Polish `Scope::LocalVarNames`

Cannot get var name recursive since they could be same.

paddle/framework/scope.cc

@@ -74,17 +74,9 @@ void Scope::DropKids() {
   kids_.clear();
 }
 
-std::vector<std::string> Scope::GetAllNames(bool recursive) const {
-  std::vector<std::string> known_vars(vars_.size());
-
-  if (recursive) {
-    for (auto& kid : kids_) {
-      auto kid_vars = kid->GetAllNames();
-      for (auto& p : kid_vars) {
-        known_vars.emplace_back(p);
-      }
-    }
-  }
+std::vector<std::string> Scope::LocalVarNames() const {
+  std::vector<std::string> known_vars;
+  known_vars.reserve(this->vars_.size());
   for (auto& p : vars_) {
     known_vars.emplace_back(p.first);
   }

paddle/framework/scope.h

@@ -66,7 +66,7 @@ class Scope {
   void DropKids();
 
   // enumerate all the variables current contains.
-  std::vector<std::string> GetAllNames(bool recursive = false) const;
+  std::vector<std::string> LocalVarNames() const;
 
   // Rename variable to a new name
   void Rename(const std::string& origin_name,

paddle/framework/scope_test.cc

@@ -61,7 +61,7 @@ TEST(Scope, GetAllNames) {
   Variable* v = s.Var("a");
   EXPECT_EQ(&s, s.FindScope(v));
 
-  std::vector<std::string> ans = s.GetAllNames();
+  std::vector<std::string> ans = s.LocalVarNames();
   std::string str;
   for (auto& var : ans) {
     str += var;

paddle/operators/recurrent_op.cc

@@ -491,7 +491,7 @@ class RecurrentGradOp : public RecurrentBase {
 
   std::unordered_set<std::string> LocalVarNames(
       const framework::Scope &scope) const {
-    return this->List2Set(scope.GetAllNames(false));
+    return this->List2Set(scope.LocalVarNames());
   }
   static std::vector<std::string> GradVarLists(
       const std::vector<std::string> &var_names) {