/* -*- 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"
/*
* Recursive Doubling Algorithm:
*
* Restrictions: power-of-two no. of processes
*
* Cost = lgp.alpha + n.((p-1)/p).beta
*
* TODO: On TCP, we may want to use recursive doubling instead of the
* Bruck's algorithm in all cases because of the pairwise-exchange
* property of recursive doubling (see Benson et al paper in Euro
* PVM/MPI 2003).
*/
#undef FUNCNAME
#define FUNCNAME MPIR_Allgatherv_intra_recursive_doubling
#undef FCNAME
#define FCNAME MPL_QUOTE(FUNCNAME)
int MPIR_Allgatherv_intra_recursive_doubling(const void *sendbuf,
int sendcount,
MPI_Datatype sendtype,
void *recvbuf,
const int *recvcounts,
const int *displs,
MPI_Datatype recvtype,
MPIR_Comm * comm_ptr, MPIR_Errflag_t * errflag)
{
int comm_size, rank, j, i;
int mpi_errno = MPI_SUCCESS;
int mpi_errno_ret = MPI_SUCCESS;
MPI_Status status;
MPI_Aint recvtype_extent, recvtype_true_extent, recvtype_true_lb;
MPI_Aint curr_cnt, last_recv_cnt;
int dst, total_count;
void *tmp_buf;
int mask, dst_tree_root, my_tree_root, position,
send_offset, recv_offset, nprocs_completed, k, offset, tmp_mask, tree_root;
MPIR_CHKLMEM_DECL(1);
comm_size = comm_ptr->local_size;
rank = comm_ptr->rank;
#ifdef HAVE_ERROR_CHECKING
/* Currently this algorithm can only handle power-of-2 comm_size.
* Non power-of-2 comm_size is still experimental */
MPIR_Assert(!(comm_size & (comm_size - 1)));
#endif /* HAVE_ERROR_CHECKING */
total_count = 0;
for (i = 0; i < comm_size; i++)
total_count += recvcounts[i];
if (total_count == 0)
goto fn_exit;
MPIR_Datatype_get_extent_macro(recvtype, recvtype_extent);
/* need to receive contiguously into tmp_buf because
* displs could make the recvbuf noncontiguous */
MPIR_Type_get_true_extent_impl(recvtype, &recvtype_true_lb, &recvtype_true_extent);
MPIR_Ensure_Aint_fits_in_pointer(total_count *
(MPL_MAX(recvtype_true_extent, recvtype_extent)));
MPIR_CHKLMEM_MALLOC(tmp_buf, void *,
total_count * (MPL_MAX(recvtype_true_extent, recvtype_extent)),
mpi_errno, "tmp_buf", MPL_MEM_BUFFER);
/* adjust for potential negative lower bound in datatype */
tmp_buf = (void *) ((char *) tmp_buf - recvtype_true_lb);
/* copy local data into right location in tmp_buf */
position = 0;
for (i = 0; i < rank; i++)
position += recvcounts[i];
if (sendbuf != MPI_IN_PLACE) {
mpi_errno = MPIR_Localcopy(sendbuf, sendcount, sendtype,
((char *) tmp_buf + position *
recvtype_extent), recvcounts[rank], recvtype);
if (mpi_errno)
MPIR_ERR_POP(mpi_errno);
} else {
/* if in_place specified, local data is found in recvbuf */
mpi_errno = MPIR_Localcopy(((char *) recvbuf +
displs[rank] * recvtype_extent),
recvcounts[rank], recvtype,
((char *) tmp_buf + position *
recvtype_extent), recvcounts[rank], recvtype);
if (mpi_errno)
MPIR_ERR_POP(mpi_errno);
}
curr_cnt = recvcounts[rank];
mask = 0x1;
i = 0;
while (mask < comm_size) {
dst = rank ^ mask;
/* find offset into send and recv buffers. zero out
* the least significant "i" bits of rank and dst to
* find root of src and dst subtrees. Use ranks of
* roots as index to send from and recv into buffer */
dst_tree_root = dst >> i;
dst_tree_root <<= i;
my_tree_root = rank >> i;
my_tree_root <<= i;
if (dst < comm_size) {
send_offset = 0;
for (j = 0; j < my_tree_root; j++)
send_offset += recvcounts[j];
recv_offset = 0;
for (j = 0; j < dst_tree_root; j++)
recv_offset += recvcounts[j];
mpi_errno = MPIC_Sendrecv(((char *) tmp_buf + send_offset * recvtype_extent),
