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openmpi/ompi/mca/coll/basic/coll_basic_reduce_scatter.c
Nathan Hjelm a31e617d17 Remove outdated comments in coll_basic_reduce_scatter.c. 
Refs trac:1559

This commit was SVN r29566.

The following Trac tickets were found above:
  Ticket 1559 --> https://svn.open-mpi.org/trac/ompi/ticket/1559
2013-10-30 16:20:20 +00:00

489 строки
18 KiB
C
Исходник Ответственный История

/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
/*
* Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
* University Research and Technology
* Corporation. All rights reserved.
* Copyright (c) 2004-2006 The University of Tennessee and The University
* of Tennessee Research Foundation. All rights
* reserved.
* Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
* University of Stuttgart. All rights reserved.
* Copyright (c) 2004-2005 The Regents of the University of California.
* All rights reserved.
* Copyright (c) 2008 Sun Microsystems, Inc. All rights reserved.
* Copyright (c) 2012 Oak Ridge National Labs. All rights reserved.
* Copyright (c) 2013 Los Alamos National Security, LLC. All rights
* reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*/
#include "ompi_config.h"
#include "coll_basic.h"
#include <stdio.h>
#include <errno.h>
#include "mpi.h"
#include "opal/util/bit_ops.h"
#include "ompi/constants.h"
#include "ompi/mca/coll/coll.h"
#include "ompi/mca/coll/base/coll_tags.h"
#include "ompi/mca/pml/pml.h"
#include "ompi/datatype/ompi_datatype.h"
#include "coll_basic.h"
#include "ompi/op/op.h"
#define COMMUTATIVE_LONG_MSG 8 * 1024 * 1024
/*
* reduce_scatter
*
* Function: - reduce then scatter
* Accepts: - same as MPI_Reduce_scatter()
* Returns: - MPI_SUCCESS or error code
*
* Algorithm:
* Cummutative, reasonable sized messages
* recursive halving algorithm
* Others:
* reduce and scatterv (needs to be cleaned
* up at some point)
*
* NOTE: that the recursive halving algorithm should be faster than
* the reduce/scatter for all message sizes. However, the memory
* usage for the recusive halving is msg_size + 2 * comm_size greater
* for the recursive halving, so I've limited where the recursive
* halving is used to be nice to the app memory wise. There are much
* better algorithms for large messages with cummutative operations,
* so this should be investigated further.
*/
int
mca_coll_basic_reduce_scatter_intra(void *sbuf, void *rbuf, int *rcounts,
struct ompi_datatype_t *dtype,
struct ompi_op_t *op,
struct ompi_communicator_t *comm,
mca_coll_base_module_t *module)
{
int i, rank, size, count, err = OMPI_SUCCESS;
ptrdiff_t true_lb, true_extent, lb, extent, buf_size;
int *disps = NULL;
char *recv_buf = NULL, *recv_buf_free = NULL;
char *result_buf = NULL, *result_buf_free = NULL;
/* Initialize */
rank = ompi_comm_rank(comm);
size = ompi_comm_size(comm);
/* Find displacements and the like */
disps = (int*) malloc(sizeof(int) * size);
if (NULL == disps) return OMPI_ERR_OUT_OF_RESOURCE;
disps[0] = 0;
for (i = 0; i < (size - 1); ++i) {
disps[i + 1] = disps[i] + rcounts[i];
}
count = disps[size - 1] + rcounts[size - 1];
/* short cut the trivial case */
if (0 == count) {
free(disps);
return OMPI_SUCCESS;
}
/* get datatype information */
ompi_datatype_get_extent(dtype, &lb, &extent);
ompi_datatype_get_true_extent(dtype, &true_lb, &true_extent);
buf_size = true_extent + (count - 1) * extent;
/* Handle MPI_IN_PLACE */
if (MPI_IN_PLACE == sbuf) {
sbuf = rbuf;
}
if ((op->o_flags & OMPI_OP_FLAGS_COMMUTE) &&
(buf_size < COMMUTATIVE_LONG_MSG)) {
int tmp_size, remain = 0, tmp_rank;
/* temporary receive buffer. See coll_basic_reduce.c for details on sizing */
