44acc92104
Add check for bounds of sindex[] and rindex[]. Signed-off-by: Mikhail Kurnosov <mkurnosov@gmail.com>
356 строки
16 KiB
C
356 строки
16 KiB
C
/*
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* $COPYRIGHT$
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*
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* Additional copyrights may follow
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*
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* $HEADER$
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*/
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#include "ompi_config.h"
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#include "coll_spacc.h"
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#include "mpi.h"
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#include "ompi/constants.h"
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#include "opal/util/bit_ops.h"
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#include "ompi/datatype/ompi_datatype.h"
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#include "ompi/communicator/communicator.h"
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#include "ompi/mca/coll/coll.h"
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#include "ompi/mca/coll/base/coll_base_functions.h"
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#include "ompi/mca/coll/base/coll_tags.h"
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#include "ompi/mca/coll/base/coll_base_util.h"
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#include "ompi/mca/pml/pml.h"
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#include "ompi/op/op.h"
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/*
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* mca_coll_spacc_allreduce_intra_redscat_gather
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*
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* Function: Allreduce using Rabenseifner's algorithm.
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* Accepts: Same arguments as MPI_Allreduce
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* Returns: MPI_SUCCESS or error code
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*
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* Description: an implementation of Rabenseifner's allreduce algorithm [1, 2].
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* [1] Rajeev Thakur, Rolf Rabenseifner and William Gropp.
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* Optimization of Collective Communication Operations in MPICH //
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* The Int. Journal of High Performance Computing Applications. Vol 19,
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* Issue 1, pp. 49--66.
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* [2] http://www.hlrs.de/mpi/myreduce.html.
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*
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* This algorithm is a combination of a reduce-scatter implemented with
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* recursive vector halving and recursive distance doubling, followed either
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* by an allgather implemented with recursive doubling [1].
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*
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* Step 1. If the number of processes is not a power of two, reduce it to
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* the nearest lower power of two (p' = 2^{\floor{\log_2 p}})
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* by removing r = p - p' extra processes as follows. In the first 2r processes
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* (ranks 0 to 2r - 1), all the even ranks send the second half of the input
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* vector to their right neighbor (rank + 1), and all the odd ranks send
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* the first half of the input vector to their left neighbor (rank - 1).
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* The even ranks compute the reduction on the first half of the vector and
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* the odd ranks compute the reduction on the second half. The odd ranks then
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* send the result to their left neighbors (the even ranks). As a result,
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* the even ranks among the first 2r processes now contain the reduction with
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* the input vector on their right neighbors (the odd ranks). These odd ranks
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* do not participate in the rest of the algorithm, which leaves behind
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* a power-of-two number of processes. The first r even-ranked processes and
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* the last p - 2r processes are now renumbered from 0 to p' - 1.
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*
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* Step 2. The remaining processes now perform a reduce-scatter by using
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* recursive vector halving and recursive distance doubling. The even-ranked
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* processes send the second half of their buffer to rank + 1 and the odd-ranked
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* processes send the first half of their buffer to rank - 1. All processes
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* then compute the reduction between the local buffer and the received buffer.
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* In the next log_2(p') - 1 steps, the buffers are recursively halved, and the
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* distance is doubled. At the end, each of the p' processes has 1 / p' of the
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* total reduction result.
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*
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* Step 3. An allgather is performed by using recursive vector doubling and
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* distance halving. All exchanges are executed in reverse order relative
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* to recursive doubling on previous step. If the number of processes is not
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* a power of two, the total result vector must be sent to the r processes
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* that were removed in the first step.
