openmpi/ompi/mca/coll/basic/coll_basic_gather.c

/*
 * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
 *                         University Research and Technology
 *                         Corporation.  All rights reserved.
 * Copyright (c) 2004-2015 The University of Tennessee and The University
 *                         of Tennessee Research Foundation.  All rights
 *                         reserved.
 * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart, 
 *                         University of Stuttgart.  All rights reserved.
 * Copyright (c) 2004-2005 The Regents of the University of California.
 *                         All rights reserved.
 * $COPYRIGHT$
 * 
 * Additional copyrights may follow
 * 
 * $HEADER$
 */

#include "ompi_config.h"
#include "coll_basic.h"

#include "mpi.h"
#include "ompi/constants.h"
#include "coll_basic.h"
#include "ompi/datatype/ompi_datatype.h"
#include "ompi/mca/coll/coll.h"
#include "ompi/mca/coll/base/coll_tags.h"
#include "ompi/mca/pml/pml.h"


/*
 *	gather_inter
 *
 *	Function:	- basic gather operation
 *	Accepts:	- same arguments as MPI_Gather()
 *	Returns:	- MPI_SUCCESS or error code
 */
int
mca_coll_basic_gather_inter(void *sbuf, int scount,
                            struct ompi_datatype_t *sdtype,
                            void *rbuf, int rcount,
                            struct ompi_datatype_t *rdtype,
                            int root, struct ompi_communicator_t *comm,
                            mca_coll_base_module_t *module)
{
    int i;
    int err;
    int size;
    char *ptmp;
    MPI_Aint incr;
    MPI_Aint extent;
    MPI_Aint lb;

    size = ompi_comm_remote_size(comm);

    if (MPI_PROC_NULL == root) {
        /* do nothing */
        err = OMPI_SUCCESS;
    } else if (MPI_ROOT != root) {
        /* Everyone but root sends data and returns. */
        err = MCA_PML_CALL(send(sbuf, scount, sdtype, root,
                                MCA_COLL_BASE_TAG_GATHER,
                                MCA_PML_BASE_SEND_STANDARD, comm));
    } else {
        /* I am the root, loop receiving the data. */
        err = ompi_datatype_get_extent(rdtype, &lb, &extent);
        if (OMPI_SUCCESS != err) {
            return OMPI_ERROR;
        }

        incr = extent * rcount;
        for (i = 0, ptmp = (char *) rbuf; i < size; ++i, ptmp += incr) {
            err = MCA_PML_CALL(recv(ptmp, rcount, rdtype, i,
                                    MCA_COLL_BASE_TAG_GATHER,
                                    comm, MPI_STATUS_IGNORE));
            if (MPI_SUCCESS != err) {
                return err;
            }
        }
    }

    /* All done */
    return err;
}