openmpi/ompi/mca/coll/tuned/coll_tuned_reduce.c

/*
 * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
 *                         University Research and Technology
 *                         Corporation.  All rights reserved.
 * Copyright (c) 2004-2009 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.
 * $COPYRIGHT$
 *
 * Additional copyrights may follow
 *
 * $HEADER$
 */

#include "ompi_config.h"

#include "mpi.h"
#include "ompi/constants.h"
#include "ompi/datatype/ompi_datatype.h"
#include "ompi/communicator/communicator.h"
#include "ompi/mca/coll/coll.h"
#include "ompi/mca/coll/base/coll_tags.h"
#include "ompi/mca/pml/pml.h"
#include "ompi/op/op.h"
#include "coll_tuned.h"
#include "coll_tuned_topo.h"

/**
 * This is a generic implementation of the reduce protocol. It used the tree
 * provided as an argument and execute all operations using a segment of
 * count times a datatype.
 * For the last communication it will update the count in order to limit
 * the number of datatype to the original count (original_count)
 *
 * Note that for non-commutative operations we cannot save memory copy
 * for the first block: thus we must copy sendbuf to accumbuf on intermediate 
 * to keep the optimized loop happy.
 */
int ompi_coll_tuned_reduce_generic( void* sendbuf, void* recvbuf, int original_count,
                                    ompi_datatype_t* datatype, ompi_op_t* op,
                                    int root, ompi_communicator_t* comm,
                                    mca_coll_base_module_t *module,
                                    ompi_coll_tree_t* tree, int count_by_segment,
                                    int max_outstanding_reqs )
{
    char *inbuf[2] = {NULL, NULL}, *inbuf_free[2] = {NULL, NULL};
    char *accumbuf = NULL, *accumbuf_free = NULL;
    char *local_op_buffer = NULL, *sendtmpbuf = NULL;
    ptrdiff_t extent, lower_bound, segment_increment;
    size_t typelng;
    ompi_request_t* reqs[2] = {MPI_REQUEST_NULL, MPI_REQUEST_NULL};
    int num_segments, line, ret, segindex, i, rank;
    int recvcount, prevcount, inbi;

    /**
     * Determine number of segments and number of elements
     * sent per operation
     */
    ompi_datatype_get_extent( datatype, &lower_bound, &extent );
    ompi_datatype_type_size( datatype, &typelng );
    num_segments = (original_count + count_by_segment - 1) / count_by_segment;
    segment_increment = count_by_segment * extent;

    sendtmpbuf = (char*) sendbuf; 
    if( sendbuf == MPI_IN_PLACE ) { 
        sendtmpbuf = (char *)recvbuf; 
    }

    OPAL_OUTPUT((ompi_coll_tuned_stream, "coll:tuned:reduce_generic count %d, msg size %ld, segsize %ld, max_requests %d", original_count, (unsigned long)(num_segments * segment_increment), (unsigned long)segment_increment, max_outstanding_reqs));

    rank = ompi_comm_rank(comm);

    /* non-leaf nodes - wait for children to send me data & forward up 
       (if needed) */
    if( tree->tree_nextsize > 0 ) {
        ptrdiff_t true_lower_bound, true_extent, real_segment_size;
        ompi_datatype_get_true_extent( datatype, &true_lower_bound, 
                                       &true_extent );

        /* handle non existant recv buffer (i.e. its NULL) and 
           protect the recv buffer on non-root nodes */
        accumbuf = (char*)recvbuf;
        if( (NULL == accumbuf) || (root != rank) ) {
            /* Allocate temporary accumulator buffer. */
            accumbuf_free = (char*)malloc(true_extent + 
                                          (original_count - 1) * extent);
            if (accumbuf_free == NULL) { 
                line = __LINE__; ret = -1; goto error_hndl; 
            }
            accumbuf = accumbuf_free - lower_bound;
        } 

        /* If this is a non-commutative operation we must copy
           sendbuf to the accumbuf, in order to simplfy the loops */
        if (!ompi_op_is_commute(op)) {
            ompi_datatype_copy_content_same_ddt(datatype, original_count, 
                                                (char*)accumbuf,
                                                (char*)sendtmpbuf);
        }
        /* Allocate two buffers for incoming segments */
        real_segment_size = true_extent + (count_by_segment - 1) * extent;
        inbuf_free[0] = (char*) malloc(real_segment_size);
        if( inbuf_free[0] == NULL ) { 
            line = __LINE__; ret = -1; goto error_hndl; 
        }
        inbuf[0] = inbuf_free[0] - lower_bound;
        /* if there is chance to overlap communication -
           allocate second buffer */
        if( (num_segments > 1) || (tree->tree_nextsize > 1) ) {
            inbuf_free[1] = (char*) malloc(real_segment_size);
            if( inbuf_free[1] == NULL ) { 
                line = __LINE__; ret = -1; goto error_hndl;
            }
            inbuf[1] = inbuf_free[1] - lower_bound;
        } 