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*
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* Limitations:
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* count >= 2^{\floor{\log_2 p}}
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* commutative operations only
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* intra-communicators only
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*
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* Memory requirements (per process):
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* count * typesize + 4 * log_2(p) * sizeof(int) = O(count)
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*/
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int mca_coll_spacc_allreduce_intra_redscat_allgather(
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const void *sbuf, void *rbuf, int count, struct ompi_datatype_t *dtype,
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struct ompi_op_t *op, struct ompi_communicator_t *comm,
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mca_coll_base_module_t *module)
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{
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int *rindex = NULL, *rcount = NULL, *sindex = NULL, *scount = NULL;
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int comm_size = ompi_comm_size(comm);
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int rank = ompi_comm_rank(comm);
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opal_output_verbose(30, mca_coll_spacc_stream,
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"coll:spacc:allreduce_intra_redscat_allgather: rank %d/%d",
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rank, comm_size);
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/* Find nearest power-of-two less than or equal to comm_size */
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int nsteps = opal_hibit(comm_size, comm->c_cube_dim + 1); /* ilog2(comm_size) */
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assert(nsteps >= 0);
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int nprocs_pof2 = 1 << nsteps; /* flp2(comm_size) */
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if (count < nprocs_pof2 || !ompi_op_is_commute(op)) {
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opal_output_verbose(20, mca_coll_spacc_stream,
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"coll:spacc:allreduce_intra_redscat_allgather: rank %d/%d count %d switching to base allreduce",
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rank, comm_size, count);
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return ompi_coll_base_allreduce_intra_basic_linear(sbuf, rbuf, count, dtype,
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op, comm, module);
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}
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int err = MPI_SUCCESS;
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ptrdiff_t lb, extent, dsize, gap = 0;
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ompi_datatype_get_extent(dtype, &lb, &extent);
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dsize = opal_datatype_span(&dtype->super, count, &gap);
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/* Temporary buffer for receiving messages */
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char *tmp_buf = NULL;
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char *tmp_buf_raw = (char *)malloc(dsize);
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if (NULL == tmp_buf_raw)
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return OMPI_ERR_OUT_OF_RESOURCE;
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tmp_buf = tmp_buf_raw - gap;
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if (sbuf != MPI_IN_PLACE) {
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/* Copy sbuf to rbuf */
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err = ompi_datatype_copy_content_same_ddt(dtype, count, (char *)rbuf,
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(char *)sbuf);
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}
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/*
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* Step 1. Reduce the number of processes to the nearest lower power of two
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* p' = 2^{\floor{\log_2 p}} by removing r = p - p' processes.
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* 1. In the first 2r processes (ranks 0 to 2r - 1), all the even ranks send
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* the second half of the input vector to their right neighbor (rank + 1)
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* and all the odd ranks send the first half of the input vector to their
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* left neighbor (rank - 1).
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* 2. All 2r processes compute the reduction on their half.
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* 3. The odd ranks then send the result to their left neighbors
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* (the even ranks).
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*
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* The even ranks (0 to 2r - 1) now contain the reduction with the input
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* vector on their right neighbors (the odd ranks). The first r even
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* processes and the p - 2r last processes are renumbered from
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* 0 to 2^{\floor{\log_2 p}} - 1.
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*/
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int vrank, step, wsize;
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int nprocs_rem = comm_size - nprocs_pof2;
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if (rank < 2 * nprocs_rem) {
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int count_lhalf = count / 2;
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int count_rhalf = count - count_lhalf;
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if (rank % 2 != 0) {
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/*
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* Odd process -- exchange with rank - 1
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* Send the left half of the input vector to the left neighbor,
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* Recv the right half of the input vector from the left neighbor
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*/
