cartmap.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>
/* stdlib.h Needed for malloc declaration */
#include <stdlib.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              *rbuf, *sbuf;
    int              new_rank;

    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 );

    /* Look at what rankings a cartesian topology MIGHT have */
    MPI_Cart_map( MPI_COMM_WORLD, 2, dims, periods, &new_rank );

    /* Check that all new ranks are used exactly once */
    rbuf = (int *)malloc( size * sizeof(int) );
    sbuf = (int *)malloc( size * sizeof(int) );
    if (!rbuf || !sbuf) {
	MPI_Abort( MPI_COMM_WORLD, 1 );
    }
    for (i=0; i<size; i++) 
	sbuf[i] = 0;
    sbuf[new_rank] = 1;
    MPI_Reduce( sbuf, rbuf, size, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD );
    if (rank == 0) {
	for (i=0; i<size; i++) {
	    if (rbuf[i] != 1) {
		errors++;
		fprintf( stderr, "Rank %d used %d times\n", i, rbuf[i] );
	    }
	}
	if (errors == 0) 
	    printf( "Cart map test passed\n" );
    }

    free( rbuf );
    free( sbuf );
    MPI_Finalize();
    return 0;
}