read_all.c

The example for Boor USING MPI2

/* noncontiguous access with a single collective I/O function */
#include "mpi.h"

#define FILESIZE      1048576    
#define INTS_PER_BLK  16

int main(int argc, char **argv)
{
    int *buf, rank, nprocs, nints, bufsize;
    MPI_File fh;
    MPI_Datatype filetype;

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

    bufsize = FILESIZE/nprocs;
    buf = (int *) malloc(bufsize);
    nints = bufsize/sizeof(int);

    MPI_File_open(MPI_COMM_WORLD, "/pfs/datafile", MPI_MODE_RDONLY,
                  MPI_INFO_NULL, &fh);

    MPI_Type_vector(nints/INTS_PER_BLK, INTS_PER_BLK, 
                    INTS_PER_BLK*nprocs, MPI_INT, &filetype);
    MPI_Type_commit(&filetype);
    MPI_File_set_view(fh, INTS_PER_BLK*sizeof(int)*rank, MPI_INT, 
		      filetype, "native", MPI_INFO_NULL);

    MPI_File_read_all(fh, buf, nints, MPI_INT, MPI_STATUS_IGNORE);
    MPI_File_close(&fh);

    MPI_Type_free(&filetype);
    free(buf);
    MPI_Finalize();
    return 0; 
}