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err = ompi_coll_base_sendrecv(rbuf, count_lhalf, dtype, rank - 1,
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MCA_COLL_BASE_TAG_ALLREDUCE,
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(char *)tmp_buf + (ptrdiff_t)count_lhalf * extent,
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count_rhalf, dtype, rank - 1,
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MCA_COLL_BASE_TAG_ALLREDUCE, comm,
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MPI_STATUS_IGNORE, rank);
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if (MPI_SUCCESS != err) { goto cleanup_and_return; }
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/* Reduce on the right half of the buffers (result in rbuf) */
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ompi_op_reduce(op, (char *)tmp_buf + (ptrdiff_t)count_lhalf * extent,
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(char *)rbuf + count_lhalf * extent, count_rhalf, dtype);
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/* Send the right half to the left neighbor */
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err = MCA_PML_CALL(send((char *)rbuf + (ptrdiff_t)count_lhalf * extent,
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count_rhalf, dtype, rank - 1,
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MCA_COLL_BASE_TAG_ALLREDUCE,
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MCA_PML_BASE_SEND_STANDARD, comm));
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if (MPI_SUCCESS != err) { goto cleanup_and_return; }
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/* This process does not pariticipate in recursive doubling phase */
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vrank = -1;
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} else {
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/*
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* Even process -- exchange with rank + 1
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* Send the right half of the input vector to the right neighbor,
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* Recv the left half of the input vector from the right neighbor
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*/
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err = ompi_coll_base_sendrecv((char *)rbuf + (ptrdiff_t)count_lhalf * extent,
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count_rhalf, dtype, rank + 1,
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MCA_COLL_BASE_TAG_ALLREDUCE,
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tmp_buf, count_lhalf, dtype, rank + 1,
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MCA_COLL_BASE_TAG_ALLREDUCE, comm,
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MPI_STATUS_IGNORE, rank);
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if (MPI_SUCCESS != err) { goto cleanup_and_return; }
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/* Reduce on the right half of the buffers (result in rbuf) */
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ompi_op_reduce(op, tmp_buf, rbuf, count_lhalf, dtype);
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/* Recv the right half from the right neighbor */
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err = MCA_PML_CALL(recv((char *)rbuf + (ptrdiff_t)count_lhalf * extent,
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count_rhalf, dtype, rank + 1,
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MCA_COLL_BASE_TAG_ALLREDUCE, comm,
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MPI_STATUS_IGNORE));
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if (MPI_SUCCESS != err) { goto cleanup_and_return; }
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vrank = rank / 2;
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}
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} else { /* rank >= 2 * nprocs_rem */
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vrank = rank - nprocs_rem;
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}
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/*
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* Step 2. Reduce-scatter implemented with recursive vector halving and
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* recursive distance doubling. We have p' = 2^{\floor{\log_2 p}}
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* power-of-two number of processes with new ranks (vrank) and result in rbuf.
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*
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* The even-ranked processes send the right half of their buffer to rank + 1
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* and the odd-ranked processes send the left half of their buffer to
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* rank - 1. All processes then compute the reduction between the local
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* buffer and the received buffer. In the next \log_2(p') - 1 steps, the
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* buffers are recursively halved, and the distance is doubled. At the end,
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* each of the p' processes has 1 / p' of the total reduction result.
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*/
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rindex = malloc(sizeof(*rindex) * nsteps);
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sindex = malloc(sizeof(*sindex) * nsteps);
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rcount = malloc(sizeof(*rcount) * nsteps);
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scount = malloc(sizeof(*scount) * nsteps);
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if (NULL == rindex || NULL == sindex || NULL == rcount || NULL == scount) {
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err = OMPI_ERR_OUT_OF_RESOURCE;
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goto cleanup_and_return;
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}
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if (vrank != -1) {
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step = 0;
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wsize = count;
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sindex[0] = rindex[0] = 0;
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for (int mask = 1; mask < nprocs_pof2; mask <<= 1) {
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/*
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* On each iteration: rindex[step] = sindex[step] -- begining of the
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* current window. Length of the current window is storded in wsize.
