coll/base/scatter: replaces right skewed binomial tree (in order) with left skewed binomial tree
Current implementation of `coll/base/MPI_Scatter` is based on in-order binomial tree. This tree is right skewed and it provides good performance for a MPI_Gather operation. But for a MPI_Scatter operation left skewed binomial tree is effective. Signed-off-by: Mikhail Kurnosov <mkurnosov@gmail.com>
Этот коммит содержится в:
Mikhail Kurnosov
Nathan Hjelm
родитель
77057ade33
Коммит
22fa5a8a67
@ -34,47 +34,66 @@
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#include "coll_base_topo.h"
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#include "coll_base_util.h"
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/*
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* ompi_coll_base_scatter_intra_binomial
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*
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* Function: Binomial tree algorithm for scatter
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* Accepts: Same as MPI_Scatter
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* Returns: MPI_SUCCESS or error code
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*
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* Time complexity: \alpha\log(p) + \beta*m((p-1)/p),
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* where m = scount * comm_size, p = comm_size
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*
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* Memory requirements (per process):
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* root process (root > 0): scount * comm_size * sdtype_size
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* non-root, non-leaf process: rcount * comm_size * rdtype_size
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*
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* Examples:
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* comm_size=8 comm_size=10 comm_size=12
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* 0 0 0
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* / | \ / / | \ / / \ \
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* 4 2 1 8 4 2 1 8 4 2 1
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* / | | / / | | / | / | |
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* 6 5 3 9 6 5 3 10 9 6 5 3
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* | | | |
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* 7 7 11 7
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*/
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int
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ompi_coll_base_scatter_intra_binomial( const void *sbuf, int scount,
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struct ompi_datatype_t *sdtype,
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void *rbuf, int rcount,
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struct ompi_datatype_t *rdtype,
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int root,
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struct ompi_communicator_t *comm,
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mca_coll_base_module_t *module)
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ompi_coll_base_scatter_intra_binomial(
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const void *sbuf, int scount, struct ompi_datatype_t *sdtype,
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void *rbuf, int rcount, struct ompi_datatype_t *rdtype,
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int root, struct ompi_communicator_t *comm,
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mca_coll_base_module_t *module)
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{
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int line = -1, i, rank, vrank, size, total_send = 0, err;
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int line = -1, rank, vrank, size, err;
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char *ptmp, *tempbuf = NULL;
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ompi_coll_tree_t* bmtree;
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MPI_Status status;
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mca_coll_base_module_t *base_module = (mca_coll_base_module_t*) module;
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mca_coll_base_module_t *base_module = (mca_coll_base_module_t*)module;
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mca_coll_base_comm_t *data = base_module->base_data;
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ptrdiff_t sextent, rextent, ssize, rsize, sgap = 0, rgap = 0;
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size = ompi_comm_size(comm);
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rank = ompi_comm_rank(comm);
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OPAL_OUTPUT((ompi_coll_base_framework.framework_output,
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"ompi_coll_base_scatter_intra_binomial rank %d", rank));
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"coll:base:scatter_intra_binomial rank %d/%d", rank, size));
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/* create the binomial tree */
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COLL_BASE_UPDATE_IN_ORDER_BMTREE( comm, base_module, root );
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bmtree = data->cached_in_order_bmtree;
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ompi_datatype_type_extent(rdtype, &rextent);
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rsize = opal_datatype_span(&rdtype->super, (int64_t)rcount * size, &rgap);
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/* Create the binomial tree */
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COLL_BASE_UPDATE_IN_ORDER_BMTREE(comm, base_module, root);
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if (NULL == data->cached_in_order_bmtree) {
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err = OMPI_ERR_OUT_OF_RESOURCE; line = __LINE__; goto err_hndl;
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}
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ompi_coll_tree_t *bmtree = data->cached_in_order_bmtree;
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vrank = (rank - root + size) % size;
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ptmp = (char *) rbuf; /* by default suppose leaf nodes, just use rbuf */
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ptmp = (char *)rbuf; /* by default suppose leaf nodes, just use rbuf */
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if (rank == root) {
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ompi_datatype_type_extent(sdtype, &sextent);
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ssize = opal_datatype_span(&sdtype->super, (int64_t)scount * size, &sgap);
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if (0 == root) {
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/* root on 0, just use the send buffer */
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ptmp = (char *) sbuf;
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ptmp = (char *)sbuf;
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if (rbuf != MPI_IN_PLACE) {
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/* local copy to rbuf */
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err = ompi_datatype_sndrcv(sbuf, scount, sdtype,
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@ -83,7 +102,7 @@ ompi_coll_base_scatter_intra_binomial( const void *sbuf, int scount,
