ObjectCommunicator.hpp

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#ifndef _OBJECTCOMMUNICATOR_HPP_
#define _OBJECTCOMMUNICATOR_HPP_

// Serialisation headers - must come first
#include <boost/archive/binary_oarchive.hpp>
#include <boost/archive/binary_iarchive.hpp>

#include <boost/scoped_array.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include "PetscTools.hpp" // For MPI methods
#include "Exception.hpp"

const unsigned MAX_BUFFER_SIZE = 1000000;

template<typename CLASS>
class ObjectCommunicator
{
private:

    char* mRecvBuffer;

    std::vector<char* > mSendBuffer;

    std::vector<std::string> mSendString;

    unsigned mRecvBufferLength;

    unsigned mSendBufferLength;

    MPI_Request mMpiRequest;

    bool mIsWriting;

public:

    ObjectCommunicator();

    void SendObject(boost::shared_ptr<CLASS> const pObject, unsigned destinationProcess, unsigned tag);

    void ISendObject(boost::shared_ptr<CLASS> const pObject, unsigned destinationProcess, unsigned tag);

    boost::shared_ptr<CLASS> RecvObject(unsigned sourceProcess, unsigned tag, MPI_Status& status);

    void IRecvObject(unsigned sourceProcess, unsigned tag);

    boost::shared_ptr<CLASS> GetRecvObject();

    boost::shared_ptr<CLASS> SendRecvObject(boost::shared_ptr<CLASS> const pSendObject, unsigned destinationProcess, unsigned sendTag, unsigned sourceProcess, unsigned sourceTag, MPI_Status& status);
};

#include <sstream>
#include <string>
#include <cstring>

// Implementation needs to be here, as CLASS could be anything
template<typename CLASS>
ObjectCommunicator<CLASS>::ObjectCommunicator()
    : mIsWriting(false)
{
    mSendBuffer.resize(PetscTools::GetNumProcs());
    mSendString.resize(PetscTools::GetNumProcs());
}

template<typename CLASS>
void ObjectCommunicator<CLASS>::SendObject(boost::shared_ptr<CLASS> const pObject, unsigned destinationProcess, unsigned tag)
{
    // Create an output archive
    std::ostringstream ss(std::ios::binary);
    boost::archive::binary_oarchive output_arch(ss);

    output_arch << pObject;

    const std::string send_msg = ss.str();

    // Get + send string length
    unsigned string_length = send_msg.size();
    MPI_Send(&string_length, 1, MPI_UNSIGNED, destinationProcess, tag, PetscTools::GetWorld());

    // Send archive data
    // The buffer is treated as const, but not specified as such by MPI_Send's signature
    char* send_buf = const_cast<char*>(send_msg.data());
    MPI_Send(send_buf, string_length, MPI_BYTE, destinationProcess, tag, PetscTools::GetWorld());
}

template<typename CLASS>
void ObjectCommunicator<CLASS>::ISendObject(boost::shared_ptr<CLASS> const pObject, unsigned destinationProcess, unsigned tag)
{
    MPI_Request request;

     // Create an output archive
    std::ostringstream ss(std::ios::binary);
    boost::archive::binary_oarchive output_arch(ss);

    output_arch << pObject;

    mSendString[destinationProcess] = ss.str();
    mSendBufferLength = mSendString[destinationProcess].size();

    // Make sure we are not going to overrun the asynchronous buffer size.
    assert(mSendBufferLength < MAX_BUFFER_SIZE);

    // Send archive data
    // The buffer is treated as const, but not specified as such by MPI_Send's signature
    mSendBuffer[destinationProcess] = const_cast<char*>(mSendString[destinationProcess].data());
    MPI_Isend(mSendBuffer[destinationProcess], mSendBufferLength, MPI_BYTE, destinationProcess, tag, PetscTools::GetWorld(), &request);
    MPI_Request_free(&request); //This is evil because it allows for another non-blocking send to overwrite the buffer
}

template<typename CLASS>
boost::shared_ptr<CLASS> ObjectCommunicator<CLASS>::RecvObject(unsigned sourceProcess, unsigned tag, MPI_Status& status)
{
    unsigned string_length = 0;
    MPI_Recv(&string_length, 1, MPI_UNSIGNED, sourceProcess, tag, PetscTools::GetWorld(), &status);

    char* recv_array = new char[string_length];
    MPI_Recv(recv_array, string_length, MPI_BYTE, sourceProcess , tag, PetscTools::GetWorld(), &status);

