scattern.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 <stdlib.h>
#include <stdio.h>
#include "test.h" 

/* This example sends a vector and receives individual elements */

int main( int argc, char **argv )
{
    MPI_Datatype vec;
    double *vecin, *vecout, ivalue;
    int    root, i, n, stride, err = 0;
    int    rank, size;

    MPI_Init( &argc, &argv );
    
    MPI_Comm_size( MPI_COMM_WORLD, &size );
    MPI_Comm_rank( MPI_COMM_WORLD, &rank );

    n = 12;
    stride = 10;
    vecin = (double *)malloc( n * stride * size * sizeof(double) );
    vecout = (double *)malloc( n * sizeof(double) );
    
    MPI_Type_vector( n, 1, stride, MPI_DOUBLE, &vec );
    MPI_Type_commit( &vec );

    for (i=0; i<n*stride*size; i++) vecin[i] = (double)i;
    for (root=0; root<size; root++) {
	for (i=0; i<n; i++) vecout[i] = -1.0;
	MPI_Scatter( vecin, 1, vec, vecout, n, MPI_DOUBLE, root, 
		     MPI_COMM_WORLD );
	ivalue = rank * ((n-1) * stride + 1);
	for (i=0; i<n; i++) {
	    if (vecout[i] != ivalue) {
		printf( "Expected %f but found %f\n", 
			ivalue, vecout[i] );
		err++;
	    }
	    ivalue += stride;
	}
    }
    i = err;
    MPI_Allreduce( &i, &err, 1, MPI_INT, MPI_SUM, MPI_COMM_WORLD );
    if (rank == 0) {
	if (err > 0) printf( "Found %d errors!\n", err );
	else         printf( " No Errors\n" );
    }
    MPI_Type_free( &vec );
    MPI_Finalize();
    return 0;
       
}