recv_buf_free = (char*) malloc(buf_size);
recv_buf = recv_buf_free - lb;
if (NULL == recv_buf_free) {
err = OMPI_ERR_OUT_OF_RESOURCE;
goto cleanup;
}
/* allocate temporary buffer for results */
result_buf_free = (char*) malloc(buf_size);
result_buf = result_buf_free - lb;
/* copy local buffer into the temporary results */
err = ompi_datatype_sndrcv(sbuf, count, dtype, result_buf, count, dtype);
if (OMPI_SUCCESS != err) goto cleanup;
/* figure out power of two mapping: grow until larger than
comm size, then go back one, to get the largest power of
two less than comm size */
tmp_size = opal_next_poweroftwo(size);
tmp_size >>= 1;
remain = size - tmp_size;
/* If comm size is not a power of two, have the first "remain"
procs with an even rank send to rank + 1, leaving a power of
two procs to do the rest of the algorithm */
if (rank < 2 * remain) {
if ((rank & 1) == 0) {
err = MCA_PML_CALL(send(result_buf, count, dtype, rank + 1,
MCA_COLL_BASE_TAG_REDUCE_SCATTER,
MCA_PML_BASE_SEND_STANDARD,
comm));
if (OMPI_SUCCESS != err) goto cleanup;
/* we don't participate from here on out */
tmp_rank = -1;
} else {
err = MCA_PML_CALL(recv(recv_buf, count, dtype, rank - 1,
MCA_COLL_BASE_TAG_REDUCE_SCATTER,
comm, MPI_STATUS_IGNORE));
if (OMPI_SUCCESS != err) goto cleanup;
/* integrate their results into our temp results */
ompi_op_reduce(op, recv_buf, result_buf, count, dtype);
/* adjust rank to be the bottom "remain" ranks */
tmp_rank = rank / 2;
}
} else {
/* just need to adjust rank to show that the bottom "even
remain" ranks dropped out */
tmp_rank = rank - remain;
}
/* For ranks not kicked out by the above code, perform the
recursive halving */
if (tmp_rank >= 0) {
int *tmp_disps = NULL, *tmp_rcounts = NULL;
int mask, send_index, recv_index, last_index;
/* recalculate disps and rcounts to account for the
special "remainder" processes that are no longer doing
anything */
tmp_rcounts = (int*) malloc(tmp_size * sizeof(int));
if (NULL == tmp_rcounts) {
err = OMPI_ERR_OUT_OF_RESOURCE;
goto cleanup;
}
tmp_disps = (int*) malloc(tmp_size * sizeof(int));
if (NULL == tmp_disps) {
free(tmp_rcounts);
err = OMPI_ERR_OUT_OF_RESOURCE;
goto cleanup;
}
for (i = 0 ; i < tmp_size ; ++i) {
if (i < remain) {
/* need to include old neighbor as well */
tmp_rcounts[i] = rcounts[i * 2 + 1] + rcounts[i * 2];
} else {
tmp_rcounts[i] = rcounts[i + remain];
}
}
tmp_disps[0] = 0;
for (i = 0; i < tmp_size - 1; ++i) {
tmp_disps[i + 1] = tmp_disps[i] + tmp_rcounts[i];
}
/* do the recursive halving communication. Don't use the
dimension information on the communicator because I
think the information is invalidated by our "shrinking"
of the communicator */
mask = tmp_size >> 1;
send_index = recv_index = 0;
last_index = tmp_size;
while (mask > 0) {
int tmp_peer, peer, send_count, recv_count;
struct ompi_request_t *request;
tmp_peer = tmp_rank ^ mask;
peer = (tmp_peer < remain) ? tmp_peer * 2 + 1 : tmp_peer + remain;
/* figure out if we're sending, receiving, or both */
send_count = recv_count = 0;
if (tmp_rank < tmp_peer) {
send_index = recv_index + mask;
for (i = send_index ; i < last_index ; ++i) {
send_count += tmp_rcounts[i];
}
for (i = recv_index ; i < send_index ; ++i) {
recv_count += tmp_rcounts[i];
}
} else {
recv_index = send_index + mask;
for (i = send_index ; i < recv_index ; ++i) {
send_count += tmp_rcounts[i];
}
for (i = recv_index ; i < last_index ; ++i) {
recv_count += tmp_rcounts[i];
}
}
/* actual data transfer. Send from result_buf,
receive into recv_buf */
if (recv_count > 0) {
err = MCA_PML_CALL(irecv(recv_buf + tmp_disps[recv_index] * extent,
recv_count, dtype, peer,
MCA_COLL_BASE_TAG_REDUCE_SCATTER,