        /* reset input buffer index and receive count */
        inbi = 0;
        recvcount = 0;
        /* for each segment */
        for( segindex = 0; segindex <= num_segments; segindex++ ) {
            prevcount = recvcount;
            /* recvcount - number of elements in current segment */
            recvcount = count_by_segment;
            if( segindex == (num_segments-1) )
                recvcount = original_count - count_by_segment * segindex;

            /* for each child */
            for( i = 0; i < tree->tree_nextsize; i++ ) {
                /**
                 * We try to overlap communication:
                 * either with next segment or with the next child
                 */
                /* post irecv for current segindex on current child */
                if( segindex < num_segments ) {
                    void* local_recvbuf = inbuf[inbi];
                    if( 0 == i ) {
                        /* for the first step (1st child per segment) and 
                         * commutative operations we might be able to irecv 
                         * directly into the accumulate buffer so that we can 
                         * reduce(op) this with our sendbuf in one step as 
                         * ompi_op_reduce only has two buffer pointers, 
                         * this avoids an extra memory copy.
                         *
                         * BUT if the operation is non-commutative or 
                         * we are root and are USING MPI_IN_PLACE this is wrong!
                         */
                        if( (ompi_op_is_commute(op)) &&
                            !((MPI_IN_PLACE == sendbuf) && (rank == tree->tree_root)) ) {
                            local_recvbuf = accumbuf + segindex * segment_increment;
                        }
                    }

                    ret = MCA_PML_CALL(irecv(local_recvbuf, recvcount, datatype,
                                             tree->tree_next[i], 
                                             MCA_COLL_BASE_TAG_REDUCE, comm, 
                                             &reqs[inbi]));
                    if (ret != MPI_SUCCESS) { line = __LINE__; goto error_hndl;}
                }
                /* wait for previous req to complete, if any.
                   if there are no requests reqs[inbi ^1] will be 
                   MPI_REQUEST_NULL. */
                /* wait on data from last child for previous segment */
                ret = ompi_request_wait_all( 1, &reqs[inbi ^ 1], 
                                             MPI_STATUSES_IGNORE );
                if (ret != MPI_SUCCESS) { line = __LINE__; goto error_hndl;  }
                local_op_buffer = inbuf[inbi ^ 1];
                if( i > 0 ) {
                    /* our first operation is to combine our own [sendbuf] data 
                     * with the data we recvd from down stream (but only 
                     * the operation is commutative and if we are not root and 
                     * not using MPI_IN_PLACE)
                     */
                    if( 1 == i ) {
                        if( (ompi_op_is_commute(op)) && 
                            !((MPI_IN_PLACE == sendbuf) && (rank == tree->tree_root)) ) {
                            local_op_buffer = sendtmpbuf + segindex * segment_increment;
                        }
                    }
                    /* apply operation */
                    ompi_op_reduce(op, local_op_buffer, 
                                   accumbuf + segindex * segment_increment, 
                                   recvcount, datatype );
                } else if ( segindex > 0 ) {
                    void* accumulator = accumbuf + (segindex-1) * segment_increment;
                    if( tree->tree_nextsize <= 1 ) {
                        if( (ompi_op_is_commute(op)) &&
                            !((MPI_IN_PLACE == sendbuf) && (rank == tree->tree_root)) ) {
                            local_op_buffer = sendtmpbuf + (segindex-1) * segment_increment;
                        }
                    }
                    ompi_op_reduce(op, local_op_buffer, accumulator, prevcount, 
                                   datatype );

                    /* all reduced on available data this step (i) complete, 
                     * pass to the next process unless you are the root.
                     */
                    if (rank != tree->tree_root) {
                        /* send combined/accumulated data to parent */
                        ret = MCA_PML_CALL( send( accumulator, prevcount, 
                                                  datatype, tree->tree_prev, 
                                                  MCA_COLL_BASE_TAG_REDUCE,
                                                  MCA_PML_BASE_SEND_STANDARD, 
                                                  comm) );
                        if (ret != MPI_SUCCESS) { 
                            line = __LINE__; goto error_hndl;  
                        }
                    }

