#include "stdio.h"
#include "mpi.h"
void main(argc, argv) 
int argc;
char *argv[];
{
	int nrow, mcol, i, j;
	int p, root, Iam, rank2D, ndim;
	int dims[2], coords[2];
	int periods[2], reorder;
	MPI_Comm comm2D;
	/* 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; periods[0] = 1; periods[1] = 0; reorder = 1;

	/* create cartesian topology for processes */
	dims[0] = nrow;	/* number of rows */
	dims[1] = mcol;	/* number of columns */
	MPI_Cart_create(MPI_COMM_WORLD, ndim, dims, periods, reorder, &comm2D);

	MPI_Barrier(MPI_COMM_WORLD);
	if(Iam == root) {
		printf("\n");
		printf(" Finds ranks of 2D cartesian coordinates\n");
		printf("\n");
		printf("     Row	Col     Rank\n");
		for (i=-3; i<=nrow+2; i++) {
			for (j= 0; j<=mcol-1; j++) {
				coords[0] = i;
				coords[1] = j;
				/* <em>  */
				MPI_Cart_rank(comm2D, coords, &rank2D);
				/* </em> */
				printf("%8d %8d %8d\n",coords[0], coords[1], rank2D);
			}
		}
	}

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