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

/*

 *  (C) 2017 by Argonne National Laboratory.

 *      See COPYRIGHT in top-level directory.

 */

#include "mpiimpl.h"

#undef FUNCNAME

#define FUNCNAME MPIR_Ialltoallv_sched_intra_inplace

#undef FCNAME

#define FCNAME MPL_QUOTE(FUNCNAME)

int MPIR_Ialltoallv_sched_intra_inplace(const void *sendbuf, const int sendcounts[],

                                        const int sdispls[], MPI_Datatype sendtype, void *recvbuf,

                                        const int recvcounts[], const int rdispls[],

                                        MPI_Datatype recvtype, MPIR_Comm * comm_ptr, MPIR_Sched_t s)

{

    int max_count;

    void *tmp_buf = NULL;

    int mpi_errno = MPI_SUCCESS;

    int comm_size;

    int i, j;

    MPI_Aint recv_extent;

    int dst, rank;

    MPIR_SCHED_CHKPMEM_DECL(1);

    comm_size = comm_ptr->local_size;

    rank = comm_ptr->rank;

    /* Get extent and size of recvtype, don't look at sendtype for MPI_IN_PLACE */

    MPIR_Datatype_get_extent_macro(recvtype, recv_extent);

    /* The regular MPI_Alltoallv handles MPI_IN_PLACE using pairwise

     * sendrecv_replace calls.  We don't have a sendrecv_replace, so just

     * malloc the maximum of the counts array entries and then perform the

     * pairwise exchanges manually with schedule barriers instead.

     *

     * Because of this approach all processes must agree on the global

     * schedule of "sendrecv_replace" operations to avoid deadlock.

     *

     * This keeps with the spirit of the MPI-2.2 standard, which is to

     * conserve memory when using MPI_IN_PLACE for these routines.

     * Something like MADRE would probably generate a more optimal

     * algorithm. */

    max_count = 0;

    for (i = 0; i < comm_size; ++i) {

        max_count = MPL_MAX(max_count, recvcounts[i]);

    }

    MPIR_SCHED_CHKPMEM_MALLOC(tmp_buf, void *, max_count * recv_extent, mpi_errno,

                              "Ialltoallv tmp_buf", MPL_MEM_BUFFER);

    for (i = 0; i < comm_size; ++i) {

        /* start inner loop at i to avoid re-exchanging data */

        for (j = i; j < comm_size; ++j) {

            if (rank == i && rank == j) {

                /* no need to "sendrecv_replace" for ourselves */

            } else if (rank == i || rank == j) {

                if (rank == i)

                    dst = j;

                else

                    dst = i;

                mpi_errno = MPIR_Sched_send(((char *) recvbuf + rdispls[dst] * recv_extent),

                                            recvcounts[dst], recvtype, dst, comm_ptr, s);

                if (mpi_errno)

                    MPIR_ERR_POP(mpi_errno);

                mpi_errno = MPIR_Sched_recv(tmp_buf, recvcounts[dst], recvtype, dst, comm_ptr, s);

                if (mpi_errno)

                    MPIR_ERR_POP(mpi_errno);

                MPIR_SCHED_BARRIER(s);

                mpi_errno = MPIR_Sched_copy(tmp_buf, recvcounts[dst], recvtype,

                                            ((char *) recvbuf + rdispls[dst] * recv_extent),

                                            recvcounts[dst], recvtype, s);

                if (mpi_errno)

                    MPIR_ERR_POP(mpi_errno);

                MPIR_SCHED_BARRIER(s);

            }

        }

    }

    MPIR_SCHED_BARRIER(s);

    MPIR_SCHED_CHKPMEM_COMMIT(s);

  fn_exit:

    return mpi_errno;

  fn_fail:

    MPIR_SCHED_CHKPMEM_REAP(s);

    goto fn_exit;

}