                    /* we stop when segindex = number of segments 
                       (i.e. we do num_segment+1 steps for pipelining */
                    if (segindex == num_segments) break;
                }

                /* update input buffer index */
                inbi = inbi ^ 1;
            } /* end of for each child */
        } /* end of for each segment */

        /* clean up */
        if( inbuf_free[0] != NULL) free(inbuf_free[0]);
        if( inbuf_free[1] != NULL) free(inbuf_free[1]);
        if( accumbuf_free != NULL ) free(accumbuf_free);
    }

    /* leaf nodes 
       Depending on the value of max_outstanding_reqs and 
       the number of segments we have two options:
       - send all segments using blocking send to the parent, or
       - avoid overflooding the parent nodes by limiting the number of 
       outstanding requests to max_oustanding_reqs.
       TODO/POSSIBLE IMPROVEMENT: If there is a way to determine the eager size 
       for the current communication, synchronization should be used only 
       when the message/segment size is smaller than the eager size.
    */
    else {

        /* If the number of segments is less than a maximum number of oustanding
           requests or there is no limit on the maximum number of outstanding 
           requests, we send data to the parent using blocking send */
        if ((0 == max_outstanding_reqs) || 
            (num_segments <= max_outstanding_reqs)) {
            
            segindex = 0;
            while ( original_count > 0) {
                if (original_count < count_by_segment) {
                    count_by_segment = original_count;
                }
                ret = MCA_PML_CALL( send((char*)sendbuf + 
                                         segindex * segment_increment,
                                         count_by_segment, datatype,
                                         tree->tree_prev, 
                                         MCA_COLL_BASE_TAG_REDUCE,
                                         MCA_PML_BASE_SEND_STANDARD,
                                         comm) );
                if (ret != MPI_SUCCESS) { line = __LINE__; goto error_hndl; }
                segindex++;
                original_count -= count_by_segment;
            }
        }

        /* Otherwise, introduce flow control:
           - post max_outstanding_reqs non-blocking synchronous send,
           - for remaining segments
           - wait for a ssend to complete, and post the next one.
           - wait for all outstanding sends to complete.
        */
        else {

            int creq = 0;
            ompi_request_t **sreq = NULL;

            sreq = (ompi_request_t**) calloc( max_outstanding_reqs,
                                              sizeof(ompi_request_t*) );
            if (NULL == sreq) { line = __LINE__; ret = -1; goto error_hndl; }

            /* post first group of requests */
            for (segindex = 0; segindex < max_outstanding_reqs; segindex++) {
                ret = MCA_PML_CALL( isend((char*)sendbuf +
                                          segindex * segment_increment,
                                          count_by_segment, datatype,
                                          tree->tree_prev, 
                                          MCA_COLL_BASE_TAG_REDUCE,
                                          MCA_PML_BASE_SEND_SYNCHRONOUS, comm,
                                          &sreq[segindex]) );
                if (ret != MPI_SUCCESS) { line = __LINE__; goto error_hndl;  }
                original_count -= count_by_segment;
            }

            creq = 0;
            while ( original_count > 0 ) {
                /* wait on a posted request to complete */
                ret = ompi_request_wait(&sreq[creq], MPI_STATUS_IGNORE);
                if (ret != MPI_SUCCESS) { line = __LINE__; goto error_hndl;  }
                sreq[creq] = MPI_REQUEST_NULL;

                if( original_count < count_by_segment ) {
                    count_by_segment = original_count;
                }
                ret = MCA_PML_CALL( isend((char*)sendbuf + 
                                          segindex * segment_increment, 
                                          count_by_segment, datatype, 
                                          tree->tree_prev, 
                                          MCA_COLL_BASE_TAG_REDUCE, 
                                          MCA_PML_BASE_SEND_SYNCHRONOUS, comm, 
                                          &sreq[creq]) );
                if (ret != MPI_SUCCESS) { line = __LINE__; goto error_hndl;  }
                creq = (creq + 1) % max_outstanding_reqs;
                segindex++;
                original_count -= count_by_segment;
            }

            /* Wait on the remaining request to complete */
            ret = ompi_request_wait_all( max_outstanding_reqs, sreq, 
                                         MPI_STATUSES_IGNORE );
            if (ret != MPI_SUCCESS) { line = __LINE__; goto error_hndl;  }