comm, &request));
if (OMPI_SUCCESS != err) {
free(tmp_rcounts);
free(tmp_disps);
goto cleanup;
}
}
if (send_count > 0) {
err = MCA_PML_CALL(send(result_buf + tmp_disps[send_index] * extent,
send_count, dtype, peer,
MCA_COLL_BASE_TAG_REDUCE_SCATTER,
MCA_PML_BASE_SEND_STANDARD,
comm));
if (OMPI_SUCCESS != err) {
free(tmp_rcounts);
free(tmp_disps);
goto cleanup;
}
}
/* if we received something on this step, push it into
the results buffer */
if (recv_count > 0) {
err = ompi_request_wait(&request, MPI_STATUS_IGNORE);
if (OMPI_SUCCESS != err) {
free(tmp_rcounts);
free(tmp_disps);
goto cleanup;
}
ompi_op_reduce(op,
recv_buf + tmp_disps[recv_index] * extent,
result_buf + tmp_disps[recv_index] * extent,
recv_count, dtype);
}
/* update for next iteration */
send_index = recv_index;
last_index = recv_index + mask;
mask >>= 1;
}
/* copy local results from results buffer into real receive buffer */
if (0 != rcounts[rank]) {
err = ompi_datatype_sndrcv(result_buf + disps[rank] * extent,
rcounts[rank], dtype,
rbuf, rcounts[rank], dtype);
if (OMPI_SUCCESS != err) {
free(tmp_rcounts);
free(tmp_disps);
goto cleanup;
}
}
free(tmp_rcounts);
free(tmp_disps);
}
/* Now fix up the non-power of two case, by having the odd
procs send the even procs the proper results */
if (rank < 2 * remain) {
if ((rank & 1) == 0) {
if (rcounts[rank]) {
err = MCA_PML_CALL(recv(rbuf, rcounts[rank], dtype, rank + 1,
MCA_COLL_BASE_TAG_REDUCE_SCATTER,
comm, MPI_STATUS_IGNORE));
if (OMPI_SUCCESS != err) goto cleanup;
}
} else {
if (rcounts[rank - 1]) {
err = MCA_PML_CALL(send(result_buf + disps[rank - 1] * extent,
rcounts[rank - 1], dtype, rank - 1,
MCA_COLL_BASE_TAG_REDUCE_SCATTER,
MCA_PML_BASE_SEND_STANDARD,
comm));
if (OMPI_SUCCESS != err) goto cleanup;
}
}
}
} else {
if (0 == rank) {
/* temporary receive buffer. See coll_basic_reduce.c for
details on sizing */
recv_buf_free = (char*) malloc(buf_size);
recv_buf = recv_buf_free - lb;
if (NULL == recv_buf_free) {
err = OMPI_ERR_OUT_OF_RESOURCE;
goto cleanup;
}
}
/* reduction */
err =
comm->c_coll.coll_reduce(sbuf, recv_buf, count, dtype, op, 0,
comm, comm->c_coll.coll_reduce_module);
/* scatter */
if (MPI_SUCCESS == err) {
err = comm->c_coll.coll_scatterv(recv_buf, rcounts, disps, dtype,
rbuf, rcounts[rank], dtype, 0,
comm, comm->c_coll.coll_scatterv_module);
}
}
cleanup:
if (NULL != disps) free(disps);
if (NULL != recv_buf_free) free(recv_buf_free);
if (NULL != result_buf_free) free(result_buf_free);
return err;
}
/*
* reduce_scatter_inter
*
* Function: - reduce/scatter operation
* Accepts: - same arguments as MPI_Reduce_scatter()
* Returns: - MPI_SUCCESS or error code
*/
int
mca_coll_basic_reduce_scatter_inter(void *sbuf, void *rbuf, int *rcounts,
struct ompi_datatype_t *dtype,
struct ompi_op_t *op,
struct ompi_communicator_t *comm,
mca_coll_base_module_t *module)
{
int err, i, rank, root = 0, rsize, lsize;
int totalcounts;
ptrdiff_t lb, extent;
char *tmpbuf = NULL, *tmpbuf2 = NULL;
ompi_request_t *req;
int *disps = NULL;
rank = ompi_comm_rank(comm);
rsize = ompi_comm_remote_size(comm);
lsize = ompi_comm_size(comm);
/* Figure out the total amount of data for the reduction. */
for (totalcounts = 0, i = 0; i < lsize; i++) {
totalcounts += rcounts[i];
}
/*
* The following code basically does an interreduce followed by a
* intrascatterv. This is implemented by having the roots of each
* group exchange their sbuf. Then, the roots receive the data
* from each of the remote ranks and execute the reduce. When
* this is complete, they have the reduced data available to them
* for doing the scatterv. They do this on the local communicator
* associated with the intercommunicator.
