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/*********************************************************************
*
* Copyright (C) 2019, Northwestern University and Argonne National Laboratory
* See COPYRIGHT notice in top-level directory.
*
* To compile:
* % mpicc mpi_subarray.c -o mpi_subarray
*
* To run:
* % mpiexec -n 4 ./mpi_subarray output_file
*
*********************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
#define LEN 16
#define ERROR(fname) \
if (err != MPI_SUCCESS) { \
int errorStringLen; \
char errorString[MPI_MAX_ERROR_STRING]; \
MPI_Error_string(err, errorString, &errorStringLen); \
printf("Error at line %d when calling %s: %s\n",__LINE__,fname,errorString); \
}
/*----< main() >------------------------------------------------------------*/
int main(int argc, char **argv)
{
char *filename;
int err, rank, nprocs, verbose=0, psizes[2]={0,0}, buf[LEN*LEN];
int gsizes[2], sizes[2], starts[2];
MPI_File fh;
MPI_Datatype ftype;
MPI_Status status;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
filename = "testfile";
if (argc > 1) filename = argv[1];
/* Creates a division of processors in a cartesian grid */
err = MPI_Dims_create(nprocs, 2, psizes);
ERROR("MPI_Dims_create");
/* set global array sizes, local array sizes, starting offsets */
starts[0] = LEN * (rank / psizes[1]);
starts[1] = LEN * (rank % psizes[1]);
gsizes[0] = LEN * psizes[0];
gsizes[1] = LEN * psizes[1];
sizes[0] = sizes[1] = LEN;
if (verbose)
printf("rank %d: gsizes=%d %d sizes=%d %d starts=%d %d\n", rank,
gsizes[0],gsizes[1],sizes[0],sizes[1],starts[0],starts[1]);
/* create file type: 2D subarray */
err = MPI_Type_create_subarray(2, gsizes, sizes, starts, MPI_ORDER_C, MPI_INT, &ftype);
ERROR("MPI_Type_create_subarray");
err = MPI_Type_commit(&ftype);
ERROR("MPI_Type_commit");
/* open the file */
err = MPI_File_open(MPI_COMM_WORLD, filename, MPI_MODE_CREATE | MPI_MODE_WRONLY,
MPI_INFO_NULL, &fh);
ERROR("MPI_File_open");
/* set the file view */
err = MPI_File_set_view(fh, 0, MPI_INT, ftype, "native", MPI_INFO_NULL);
ERROR("MPI_File_set_view");
err = MPI_Type_free(&ftype);
ERROR("MPI_Type_free");
/* MPI collective write */
err = MPI_File_write_all(fh, buf, LEN*LEN, MPI_INT, &status);
ERROR("MPI_File_write_all");
MPI_File_close(&fh);
MPI_Finalize();
return 0;
}
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