    // Extract a proper object from the buffer
    std::string recv_string(recv_array, string_length);
    delete[] recv_array;
    std::istringstream ss(recv_string, std::ios::binary);

    boost::shared_ptr<CLASS> p_recv_object(new CLASS);
    boost::archive::binary_iarchive input_arch(ss);

    input_arch >> p_recv_object;

    return p_recv_object;
}

template<typename CLASS>
void ObjectCommunicator<CLASS>::IRecvObject(unsigned sourceProcess, unsigned tag)
{
    assert(!mIsWriting);    // Make sure the buffers are not already being used by a previous call to IRecvObject.

    mIsWriting = true;

    mRecvBuffer = new char[MAX_BUFFER_SIZE];
    MPI_Irecv(mRecvBuffer, MAX_BUFFER_SIZE, MPI_BYTE, sourceProcess, tag, PetscTools::GetWorld(), &mMpiRequest);
}

template<typename CLASS>
boost::shared_ptr<CLASS> ObjectCommunicator<CLASS>::GetRecvObject()
{
    if (!mIsWriting)
    {
        EXCEPTION("No object to receive in ObjectCommunicator::GetRecvObject");
    }

    MPI_Status return_status;

    MPI_Wait(&mMpiRequest, &return_status);

    int recv_size;
    MPI_Get_count(&return_status, MPI_BYTE, &recv_size);

    // Extract a proper object from the buffer
    std::string recv_string(mRecvBuffer, recv_size);
    std::istringstream ss(recv_string, std::ios::binary);

    boost::shared_ptr<CLASS> p_recv_object(new CLASS);
    boost::archive::binary_iarchive input_arch(ss);

    input_arch >> p_recv_object;

    // Tidy up
    delete[] mRecvBuffer;

    mIsWriting = false;

    return p_recv_object;
}

template<typename CLASS>
boost::shared_ptr<CLASS> ObjectCommunicator<CLASS>::SendRecvObject(boost::shared_ptr<CLASS> const pSendObject, unsigned destinationProcess, unsigned sendTag, unsigned sourceProcess, unsigned sourceTag, MPI_Status& status)
{
    // Create an output archive
    std::ostringstream oss(std::ios::binary);
    boost::archive::binary_oarchive output_arch(oss);

    output_arch << pSendObject;

    std::string send_msg = oss.str();

    // Get + send string length
    unsigned send_string_length = send_msg.size();
    unsigned recv_string_length;

    MPI_Sendrecv(&send_string_length, 1, MPI_UNSIGNED, destinationProcess, sendTag, &recv_string_length, 1, MPI_UNSIGNED, sourceProcess, sourceTag, PetscTools::GetWorld(), &status);

    boost::scoped_array<char> recv_array(new char[recv_string_length]);

    // Send archive data
    char* send_buf = const_cast<char*>(send_msg.data());
    MPI_Sendrecv(send_buf, send_string_length, MPI_BYTE, destinationProcess, sendTag, recv_array.get(), recv_string_length, MPI_BYTE, sourceProcess, sourceTag, PetscTools::GetWorld(), &status);

    // Extract received object
    std::string recv_string(recv_array.get(), recv_string_length);
    std::istringstream iss(recv_string, std::ios::binary);

    boost::shared_ptr<CLASS> p_recv_object(new CLASS);
    boost::archive::binary_iarchive input_arch(iss);

    input_arch >> p_recv_object;

    return p_recv_object;
}

#endif // _OBJECTCOMMUNICATOR_HPP_