comm_mpi_smart.h

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/*****************************************************************************
* Multiscale Universal Interface Code Coupling Library                       *
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* Copyright (C) 2019 Y. H. Tang, S. Kudo, X. Bian, Z. Li, G. E. Karniadakis  *
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#ifndef COMM_MPI_SMART_H
#define COMM_MPI_SMART_H
 
#include <cstdint>
#include <cstdlib>
#include "../general/util.h"
#include "comm.h"
#include "comm_mpi.h"
#include "comm_factory.h"
#include "message/message.h"
#include "../storage/stream.h"
 
namespace mui {
 
class comm_mpi_smart : public comm_mpi {
private:
    std::list<std::pair<MPI_Request,std::shared_ptr<std::vector<char> > > > send_buf;
 
public:
    comm_mpi_smart( const char URI[], const bool quiet, MPI_Comm world = MPI_COMM_WORLD ) : comm_mpi(URI, quiet, world) {}
    virtual ~comm_mpi_smart() {
        // Call blocking MPI_Test on any remaining MPI_Isend messages in buffer and if complete, pop before destruction or warn
        test_completion_blocking();
    }
 
private:
    void send_impl_( message msg, const std::vector<bool> &is_sending ) {
      auto bytes = std::vector<char>(msg.detach());
 
        if(bytes.size() > INT_MAX) {
            std::cerr << "MUI Error [comm_mpi_smart.h]: Trying to send more data than is possible with MPI_Isend." << std::endl
                    << "This is likely because there is too much data per MPI rank." << std::endl
                    << "The program will now abort. Try increasing the number of MPI ranks." << std::endl;
            std::abort();
        }
 
        for( int i = 0; i < remote_size_; i++ ) {
            if( is_sending[i] ) {
                send_buf.emplace_back(MPI_Request(), std::make_shared<std::vector<char> >(bytes));
                MPI_Isend(send_buf.back().second->data(), send_buf.back().second->size(), MPI_BYTE, i, 0,
                          domain_remote_, &(send_buf.back().first));
            }
        }
 
        // Call non-blocking MPI_Test on outstanding MPI_Isend messages in buffer and if complete, pop
        test_completion();
    }
 
    message recv_impl_() {
        // Catch any unsent MPI_Isend calls, non-blocking
        test_completion();
 
        MPI_Status status;
        MPI_Probe(MPI_ANY_SOURCE, 0, domain_remote_, &status);
        int count;
        MPI_Get_count(&status, MPI_BYTE, &count);
        std::vector<char> rcv_buf(count);
        MPI_Recv( rcv_buf.data(), count, MPI_BYTE, status.MPI_SOURCE, status.MPI_TAG, domain_remote_, MPI_STATUS_IGNORE );
 
        // Catch any unsent MPI_Isend calls, non-blocking
        test_completion();
 
        return message::make(std::move(rcv_buf));
    }
 
    void test_completion() {
      for( auto itr=send_buf.begin(), end=send_buf.end(); itr != end; ) {
            int test = false;
            MPI_Test(&(itr->first), &test, MPI_STATUS_IGNORE);
            if( test ) itr = send_buf.erase(itr);
            else ++itr;
        }
    }
 
    void test_completion_blocking() {
      while (send_buf.size() > 0) {
            for( auto itr=send_buf.begin(), end=send_buf.end(); itr != end; ) {
                MPI_Wait(&(itr->first), MPI_STATUS_IGNORE);
                itr = send_buf.erase(itr);
            }
        }
    }
};
 
inline communicator *create_comm_mpi_smart( const char URI[], const bool quiet ) {
    return new comm_mpi_smart(URI, quiet);
}
 
const static bool registered = comm_factory::instance().link( "mpi", create_comm_mpi_smart );
 
}
#endif