From 5d134a03f1788bab1ee01904aa54382a46e25551 Mon Sep 17 00:00:00 2001
From: Yu Yang <yuyang18@baidu.com>
Date: Tue, 1 Aug 2017 15:04:43 +0800
Subject: [PATCH] Refine remove std::shared_ptr in Scope

* Make interface of Operator to `const Scope&`
---
 paddle/framework/net.h                        |  4 +-
 paddle/framework/net_op_test.cc               |  7 +-
 paddle/framework/op_registry_test.cc          | 14 +--
 paddle/framework/operator.h                   | 28 +++---
 paddle/framework/operator_test.cc             | 24 ++---
 paddle/framework/scope.cc                     | 10 +-
 paddle/framework/scope.h                      | 37 +++++---
 paddle/framework/variable.h                   |  4 +-
 paddle/operators/recurrent_network_op.cc      | 72 +++++++-------
 paddle/operators/recurrent_network_op.h       | 42 ++++-----
 paddle/operators/recurrent_network_op_test.cc | 93 ++++++++++---------
 paddle/platform/enforce.h                     | 12 +--
 paddle/pybind/pybind.cc                       | 17 +++-
 .../v2/framework/default_scope_funcs.py       | 19 ++--
 python/paddle/v2/framework/network.py         | 19 ++--
 .../paddle/v2/framework/tests/op_test_util.py |  8 +-
 .../tests/test_default_scope_funcs.py         | 10 +-
 .../paddle/v2/framework/tests/test_fc_op.py   | 12 +--
 .../paddle/v2/framework/tests/test_scope.py   | 22 ++---
 .../paddle/v2/framework/tests/test_tensor.py  |  8 +-
 20 files changed, 239 insertions(+), 223 deletions(-)

diff --git a/paddle/framework/net.h b/paddle/framework/net.h
index 089c1355951..fc98080b178 100644
--- a/paddle/framework/net.h
+++ b/paddle/framework/net.h
@@ -43,7 +43,7 @@ class NetOp : public OperatorBase {
    * Infer all the operators' input and output variables' shapes, will be called
    * before every mini-batch
    */
-  void InferShape(const std::shared_ptr<Scope>& scope) const override {
+  void InferShape(const Scope& scope) const override {
     for (auto& op : ops_) {
       op->InferShape(scope);
     }
@@ -56,7 +56,7 @@ class NetOp : public OperatorBase {
    * scope will be used instead. If no OpContext is provicded, default context
    * will be used.
    */
-  void Run(const std::shared_ptr<Scope>& scope,
+  void Run(const Scope& scope,
            const platform::DeviceContext& dev_ctx) const override {
     for (auto& op : ops_) {
       op->Run(scope, dev_ctx);
diff --git a/paddle/framework/net_op_test.cc b/paddle/framework/net_op_test.cc
index 8048311fe54..3392b033c50 100644
--- a/paddle/framework/net_op_test.cc
+++ b/paddle/framework/net_op_test.cc
@@ -16,11 +16,10 @@ static int run_cnt = 0;
 
 class TestOp : public OperatorBase {
  public:
-  void InferShape(
-      const std::shared_ptr<framework::Scope>& scope) const override {
+  void InferShape(const framework::Scope& scope) const override {
     ++infer_shape_cnt;
   }
-  void Run(const std::shared_ptr<framework::Scope>& scope,
+  void Run(const framework::Scope& scope,
            const paddle::platform::DeviceContext& dev_ctx) const override {
     ++run_cnt;
   }
@@ -62,7 +61,7 @@ TEST(OpKernel, all) {
   ASSERT_EQ(1UL, tmp_idx.size());
   ASSERT_EQ("y", net->outputs_[tmp_idx[0]]);
 
-  auto scope = std::make_shared<Scope>();
+  Scope scope;
   platform::CPUDeviceContext dev_ctx;
 
   net->InferShape(scope);
diff --git a/paddle/framework/op_registry_test.cc b/paddle/framework/op_registry_test.cc
index 2ef781bf867..d8ae3d07227 100644
--- a/paddle/framework/op_registry_test.cc
+++ b/paddle/framework/op_registry_test.cc
@@ -7,9 +7,9 @@ namespace paddle {
 namespace framework {
 class CosineOp : public OperatorBase {
  public:
-  void Run(const std::shared_ptr<Scope>& scope,
+  void Run(const Scope& scope,
            const platform::DeviceContext& dev_ctx) const override {}
-  void InferShape(const std::shared_ptr<Scope>& scope) const override {}
+  void InferShape(const Scope& scope) const override {}
 };
 
 class CosineOpProtoAndCheckerMaker : public OpProtoAndCheckerMaker {
@@ -27,8 +27,8 @@ class CosineOpProtoAndCheckerMaker : public OpProtoAndCheckerMaker {
 
 class MyTestOp : public OperatorBase {
  public:
-  void InferShape(const std::shared_ptr<Scope>& scope) const override {}
-  void Run(const std::shared_ptr<Scope>& scope,
+  void InferShape(const Scope& scope) const override {}
+  void Run(const Scope& scope,
            const platform::DeviceContext& dev_ctx) const override {}
 };
 