            /* free requests */
            free(sreq);
        }
    }
    return OMPI_SUCCESS;

 error_hndl:  /* error handler */
    OPAL_OUTPUT (( ompi_coll_tuned_stream, 
                   "ERROR_HNDL: node %d file %s line %d error %d\n", 
                   rank, __FILE__, line, ret ));
    if( inbuf_free[0] != NULL ) free(inbuf_free[0]);
    if( inbuf_free[1] != NULL ) free(inbuf_free[1]);
    if( accumbuf_free != NULL ) free(accumbuf);
    return ret;
}

/* Attention: this version of the reduce operations does not
   work for:
   - non-commutative operations
   - segment sizes which are not multiplies of the extent of the datatype
     meaning that at least one datatype must fit in the segment !
*/

int ompi_coll_tuned_reduce_intra_chain( void *sendbuf, void *recvbuf, int count,
                                        ompi_datatype_t* datatype, 
                                        ompi_op_t* op, int root, 
                                        ompi_communicator_t* comm,
                                        mca_coll_base_module_t *module,
                                        uint32_t segsize, int fanout,
                                        int max_outstanding_reqs )
{
    int segcount = count;
    size_t typelng;
    mca_coll_tuned_module_t *tuned_module = (mca_coll_tuned_module_t*) module;
    mca_coll_tuned_comm_t *data = tuned_module->tuned_data;

    OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_chain rank %d fo %d ss %5d", ompi_comm_rank(comm), fanout, segsize));

    COLL_TUNED_UPDATE_CHAIN( comm, tuned_module, root, fanout );
    /**
     * Determine number of segments and number of elements
     * sent per operation
     */
    ompi_datatype_type_size( datatype, &typelng );
    COLL_TUNED_COMPUTED_SEGCOUNT( segsize, typelng, segcount );

    return ompi_coll_tuned_reduce_generic( sendbuf, recvbuf, count, datatype, 
                                           op, root, comm, module,
                                           data->cached_chain, 
                                           segcount, max_outstanding_reqs );
}


int ompi_coll_tuned_reduce_intra_pipeline( void *sendbuf, void *recvbuf,
                                           int count, ompi_datatype_t* datatype,
                                           ompi_op_t* op, int root,
                                           ompi_communicator_t* comm,
                                           mca_coll_base_module_t *module,
                                           uint32_t segsize,
                                           int max_outstanding_reqs  )
{
    int segcount = count;
    size_t typelng;
    mca_coll_tuned_module_t *tuned_module = (mca_coll_tuned_module_t*) module;
    mca_coll_tuned_comm_t *data = tuned_module->tuned_data;

    OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_pipeline rank %d ss %5d",
                 ompi_comm_rank(comm), segsize));

    COLL_TUNED_UPDATE_PIPELINE( comm, tuned_module, root );

    /**
     * Determine number of segments and number of elements
     * sent per operation
     */
    ompi_datatype_type_size( datatype, &typelng );
    COLL_TUNED_COMPUTED_SEGCOUNT( segsize, typelng, segcount );

    return ompi_coll_tuned_reduce_generic( sendbuf, recvbuf, count, datatype, 
                                           op, root, comm, module,
                                           data->cached_pipeline, 
                                           segcount, max_outstanding_reqs );
}

int ompi_coll_tuned_reduce_intra_binary( void *sendbuf, void *recvbuf,
                                         int count, ompi_datatype_t* datatype,
                                         ompi_op_t* op, int root,
                                         ompi_communicator_t* comm, 
                                         mca_coll_base_module_t *module,
                                         uint32_t segsize, 
                                         int max_outstanding_reqs  )
{
    int segcount = count;
    size_t typelng;
    mca_coll_tuned_module_t *tuned_module = (mca_coll_tuned_module_t*) module;
    mca_coll_tuned_comm_t *data = tuned_module->tuned_data;

    OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_binary rank %d ss %5d",
                 ompi_comm_rank(comm), segsize));

    COLL_TUNED_UPDATE_BINTREE( comm, tuned_module, root );

    /**
     * Determine number of segments and number of elements
     * sent per operation
     */
    ompi_datatype_type_size( datatype, &typelng );
    COLL_TUNED_COMPUTED_SEGCOUNT( segsize, typelng, segcount );

    return ompi_coll_tuned_reduce_generic( sendbuf, recvbuf, count, datatype, 
                                           op, root, comm, module,
                                           data->cached_bintree, 
                                           segcount, max_outstanding_reqs );
}

int ompi_coll_tuned_reduce_intra_binomial( void *sendbuf, void *recvbuf,
                                           int count, ompi_datatype_t* datatype,
                                           ompi_op_t* op, int root,
                                           ompi_communicator_t* comm, 
                                           mca_coll_base_module_t *module,
                                           uint32_t segsize,
                                           int max_outstanding_reqs  )
{
    int segcount = count;
    size_t typelng;
    mca_coll_tuned_module_t *tuned_module = (mca_coll_tuned_module_t*) module;
    mca_coll_tuned_comm_t *data = tuned_module->tuned_data;

    OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_binomial rank %d ss %5d",
                 ompi_comm_rank(comm), segsize));

    COLL_TUNED_UPDATE_IN_ORDER_BMTREE( comm, tuned_module, root );

    /**
     * Determine number of segments and number of elements
     * sent per operation
     */
    ompi_datatype_type_size( datatype, &typelng );
    COLL_TUNED_COMPUTED_SEGCOUNT( segsize, typelng, segcount );

    return ompi_coll_tuned_reduce_generic( sendbuf, recvbuf, count, datatype, 
                                           op, root, comm, module,
                                           data->cached_in_order_bmtree, 
                                           segcount, max_outstanding_reqs );
}

/*
 * reduce_intra_in_order_binary 
 * 
 * Function:      Logarithmic reduce operation for non-commutative operations.
 * Acecpts:       same as MPI_Reduce()
 * Returns:       MPI_SUCCESS or error code
 */
int ompi_coll_tuned_reduce_intra_in_order_binary( void *sendbuf, void *recvbuf,
                                                  int count, 
                                                  ompi_datatype_t* datatype,
                                                  ompi_op_t* op, int root,
                                                  ompi_communicator_t* comm, 
                                                  mca_coll_base_module_t *module,
                                                  uint32_t segsize,
                                                  int max_outstanding_reqs  )
{
    int ret;
    int rank, size, io_root;
    int segcount = count;
    void *use_this_sendbuf = NULL, *use_this_recvbuf = NULL;
    size_t typelng;
    mca_coll_tuned_module_t *tuned_module = (mca_coll_tuned_module_t*) module;
    mca_coll_tuned_comm_t *data = tuned_module->tuned_data;

    rank = ompi_comm_rank(comm);
    size = ompi_comm_size(comm);
    OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_in_order_binary rank %d ss %5d",
                 rank, segsize));

    COLL_TUNED_UPDATE_IN_ORDER_BINTREE( comm, tuned_module );

    /**
     * Determine number of segments and number of elements
     * sent per operation
     */
    ompi_datatype_type_size( datatype, &typelng );
    COLL_TUNED_COMPUTED_SEGCOUNT( segsize, typelng, segcount );

    /* An in-order binary tree must use root (size-1) to preserve the order of
       operations.  Thus, if root is not rank (size - 1), then we must handle
       1. MPI_IN_PLACE option on real root, and 
       2. we must allocate temporary recvbuf on rank (size - 1).
       Note that generic function must be careful not to switch order of 
       operations for non-commutative ops.
    */
    io_root = size - 1;
    use_this_sendbuf = sendbuf;
    use_this_recvbuf = recvbuf;
    if (io_root != root) {
        ptrdiff_t tlb, text, lb, ext;
        char *tmpbuf = NULL;
    
        ompi_datatype_get_extent(datatype, &lb, &ext);
        ompi_datatype_get_true_extent(datatype, &tlb, &text);

        if ((root == rank) && (MPI_IN_PLACE == sendbuf)) {
            tmpbuf = (char *) malloc(text + (count - 1) * ext);
            if (NULL == tmpbuf) {
                return MPI_ERR_INTERN;
            }
            ompi_datatype_copy_content_same_ddt(datatype, count, 
                                                (char*)tmpbuf,
                                                (char*)recvbuf);
            use_this_sendbuf = tmpbuf;
        } else if (io_root == rank) {
            tmpbuf = (char *) malloc(text + (count - 1) * ext);
            if (NULL == tmpbuf) {
                return MPI_ERR_INTERN;
            }
            use_this_recvbuf = tmpbuf;
        }
    }

    /* Use generic reduce with in-order binary tree topology and io_root */
    ret = ompi_coll_tuned_reduce_generic( use_this_sendbuf, use_this_recvbuf, count, datatype,
                                          op, io_root, comm, module, 
                                          data->cached_in_order_bintree, 
                                          segcount, max_outstanding_reqs );
    if (MPI_SUCCESS != ret) { return ret; }

    /* Clean up */
    if (io_root != root) {
        if (root == rank) {
            /* Receive result from rank io_root to recvbuf */
            ret = MCA_PML_CALL(recv(recvbuf, count, datatype, io_root,
                                    MCA_COLL_BASE_TAG_REDUCE, comm,
                                    MPI_STATUS_IGNORE));
            if (MPI_SUCCESS != ret) { return ret; }
            if (MPI_IN_PLACE == sendbuf) {
                free(use_this_sendbuf);
            }
          
