Merge pull request #5644 from mkurnosov/coll-iallreduce-rabenseifner
coll/libnbc: add Rabenseifner's algorithm for MPI_Iallreduce
Этот коммит содержится в:
bosilca
GitHub
Коммит
593db292da
@ -71,6 +71,7 @@ BEGIN_C_DECLS
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extern bool libnbc_ibcast_skip_dt_decision;
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extern int libnbc_iallgather_algorithm;
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extern int libnbc_iallreduce_algorithm;
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extern int libnbc_ibcast_algorithm;
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extern int libnbc_ibcast_knomial_radix;
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extern int libnbc_iexscan_algorithm;
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@ -54,6 +54,15 @@ static mca_base_var_enum_value_t iallgather_algorithms[] = {
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{0, NULL}
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};
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int libnbc_iallreduce_algorithm = 0; /* iallreduce user forced algorithm */
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static mca_base_var_enum_value_t iallreduce_algorithms[] = {
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{0, "ignore"},
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{1, "ring"},
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{2, "binomial"},
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{3, "rabenseifner"},
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{0, NULL}
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};
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int libnbc_ibcast_algorithm = 0; /* ibcast user forced algorithm */
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int libnbc_ibcast_knomial_radix = 4;
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static mca_base_var_enum_value_t ibcast_algorithms[] = {
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@ -97,7 +106,6 @@ static int libnbc_init_query(bool, bool);
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static mca_coll_base_module_t *libnbc_comm_query(struct ompi_communicator_t *, int *);
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static int libnbc_module_enable(mca_coll_base_module_t *, struct ompi_communicator_t *);
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/*
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* Instantiate the public struct with all of our public information
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* and pointers to our public functions in it
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@ -213,6 +221,16 @@ libnbc_register(void)
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&libnbc_iallgather_algorithm);
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OBJ_RELEASE(new_enum);
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libnbc_iallreduce_algorithm = 0;
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(void) mca_base_var_enum_create("coll_libnbc_iallreduce_algorithms", iallreduce_algorithms, &new_enum);
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mca_base_component_var_register(&mca_coll_libnbc_component.super.collm_version,
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"iallreduce_algorithm",
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"Which iallreduce algorithm is used: 0 ignore, 1 ring, 2 binomial, 3 rabenseifner",
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MCA_BASE_VAR_TYPE_INT, new_enum, 0, MCA_BASE_VAR_FLAG_SETTABLE,
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OPAL_INFO_LVL_5, MCA_BASE_VAR_SCOPE_ALL,
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&libnbc_iallreduce_algorithm);
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OBJ_RELEASE(new_enum);
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libnbc_ibcast_algorithm = 0;
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(void) mca_base_var_enum_create("coll_libnbc_ibcast_algorithms", ibcast_algorithms, &new_enum);
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mca_base_component_var_register(&mca_coll_libnbc_component.super.collm_version,
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@ -264,8 +282,6 @@ libnbc_register(void)
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return OMPI_SUCCESS;
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}
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/*
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* Initial query function that is invoked during MPI_INIT, allowing
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* this component to disqualify itself if it doesn't support the
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@ -22,6 +22,7 @@
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#include "ompi/communicator/communicator.h"
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#include "ompi/datatype/ompi_datatype.h"
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#include "ompi/op/op.h"
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#include "opal/util/bit_ops.h"
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#include <assert.h>
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@ -33,6 +34,10 @@ static inline int allred_sched_ring(int rank, int p, int count, MPI_Datatype dat
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static inline int allred_sched_linear(int rank, int p, const void *sendbuf, void *recvbuf, int count,
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MPI_Datatype datatype, ptrdiff_t gap, MPI_Op op, int ext, int size,
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NBC_Schedule *schedule, void *tmpbuf);
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static inline int allred_sched_redscat_allgather(
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int rank, int comm_size, int count, MPI_Datatype datatype, ptrdiff_t gap,
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const void *sbuf, void *rbuf, MPI_Op op, char inplace,
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NBC_Schedule *schedule, void *tmpbuf, struct ompi_communicator_t *comm);
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#ifdef NBC_CACHE_SCHEDULE
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/* tree comparison function for schedule cache */
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@ -64,7 +69,7 @@ static int nbc_allreduce_init(const void* sendbuf, void* recvbuf, int count, MPI
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#ifdef NBC_CACHE_SCHEDULE