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*/
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int vdest = vrank ^ mask;
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/* Translate vdest virtual rank to real rank */
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int dest = (vdest < nprocs_rem) ? vdest * 2 : vdest + nprocs_rem;
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if (rank < dest) {
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/*
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* Recv into the left half of the current window, send the right
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* half of the window to the peer (perform reduce on the left
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* half of the current window)
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*/
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rcount[step] = wsize / 2;
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scount[step] = wsize - rcount[step];
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sindex[step] = rindex[step] + rcount[step];
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} else {
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/*
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* Recv into the right half of the current window, send the left
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* half of the window to the peer (perform reduce on the right
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* half of the current window)
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*/
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scount[step] = wsize / 2;
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rcount[step] = wsize - scount[step];
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rindex[step] = sindex[step] + scount[step];
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}
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/* Send part of data from the rbuf, recv into the tmp_buf */
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err = ompi_coll_base_sendrecv((char *)rbuf + (ptrdiff_t)sindex[step] * extent,
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scount[step], dtype, dest,
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MCA_COLL_BASE_TAG_ALLREDUCE,
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(char *)tmp_buf + (ptrdiff_t)rindex[step] * extent,
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rcount[step], dtype, dest,
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MCA_COLL_BASE_TAG_ALLREDUCE, comm,
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MPI_STATUS_IGNORE, rank);
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if (MPI_SUCCESS != err) { goto cleanup_and_return; }
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/* Local reduce: rbuf[] = tmp_buf[] <op> rbuf[] */
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ompi_op_reduce(op, (char *)tmp_buf + (ptrdiff_t)rindex[step] * extent,
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(char *)rbuf + (ptrdiff_t)rindex[step] * extent,
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rcount[step], dtype);
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/* Move the current window to the received message */
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if (step + 1 < nsteps) {
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rindex[step + 1] = rindex[step];
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sindex[step + 1] = rindex[step];
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wsize = rcount[step];
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step++;
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}
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}
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/*
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* Assertion: each process has 1 / p' of the total reduction result:
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* rcount[nsteps - 1] elements in the rbuf[rindex[nsteps - 1], ...].
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*/
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/*
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* Step 3. Allgather by the recursive doubling algorithm.
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* Each process has 1 / p' of the total reduction result:
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* rcount[nsteps - 1] elements in the rbuf[rindex[nsteps - 1], ...].
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* All exchanges are executed in reverse order relative
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* to recursive doubling (previous step).
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*/
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step--;
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for (int mask = nprocs_pof2 >> 1; mask > 0; mask >>= 1) {
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int vdest = vrank ^ mask;
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/* Translate vdest virtual rank to real rank */
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int dest = (vdest < nprocs_rem) ? vdest * 2 : vdest + nprocs_rem;
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/*
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* Send rcount[step] elements from rbuf[rindex[step]...]
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* Recv scount[step] elements to rbuf[sindex[step]...]
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*/
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err = ompi_coll_base_sendrecv((char *)rbuf + (ptrdiff_t)rindex[step] * extent,
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rcount[step], dtype, dest,
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MCA_COLL_BASE_TAG_ALLREDUCE,
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(char *)rbuf + (ptrdiff_t)sindex[step] * extent,
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scount[step], dtype, dest,
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MCA_COLL_BASE_TAG_ALLREDUCE, comm,
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MPI_STATUS_IGNORE, rank);
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if (MPI_SUCCESS != err) { goto cleanup_and_return; }
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step--;
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}
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}
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/*
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* Step 4. Send total result to excluded odd ranks.
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*/
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if (rank < 2 * nprocs_rem) {
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if (rank % 2 != 0) {
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/* Odd process -- recv result from rank - 1 */
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err = MCA_PML_CALL(recv(rbuf, count, dtype, rank - 1,
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MCA_COLL_BASE_TAG_ALLREDUCE, comm,
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MPI_STATUS_IGNORE));
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if (OMPI_SUCCESS != err) { goto cleanup_and_return; }
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} else {
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/* Even process -- send result to rank + 1 */
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err = MCA_PML_CALL(send(rbuf, count, dtype, rank + 1,
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MCA_COLL_BASE_TAG_ALLREDUCE,
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MCA_PML_BASE_SEND_STANDARD, comm));
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if (MPI_SUCCESS != err) { goto cleanup_and_return; }
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}
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}
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cleanup_and_return:
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if (NULL != tmp_buf_raw)
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free(tmp_buf_raw);
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if (NULL != rindex)
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free(rindex);
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if (NULL != sindex)
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free(sindex);
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if (NULL != rcount)
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free(rcount);
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if (NULL != scount)
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free(scount);
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return err;
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}
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