        } else if (io_root == rank) {
            /* Send result from use_this_recvbuf to root */
            ret = MCA_PML_CALL(send(use_this_recvbuf, count, datatype, root,
                                    MCA_COLL_BASE_TAG_REDUCE, 
                                    MCA_PML_BASE_SEND_STANDARD, comm));
            if (MPI_SUCCESS != ret) { return ret; }
            free(use_this_recvbuf);
        }
    }

    return MPI_SUCCESS;
}

/*
 * Linear functions are copied from the BASIC coll module
 * they do not segment the message and are simple implementations
 * but for some small number of nodes and/or small data sizes they 
 * are just as fast as tuned/tree based segmenting operations 
 * and as such may be selected by the decision functions
 * These are copied into this module due to the way we select modules
 * in V1. i.e. in V2 we will handle this differently and so will not
 * have to duplicate code.
 * GEF Oct05 after asking Jeff.
 */

/* copied function (with appropriate renaming) starts here */

/*
 *  reduce_lin_intra
 *
 *  Function:   - reduction using O(N) algorithm
 *  Accepts:    - same as MPI_Reduce()
 *  Returns:    - MPI_SUCCESS or error code
 */
int
ompi_coll_tuned_reduce_intra_basic_linear(void *sbuf, void *rbuf, int count,
                                          struct ompi_datatype_t *dtype,
                                          struct ompi_op_t *op,
                                          int root,
                                          struct ompi_communicator_t *comm,
                                          mca_coll_base_module_t *module)
{
    int i, rank, err, size;
    ptrdiff_t true_lb, true_extent, lb, extent;
    char *free_buffer = NULL;
    char *pml_buffer = NULL;
    char *inplace_temp = NULL;
    char *inbuf;

    /* Initialize */

    rank = ompi_comm_rank(comm);
    size = ompi_comm_size(comm);

    OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_basic_linear rank %d", rank));

    /* If not root, send data to the root. */

    if (rank != root) {
        err = MCA_PML_CALL(send(sbuf, count, dtype, root,
                                MCA_COLL_BASE_TAG_REDUCE,
                                MCA_PML_BASE_SEND_STANDARD, comm));
        return err;
    }

    /* see discussion in ompi_coll_basic_reduce_lin_intra about 
       extent and true extent */
    /* for reducing buffer allocation lengths.... */

    ompi_datatype_get_extent(dtype, &lb, &extent);
    ompi_datatype_get_true_extent(dtype, &true_lb, &true_extent);

    if (MPI_IN_PLACE == sbuf) {
        sbuf = rbuf;
        inplace_temp = (char*)malloc(true_extent + (count - 1) * extent);
        if (NULL == inplace_temp) {
            return OMPI_ERR_OUT_OF_RESOURCE;
        }
        rbuf = inplace_temp - lb;
    }

    if (size > 1) {
        free_buffer = (char*)malloc(true_extent + (count - 1) * extent);
        if (NULL == free_buffer) {
            return OMPI_ERR_OUT_OF_RESOURCE;
        }
        pml_buffer = free_buffer - lb;
    }

    /* Initialize the receive buffer. */

    if (rank == (size - 1)) {
        err = ompi_datatype_copy_content_same_ddt(dtype, count, (char*)rbuf, 
                                                  (char*)sbuf);
    } else {
        err = MCA_PML_CALL(recv(rbuf, count, dtype, size - 1,
                                MCA_COLL_BASE_TAG_REDUCE, comm,
                                MPI_STATUS_IGNORE));
    }
    if (MPI_SUCCESS != err) {
        if (NULL != free_buffer) {
            free(free_buffer);
        }
        return err;
    }

    /* Loop receiving and calling reduction function (C or Fortran). */

    for (i = size - 2; i >= 0; --i) {
        if (rank == i) {
            inbuf = (char*)sbuf;
        } else {
            err = MCA_PML_CALL(recv(pml_buffer, count, dtype, i,
                                    MCA_COLL_BASE_TAG_REDUCE, comm,
                                    MPI_STATUS_IGNORE));
            if (MPI_SUCCESS != err) {
                if (NULL != free_buffer) {
                    free(free_buffer);
                }
                return err;
            }

            inbuf = pml_buffer;
        }

        /* Perform the reduction */
        ompi_op_reduce(op, inbuf, rbuf, count, dtype);
    }

    if (NULL != inplace_temp) {
        err = ompi_datatype_copy_content_same_ddt(dtype, count, (char*)sbuf, 
                                                  inplace_temp);
        free(inplace_temp);
    }
    if (NULL != free_buffer) {
        free(free_buffer);
    }

