red_scat.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_scatter */
#if defined(HAVE_PRAGMA_WEAK)
#pragma weak MPI_Reduce_scatter = PMPI_Reduce_scatter
#elif defined(HAVE_PRAGMA_HP_SEC_DEF)
#pragma _HP_SECONDARY_DEF PMPI_Reduce_scatter  MPI_Reduce_scatter
#elif defined(HAVE_PRAGMA_CRI_DUP)
#pragma _CRI duplicate MPI_Reduce_scatter as PMPI_Reduce_scatter
#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_scatter PMPI_Reduce_scatter

/* This is the default implementation of reduce_scatter. The algorithm is:
   
   Algorithm: MPI_Reduce_scatter

   If the operation is commutative, for short and medium-size
   messages, we use a recursive-halving
   algorithm in which the first p/2 processes send the second n/2 data
   to their counterparts in the other half and receive the first n/2
   data from them. This procedure continues recursively, halving the
   data communicated at each step, for a total of lgp steps. If the
   number of processes is not a power-of-two, we convert it to the
   nearest lower power-of-two by having the first few even-numbered
   processes send their data to the neighboring odd-numbered process
   at (rank+1). Those odd-numbered processes compute the result for
   their left neighbor as well in the recursive halving algorithm, and
   then at  the end send the result back to the processes that didn't
   participate. 
   Therefore, if p is a power-of-two,
   Cost = lgp.alpha + n.((p-1)/p).beta + n.((p-1)/p).gamma
   If p is not a power-of-two,
   Cost = (floor(lgp)+2).alpha + n.(1+(p-1+n)/p).beta + n.(1+(p-1)/p).gamma
   The above cost in the non power-of-two case is approximate because
   there is some imbalance in the amount of work each process does
   because some processes do the work of their neighbors as well.

   For commutative operations and very long messages we use 
   we use a pairwise exchange algorithm similar to
   the one used in MPI_Alltoall. At step i, each process sends n/p
   amount of data to (rank+i) and receives n/p amount of data from 
   (rank-i).
   Cost = (p-1).alpha + n.((p-1)/p).beta + n.((p-1)/p).gamma


   If the operation is not commutative, we do the following:

   For very short messages, we use a recursive doubling algorithm, which
   takes lgp steps. At step 1, processes exchange (n-n/p) amount of
   data; at step 2, (n-2n/p) amount of data; at step 3, (n-4n/p)
   amount of data, and so forth.

   Cost = lgp.alpha + n.(lgp-(p-1)/p).beta + n.(lgp-(p-1)/p).gamma

   For medium and long messages, we use pairwise exchange as above.

   Possible improvements: 

   End Algorithm: MPI_Reduce_scatter
*/

/* begin:nested */
/* not declared static because a machine-specific function may call this one in some cases */
int MPIR_Reduce_scatter ( 
    void *sendbuf, 
    void *recvbuf, 
    int *recvcnts, 
    MPI_Datatype datatype, 
    MPI_Op op, 
    MPID_Comm *comm_ptr )
{
    static const char FCNAME[] = "MPIR_Reduce_scatter";
    int   rank, comm_size, i;
    MPI_Aint extent, true_extent, true_lb; 
    int  *disps;
    void *tmp_recvbuf, *tmp_results;
    int   mpi_errno = MPI_SUCCESS;
    int type_size, dis[2], blklens[2], total_count, nbytes, src, dst;
    int mask, dst_tree_root, my_tree_root, j, k;
    int *newcnts, *newdisps, rem, newdst, send_idx, recv_idx,
        last_idx, send_cnt, recv_cnt;
    int pof2, old_i, newrank, received;
    MPI_Datatype sendtype, recvtype;
    int nprocs_completed, tmp_mask, tree_root, is_commutative;
    MPI_User_function *uop;
    MPID_Op *op_ptr;
    MPI_Comm comm;
    MPICH_PerThread_t *p;
#ifdef HAVE_CXX_BINDING
    int is_cxx_uop = 0;
#endif
    
    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;

    MPID_Datatype_get_extent_macro(datatype, extent);
    mpi_errno = NMPI_Type_get_true_extent(datatype, &true_lb,
                                          &true_extent);  
    /* --BEGIN ERROR HANDLING-- */
    if (mpi_errno)
    {
	mpi_errno = MPIR_Err_create_code(mpi_errno, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**fail", 0);
	return mpi_errno;
    }
    /* --END ERROR HANDLING-- */
    
    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;
    }

    disps = MPIU_Malloc(comm_size*sizeof(int));
    /* --BEGIN ERROR HANDLING-- */
    if (!disps) {
        mpi_errno = MPIR_Err_create_code( MPI_SUCCESS, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**nomem", 0 );
        return mpi_errno;
    }
    /* --END ERROR HANDLING-- */

    total_count = 0;
    for (i=0; i<comm_size; i++) {
        disps[i] = total_count;
        total_count += recvcnts[i];
    }
    
    if (total_count == 0) {
        MPIU_Free(disps);
        return MPI_SUCCESS;
    }

    MPID_Datatype_get_size_macro(datatype, type_size);
    nbytes = total_count * type_size;
    