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NBC_Allreduce_args *args, *found, search;
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#endif
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enum { NBC_ARED_BINOMIAL, NBC_ARED_RING } alg;
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enum { NBC_ARED_BINOMIAL, NBC_ARED_RING, NBC_ARED_REDSCAT_ALLGATHER } alg;
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char inplace;
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void *tmpbuf = NULL;
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ompi_coll_libnbc_module_t *libnbc_module = (ompi_coll_libnbc_module_t*) module;
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@ -105,12 +110,25 @@ static int nbc_allreduce_init(const void* sendbuf, void* recvbuf, int count, MPI
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}
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/* algorithm selection */
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if(p < 4 || size*count < 65536 || !ompi_op_is_commute(op) || inplace) {
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alg = NBC_ARED_BINOMIAL;
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int nprocs_pof2 = opal_next_poweroftwo(p) >> 1;
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if (libnbc_iallreduce_algorithm == 0) {
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if(p < 4 || size*count < 65536 || !ompi_op_is_commute(op) || inplace) {
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alg = NBC_ARED_BINOMIAL;
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} else if (count >= nprocs_pof2 && ompi_op_is_commute(op)) {
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alg = NBC_ARED_REDSCAT_ALLGATHER;
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} else {
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alg = NBC_ARED_RING;
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}
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} else {
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alg = NBC_ARED_RING;
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if (libnbc_iallreduce_algorithm == 1)
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alg = NBC_ARED_RING;
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else if (libnbc_iallreduce_algorithm == 2)
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alg = NBC_ARED_BINOMIAL;
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else if (libnbc_iallreduce_algorithm == 3 && count >= nprocs_pof2 && ompi_op_is_commute(op)) {
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alg = NBC_ARED_REDSCAT_ALLGATHER;
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} else
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alg = NBC_ARED_RING;
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}
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#ifdef NBC_CACHE_SCHEDULE
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/* search schedule in communicator specific tree */
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search.sendbuf = sendbuf;
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@ -135,6 +153,9 @@ static int nbc_allreduce_init(const void* sendbuf, void* recvbuf, int count, MPI
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case NBC_ARED_BINOMIAL:
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res = allred_sched_diss(rank, p, count, datatype, gap, sendbuf, recvbuf, op, inplace, schedule, tmpbuf);
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break;
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case NBC_ARED_REDSCAT_ALLGATHER:
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res = allred_sched_redscat_allgather(rank, p, count, datatype, gap, sendbuf, recvbuf, op, inplace, schedule, tmpbuf, comm);
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break;
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case NBC_ARED_RING:
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res = allred_sched_ring(rank, p, count, datatype, sendbuf, recvbuf, op, size, ext, schedule, tmpbuf);
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break;
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@ -735,6 +756,271 @@ static inline int allred_sched_linear(int rank, int rsize, const void *sendbuf,
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return OMPI_SUCCESS;
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}
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/*
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* allred_sched_redscat_allgather:
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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.
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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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* Schedule length (rounds): O(\log(p))
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*/
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static inline int allred_sched_redscat_allgather(
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int rank, int comm_size, int count, MPI_Datatype datatype, ptrdiff_t gap,
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const void *sbuf, void *rbuf, MPI_Op op, char inplace,
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NBC_Schedule *schedule, void *tmpbuf, struct ompi_communicator_t *comm)
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{
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int res = OMPI_SUCCESS;
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int *rindex = NULL, *rcount = NULL, *sindex = NULL, *scount = NULL;
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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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int nprocs_pof2 = 1 << nsteps; /* flp2(comm_size) */
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if (!inplace) {
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res = NBC_Sched_copy((char *)sbuf, false, count, datatype,
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rbuf, false, count, datatype, schedule, true);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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}
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char *tmp_buf = (char *)tmpbuf - gap;
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ptrdiff_t lb, extent;
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ompi_datatype_get_extent(datatype, &lb, &extent);