@@ -69,7 +69,7 @@ TEST(OpRegistry, CreateOp) {
 
   std::shared_ptr<paddle::framework::OperatorBase> op =
       paddle::framework::OpRegistry::CreateOp(op_desc);
-  auto scope = std::make_shared<paddle::framework::Scope>();
+  paddle::framework::Scope scope;
   paddle::platform::CPUDeviceContext dev_ctx;
   op->Run(scope, dev_ctx);
   float scale_get = op->GetAttr<float>("scale");
@@ -111,7 +111,7 @@ TEST(OpRegistry, DefaultValue) {
 
   std::shared_ptr<paddle::framework::OperatorBase> op =
       paddle::framework::OpRegistry::CreateOp(op_desc);
-  auto scope = std::make_shared<paddle::framework::Scope>();
+  paddle::framework::Scope scope;
   paddle::platform::CPUDeviceContext dev_ctx;
   op->Run(scope, dev_ctx);
   ASSERT_EQ(op->GetAttr<float>("scale"), 1.0);
@@ -173,7 +173,7 @@ TEST(OpRegistry, CustomChecker) {
   SetInputFormat(&op_desc);
   auto op = paddle::framework::OpRegistry::CreateOp(op_desc);
   paddle::platform::CPUDeviceContext dev_ctx;
-  auto scope = std::make_shared<paddle::framework::Scope>();
+  paddle::framework::Scope scope;
   op->Run(scope, dev_ctx);
   int test_attr = op->GetAttr<int>("test_attr");
   ASSERT_EQ(test_attr, 4);
diff --git a/paddle/framework/operator.h b/paddle/framework/operator.h
index a78d91f1b9d..4912a5f290b 100644
--- a/paddle/framework/operator.h
+++ b/paddle/framework/operator.h
@@ -84,10 +84,10 @@ class OperatorBase {
 
   /// InferShape infer the size of Variables used by this Operator with
   /// information inside scope
-  virtual void InferShape(const std::shared_ptr<Scope>& scope) const = 0;
+  virtual void InferShape(const Scope& scope) const = 0;
 
   /// Net will call this function to Run an op.
-  virtual void Run(const std::shared_ptr<Scope>& scope,
+  virtual void Run(const Scope& scope,
                    const platform::DeviceContext& dev_ctx) const = 0;
 
   virtual bool IsNetOp() const { return false; }
@@ -114,24 +114,24 @@ class OperatorBase {
 
 class KernelContext {
  public:
-  KernelContext(const OperatorBase* op, const std::shared_ptr<Scope>& scope,
+  KernelContext(const OperatorBase* op, const Scope& scope,
                 const platform::DeviceContext& device_context)
       : op_(*op), scope_(scope), device_context_(device_context) {}
 
   const Variable* Input(int index) const {
-    return scope_->FindVar(op_.inputs_[index]);
+    return scope_.FindVar(op_.inputs_[index]);
   }
 
   Variable* Output(int index) const {
-    return scope_->FindVar(op_.outputs_[index]);
+    return scope_.FindVar(op_.outputs_[index]);
   }
 
   const Variable* Input(const std::string& name) const {
-    return scope_->FindVar(op_.Input(name));
+    return scope_.FindVar(op_.Input(name));
   }
 
   const Variable* Output(const std::string& name) const {
-    return scope_->FindVar(op_.Output(name));
+    return scope_.FindVar(op_.Output(name));
   }
 
   const std::vector<const Variable*> Inputs(const std::string& name) const {
@@ -139,7 +139,7 @@ class KernelContext {
     std::vector<const Variable*> res;
     std::transform(
         names.begin(), names.end(), res.begin(),
-        [this](const std::string& name) { return scope_->FindVar(name); });
+        [this](const std::string& name) { return scope_.FindVar(name); });
     return res;
   }
 
@@ -148,7 +148,7 @@ class KernelContext {
     std::vector<const Variable*> res;
     std::transform(
         names.begin(), names.end(), res.begin(),
-        [this](const std::string& name) { return scope_->FindVar(name); });
+        [this](const std::string& name) { return scope_.FindVar(name); });
     return res;
   }
 
