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/*
* ADIOS is freely available under the terms of the BSD license described
* in the COPYING file in the top level directory of this source distribution.
*
* Copyright (c) 2008 - 2009. UT-BATTELLE, LLC. All rights reserved.
*/
/* ADIOS C Example: read global arrays from a BP file
*
* This code is using the generic read API, which can read in
* arbitrary slices of an array and thus we can read in an array
* on arbitrary number of processes (provided our code is smart
* enough to do the domain decomposition).
*
* Run this example after adios_global, which generates
* adios_global.bp. Run this example on equal or less
* number of processes since we decompose only on one
* dimension of the global array here.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "mpi.h"
#include "adios_read.h"
int main (int argc, char ** argv)
{
int rank, size, i, j, npl, token;
MPI_Comm comm = MPI_COMM_WORLD;
MPI_Status status;
enum ADIOS_READ_METHOD method = ADIOS_READ_METHOD_BP;
ADIOS_SELECTION * sel;
void * data = NULL;
uint64_t start[1], count[1];
MPI_Init (&argc, &argv);
MPI_Comm_rank (comm, &rank);
MPI_Comm_size (comm, &size);
adios_read_init_method (method, comm, "verbose=3");
ADIOS_FILE * f = adios_read_open ("no_xml_write_byid.bp", method,
comm, ADIOS_LOCKMODE_NONE, 0);
if (f == NULL)
{
printf ("%s\n", adios_errmsg());
return -1;
}
ADIOS_VARINFO * v = adios_inq_var (f, "temperature");
/* Using less readers to read the global array back, i.e., non-uniform */
uint64_t slice_size = v->dims[0]/size;
start[0] = slice_size * rank;
if (rank == size-1) /* last rank may read more lines */
slice_size = slice_size + v->dims[0]%size;
count[0] = slice_size;
data = malloc (slice_size * sizeof (double));
if (data == NULL)
{
fprintf (stderr, "malloc failed.\n");
return -1;
}
/* Read a subset of the temperature array */
sel = adios_selection_boundingbox (v->ndim, start, count);
adios_schedule_read (f, sel, "temperature", 0, 1, data);
adios_perform_reads (f, 1);
if (rank > 0) {
MPI_Recv (&token, 1, MPI_INT, rank-1, 0, comm, &status);
}
printf (" ======== Rank %d ========== \n", rank);
npl = 10;
for (i = 0; i < slice_size; i+=npl) {
printf ("[%4.4" PRIu64 "] ", rank*slice_size+i);
for (j= 0; j < npl; j++) {
printf (" %6.6g", * ((double *)data + i + j));
}
printf ("\n");
}
fflush(stdout);
sleep(1);
if (rank < size-1) {
MPI_Send (&token, 1, MPI_INT, rank+1, 0, comm);
}
free (data);
adios_selection_delete (sel);
adios_free_varinfo (v);
adios_read_close (f);
MPI_Barrier (comm);
adios_read_finalize_method (method);
MPI_Finalize ();
return 0;
}
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