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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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res = NBC_Sched_send(rbuf, false, count_lhalf, datatype, rank - 1,
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schedule, false);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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res = NBC_Sched_recv(tmp_buf + (ptrdiff_t)count_lhalf * extent,
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false, count_rhalf, datatype, rank - 1, schedule, true);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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res = NBC_Sched_op(tmp_buf + (ptrdiff_t)count_lhalf * extent,
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false, (char *)rbuf + (ptrdiff_t)count_lhalf * extent,
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false, count_rhalf, datatype, op, schedule, true);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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/* Send the right half to the left neighbor */
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res = NBC_Sched_send((char *)rbuf + (ptrdiff_t)count_lhalf * extent,
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false, count_rhalf, datatype, rank - 1, schedule, true);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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/* This process does not participate 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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res = NBC_Sched_send((char *)rbuf + (ptrdiff_t)count_lhalf * extent,
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false, count_rhalf, datatype, rank + 1, schedule, false);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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res = NBC_Sched_recv(tmp_buf, false, count_lhalf, datatype, rank + 1,
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schedule, true);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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res = NBC_Sched_op(tmp_buf, false, rbuf, false, count_lhalf,
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datatype, op, schedule, true);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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/* Recv the right half from the right neighbor */
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res = NBC_Sched_recv((char *)rbuf + (ptrdiff_t)count_lhalf * extent,
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false, count_rhalf, datatype, rank + 1, schedule, true);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { 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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res = 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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res = NBC_Sched_send((char *)rbuf + (ptrdiff_t)sindex[step] * extent,
|
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false, scount[step], datatype, dest, schedule, false);
|
||||
if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
|
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res = NBC_Sched_recv((char *)tmp_buf + (ptrdiff_t)rindex[step] * extent,
|
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false, rcount[step], datatype, dest, schedule, true);
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
|
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/* Local reduce: rbuf[] = tmp_buf[] <op> rbuf[] */
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res = NBC_Sched_op((char *)tmp_buf + (ptrdiff_t)rindex[step] * extent,
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false, (char *)rbuf + (ptrdiff_t)rindex[step] * extent,
|
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false, rcount[step], datatype, op, schedule, true);
|
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if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
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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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/*
|
||||
* Step 3. Allgather by the recursive doubling algorithm.
|
||||
* Each process has 1 / p' of the total reduction result:
|
||||
* rcount[nsteps - 1] elements in the rbuf[rindex[nsteps - 1], ...].
|
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* All exchanges are executed in reverse order relative
|
||||
* to recursive doubling (previous step).
|
||||
*/
|
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step = nsteps - 1;
|
||||
for (int mask = nprocs_pof2 >> 1; mask > 0; mask >>= 1) {
|
||||
int vdest = vrank ^ mask;
|
||||
/* Translate vdest virtual rank to real rank */
|
||||
int dest = (vdest < nprocs_rem) ? vdest * 2 : vdest + nprocs_rem;
|
||||
/*
|
||||
* Send rcount[step] elements from rbuf[rindex[step]...]
|
||||
* Recv scount[step] elements to rbuf[sindex[step]...]
|
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*/
|
||||
res = NBC_Sched_send((char *)rbuf + (ptrdiff_t)rindex[step] * extent,
|
||||
false, rcount[step], datatype, dest, schedule, false);
|
||||
if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
|
||||
res = NBC_Sched_recv((char *)rbuf + (ptrdiff_t)sindex[step] * extent,
|
||||
false, scount[step], datatype, dest, schedule, true);
|
||||
if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
|
||||
step--;
|
||||
}
|
||||
}
|
||||
/*
|
||||
* Step 4. Send total result to excluded odd ranks.
|
||||
*/
|
||||
if (rank < 2 * nprocs_rem) {
|
||||
if (rank % 2 != 0) {
|
||||
/* Odd process -- recv result from rank - 1 */
|
||||
res = NBC_Sched_recv(rbuf, false, count, datatype, rank - 1, schedule, false);
|
||||
if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
|
||||
} else {
|
||||
/* Even process -- send result to rank + 1 */
|
||||
res = NBC_Sched_send(rbuf, false, count, datatype, rank + 1, schedule, false);
|
||||
if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) { goto cleanup_and_return; }
|
||||
}
|
||||
}
|
||||
cleanup_and_return:
|
||||
if (NULL != rindex)
|
||||
free(rindex);
|
||||
if (NULL != sindex)
|
||||
free(sindex);
|
||||
if (NULL != rcount)
|
||||
free(rcount);
|
||||
if (NULL != scount)
|
||||
free(scount);
|
||||
return res;
|
||||
}
|
||||
|
||||
int ompi_coll_libnbc_allreduce_init(const void* sendbuf, void* recvbuf, int count, MPI_Datatype datatype, MPI_Op op,
|
||||
struct ompi_communicator_t *comm, MPI_Info info, ompi_request_t ** request,
|
||||
struct mca_coll_base_module_2_3_0_t *module) {
|
||||
|
||||
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