@@ -160,7 +160,7 @@ class KernelContext {
   platform::Place GetPlace() const { return device_context_.GetPlace(); }
 
   const OperatorBase& op_;
-  const std::shared_ptr<Scope>& scope_;
+  const Scope& scope_;
   const platform::DeviceContext& device_context_;
 };
 
@@ -216,7 +216,7 @@ class OperatorWithKernel : public OperatorBase {
   using OpKernelMap =
       std::unordered_map<OpKernelKey, std::unique_ptr<OpKernel>, OpKernelHash>;
 
-  void Run(const std::shared_ptr<Scope>& scope,
+  void Run(const Scope& scope,
            const platform::DeviceContext& dev_ctx) const final {
     auto& opKernel = AllOpKernels().at(type_).at(OpKernelKey(dev_ctx));
     opKernel->Compute(KernelContext(this, scope, dev_ctx));
@@ -228,7 +228,7 @@ class OperatorWithKernel : public OperatorBase {
     return g_all_op_kernels;
   }
 
-  void InferShape(const std::shared_ptr<Scope>& scope) const final {
+  void InferShape(const Scope& scope) const final {
     std::vector<const Tensor*> ins;
     VarNamesToTensors(scope, inputs_, &ins);
     std::vector<Tensor*> outs;
@@ -238,13 +238,13 @@ class OperatorWithKernel : public OperatorBase {
 
  private:
   template <typename T>
-  void VarNamesToTensors(const std::shared_ptr<Scope>& scope,
+  void VarNamesToTensors(const Scope& scope,
                          const std::vector<std::string>& var_names,
                          std::vector<T>* container) const {
     container->reserve(var_names.size());
     VarToTensor<T> convert;
     for (auto& name : var_names) {
-      auto var = scope->FindVar(name);
+      auto var = scope.FindVar(name);
       if (var != nullptr) {
         container->push_back(convert(var));
       } else {
diff --git a/paddle/framework/operator_test.cc b/paddle/framework/operator_test.cc
index 2eeb2946fc4..1fcaf2d48d9 100644
--- a/paddle/framework/operator_test.cc
+++ b/paddle/framework/operator_test.cc
@@ -24,15 +24,15 @@ static int op_run_num = 0;
 class OpWithoutKernelTest : public OperatorBase {
  public:
   void Init() override { x = 1; }
-  void InferShape(const std::shared_ptr<Scope>& scope) const override {}
-  void Run(const std::shared_ptr<Scope>& scope,
+  void InferShape(const Scope& scope) const override {}
+  void Run(const Scope& scope,
            const platform::DeviceContext& dev_ctx) const override {
     op_run_num++;
     ASSERT_EQ((int)inputs_.size(), 1);
     ASSERT_EQ((int)outputs_.size(), 1);
-    ASSERT_EQ(scope->FindVar(inputs_[0]), nullptr);
+    ASSERT_EQ(scope.FindVar(inputs_[0]), nullptr);
     ASSERT_EQ(x, 1);
-    ASSERT_NE(scope->FindVar(outputs_[0]), nullptr);
+    ASSERT_NE(scope.FindVar(outputs_[0]), nullptr);
   }
 
  public:
@@ -68,10 +68,10 @@ TEST(OperatorBase, all) {
   attr->set_f(3.14);
 
   paddle::platform::CPUDeviceContext device_context;
-  auto scope = std::make_shared<paddle::framework::Scope>();
+  paddle::framework::Scope scope;
 
   auto op = paddle::framework::OpRegistry::CreateOp(op_desc);
-  scope->NewVar("OUT1");
+  scope.NewVar("OUT1");
   ASSERT_EQ(paddle::framework::op_run_num, 0);
   op->Run(scope, device_context);
   ASSERT_EQ(paddle::framework::op_run_num, 1);
@@ -117,12 +117,12 @@ class CPUKernelTest : public OpKernel {
 class OperatorMultiInputsTest : public OperatorBase {
  public:
   void Init() override { x = 1; }
-  void InferShape(const std::shared_ptr<Scope>& scope) const override {}
-  void Run(const std::shared_ptr<Scope>& scope,
+  void InferShape(const Scope& scope) const override {}
+  void Run(const Scope& scope,
            const platform::DeviceContext& dev_ctx) const override {
-    ASSERT_EQ(scope->FindVar(inputs_[0]), nullptr);
+    ASSERT_EQ(scope.FindVar(inputs_[0]), nullptr);
     ASSERT_EQ(x, 1);
-    ASSERT_NE(scope->FindVar(outputs_[0]), nullptr);
+    ASSERT_NE(scope.FindVar(outputs_[0]), nullptr);
     ASSERT_EQ(Input("x"), "IN1");
     ASSERT_EQ(Input("y"), "OUT1");
   }
@@ -186,7 +186,7 @@ TEST(OpKernel, all) {
   attr->set_f(3.14);
 