    /* All done */
    return MPI_SUCCESS;
}

/* copied function (with appropriate renaming) ends here */


/**
 * The following are used by dynamic and forced rules
 *
 * publish details of each algorithm and if its forced/fixed/locked in
 * as you add methods/algorithms you must update this and the query/map routines
 *
 * this routine is called by the component only
 * this makes sure that the mca parameters are set to their initial values and 
 * perms module does not call this they call the forced_getvalues routine 
 * instead.
 */
int ompi_coll_tuned_reduce_intra_check_forced_init (coll_tuned_force_algorithm_mca_param_indices_t *mca_param_indices)
{
    int rc, requested_alg, max_alg = 6, max_requests;

    ompi_coll_tuned_forced_max_algorithms[REDUCE] = max_alg;

    rc = mca_base_param_reg_int (&mca_coll_tuned_component.super.collm_version,
                                 "reduce_algorithm_count",
                                 "Number of reduce algorithms available",
                                 false, true, max_alg, NULL);

    mca_param_indices->algorithm_param_index
        = mca_base_param_reg_int(&mca_coll_tuned_component.super.collm_version,
                                 "reduce_algorithm",
                                 "Which reduce algorithm is used. Can be locked down to choice of: 0 ignore, 1 linear, 2 chain, 3 pipeline, 4 binary, 5 binomial, 6 in-order binary",
                                 false, false, 0, NULL);
    if (mca_param_indices->algorithm_param_index < 0) {
        return mca_param_indices->algorithm_param_index;
    }
    mca_base_param_lookup_int(mca_param_indices->algorithm_param_index, &(requested_alg));
    if( 0 > requested_alg || requested_alg > max_alg ) {
        if( 0 == ompi_comm_rank( MPI_COMM_WORLD ) ) {
            opal_output( 0, "Reduce algorithm #%d is not available (range [0..%d]). Switching back to ignore(0)\n",
                         requested_alg, max_alg );
        }
        mca_base_param_set_int( mca_param_indices->algorithm_param_index, 0);
    }

    mca_param_indices->segsize_param_index
        = mca_base_param_reg_int(&mca_coll_tuned_component.super.collm_version,
                                 "reduce_algorithm_segmentsize",
                                 "Segment size in bytes used by default for reduce algorithms. Only has meaning if algorithm is forced and supports segmenting. 0 bytes means no segmentation.",
                                 false, false, 0, NULL);

    mca_param_indices->tree_fanout_param_index
        = mca_base_param_reg_int(&mca_coll_tuned_component.super.collm_version,
                                 "reduce_algorithm_tree_fanout",
                                 "Fanout for n-tree used for reduce algorithms. Only has meaning if algorithm is forced and supports n-tree topo based operation.",
                                 false, false,
                                 ompi_coll_tuned_init_tree_fanout, /* get system wide default */
                                 NULL);

    mca_param_indices->chain_fanout_param_index
        = mca_base_param_reg_int(&mca_coll_tuned_component.super.collm_version,
                                 "reduce_algorithm_chain_fanout",
                                 "Fanout for chains used for reduce algorithms. Only has meaning if algorithm is forced and supports chain topo based operation.",
                                 false, false,
                                 ompi_coll_tuned_init_chain_fanout, /* get system wide default */
                                 NULL);

    mca_param_indices->max_requests_param_index
        = mca_base_param_reg_int(&mca_coll_tuned_component.super.collm_version,
                                 "reduce_algorithm_max_requests",
                                 "Maximum number of outstanding send requests on leaf nodes. 0 means no limit.",
                                 false, false, 0, /* no limit for reduce by default */
                                 NULL);

    if (mca_param_indices->max_requests_param_index < 0) {
        return mca_param_indices->max_requests_param_index;
    }
    mca_base_param_lookup_int(mca_param_indices->max_requests_param_index, &(max_requests));
    if( max_requests < 0 ) {
        if( 0 == ompi_comm_rank( MPI_COMM_WORLD ) ) {
            opal_output( 0, "Maximum outstanding requests must be positive number or 0.  Initializing to 0 (no limit).\n" );
        }
        mca_base_param_set_int( mca_param_indices->max_requests_param_index, 0);
    }

