/*!
Discover the receives inspecting the sends that the user has already set.
\param discoverTag is the tag to be used for the communications needed
to discover the receives
*/
void DataCommunicator::discoverRecvs(int discoverTag)
{
// Cancel current receives
clearAllRecvs();
// Send the size of the messages that will be send
for (auto &entry : m_sendIds) {
int rank = entry.first;
SendBuffer &buffer = getSendBuffer(rank);
long dataSize = buffer.capacity();
MPI_Request dataSizeRequest;
MPI_Isend(&dataSize, 1, MPI_LONG, rank, discoverTag, m_communicator, &dataSizeRequest);
// MPI_Isend initiates an asynchronous (background) data transfer.
// The actual data transfer might not happen unless one of the
// MPI_Wait* or MPI_Test* calls has been made on the request.
int completeFlag;
MPI_Test(&dataSizeRequest, &completeFlag, MPI_STATUS_IGNORE);
}
// Raise a barrier to make sure that all the sends starts
MPI_Barrier(m_communicator);
// Receive the data size of the sends
std::unordered_map<int, long> dataSizes;
while (true) {
// Probe for messages
int messageAvailable;
MPI_Status status;
MPI_Iprobe(MPI_ANY_SOURCE, discoverTag, m_communicator, &messageAvailable, &status);
if (!messageAvailable) {
break;
}
// Receive the data size that will be received from the source
long dataSize;
MPI_Recv(&dataSize, 1, MPI_LONG, status.MPI_SOURCE, discoverTag, m_communicator, MPI_STATUS_IGNORE);
dataSizes[status.MPI_SOURCE] = dataSize;
}
// Wait that all processors correctly receive the data to communicate.
//
// Without the barrier some processors may start the receives while other
// are still waiting to receive the data sizes. Since the probe for the
// data size will accept message for all sources, if a processor start
// receiveing data it will intefere with the other processors still
// receiving the data sizes.
if (discoverTag == m_tag) {
MPI_Barrier(m_communicator);
}
// Set the receives
for (auto &entry : dataSizes) {
setRecv(entry.first, entry.second);
}
}
void sendMsg(unsigned id, F f, O o, Message msg)
{
if (hasConnection(id)) {
PtrBuffer buffer = getSendBuffer(id);
ostream os(&(*buffer));
os << msg.serialize() << '\0';
async_write(*getSocket(id), *buffer,
bind(&ConnectionList::_sendMsg<F, O>, this, id, f, o, msg, _1, _2));
}
}