*
* Note: There are other ways to implement MPI_Reduce_scatter on
* intercommunicators. For example, one could do a MPI_Reduce locally,
* then send the results to the other root which could scatter it.
*
* Note: It is also worth pointing out that the rcounts argument
* represents how the data is going to be scatter locally. Therefore,
* its size is the same as the local communicator size.
*/
if (rank == root) {
err = ompi_datatype_get_extent(dtype, &lb, &extent);
if (OMPI_SUCCESS != err) {
return OMPI_ERROR;
}
/* Generate displacements for the scatterv part */
disps = (int*) malloc(sizeof(int) * lsize);
if (NULL == disps) {
return OMPI_ERR_OUT_OF_RESOURCE;
}
disps[0] = 0;
for (i = 0; i < (lsize - 1); ++i) {
disps[i + 1] = disps[i] + rcounts[i];
}
tmpbuf = (char *) malloc(totalcounts * extent);
tmpbuf2 = (char *) malloc(totalcounts * extent);
if (NULL == tmpbuf || NULL == tmpbuf2) {
return OMPI_ERR_OUT_OF_RESOURCE;
}
/* Do a send-recv between the two root procs. to avoid deadlock */
err = MCA_PML_CALL(isend(sbuf, totalcounts, dtype, 0,
MCA_COLL_BASE_TAG_REDUCE_SCATTER,
MCA_PML_BASE_SEND_STANDARD, comm, &req));
if (OMPI_SUCCESS != err) {
goto exit;
}
err = MCA_PML_CALL(recv(tmpbuf2, totalcounts, dtype, 0,
MCA_COLL_BASE_TAG_REDUCE_SCATTER, comm,
MPI_STATUS_IGNORE));
if (OMPI_SUCCESS != err) {
goto exit;
}
err = ompi_request_wait_all(1, &req, MPI_STATUS_IGNORE);
if (OMPI_SUCCESS != err) {
goto exit;
}
/* Loop receiving and calling reduction function (C or Fortran)
* The result of this reduction operations is then in
* tmpbuf2.
*/
for (i = 1; i < rsize; i++) {
err = MCA_PML_CALL(recv(tmpbuf, totalcounts, dtype, i,
MCA_COLL_BASE_TAG_REDUCE_SCATTER, comm,
MPI_STATUS_IGNORE));
if (MPI_SUCCESS != err) {
goto exit;
}
/* Perform the reduction */
ompi_op_reduce(op, tmpbuf, tmpbuf2, totalcounts, dtype);
}
} else {
/* If not root, send data to the root. */
err = MCA_PML_CALL(send(sbuf, totalcounts, dtype, root,
MCA_COLL_BASE_TAG_REDUCE_SCATTER,
MCA_PML_BASE_SEND_STANDARD, comm));
if (OMPI_SUCCESS != err) {
goto exit;
}
}
/* Now do a scatterv on the local communicator */
err = comm->c_local_comm->c_coll.coll_scatterv(tmpbuf2, rcounts, disps, dtype,
rbuf, rcounts[rank], dtype, 0,
comm->c_local_comm,
comm->c_local_comm->c_coll.coll_scatterv_module);
exit:
if (NULL != tmpbuf) {
free(tmpbuf);
}
if (NULL != tmpbuf2) {
free(tmpbuf2);
}
if (NULL != disps) {
free(disps);
}
return err;
}
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