fix 1gpu test=develop

paddle/fluid/framework/details/all_reduce_op_handle.cc

@@ -51,7 +51,8 @@ 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.
+  // All-reduce op_handle can run on the sub-scope, find the nccl id from
+  // the global scope.
   if (NoDummyInputSize() == 1 &&
       local_scopes_[0]->FindVar(NCCL_ID_VARNAME) == nullptr) {
 #else

paddle/fluid/framework/details/parallel_ssa_graph_executor.cc

@@ -59,7 +59,7 @@ FeedFetchList ParallelSSAGraphExecutor::Run(
     if (pool_) {
       run_futures.emplace_back(pool_->enqueue(std::move(call)));
     } else {
-      call();
+      fetch_datas.emplace_back(std::move(call()));
     }
   }
 

paddle/fluid/framework/parallel_executor.cc

@@ -231,7 +231,7 @@ ParallelExecutor::ParallelExecutor(
 #if defined(PADDLE_WITH_CUDA) && !defined(_WIN32)
     auto *nccl_id_var = scope->FindVar(NCCL_ID_VARNAME);
     ncclUniqueId *nccl_id = nullptr;
-    if (build_strategy.enable_parallel_graph_) {
+    if (build_strategy.enable_parallel_graph_ && places.size() > 1) {
       // parallel graph mode should initialize nccl by ncclCommInitRank since
       // it call nccl operator per device per thread.
       if (nccl_id_var == nullptr) {