read.c

The example for Boor USING MPI2

/* read from a common file using individual file pointers */
#include "mpi.h"

#define FILESIZE (1024 * 1024)

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

    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_File_seek(fh, rank*bufsize, MPI_SEEK_SET);
    MPI_File_read(fh, buf, nints, MPI_INT, &status);
    MPI_File_close(&fh);

    free(buf);
    MPI_Finalize();
    return 0; 
}