   paddle::platform::CPUDeviceContext cpu_device_context;
-  auto scope = std::make_shared<paddle::framework::Scope>();
+  paddle::framework::Scope scope;
 
   auto op = paddle::framework::OpRegistry::CreateOp(op_desc);
   ASSERT_EQ(paddle::framework::cpu_kernel_run_num, 0);
@@ -232,7 +232,7 @@ TEST(OpKernel, multi_inputs) {
   output_format->Add(2);  // y1
 
   paddle::platform::CPUDeviceContext cpu_device_context;
-  auto scope = std::make_shared<Scope>();
+  paddle::framework::Scope scope;
 
   auto op = paddle::framework::OpRegistry::CreateOp(op_desc);
   op->Run(scope, cpu_device_context);
diff --git a/paddle/framework/scope.cc b/paddle/framework/scope.cc
index 3c9ec92d720..080b4ac621c 100644
--- a/paddle/framework/scope.cc
+++ b/paddle/framework/scope.cc
@@ -19,11 +19,11 @@ namespace paddle {
 namespace framework {
 
 Scope::~Scope() {
+  DropKids();
   for (auto& kv : vars_) delete kv.second;
-  for (Scope* s : kids_) delete s;
 }
 
-Scope& Scope::NewScope() {
+Scope& Scope::NewScope() const {
   kids_.push_back(new Scope(this));
   return *kids_.back();
 }
@@ -49,7 +49,7 @@ Variable* Scope::FindVar(const std::string& name) const {
   return (parent_ == nullptr) ? nullptr : parent_->FindVar(name);
 }
 
-Scope* Scope::FindScope(const Variable* var) {
+const Scope* Scope::FindScope(const Variable* var) const {
   for (auto& kv : vars_) {
     if (kv.second == var) {
       return this;
@@ -57,6 +57,10 @@ Scope* Scope::FindScope(const Variable* var) {
   }
   return (parent_ == nullptr) ? nullptr : parent_->FindScope(var);
 }
+void Scope::DropKids() {
+  for (Scope* s : kids_) delete s;
+  kids_.clear();
+}
 
 }  // namespace framework
 }  // namespace paddle
diff --git a/paddle/framework/scope.h b/paddle/framework/scope.h
index 9b4fffb9a62..2ba3f8ed355 100644
--- a/paddle/framework/scope.h
+++ b/paddle/framework/scope.h
@@ -15,8 +15,8 @@ limitations under the License. */
 #pragma once
 
 #include <list>
-#include <map>
 #include <string>
+#include <unordered_map>
 
 #include "paddle/framework/variable.h"
 
@@ -38,30 +38,39 @@ class Scope {
   Scope() {}
   ~Scope();
 
-  // Create a sub-scope. Returns a reference other than a pointer so
-  // to prevent from manual deletion.
-  Scope& NewScope();
+  // Disable Copy, Assign, Move.
+  Scope(const Scope& other) = delete;
+  Scope& operator=(const Scope& other) = delete;
+  Scope(Scope&& other) = delete;
 
-  // Create a variable with given name if it doesn't exist.
+  /// Create a sub-scope. Returns a reference other than a pointer so
+  /// to prevent from manual deletion.
+  /// Mark it to const because that new kid scope cannot change parent scope.
+  Scope& NewScope() const;
+
+  /// Create a variable with given name if it doesn't exist.
   Variable* NewVar(const std::string& name);
 
-  // Create a variable with a scope-unique name.
+  /// Create a variable with a scope-unique name.
   Variable* NewVar();
 
-  // Find a variable in the scope or any of its ancestors.  Returns
-  // nullptr if cannot find.
+  /// Find a variable in the scope or any of its ancestors.  Returns
+  /// nullptr if cannot find.
   Variable* FindVar(const std::string& name) const;
 
-  // Find the scope or an ancestor scope that contains the given variable.
-  Scope* FindScope(const Variable* var);
+  /// Find the scope or an ancestor scope that contains the given variable.
+  const Scope* FindScope(const Variable* var) const;
+
+  /// Drop all kids scopes belonged to this scope.
+  void DropKids();
 
  private:
   // Call Scope::NewScope for a sub-scope.
-  explicit Scope(Scope* parent) : parent_(parent) {}
+  explicit Scope(Scope const* parent) : parent_(parent) {}
 
