/* -*- 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_Ialltoallw_sched_inter_pairwise_exchange
#undef FCNAME
#define FCNAME MPL_QUOTE(FUNCNAME)
int MPIR_Ialltoallw_sched_inter_pairwise_exchange(const void *sendbuf, const int sendcounts[],
const int sdispls[],
const MPI_Datatype sendtypes[], void *recvbuf,
const int recvcounts[], const int rdispls[],
const MPI_Datatype recvtypes[],
MPIR_Comm * comm_ptr, MPIR_Sched_t s)
{
/* Intercommunicator alltoallw. We use a pairwise exchange algorithm
similar to the one used in intracommunicator alltoallw. 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.
FIXME: change algorithm to match intracommunicator alltoallw
*/
int mpi_errno = MPI_SUCCESS;
int local_size, remote_size, max_size, i;
int src, dst, rank, sendcount, recvcount;
char *sendaddr, *recvaddr;
MPI_Datatype sendtype, recvtype;
local_size = comm_ptr->local_size;
remote_size = comm_ptr->remote_size;
rank = comm_ptr->rank;
/* 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;
recvtype = MPI_DATATYPE_NULL;
} else {
recvaddr = (char *) recvbuf + rdispls[src];
recvcount = recvcounts[src];
recvtype = recvtypes[src];
}
if (dst >= remote_size) {
dst = MPI_PROC_NULL;
sendaddr = NULL;
sendcount = 0;
sendtype = MPI_DATATYPE_NULL;
} else {
sendaddr = (char *) sendbuf + sdispls[dst];
sendcount = sendcounts[dst];
sendtype = sendtypes[dst];
}
mpi_errno = MPIR_Sched_send(sendaddr, sendcount, sendtype, dst, comm_ptr, s);
if (mpi_errno)
MPIR_ERR_POP(mpi_errno);
/* sendrecv, no barrier here */
mpi_errno = MPIR_Sched_recv(recvaddr, recvcount, recvtype, src, comm_ptr, s);
if (mpi_errno)
MPIR_ERR_POP(mpi_errno);
MPIR_SCHED_BARRIER(s);
}
fn_exit:
return mpi_errno;
fn_fail:
goto fn_exit;
}