reduce.c

mpi并行计算的c++代码 可用vc或gcc编译通过 可以用来搭建并行计算试验环境

/* -*- Mode: C; c-basic-offset:4 ; -*- */
/*
 *
 *  (C) 2001 by Argonne National Laboratory.
 *      See COPYRIGHT in top-level directory.
 */

#include "mpiimpl.h"

/* -- Begin Profiling Symbol Block for routine MPI_Reduce */
#if defined(HAVE_PRAGMA_WEAK)
#pragma weak MPI_Reduce = PMPI_Reduce
#elif defined(HAVE_PRAGMA_HP_SEC_DEF)
#pragma _HP_SECONDARY_DEF PMPI_Reduce  MPI_Reduce
#elif defined(HAVE_PRAGMA_CRI_DUP)
#pragma _CRI duplicate MPI_Reduce as PMPI_Reduce
#endif
/* -- End Profiling Symbol Block */

/* Define MPICH_MPI_FROM_PMPI if weak symbols are not supported to build
   the MPI routines */
#ifndef MPICH_MPI_FROM_PMPI
#define MPI_Reduce PMPI_Reduce

/* This is the default implementation of reduce. The algorithm is:
   
   Algorithm: MPI_Reduce

   For long messages and for builtin ops and if count >= pof2 (where
   pof2 is the nearest power-of-two less than or equal to the number
   of processes), we use Rabenseifner's algorithm (see 
   http://www.hlrs.de/organization/par/services/models/mpi/myreduce.html ).
   This algorithm implements the reduce in two steps: first a
   reduce-scatter, followed by a gather to the root. A
   recursive-halving algorithm (beginning with processes that are
   distance 1 apart) is used for the reduce-scatter, and a binomial tree
   algorithm is used for the gather. The non-power-of-two case is
   handled by dropping to the nearest lower power-of-two: the first
   few odd-numbered processes send their data to their left neighbors
   (rank-1), and the reduce-scatter happens among the remaining
   power-of-two processes. If the root is one of the excluded
   processes, then after the reduce-scatter, rank 0 sends its result to
   the root and exits; the root now acts as rank 0 in the binomial tree
   algorithm for gather.

   For the power-of-two case, the cost for the reduce-scatter is 
   lgp.alpha + n.((p-1)/p).beta + n.((p-1)/p).gamma. The cost for the
   gather to root is lgp.alpha + n.((p-1)/p).beta. Therefore, the
   total cost is:
   Cost = 2.lgp.alpha + 2.n.((p-1)/p).beta + n.((p-1)/p).gamma

   For the non-power-of-two case, assuming the root is not one of the
   odd-numbered processes that get excluded in the reduce-scatter,
   Cost = (2.floor(lgp)+1).alpha + (2.((p-1)/p) + 1).n.beta + n.(1+(p-1)/p).gamma


   For short messages, user-defined ops, and count < pof2, we use a
   binomial tree algorithm for both short and long messages. 

   Cost = lgp.alpha + n.lgp.beta + n.lgp.gamma


   We use the binomial tree algorithm in the case of user-defined ops
   because in this case derived datatypes are allowed, and the user
   could pass basic datatypes on one process and derived on another as
   long as the type maps are the same. Breaking up derived datatypes
   to do the reduce-scatter is tricky. 

   Possible improvements: 

   End Algorithm: MPI_Reduce
*/

/* begin:nested */
/* not declared static because a machine-specific function may call this one in some cases */
int MPIR_Reduce ( 
    void *sendbuf, 
    void *recvbuf, 
    int count, 
    MPI_Datatype datatype, 
    MPI_Op op, 
    int root, 
    MPID_Comm *comm_ptr )
{
    static const char FCNAME[] = "MPIR_Reduce";
    MPI_Status status;
    int        comm_size, rank, is_commutative, type_size, pof2, rem, newrank;
    int        mask, relrank, source, lroot, *cnts, *disps, i, j, send_idx=0;
    int        mpi_errno = MPI_SUCCESS, recv_idx, last_idx=0, newdst;
    int    dst, send_cnt, recv_cnt, newroot, newdst_tree_root,
        newroot_tree_root; 
    MPI_User_function *uop;
    MPI_Aint   true_lb, true_extent, extent; 
    void       *tmp_buf;
    MPID_Op *op_ptr;
    MPI_Comm comm;
    MPICH_PerThread_t *p;
#ifdef HAVE_CXX_BINDING
    int is_cxx_uop = 0;
#endif
    MPIU_CHKLMEM_DECL(4);
    
    if (count == 0) return MPI_SUCCESS;

