pnetcdf-write-flexible.c

/*********************************************************************
 *
 *  Copyright (C) 2012, Northwestern University and Argonne National Laboratory
 *  See COPYRIGHT notice in top-level directory.
 *
 *********************************************************************/
/* $Id$ */

/* simple demonstration of pnetcdf
 * text attribute on dataset
 * write out rank into 1-d array collectively.
 * This example demonstrates the flexible interface */

/* This program creates a file, say named output.nc, with the following
   contents, shown by running ncmpidump command .

    % mpiexec -n 4 pnetcdf-write-flexible /orangefs/wkliao/output.nc

    % ncmpidump /orangefs/wkliao/output.nc
    netcdf output {
    // file format: CDF-2 (large file)
    dimensions:
            d1 = 4 ;
    variables:
            int v1(d1) ;
            int v2(d1) ;

    // global attributes:
                :string = "Hello World\n",
        "" ;
    data:

         v1 = 0, 1, 2, 3 ;

         v2 = 0, 1, 2, 3 ;
    }
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <mpi.h>
#include <pnetcdf.h>

static void handle_error(int status, int lineno)
{
    fprintf(stderr, "Error at line %d: %s\n", lineno, ncmpi_strerror(status));
    MPI_Abort(MPI_COMM_WORLD, 1);
}

int main(int argc, char **argv) {

    int ret, ncfile, nprocs, rank, dimid, varid1, varid2, ndims=1;
    MPI_Offset start, count=1;
    char filename[256], buf[13] = "Hello World\n";
    int data;

    MPI_Init(&argc, &argv);

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

    if (argc > 2) {
        if (rank == 0) printf("Usage: %s filename\n", argv[0]);
        MPI_Finalize();
        exit(-1);
    }
    if (argc > 1) snprintf(filename, 256, "%s", argv[1]);
    else          strcpy(filename, "testfile.nc");

    ret = ncmpi_create(MPI_COMM_WORLD, filename,
                       NC_CLOBBER|NC_64BIT_OFFSET, MPI_INFO_NULL, &ncfile);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    ret = ncmpi_def_dim(ncfile, "d1", nprocs, &dimid);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    ret = ncmpi_def_var(ncfile, "v1", NC_INT, ndims, &dimid, &varid1);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    ret = ncmpi_def_var(ncfile, "v2", NC_INT, ndims, &dimid, &varid2);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    ret = ncmpi_put_att_text(ncfile, NC_GLOBAL, "string", 13, buf);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    /* all processors defined the dimensions, attributes, and variables,
     * but here in ncmpi_enddef is the one place where metadata I/O
     * happens.  Behind the scenes, rank 0 takes the information and writes
     * the netcdf header.  All processes communicate to ensure they have
     * the same (cached) view of the dataset */

    ret = ncmpi_enddef(ncfile);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    start=rank, count=1, data=rank;

    /* in this simple example every process writes its rank to two 1d variables */
    /* we used a basic MPI_INT type to this flexible mode call, but could
     * have used any derived MPI datatype that describes application data
     * structures */
    ret = ncmpi_put_vara_all(ncfile, varid1, &start, &count, &data, count, MPI_INT);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    ret = ncmpi_put_vara_all(ncfile, varid2, &start, &count, &data, count, MPI_INT);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    ret = ncmpi_close(ncfile);
    if (ret != NC_NOERR) handle_error(ret, __LINE__);

    MPI_Finalize();

    return 0;
}