-  std::map<std::string, Variable*> vars_;
-  std::list<Scope*> kids_;
-  Scope* parent_{nullptr};
+  std::unordered_map<std::string, Variable*> vars_;
+  mutable std::list<Scope*> kids_;
+  Scope const* parent_{nullptr};
 };
 
 }  // namespace framework
diff --git a/paddle/framework/variable.h b/paddle/framework/variable.h
index 10a3866b850..38fc2720a30 100644
--- a/paddle/framework/variable.h
+++ b/paddle/framework/variable.h
@@ -16,7 +16,7 @@
 #include <typeindex>
 #include <typeinfo>
 
-#include "paddle/platform/assert.h"
+#include "paddle/platform/enforce.h"
 
 namespace paddle {
 namespace framework {
@@ -25,7 +25,7 @@ class Variable {
  public:
   template <typename T>
   const T& Get() const {
-    PADDLE_ASSERT(IsType<T>());
+    PADDLE_ENFORCE(IsType<T>(), "Variable must be type %s", typeid(T).name());
     return *static_cast<const T*>(holder_->Ptr());
   }
 
diff --git a/paddle/operators/recurrent_network_op.cc b/paddle/operators/recurrent_network_op.cc
index 71eef6a316a..224bb1432ac 100644
--- a/paddle/operators/recurrent_network_op.cc
+++ b/paddle/operators/recurrent_network_op.cc
@@ -27,7 +27,7 @@ namespace operators {
 
 namespace rnn {
 
-void SegmentInputs(std::vector<std::shared_ptr<Scope>>& step_scopes,
+void SegmentInputs(const std::vector<Scope*>& step_scopes,
                    const std::vector<Link>& inlinks,
                    const size_t seq_len) {
   PADDLE_ENFORCE(!inlinks.empty(), "no in links are provided.");
@@ -47,7 +47,7 @@ void SegmentInputs(std::vector<std::shared_ptr<Scope>>& step_scopes,
   }
 }
 
-void ConcatOutputs(std::vector<std::shared_ptr<Scope>>& step_scopes,
+void ConcatOutputs(const std::vector<Scope*>& step_scopes,
                    const std::vector<Link>& outlinks,
                    const size_t seq_len) {
   for (size_t i = 0; i < outlinks.size(); i++) {
@@ -75,7 +75,7 @@ void ConcatOutputs(std::vector<std::shared_ptr<Scope>>& step_scopes,
   }
 }
 
-void LinkMemories(std::vector<std::shared_ptr<Scope>>& scopes,
+void LinkMemories(const std::vector<Scope*>& scopes,
                   const std::vector<rnn::MemoryAttr>& memories,
                   size_t step_id,
                   int offset) {
@@ -92,8 +92,8 @@ void LinkMemories(std::vector<std::shared_ptr<Scope>>& scopes,
                  offset,
                  scopes.size(),
                  step_id);
-  std::shared_ptr<Scope> scope = scopes[step_id];
-  std::shared_ptr<Scope> linked_scope = scopes[step_id + offset];
+  auto scope = scopes[step_id];
+  auto linked_scope = scopes[step_id + offset];
   for (auto& attr : memories) {
     auto mem = scope->NewVar(attr.pre_var)->GetMutable<Tensor>();
     // maybe share variable is better?
@@ -169,8 +169,8 @@ void InitArgument(const ArgumentName& name,
 
 }  // namespace rnn
 
-void RecurrentAlgorithm::InferShape(const std::shared_ptr<Scope>& scope) const {
-  seq_len_ = scope->FindVar((arg_->inlinks[0]).external)
+void RecurrentAlgorithm::InferShape(const Scope& scope) const {
+  seq_len_ = scope.FindVar((arg_->inlinks[0]).external)
                  ->GetMutable<Tensor>()
                  ->dims()[0];
   CreateScopes(scope);
@@ -185,10 +185,10 @@ void RecurrentAlgorithm::InferShape(const std::shared_ptr<Scope>& scope) const {
 
   InitMemories(step_scopes[0]);
 
-  PADDLE_ENFORCE(scope->FindVar(arg_->step_net),
+  PADDLE_ENFORCE(scope.FindVar(arg_->step_net) != nullptr,
                  "stepnet [%s] is not in scope.",
                  arg_->step_net);
-  Variable* net = scope->FindVar(arg_->step_net);
+  Variable* net = scope.FindVar(arg_->step_net);
   PADDLE_ENFORCE(net != nullptr, "failed to get step net");
   // If the InferShape is called in OperatorBase's run function,
   // the rnn op only needs to do InferShape for the first time step
@@ -196,7 +196,7 @@ void RecurrentAlgorithm::InferShape(const std::shared_ptr<Scope>& scope) const {
     if (i > 0) {
       rnn::LinkMemories(step_scopes, arg_->memories, i, -1);
     }
-    net->GetMutable<NetOp>()->InferShape(step_scopes[i]);
+    net->GetMutable<NetOp>()->InferShape(*step_scopes[i]);
   }
 
   auto outlinks = arg_->outlinks;
@@ -214,51 +214,51 @@ void RecurrentAlgorithm::InferShape(const std::shared_ptr<Scope>& scope) const {
   }
 }
 