    return (MPI_SUCCESS);
}


int ompi_coll_tuned_reduce_intra_do_forced(void *sbuf, void* rbuf, int count,
                                           struct ompi_datatype_t *dtype,
                                           struct ompi_op_t *op, int root,
                                           struct ompi_communicator_t *comm,
                                           mca_coll_base_module_t *module)
{
    mca_coll_tuned_module_t *tuned_module = (mca_coll_tuned_module_t*) module;
    mca_coll_tuned_comm_t *data = tuned_module->tuned_data;

    const int segsize      = data->user_forced[REDUCE].segsize;
    const int chain_fanout = data->user_forced[REDUCE].chain_fanout;
    const int max_requests = data->user_forced[REDUCE].max_requests;

    OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_do_forced selected algorithm %d", 
                 data->user_forced[REDUCE].algorithm));


    switch (data->user_forced[REDUCE].algorithm) {
    case (0):  return ompi_coll_tuned_reduce_intra_dec_fixed (sbuf, rbuf, count, dtype, 
                                                              op, root, comm, module);
    case (1):  return ompi_coll_tuned_reduce_intra_basic_linear (sbuf, rbuf, count, dtype,
                                                                 op, root, comm, module);
    case (2):  return ompi_coll_tuned_reduce_intra_chain (sbuf, rbuf, count, dtype,
                                                          op, root, comm, module,
                                                          segsize, chain_fanout, max_requests);
    case (3):  return ompi_coll_tuned_reduce_intra_pipeline (sbuf, rbuf, count, dtype,
                                                             op, root, comm, module,
                                                             segsize, max_requests);
    case (4):  return ompi_coll_tuned_reduce_intra_binary (sbuf, rbuf, count, dtype,
                                                           op, root, comm, module,
                                                           segsize, max_requests);
    case (5):  return ompi_coll_tuned_reduce_intra_binomial (sbuf, rbuf, count, dtype,
                                                             op, root, comm, module,
                                                             segsize, max_requests);
    case (6):  return ompi_coll_tuned_reduce_intra_in_order_binary(sbuf, rbuf, count, dtype,
                                                                   op, root, comm, module,
                                                                   segsize, max_requests);
    default:
        OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_do_forced attempt to select algorithm %d when only 0-%d is valid?",
                     data->user_forced[REDUCE].algorithm, ompi_coll_tuned_forced_max_algorithms[REDUCE]));
        return (MPI_ERR_ARG);
    } /* switch */
}


int ompi_coll_tuned_reduce_intra_do_this(void *sbuf, void* rbuf, int count,
                                         struct ompi_datatype_t *dtype,
                                         struct ompi_op_t *op, int root,
                                         struct ompi_communicator_t *comm,
                                         mca_coll_base_module_t *module,
                                         int algorithm, int faninout, 
                                         int segsize, int max_requests )
{
    OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_do_this selected algorithm %d topo faninout %d segsize %d",
                 algorithm, faninout, segsize));

    switch (algorithm) {
    case (0):  return ompi_coll_tuned_reduce_intra_dec_fixed (sbuf, rbuf, count, dtype,
                                                              op, root, comm, module);
    case (1):  return ompi_coll_tuned_reduce_intra_basic_linear (sbuf, rbuf, count, dtype, 
                                                                 op, root, comm, module);
    case (2):  return ompi_coll_tuned_reduce_intra_chain (sbuf, rbuf, count, dtype,
                                                          op, root, comm, module,
                                                          segsize, faninout, max_requests);
    case (3):  return ompi_coll_tuned_reduce_intra_pipeline (sbuf, rbuf, count, dtype,
                                                             op, root, comm, module,
                                                             segsize, max_requests);
    case (4):  return ompi_coll_tuned_reduce_intra_binary (sbuf, rbuf, count, dtype,
                                                           op, root, comm, module,
                                                           segsize, max_requests); 
    case (5):  return ompi_coll_tuned_reduce_intra_binomial (sbuf, rbuf, count, dtype,
                                                             op, root, comm, module,
                                                             segsize, max_requests); 
    case (6):  return ompi_coll_tuned_reduce_intra_in_order_binary(sbuf, rbuf, count, dtype,
                                                                   op, root, comm, module,
                                                                   segsize, max_requests);
    default:
        OPAL_OUTPUT((ompi_coll_tuned_stream,"coll:tuned:reduce_intra_do_this attempt to select algorithm %d when only 0-%d is valid?",
                     algorithm, ompi_coll_tuned_forced_max_algorithms[REDUCE]));
        return (MPI_ERR_ARG);
    } /* switch */
}