diff --git a/paddle/fluid/framework/details/ssa_graph.h b/paddle/fluid/framework/details/ssa_graph.h
index c1e041b8c0b4a894c152ce1ff6e8efe6b7056311..ac3e2d86993aee31b79f4481c4d5a47cd9cdf5b4 100644
--- a/paddle/fluid/framework/details/ssa_graph.h
+++ b/paddle/fluid/framework/details/ssa_graph.h
@@ -25,6 +25,7 @@ namespace details {
 
 struct SSAGraph {
   std::vector<std::unordered_map<std::string, std::map<int, VarHandle>>> vars_;
+  // aux variables to represent dependency. Useful to resolve data hazard.
   std::unordered_set<std::unique_ptr<VarHandleBase>> dep_vars_;
   std::vector<std::unique_ptr<OpHandleBase>> ops_;
 };
diff --git a/paddle/fluid/framework/details/threaded_ssa_graph_executor.cc b/paddle/fluid/framework/details/threaded_ssa_graph_executor.cc
index 2603aed62ac458a41e700669e3f5f1ae1877613f..3f8655147b688239509dea98925df310a46cbef8 100644
--- a/paddle/fluid/framework/details/threaded_ssa_graph_executor.cc
+++ b/paddle/fluid/framework/details/threaded_ssa_graph_executor.cc
@@ -15,7 +15,6 @@
 #include "paddle/fluid/framework/details/threaded_ssa_graph_executor.h"
 
 #include "paddle/fluid/framework/details/fetch_op_handle.h"
-#include "paddle/fluid/framework/scope.h"
 
 namespace paddle {
 namespace framework {