MPISynchroShuffleAllToAllComm.cpp

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#include "MPISynchroShuffleAllToAllComm.h"
#include <algorithm>

using std::cerr;
using std::copy;

MPISynchroShuffleAllToAllComm::MPISynchroShuffleAllToAllComm(MPIInputBufferVector & mpiInputBuffers,
        MPIOutputBufferVector & mpiOutputBuffers,
        MPI::Intracomm & comm,
        vector<bool> &incomingConnections,
        vector<bool> &outgoingConnections) :
        MPIAllToAllCommunicator(mpiInputBuffers, mpiOutputBuffers, comm, 
                                                        incomingConnections, outgoingConnections)

{
    needsToSend.resize(numNodes);
    needsToReceive.resize(numNodes);
}

MPISynchroShuffleAllToAllComm::~MPISynchroShuffleAllToAllComm()
{}

void MPISynchroShuffleAllToAllComm::prepare()
{
    copy(outgoing_connections.begin(), outgoing_connections.end(), needsToSend.begin());
    copy(outgoing_connections.begin(), outgoing_connections.end(), hasNextToSend.begin());
    copy(incoming_connections.begin(), incoming_connections.end(), needsToReceive.begin());
}

void MPISynchroShuffleAllToAllComm::doExchangeAlgorithm()
{
    // adjust the hasNextToSend[i] indicators
    for (int i = 0 ; i < numNodes ; ++i) {
        outputBuffers[i].setFinishedFlag(!hasNextToSend[i]);
    }
    
    MPIExchangeBlocksInfo & input_blocks = inputBuffers.getMPIExchangeBlocksInfo();
    
    MPIExchangeBlocksInfo & output_blocks = outputBuffers.getMPIExchangeBlocksInfo();
    
    int myid = mpi_comm.Get_rank();
    int tag = 100;

    // do the actual exchange
    for (int i = 1; i < numNodes; ++i) {
        int to = (myid+i) % numNodes;
        int from = (myid+numNodes-i) % numNodes;
        int order;
        if (i % 2 == 0) {
            order = ( myid + ((myid - myid % i) / i) % 2 ) % 2 ;
        } else {
            order = myid % 2;
        }
        if (order) {
            if (needsToSend[to]) {
                mpi_comm.Send(output_blocks.buffers[to],output_blocks.counts[to], output_blocks.datatypes[to], to, tag);
            }
            if (needsToReceive[from]) {
                mpi_comm.Recv(input_blocks.buffers[from], input_blocks.counts[from], input_blocks.datatypes[from], from, MPI::ANY_TAG);
            }
        } else {
            if (needsToReceive[from]) {
                mpi_comm.Recv(input_blocks.buffers[from], input_blocks.counts[from], input_blocks.datatypes[from], from, MPI::ANY_TAG);
            }
            if (needsToSend[to]) {
                mpi_comm.Send(output_blocks.buffers[to], output_blocks.counts[to], output_blocks.datatypes[to], to, tag);
            }
        }
    }
}

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