cart.c

MPICH是MPI的重要研究,提供了一系列的接口函数,为并行计算的实现提供了编程环境.

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

#define NUM_DIMS 2

int main( int argc, char **argv )
{
    int              rank, size, i;
    int              errors=0;
    int              dims[NUM_DIMS];
    int              periods[NUM_DIMS];
    int              coords[NUM_DIMS];
    int              new_coords[NUM_DIMS];
    int              reorder = 1;
    MPI_Comm         comm_temp, comm_cart, new_comm;
    int              topo_status;
    int              ndims;
    int              new_rank;
    int              remain_dims[NUM_DIMS];
    int              newnewrank;

    MPI_Init( &argc, &argv );

    MPI_Comm_rank( MPI_COMM_WORLD, &rank );
    MPI_Comm_size( MPI_COMM_WORLD, &size );

    /* Clear dims array and get dims for topology */
    for(i=0;i<NUM_DIMS;i++) { dims[i] = 0; periods[i] = 0; }
    MPI_Dims_create ( size, NUM_DIMS, dims );

    /* Make a new communicator with a topology */
    MPI_Cart_create ( MPI_COMM_WORLD, 2, dims, periods, reorder, &comm_temp );
    MPI_Comm_dup ( comm_temp, &comm_cart );

    /* Determine the status of the new communicator */
    MPI_Topo_test ( comm_cart, &topo_status );
    if (topo_status != MPI_CART) {
	printf( "topo_status of duped comm is not MPI_CART\n" );
	errors++;
    }

    /* How many dims do we have? */
    MPI_Cartdim_get( comm_cart, &ndims );
    if ( ndims != NUM_DIMS ) {
	printf( "Number of dims of duped comm (%d) should be %d\n", 
		ndims, NUM_DIMS );
	errors++;
    }

    /* Get the topology, does it agree with what we put in? */
    for(i=0;i<NUM_DIMS;i++) { dims[i] = 0; periods[i] = 0; }
    MPI_Cart_get ( comm_cart, NUM_DIMS, dims, periods, coords );

    /* Does the mapping from coords to rank work? */
    MPI_Cart_rank ( comm_cart, coords, &new_rank );
    if ( new_rank != rank ) {
	printf( "New rank of duped comm (%d) != old rank (%d)\n", 
		new_rank, rank );
	errors++;
    }

    /* Does the mapping from rank to coords work */
    MPI_Cart_coords ( comm_cart, rank, NUM_DIMS, new_coords );
    for (i=0;i<NUM_DIMS;i++) 
	if ( coords[i] != new_coords[i] ) {
	    printf( "Old coords[%d] of duped comm (%d) != new_coords (%d)\n", 
		    i, coords[i], new_coords[i] );
	    errors++;
	}

    /* Let's shift in each dimension and see how it works!   */
    /* Because it's late and I'm tired, I'm not making this  */
    /* automatically test itself.                            */
    for (i=0;i<NUM_DIMS;i++) {
      int source, dest;
      MPI_Cart_shift(comm_cart, i, 1, &source, &dest);
#ifdef VERBOSE      
      printf ("[%d] Shifting %d in the %d dimension\n",rank,1,i);
      printf ("[%d]    source = %d  dest = %d\n",rank,source,dest); 
#endif
    }

    /* Subdivide */
    remain_dims[0] = 0; 
    for (i=1; i<NUM_DIMS; i++) remain_dims[i] = 1;
    MPI_Cart_sub ( comm_cart, remain_dims, &new_comm );

    /* Determine the status of the new communicator */
    MPI_Topo_test ( new_comm, &topo_status );
    if (topo_status != MPI_CART) {
	printf( "topo_status of cartsub comm is not MPI_CART\n" );
	errors++;
    }

    /* How many dims do we have? */
    MPI_Cartdim_get( new_comm, &ndims );
    if ( ndims != NUM_DIMS-1 ) {
	printf( "Number of dims of cartsub comm (%d) should be %d\n", 
		ndims, NUM_DIMS-1 );
	errors++;
    }

    /* Get the topology, does it agree with what we put in? */
    for(i=0;i<NUM_DIMS-1;i++) { dims[i] = 0; periods[i] = 0; }
    MPI_Cart_get ( new_comm, ndims, dims, periods, coords );
    
    /* Does the mapping from coords to rank work? */
    MPI_Comm_rank ( new_comm, &newnewrank );
    MPI_Cart_rank ( new_comm, coords, &new_rank );
    if ( new_rank != newnewrank ) {
	printf( "New rank of cartsub comm (%d) != old rank (%d)\n", 
		new_rank, newnewrank );
	errors++;
    }

    /* Does the mapping from rank to coords work */
    MPI_Cart_coords ( new_comm, new_rank, NUM_DIMS -1, new_coords );
    for (i=0;i<NUM_DIMS-1;i++) 
	if ( coords[i] != new_coords[i] ) {
	    printf( "Old coords[%d] of cartsub comm (%d) != new_coords (%d)\n", 
		    i, coords[i], new_coords[i] );
	    errors++;
	}

    /* We're at the end */
    MPI_Comm_free( &new_comm );
    MPI_Comm_free( &comm_temp );
    MPI_Comm_free( &comm_cart );
    Test_Waitforall( );
    if (errors) printf( "[%d] done with %d ERRORS!\n", rank,errors );
    MPI_Finalize();
    return 0;
}