    /* check if multiple threads are calling this collective function */
    MPIDU_ERR_CHECK_MULTIPLE_THREADS_ENTER( comm_ptr );
    MPIR_Nest_incr();

    if ((is_commutative) && (nbytes < MPIR_REDSCAT_COMMUTATIVE_LONG_MSG)) {
        /* commutative and short. use recursive halving algorithm */

        /* allocate temp. buffer to receive incoming data */
        tmp_recvbuf = MPIU_Malloc(total_count*(MPIR_MAX(true_extent,extent)));
	/* --BEGIN ERROR HANDLING-- */
        if (!tmp_recvbuf) {
            mpi_errno = MPIR_Err_create_code( MPI_SUCCESS, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**nomem", 0 );
            return mpi_errno;
        }
	/* --END ERROR HANDLING-- */
        /* adjust for potential negative lower bound in datatype */
        tmp_recvbuf = (void *)((char*)tmp_recvbuf - true_lb);
            
        /* need to allocate another temporary buffer to accumulate
           results because recvbuf may not be big enough */
        tmp_results = MPIU_Malloc(total_count*(MPIR_MAX(true_extent,extent)));
	/* --BEGIN ERROR HANDLING-- */
        if (!tmp_results) {
            mpi_errno = MPIR_Err_create_code( MPI_SUCCESS, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**nomem", 0 );
            return mpi_errno;
        }        
	/* --END ERROR HANDLING-- */
        /* adjust for potential negative lower bound in datatype */
        tmp_results = (void *)((char*)tmp_results - true_lb);
        
        /* copy sendbuf into tmp_results */
        if (sendbuf != MPI_IN_PLACE)
            mpi_errno = MPIR_Localcopy(sendbuf, total_count, datatype,
                                       tmp_results, total_count, datatype);
        else
            mpi_errno = MPIR_Localcopy(recvbuf, total_count, datatype,
                                       tmp_results, total_count, datatype);
        
	/* --BEGIN ERROR HANDLING-- */
        if (mpi_errno)
	{
	    mpi_errno = MPIR_Err_create_code(mpi_errno, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**fail", 0);
	    return mpi_errno;
	}
	/* --END ERROR HANDLING-- */

        pof2 = 1;
        while (pof2 <= comm_size) pof2 <<= 1;
        pof2 >>=1;

        rem = comm_size - pof2;

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

        if (rank < 2*rem) {
            if (rank % 2 == 0) { /* even */
                mpi_errno = MPIC_Send(tmp_results, total_count, 
                                      datatype, rank+1,
                                      MPIR_REDUCE_SCATTER_TAG, comm);
		/* --BEGIN ERROR HANDLING-- */
                if (mpi_errno)
		{
		    mpi_errno = MPIR_Err_create_code(mpi_errno, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**fail", 0);
		    return mpi_errno;
		}
		/* --END ERROR HANDLING-- */
                
                /* temporarily set the rank to -1 so that this
                   process does not pariticipate in recursive
                   doubling */
                newrank = -1; 
            }
            else { /* odd */
                mpi_errno = MPIC_Recv(tmp_recvbuf, total_count, 
                                      datatype, rank-1,
                                      MPIR_REDUCE_SCATTER_TAG, comm,
                                      MPI_STATUS_IGNORE);
		/* --BEGIN ERROR HANDLING-- */
                if (mpi_errno)
		{
		    mpi_errno = MPIR_Err_create_code(mpi_errno, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**fail", 0);
		    return mpi_errno;
		}
		/* --END ERROR HANDLING-- */
                
                /* do the reduction on received data. since the
                   ordering is right, it doesn't matter whether
                   the operation is commutative or not. */
#ifdef HAVE_CXX_BINDING
                if (is_cxx_uop) {
                    (*MPIR_Process.cxx_call_op_fn)( tmp_recvbuf, tmp_results, 
                                                    total_count,
                                                    datatype,
                                                    uop ); 
                }
                else 
#endif
                    (*uop)(tmp_recvbuf, tmp_results, &total_count, &datatype);
                
                /* change the rank */
                newrank = rank / 2;
            }
        }
        else  /* rank >= 2*rem */
            newrank = rank - rem;

        if (newrank != -1) {
            /* recalculate the recvcnts and disps arrays because the
               even-numbered processes who no longer participate will
               have their result calculated by the process to their
               right (rank+1). */

            newcnts = (int *) MPIU_Malloc(pof2*sizeof(int));
	    /* --BEGIN ERROR HANDLING-- */
            if (!newcnts) {
                mpi_errno = MPIR_Err_create_code( MPI_SUCCESS, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**nomem", 0 );
                return mpi_errno;
            }
	    /* --END ERROR HANDLING-- */
            newdisps = (int *) MPIU_Malloc(pof2*sizeof(int));
	    /* --BEGIN ERROR HANDLING-- */
            if (!newdisps) {
                mpi_errno = MPIR_Err_create_code( MPI_SUCCESS, MPIR_ERR_RECOVERABLE, FCNAME, __LINE__, MPI_ERR_OTHER, "**nomem", 0 );
                return mpi_errno;
            }
	    /* --END ERROR HANDLING-- */
            
            for (i=0; i<pof2; i++) {
                /* what does i map to in the old ranking? */