Created by: typhoonzero

If there are too many parameter servers or too many parameter server ports(or sparse ports), some parameter servers will wait forever.

When parameter start up, ti says:

W0522 12:00:09.495564 35864 ParameterServer2.cpp:269] --ports_num or --ports_num_for_sparse might be too large, or total dense parameter size or sparse parameters size might be too small, this psever doesn't store any parameter.

In ParameterServer2.cpp:

void ParameterServer2::setParameter(const SendParameterRequest& request,
                                    std::vector<Buffer>& inputBuffers,
                                    SendParameterResponse* response,
                                    std::vector<Buffer>* outputBuffers) {
...
if (!request.blocks().size()) {
    LOG(WARNING)
        << "--ports_num or --ports_num_for_sparse might be too large, "
        << "or total dense parameter size or sparse parameters size "
        << "might be too small, this psever doesn't store any parameter.";
    return;
  }

...


void ParameterServer2::addGradient(const SendParameterRequest& request,
                                   std::vector<Buffer>& inputBuffers,
                                   SendParameterResponse* response,
                                   std::vector<Buffer>* outputBuffers) {

if (!numPassFinishClients_) {
    REGISTER_BARRIER_DELTA_SERVER_SET(
        *statSet_,
        "forwardbackwardDelta",
        FLAGS_num_gradient_servers,
        request.trainer_id(),
        request.forwardbackward_time(),
        isSparseServer_ ? "_sparseUpdater" : "_denseUpdater");
  }

It seems that the hanging problem is due to some other reason. But I still need to figure out the details when parameter block is more than pserver instances