-void RecurrentAlgorithm::Run(const std::shared_ptr<Scope>& scope,
+void RecurrentAlgorithm::Run(const Scope& scope,
                              const platform::DeviceContext& dev_ctx) const {
   auto step_scopes = GetStepScopes(scope);
 
-  Variable* net = scope->FindVar(arg_->step_net);
+  Variable* net = scope.FindVar(arg_->step_net);
   for (size_t step_id = 0; step_id < seq_len_; step_id++) {
     // the link memory is done in InferShape
     // maybe remove following code after testing
     if (step_id > 0) {
       rnn::LinkMemories(step_scopes, arg_->memories, step_id, -1);
     }
-    net->GetMutable<NetOp>()->Run(step_scopes[step_id], dev_ctx);
+    net->GetMutable<NetOp>()->Run(*step_scopes[step_id], dev_ctx);
   }
 
   rnn::ConcatOutputs(step_scopes, arg_->outlinks, seq_len_);
 }
 
-void RecurrentAlgorithm::CreateScopes(std::shared_ptr<Scope> scope) const {
+void RecurrentAlgorithm::CreateScopes(const Scope& scope) const {
   // TODO(xxx) Only two scopes are needed for inference, this case will be
   // supported later.
-  auto step_scopes = scope->FindVar(arg_->step_scopes)
-                         ->GetMutable<std::vector<std::shared_ptr<Scope>>>();
+  auto step_scopes =
+      scope.FindVar(arg_->step_scopes)->GetMutable<std::vector<Scope*>>();
 
   if (seq_len_ > step_scopes->size()) {
     for (size_t i = step_scopes->size(); i < seq_len_; ++i) {
-      std::shared_ptr<Scope> step_scope = std::make_shared<Scope>(scope);
+      auto& step_scope = scope.NewScope();
 
       // Now all variables in scope must be created outside of op.
-      auto net_op = scope->FindVar(arg_->step_net)->GetMutable<NetOp>();
+      auto net_op = scope.FindVar(arg_->step_net)->GetMutable<NetOp>();
       for (auto& input : net_op->inputs_) {
-        step_scope->NewVar(input);
+        if (!step_scope.FindVar(input)) step_scope.NewVar(input);
       }
       for (auto& output : net_op->outputs_) {
-        step_scope->NewVar(output);
+        step_scope.NewVar(output);
       }
 
-      step_scopes->push_back(std::make_shared<Scope>(step_scope));
+      step_scopes->emplace_back(&step_scope);
     }
   }
 }
 
-void RecurrentAlgorithm::InitMemories(std::shared_ptr<Scope> step_scope) const {
+void RecurrentAlgorithm::InitMemories(Scope* step_scope) const {
   for (auto& attr : arg_->memories) {
     Tensor* pre_mem = step_scope->NewVar(attr.pre_var)->GetMutable<Tensor>();
-    PADDLE_ENFORCE(step_scope->FindVar(attr.boot_var),
+    PADDLE_ENFORCE(step_scope->FindVar(attr.boot_var) != nullptr,
                    "memory [%s]'s boot variable [%s] not exists",
                    attr.var,
                    attr.boot_var);
@@ -328,30 +328,30 @@ public:
 };
 
 void RecurrentGradientAlgorithm::Run(
-    const std::shared_ptr<Scope>& scope,
-    const platform::DeviceContext& dev_ctx) const {
+    const Scope& scope, const platform::DeviceContext& dev_ctx) const {
   auto step_scopes = GetStepScopes(scope);
   rnn::SegmentInputs(step_scopes, arg_->inlinks, seq_len_);
-  PADDLE_ENFORCE(scope->FindVar(arg_->step_net), "step net is not in scope.");
-  Variable* net = scope->FindVar(arg_->step_net);
+  PADDLE_ENFORCE(scope.FindVar(arg_->step_net) != nullptr,
+                 "step net is not in scope.");
+  Variable* net = scope.FindVar(arg_->step_net);
   PADDLE_ENFORCE(net != nullptr, "failed to get step net");
   for (int step_id = seq_len_ - 1; step_id >= 0; --step_id) {
     if (static_cast<size_t>(step_id) != seq_len_ - 1) {
       rnn::LinkMemories(step_scopes, arg_->memories, step_id, 1);
     }
-    net->GetMutable<NetOp>()->Run(step_scopes[step_id], dev_ctx);
+    net->GetMutable<NetOp>()->Run(*step_scopes[step_id], dev_ctx);
   }
   LinkBootMemoryGradients(step_scopes[0]);
   rnn::ConcatOutputs(step_scopes, arg_->outlinks, seq_len_);
 }
 