    MPIR_Nest_incr();
    
    comm = comm_ptr->handle;
    comm_size = comm_ptr->local_size;
    rank = comm_ptr->rank;
    
    /* set op_errno to 0. stored in perthread structure */
    MPIR_GetPerThread(&p);
    p->op_errno = 0;

    if (HANDLE_GET_KIND(op) == HANDLE_KIND_BUILTIN) {
        is_commutative = 1;
        /* get the function by indexing into the op table */
        uop = MPIR_Op_table[op%16 - 1];
    }
    else {
        MPID_Op_get_ptr(op, op_ptr);
        if (op_ptr->kind == MPID_OP_USER_NONCOMMUTE)
            is_commutative = 0;
        else
            is_commutative = 1;
        
#ifdef HAVE_CXX_BINDING            
            if (op_ptr->language == MPID_LANG_CXX) {
                uop = (MPI_User_function *) op_ptr->function.c_function;
		is_cxx_uop = 1;
	    }
	    else
#endif
        if ((op_ptr->language == MPID_LANG_C))
            uop = (MPI_User_function *) op_ptr->function.c_function;
        else
            uop = (MPI_User_function *) op_ptr->function.f77_function;
    }
    
    /* Create a temporary buffer */

    mpi_errno = NMPI_Type_get_true_extent(datatype, &true_lb, &true_extent);  
    MPIU_ERR_CHKANDJUMP((mpi_errno), mpi_errno, MPI_ERR_OTHER, "**fail");
    MPID_Datatype_get_extent_macro(datatype, extent);

    MPIU_CHKLMEM_MALLOC(tmp_buf, void *, count*(MPIR_MAX(extent,true_extent)), mpi_errno, "temporary buffer");
    /* adjust for potential negative lower bound in datatype */
    tmp_buf = (void *)((char*)tmp_buf - true_lb);
    
    /* If I'm not the root, then my recvbuf may not be valid, therefore
       I have to allocate a temporary one */
    if (rank != root) {
	MPIU_CHKLMEM_MALLOC(recvbuf, void *, count*(MPIR_MAX(extent,true_extent)), mpi_errno, "receive buffer");
        recvbuf = (void *)((char*)recvbuf - true_lb);
    }

    if ((rank != root) || (sendbuf != MPI_IN_PLACE)) {
        mpi_errno = MPIR_Localcopy(sendbuf, count, datatype, recvbuf,
                                   count, datatype);
	MPIU_ERR_CHKANDJUMP((mpi_errno), mpi_errno, MPI_ERR_OTHER, "**fail");
    }

    MPID_Datatype_get_size_macro(datatype, type_size);

    /* find nearest power-of-two less than or equal to comm_size */
    pof2 = 1;
    while (pof2 <= comm_size) pof2 <<= 1;
    pof2 >>=1;

    /* check if multiple threads are calling this collective function */
    MPIDU_ERR_CHECK_MULTIPLE_THREADS_ENTER( comm_ptr );
        
    if ((count*type_size > MPIR_REDUCE_SHORT_MSG) &&
        (HANDLE_GET_KIND(op) == HANDLE_KIND_BUILTIN) && (count >= pof2)) {
        /* do a reduce-scatter followed by gather to root. */

        rem = comm_size - pof2;

        /* In the non-power-of-two case, all odd-numbered
           processes of rank < 2*rem send their data to
           (rank-1). These odd-numbered processes no longer
           participate in the algorithm until the very end. The
           remaining processes form a nice power-of-two. 

