/* -*- 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_inter_pairwise_exchange
#undef FCNAME
#define FCNAME MPL_QUOTE(FUNCNAME)
int MPIR_Ialltoallv_sched_inter_pairwise_exchange(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)
{
/* Intercommunicator alltoallv. We use a pairwise exchange algorithm
* similar to the one used in intracommunicator alltoallv. Since the
* local and remote groups can be of different
* sizes, we first compute the max of local_group_size,
* remote_group_size. At step i, 0 <= i < max_size, each process
* receives from src = (rank - i + max_size) % max_size if src <
* remote_size, and sends to dst = (rank + i) % max_size if dst <
* remote_size.
*/
int mpi_errno = MPI_SUCCESS;
int local_size, remote_size, max_size, i;
MPI_Aint send_extent, recv_extent, sendtype_size, recvtype_size;
int src, dst, rank, sendcount, recvcount;
char *sendaddr, *recvaddr;
MPIR_Assert(comm_ptr->comm_kind == MPIR_COMM_KIND__INTERCOMM);
local_size = comm_ptr->local_size;
remote_size = comm_ptr->remote_size;
rank = comm_ptr->rank;
/* Get extent of send and recv types */
MPIR_Datatype_get_extent_macro(sendtype, send_extent);
MPIR_Datatype_get_extent_macro(recvtype, recv_extent);
MPIR_Datatype_get_size_macro(sendtype, sendtype_size);
MPIR_Datatype_get_size_macro(recvtype, recvtype_size);
/* Use pairwise exchange algorithm. */
max_size = MPL_MAX(local_size, remote_size);
for (i = 0; i < max_size; i++) {
src = (rank - i + max_size) % max_size;
dst = (rank + i) % max_size;
if (src >= remote_size) {
src = MPI_PROC_NULL;
recvaddr = NULL;
recvcount = 0;
} else {
MPIR_Ensure_Aint_fits_in_pointer(MPIR_VOID_PTR_CAST_TO_MPI_AINT recvbuf +
rdispls[src] * recv_extent);
recvaddr = (char *) recvbuf + rdispls[src] * recv_extent;
recvcount = recvcounts[src];
}
if (dst >= remote_size) {
dst = MPI_PROC_NULL;
sendaddr = NULL;
sendcount = 0;
} else {
MPIR_Ensure_Aint_fits_in_pointer(MPIR_VOID_PTR_CAST_TO_MPI_AINT sendbuf +
sdispls[dst] * send_extent);
sendaddr = (char *) sendbuf + sdispls[dst] * send_extent;
sendcount = sendcounts[dst];
}
if (sendcount * sendtype_size == 0)
dst = MPI_PROC_NULL;
if (recvcount * recvtype_size == 0)
src = MPI_PROC_NULL;
mpi_errno = MPIR_Sched_send(sendaddr, sendcount, sendtype, dst, comm_ptr, s);
if (mpi_errno)
MPIR_ERR_POP(mpi_errno);
mpi_errno = MPIR_Sched_recv(recvaddr, recvcount, recvtype, src, comm_ptr, s);
if (mpi_errno)
MPIR_ERR_POP(mpi_errno);
mpi_errno = MPIR_Sched_barrier(s);
if (mpi_errno)
MPIR_ERR_POP(mpi_errno);
}
fn_exit:
return mpi_errno;
fn_fail:
goto fn_exit;
}