/* -*- 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"
/*
* Pairwise Exchange
*
* 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 alltoallv
*/
#undef FUNCNAME
#define FUNCNAME MPIR_Alltoallw_inter_pairwise_exchange
#undef FCNAME
#define FCNAME MPL_QUOTE(FUNCNAME)
int MPIR_Alltoallw_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_Errflag_t * errflag)
{
int local_size, remote_size, max_size, i;
int mpi_errno = MPI_SUCCESS;
int mpi_errno_ret = MPI_SUCCESS;
MPI_Status status;
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 = MPIC_Sendrecv(sendaddr, sendcount, sendtype,
dst, MPIR_ALLTOALLW_TAG, recvaddr,
recvcount, recvtype, src,
MPIR_ALLTOALLW_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);
}
}
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;
}