/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */

/*

 *

 *  (C) 2001 by Argonne National Laboratory.

 *      See COPYRIGHT in top-level directory.

 */

#include "mpiimpl.h"

/* Local gather remote send

 *

 * Remote group does a local intracommunicator gather to rank 0. Rank

 * 0 then sends data to root.

 *

 * Cost: (lgp+1).alpha + n.((p-1)/p).beta + n.beta

 */

#undef FUNCNAME

#define FUNCNAME MPIR_Gather_inter_local_gather_remote_send

#undef FCNAME

#define FCNAME MPL_QUOTE(FUNCNAME)

int MPIR_Gather_inter_local_gather_remote_send(const void *sendbuf, int sendcount,

                                               MPI_Datatype sendtype, void *recvbuf, int recvcount,

                                               MPI_Datatype recvtype, int root,

                                               MPIR_Comm * comm_ptr, MPIR_Errflag_t * errflag)

{

    int rank, local_size, remote_size, mpi_errno = MPI_SUCCESS;

    int mpi_errno_ret = MPI_SUCCESS;

    MPI_Status status;

    MPI_Aint extent, true_extent, true_lb = 0;

    void *tmp_buf = NULL;

    MPIR_Comm *newcomm_ptr = NULL;

    MPIR_CHKLMEM_DECL(1);

    if (root == MPI_PROC_NULL) {

        /* local processes other than root do nothing */

        return MPI_SUCCESS;

    }

    remote_size = comm_ptr->remote_size;

    local_size = comm_ptr->local_size;

    if (root == MPI_ROOT) {

        /* root receives data from rank 0 on remote group */

        mpi_errno =

            MPIC_Recv(recvbuf, recvcount * remote_size, recvtype, 0, MPIR_GATHER_TAG, comm_ptr,

                      &status, errflag);

        if (mpi_errno) {

            /* for communication errors, just record the error but continue */

            *errflag =

                MPIX_ERR_PROC_FAILED ==

                MPIR_ERR_GET_CLASS(mpi_errno) ? MPIR_ERR_PROC_FAILED : MPIR_ERR_OTHER;

            MPIR_ERR_SET(mpi_errno, *errflag, "**fail");

            MPIR_ERR_ADD(mpi_errno_ret, mpi_errno);

        }

    } else {

        /* remote group. Rank 0 allocates temporary buffer, does

         * local intracommunicator gather, and then sends the data

         * to root. */

        rank = comm_ptr->rank;

        if (rank == 0) {

            MPIR_Type_get_true_extent_impl(sendtype, &true_lb, &true_extent);

            MPIR_Datatype_get_extent_macro(sendtype, extent);

            MPIR_Ensure_Aint_fits_in_pointer(sendcount * local_size *

                                             (MPL_MAX(extent, true_extent)));

            MPIR_CHKLMEM_MALLOC(tmp_buf, void *,

                                sendcount * local_size * (MPL_MAX(extent, true_extent)), mpi_errno,

                                "tmp_buf", MPL_MEM_BUFFER);

            /* adjust for potential negative lower bound in datatype */

            tmp_buf = (void *) ((char *) tmp_buf - true_lb);

        }

        /* all processes in remote group form new intracommunicator */

        if (!comm_ptr->local_comm) {

            mpi_errno = MPII_Setup_intercomm_localcomm(comm_ptr);

            if (mpi_errno)

                MPIR_ERR_POP(mpi_errno);

        }

        newcomm_ptr = comm_ptr->local_comm;

        /* now do the a local gather on this intracommunicator */

        mpi_errno =

            MPIR_Gather(sendbuf, sendcount, sendtype, tmp_buf, sendcount, sendtype, 0, newcomm_ptr,

                        errflag);

        if (mpi_errno) {

            /* for communication errors, just record the error but continue */

            *errflag =

                MPIX_ERR_PROC_FAILED ==

                MPIR_ERR_GET_CLASS(mpi_errno) ? MPIR_ERR_PROC_FAILED : MPIR_ERR_OTHER;

            MPIR_ERR_SET(mpi_errno, *errflag, "**fail");

            MPIR_ERR_ADD(mpi_errno_ret, mpi_errno);

        }

        if (rank == 0) {

            mpi_errno =

                MPIC_Send(tmp_buf, sendcount * local_size, sendtype, root, MPIR_GATHER_TAG,

                          comm_ptr, errflag);

            if (mpi_errno) {

                /* for communication errors, just record the error but continue */

                *errflag =

                    MPIX_ERR_PROC_FAILED ==

                    MPIR_ERR_GET_CLASS(mpi_errno) ? MPIR_ERR_PROC_FAILED : MPIR_ERR_OTHER;

                MPIR_ERR_SET(mpi_errno, *errflag, "**fail");

                MPIR_ERR_ADD(mpi_errno_ret, mpi_errno);

            }

        }

    }

  fn_exit:

    MPIR_CHKLMEM_FREEALL();

    if (mpi_errno_ret)

        mpi_errno = mpi_errno_ret;

    else if (*errflag != MPIR_ERR_NONE)

        MPIR_ERR_SET(mpi_errno, *errflag, "**coll_fail");

    return mpi_errno;

  fn_fail:

    goto fn_exit;

}