delete unused code test=develop

paddle/fluid/framework/details/all_reduce_op_handle.cc

@@ -51,6 +51,7 @@ void AllReduceOpHandle::RunImpl() {
 // FIXME(typhoonzero): If scope0(global scope) have NCCL_ID_VAR,
 // this is a distributed or inter-process call, find a better way.
 #ifdef PADDLE_WITH_CUDA
+  // Find NCCL ID from the global scope.
   if (NoDummyInputSize() == 1 &&
       local_scopes_[0]->FindVar(NCCL_ID_VARNAME) == nullptr) {
 #else

paddle/fluid/framework/details/multi_devices_graph_pass.cc

@@ -134,7 +134,6 @@ static const char kParams[] = "params";
 static const char kLocalScopes[] = "local_scopes";
 static const char kStrategy[] = "strategy";
 static const char kNumTrainers[] = "num_trainers";
-static const char kNumLossScaled[] = "num_loss_scaled";
 
 void MultiDevSSAGraphBuilder::Init() const {
   all_vars_.clear();