 void RecurrentGradientAlgorithm::LinkBootMemoryGradients(
-    std::shared_ptr<Scope> step_scope) const {
+    Scope* step_scope) const {
   for (auto& attr : arg_->memories) {
     Tensor* mem_grad = step_scope->NewVar(attr.var)->GetMutable<Tensor>();
     PADDLE_ENFORCE(mem_grad != nullptr,
                    "boot_tensor should be retrieved before");
-    PADDLE_ENFORCE(step_scope->FindVar(attr.boot_var),
+    PADDLE_ENFORCE(step_scope->FindVar(attr.boot_var) != nullptr,
                    "memory [%s]'s boot variable [%s] not exists",
                    attr.var,
                    attr.boot_var);
@@ -361,23 +361,23 @@ void RecurrentGradientAlgorithm::LinkBootMemoryGradients(
   }
 }
 
-void RecurrentGradientAlgorithm::InferShape(
-    const std::shared_ptr<Scope>& scope) const {
-  seq_len_ = scope->FindVar((arg_->inlinks[0]).external)
+void RecurrentGradientAlgorithm::InferShape(const Scope& scope) const {
+  seq_len_ = scope.FindVar((arg_->inlinks[0]).external)
                  ->GetMutable<Tensor>()
                  ->dims()[0];
   auto step_scopes = GetStepScopes(scope);
   rnn::SegmentInputs(step_scopes, arg_->inlinks, seq_len_);
 
-  PADDLE_ENFORCE(scope->FindVar(arg_->step_net), "step net is not in scope.");
-  Variable* net = scope->FindVar(arg_->step_net);
+  PADDLE_ENFORCE(scope.FindVar(arg_->step_net) != nullptr,
+                 "step net is not in scope.");
+  Variable* net = scope.FindVar(arg_->step_net);
   PADDLE_ENFORCE(net != nullptr, "failed to get step net");
 
   for (int step_id = seq_len_ - 1; step_id >= 0; --step_id) {
     if (static_cast<size_t>(step_id) != seq_len_ - 1) {
       rnn::LinkMemories(step_scopes, arg_->memories, step_id, 1);
     }
-    net->GetMutable<NetOp>()->InferShape(step_scopes[step_id]);
+    net->GetMutable<NetOp>()->InferShape(*step_scopes[step_id]);
   }
 
   auto outlinks = arg_->outlinks;
diff --git a/paddle/operators/recurrent_network_op.h b/paddle/operators/recurrent_network_op.h
index eabcc52f6b8..d57a1a2e51c 100644
--- a/paddle/operators/recurrent_network_op.h
+++ b/paddle/operators/recurrent_network_op.h
@@ -70,18 +70,18 @@ struct ArgumentName {
 /**
  * Prepare inputs for each step net.
  */
-void SegmentInputs(std::vector<std::shared_ptr<Scope>>& step_scopes,
+void SegmentInputs(const std::vector<Scope*>& step_scopes,
                    const std::vector<Link>& inlinks,
                    const size_t seq_len);
 
 /**
  * Process outputs of step nets and merge to variables.
  */
-void ConcatOutputs(std::vector<std::shared_ptr<Scope>>& step_scopes,
+void ConcatOutputs(const std::vector<Scope*>& step_scopes,
                    const std::vector<Link>& outlinks,
                    const size_t seq_len);
 
-void LinkMemories(std::vector<std::shared_ptr<Scope>>& step_scopes,
+void LinkMemories(const std::vector<Scope*>& step_scopes,
                   const std::vector<MemoryAttr>& memories,
                   size_t step_id,
                   int offset);
@@ -100,15 +100,14 @@ void InitArgument(const ArgumentName& name, Argument* arg);
 
 class RecurrentAlgorithm {
 public:
-  void Run(const std::shared_ptr<Scope>& scope,
-           const platform::DeviceContext& dev_ctx) const;
+  void Run(const Scope& scope, const platform::DeviceContext& dev_ctx) const;
 
   void Init(std::unique_ptr<rnn::Argument> arg) { arg_ = std::move(arg); }
 
   /**
    * InferShape must be called before Run.
    */
-  void InferShape(const std::shared_ptr<Scope>& scope) const;
+  void InferShape(const Scope& scope) const;
 
 protected:
   /*
@@ -117,15 +116,13 @@ protected:
    * NOTE the scopes are reused in both the forward and backward, so just
    * create once and expand its size if more steps need.
    */
-  void CreateScopes(std::shared_ptr<Scope> scope) const;
+  void CreateScopes(const Scope& scope) const;
 
