Merge pull request #13347 from Yancey1989/fix_reduce_bast

fix bcast in reduce strategy

paddle/fluid/framework/details/multi_devices_graph_pass.cc

@@ -442,8 +442,7 @@ std::unique_ptr<ir::Graph> MultiDevSSAGraphBuilder::ApplyImpl(
   use_gpu = nccl_ctxs_ != nullptr;
 #endif
 
-  if (use_gpu ||
-      strategy_.reduce_ == BuildStrategy::ReduceStrategy::kAllReduce) {
+  if (use_gpu && strategy_.reduce_ == BuildStrategy::ReduceStrategy::kReduce) {
     // Insert BCast Ops
     for (size_t dev_id = 0; dev_id < bcast_var_name_set.size(); ++dev_id) {
       auto &to_bcast_set = bcast_var_name_set[dev_id];