curr_cnt, recvtype, dst,
MPIR_ALLGATHERV_TAG,
((char *) tmp_buf + recv_offset * recvtype_extent),
total_count - recv_offset, recvtype, dst,
MPIR_ALLGATHERV_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);
last_recv_cnt = 0;
} else
/* for convenience, recv is posted for a bigger amount
* than will be sent */
MPIR_Get_count_impl(&status, recvtype, &last_recv_cnt);
curr_cnt += last_recv_cnt;
}
/* if some processes in this process's subtree in this step
* did not have any destination process to communicate with
* because of non-power-of-two, we need to send them the
* data that they would normally have received from those
* processes. That is, the haves in this subtree must send to
* the havenots. We use a logarithmic
* recursive-halfing algorithm for this. */
/* This part of the code will not currently be
* executed because we are not using recursive
* doubling for non power of two. Mark it as experimental
* so that it doesn't show up as red in the coverage
* tests. */
/* --BEGIN EXPERIMENTAL-- */
if (dst_tree_root + mask > comm_size) {
nprocs_completed = comm_size - my_tree_root - mask;
/* nprocs_completed is the number of processes in this
* subtree that have all the data. Send data to others
* in a tree fashion. First find root of current tree
* that is being divided into two. k is the number of
* least-significant bits in this process's rank that
* must be zeroed out to find the rank of the root */
j = mask;
k = 0;
while (j) {
j >>= 1;
k++;
}
k--;
tmp_mask = mask >> 1;
while (tmp_mask) {
dst = rank ^ tmp_mask;
tree_root = rank >> k;
tree_root <<= k;
/* send only if this proc has data and destination
* doesn't have data. at any step, multiple processes
* can send if they have the data */
if ((dst > rank) && (rank < tree_root + nprocs_completed)
&& (dst >= tree_root + nprocs_completed)) {
offset = 0;
for (j = 0; j < (my_tree_root + mask); j++)
offset += recvcounts[j];
offset *= recvtype_extent;
mpi_errno = MPIC_Send(((char *) tmp_buf + offset),
last_recv_cnt,
recvtype, dst, MPIR_ALLGATHERV_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);
}
/* last_recv_cnt was set in the previous
* receive. that's the amount of data to be
* sent now. */
}
/* recv only if this proc. doesn't have data and sender
* has data */
else if ((dst < rank) &&
(dst < tree_root + nprocs_completed) &&
(rank >= tree_root + nprocs_completed)) {
offset = 0;
for (j = 0; j < (my_tree_root + mask); j++)
offset += recvcounts[j];
mpi_errno = MPIC_Recv(((char *) tmp_buf + offset * recvtype_extent),
total_count - offset, recvtype,
dst, MPIR_ALLGATHERV_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);
last_recv_cnt = 0;
} else
/* for convenience, recv is posted for a
* bigger amount than will be sent */
MPIR_Get_count_impl(&status, recvtype, &last_recv_cnt);
curr_cnt += last_recv_cnt;
}
tmp_mask >>= 1;
k--;
}
}
/* --END EXPERIMENTAL-- */
mask <<= 1;
i++;
}
/* copy data from tmp_buf to recvbuf */
position = 0;
for (j = 0; j < comm_size; j++) {
if ((sendbuf != MPI_IN_PLACE) || (j != rank)) {
/* not necessary to copy if in_place and
* j==rank. otherwise copy. */
mpi_errno = MPIR_Localcopy(((char *) tmp_buf + position * recvtype_extent),
recvcounts[j], recvtype,
((char *) recvbuf + displs[j] * recvtype_extent),
recvcounts[j], recvtype);
if (mpi_errno)
MPIR_ERR_POP(mpi_errno);
}
position += recvcounts[j];
}
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;
}