if(Iam == root) {
		printf("\n");
		printf("There are six (6) processes\n");
		printf("use 4 to create 2x2 cartesian topology\n");
		printf("    Cart. Coords.     Cart\n");
		printf("       i        j     rank      Iam\n");
	}
	MPI_Barrier(MPI_COMM_WORLD);
	dims[0] = 2;		/* rows */
	dims[1] = 2;		/* columns */
	/* <em> */
	MPI_Cart_create(MPI_COMM_WORLD, ndim, dims, cyclic, reorder, &comm2Dp);
	/* </em> */

	if (comm2Dp != MPI_COMM_NULL) {
		MPI_Cart_coords(comm2Dp, Iam, ndim, coords);
		MPI_Cart_rank(comm2Dp, coords, &rank);
		printf("%8d %8d %8d %8d\n",coords[0], coords[1], rank, Iam);
	}

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