           Note that in MPI_Allreduce we have the even-numbered processes
           send data to odd-numbered processes. That is better for
           non-commutative operations because it doesn't require a
           buffer copy. However, for MPI_Reduce, the most common case
           is commutative operations with root=0. Therefore we want
           even-numbered processes to participate the computation for
           the root=0 case, in order to avoid an extra send-to-root
           communication after the reduce-scatter. In MPI_Allreduce it
           doesn't matter because all processes must get the result. */
        
        if (rank < 2*rem) {
            if (rank % 2 != 0) { /* odd */
                mpi_errno = MPIC_Send(recvbuf, count, 
                                      datatype, rank-1,
                                      MPIR_REDUCE_TAG, comm);
		MPIU_ERR_CHKANDJUMP((mpi_errno), mpi_errno, MPI_ERR_OTHER, "**fail");
                
                /* temporarily set the rank to -1 so that this
                   process does not pariticipate in recursive
                   doubling */
                newrank = -1; 
            }
            else { /* even */
                mpi_errno = MPIC_Recv(tmp_buf, count, 
                                      datatype, rank+1,
                                      MPIR_REDUCE_TAG, comm,
                                      MPI_STATUS_IGNORE);
		MPIU_ERR_CHKANDJUMP((mpi_errno), mpi_errno, MPI_ERR_OTHER, "**fail");
                
                /* do the reduction on received data. */
                /* This algorithm is used only for predefined ops
                   and predefined ops are always commutative. */
#ifdef HAVE_CXX_BINDING
                if (is_cxx_uop) {
                    (*MPIR_Process.cxx_call_op_fn)( tmp_buf, recvbuf, 
                                                    count,
                                                    datatype,
                                                    uop ); 
                }
                else 
#endif
                    (*uop)(tmp_buf, recvbuf, &count, &datatype);

                /* change the rank */
                newrank = rank / 2;
            }
        }
        else  /* rank >= 2*rem */
            newrank = rank - rem;
        
        /* for the reduce-scatter, calculate the count that
           each process receives and the displacement within
           the buffer */

        /* We allocate these arrays on all processes, even if newrank=-1,
           because if root is one of the excluded processes, we will
           need them on the root later on below. */
	MPIU_CHKLMEM_MALLOC(cnts, int *, pof2*sizeof(int), mpi_errno, "counts");
	MPIU_CHKLMEM_MALLOC(disps, int *, pof2*sizeof(int), mpi_errno, "displacements");
        
        if (newrank != -1) {
            for (i=0; i<(pof2-1); i++) 
                cnts[i] = count/pof2;
            cnts[pof2-1] = count - (count/pof2)*(pof2-1);
            
            disps[0] = 0;
            for (i=1; i<pof2; i++)
                disps[i] = disps[i-1] + cnts[i-1];
            
            mask = 0x1;
            send_idx = recv_idx = 0;
            last_idx = pof2;
            while (mask < pof2) {
                newdst = newrank ^ mask;
                /* find real rank of dest */
                dst = (newdst < rem) ? newdst*2 : newdst + rem;
                
                send_cnt = recv_cnt = 0;
                if (newrank < newdst) {
                    send_idx = recv_idx + pof2/(mask*2);
                    for (i=send_idx; i<last_idx; i++)
                        send_cnt += cnts[i];
                    for (i=recv_idx; i<send_idx; i++)
                        recv_cnt += cnts[i];
                }
                else {
                    recv_idx = send_idx + pof2/(mask*2);
                    for (i=send_idx; i<recv_idx; i++)
                        send_cnt += cnts[i];
                    for (i=recv_idx; i<last_idx; i++)
                        recv_cnt += cnts[i];
                }
                
/*                    printf("Rank %d, send_idx %d, recv_idx %d, send_cnt %d, recv_cnt %d, last_idx %d\n", newrank, send_idx, recv_idx,
                      send_cnt, recv_cnt, last_idx);
*/
                /* Send data from recvbuf. Recv into tmp_buf */ 
                mpi_errno = MPIC_Sendrecv((char *) recvbuf +
                                          disps[send_idx]*extent,
                                          send_cnt, datatype,