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}
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} else {
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/* root is not on 0, allocate temp buffer for send */
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tempbuf = (char *) malloc(ssize);
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tempbuf = (char *)malloc(ssize);
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if (NULL == tempbuf) {
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err = OMPI_ERR_OUT_OF_RESOURCE; line = __LINE__; goto err_hndl;
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}
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@ -94,7 +113,6 @@ ompi_coll_base_scatter_intra_binomial( const void *sbuf, int scount,
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ptmp, (char *) sbuf + sextent * (ptrdiff_t)root * (ptrdiff_t)scount);
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if (MPI_SUCCESS != err) { line = __LINE__; goto err_hndl; }
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err = ompi_datatype_copy_content_same_ddt(sdtype, (ptrdiff_t)scount * (ptrdiff_t)root,
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ptmp + sextent * (ptrdiff_t)scount * (ptrdiff_t)(size - root), (char *)sbuf);
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if (MPI_SUCCESS != err) { line = __LINE__; goto err_hndl; }
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@ -106,53 +124,54 @@ ompi_coll_base_scatter_intra_binomial( const void *sbuf, int scount,
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if (MPI_SUCCESS != err) { line = __LINE__; goto err_hndl; }
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}
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}
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total_send = scount;
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} else if (!(vrank % 2)) {
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/* non-root, non-leaf nodes, allocte temp buffer for recv
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/* non-root, non-leaf nodes, allocate temp buffer for recv
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* the most we need is rcount*size/2 */
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tempbuf = (char *) malloc(rsize);
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ompi_datatype_type_extent(rdtype, &rextent);
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rsize = opal_datatype_span(&rdtype->super, (int64_t)rcount * size, &rgap);
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tempbuf = (char *)malloc(rsize / 2);
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if (NULL == tempbuf) {
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err= OMPI_ERR_OUT_OF_RESOURCE; line = __LINE__; goto err_hndl;
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err = OMPI_ERR_OUT_OF_RESOURCE; line = __LINE__; goto err_hndl;
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}
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ptmp = tempbuf - rgap;
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sdtype = rdtype;
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scount = rcount;
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sextent = rextent;
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total_send = scount;
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}
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int curr_count = (rank == root) ? scount * size : 0;
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if (!(vrank % 2)) {
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if (rank != root) {
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/* recv from parent on non-root */
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err = MCA_PML_CALL(recv(ptmp, (ptrdiff_t)rcount * (ptrdiff_t)size, rdtype, bmtree->tree_prev,
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MCA_COLL_BASE_TAG_SCATTER, comm, &status));
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if (MPI_SUCCESS != err) { line = __LINE__; goto err_hndl; }
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/* Get received count */
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size_t rdtype_size;
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ompi_datatype_type_size(rdtype, &rdtype_size);
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curr_count = (int)(status._ucount / rdtype_size);
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/* local copy to rbuf */
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err = ompi_datatype_sndrcv(ptmp, scount, sdtype,
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rbuf, rcount, rdtype);
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if (MPI_SUCCESS != err) { line = __LINE__; goto err_hndl; }
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}
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/* send to children on all non-leaf */
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for (i = 0; i < bmtree->tree_nextsize; i++) {
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size_t mycount = 0;
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int vkid;
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for (int i = bmtree->tree_nextsize - 1; i >= 0; i--) {
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/* figure out how much data I have to send to this child */
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vkid = (bmtree->tree_next[i] - root + size) % size;
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mycount = vkid - vrank;
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if( (int)mycount > (size - vkid) )
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mycount = size - vkid;
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mycount *= scount;
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err = MCA_PML_CALL(send(ptmp + (ptrdiff_t)total_send * sextent, mycount, sdtype,
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bmtree->tree_next[i],
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int vchild = (bmtree->tree_next[i] - root + size) % size;
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int send_count = vchild - vrank;
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if (send_count > size - vchild)
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send_count = size - vchild;
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send_count *= scount;
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err = MCA_PML_CALL(send(ptmp + (ptrdiff_t)(curr_count - send_count) * sextent,
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send_count, sdtype, bmtree->tree_next[i],
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MCA_COLL_BASE_TAG_SCATTER,
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MCA_PML_BASE_SEND_STANDARD, comm));
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if (MPI_SUCCESS != err) { line = __LINE__; goto err_hndl; }
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total_send += mycount;
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curr_count -= send_count;
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}
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if (NULL != tempbuf)
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free(tempbuf);
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} else {
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