-  inline const std::vector<std::shared_ptr<Scope>>& GetStepScopes(
-      std::shared_ptr<Scope> scope) const {
-    return *(scope->FindVar(arg_->step_scopes))
-                ->GetMutable<std::vector<std::shared_ptr<Scope>>>();
+  const std::vector<Scope*>& GetStepScopes(const Scope& scope) const {
+    return *scope.FindVar(arg_->step_scopes)->GetMutable<std::vector<Scope*>>();
   }
 
-  void InitMemories(std::shared_ptr<Scope> step_scopes) const;
+  void InitMemories(Scope* step_scopes) const;
 
 private:
   std::unique_ptr<rnn::Argument> arg_;
@@ -146,21 +143,18 @@ class RecurrentGradientAlgorithm {
 public:
   void Init(std::unique_ptr<rnn::Argument> arg) { arg_ = std::move(arg); }
 
-  void Run(const std::shared_ptr<Scope>& scope,
-           const platform::DeviceContext& dev_ctx) const;
+  void Run(const Scope& scope, const platform::DeviceContext& dev_ctx) const;
 
-  void LinkBootMemoryGradients(std::shared_ptr<Scope> step_scopes) const;
+  void LinkBootMemoryGradients(Scope* step_scopes) const;
 
   /**
    * InferShape must be called before Run.
    */
-  void InferShape(const std::shared_ptr<Scope>& scope) const;
+  void InferShape(const Scope& scope) const;
 
 protected:
-  inline const std::vector<std::shared_ptr<Scope>>& GetStepScopes(
-      std::shared_ptr<Scope> scope) const {
-    return *(scope->FindVar(arg_->step_scopes))
-                ->GetMutable<std::vector<std::shared_ptr<Scope>>>();
+  inline const std::vector<Scope*>& GetStepScopes(const Scope& scope) const {
+    return *scope.FindVar(arg_->step_scopes)->GetMutable<std::vector<Scope*>>();
   }
 
 private:
@@ -175,11 +169,11 @@ public:
   /**
    * InferShape must be called before Run.
    */
-  virtual void InferShape(const std::shared_ptr<Scope>& scope) const override {
+  virtual void InferShape(const Scope& scope) const override {
     alg_.InferShape(scope);
   }
 
-  virtual void Run(const std::shared_ptr<Scope>& scope,
+  virtual void Run(const Scope& scope,
                    const platform::DeviceContext& dev_ctx) const override {
     alg_.Run(scope, dev_ctx);
   }
@@ -197,11 +191,11 @@ public:
   /**
    * InferShape must be called before Run.
    */
-  virtual void InferShape(const std::shared_ptr<Scope>& scope) const override {
+  virtual void InferShape(const Scope& scope) const override {
     alg_.InferShape(scope);
   }
 
-  virtual void Run(const std::shared_ptr<Scope>& scope,
+  virtual void Run(const Scope& scope,
                    const platform::DeviceContext& dev_ctx) const override {
     alg_.Run(scope, dev_ctx);
   }
diff --git a/paddle/operators/recurrent_network_op_test.cc b/paddle/operators/recurrent_network_op_test.cc
index b22cb40f286..b0e61fbee61 100644
--- a/paddle/operators/recurrent_network_op_test.cc
+++ b/paddle/operators/recurrent_network_op_test.cc
@@ -34,41 +34,40 @@ protected:
   virtual void TearDown() override {}
 
   void CreateGlobalVariables() {
-    scope_ = std::make_shared<Scope>();
     // create input, and init content
     LOG(INFO) << "create global variable x";
     for (auto inlink : std::vector<std::string>{"x", "x0", "x1", "h"}) {
-      Variable* x = scope_->NewVar(inlink);
+      Variable* x = scope_.NewVar(inlink);
       DDim dims = make_ddim(std::vector<int>{
           10 /*sent size*/, 20 /*batch size*/, 30 /*input dim*/});
       x->GetMutable<Tensor>()->mutable_data<float>(dims, platform::CPUPlace());
     }
     // create output alias just for test
     for (auto inlink : std::vector<std::string>{"h@alias"}) {
-      Variable* x = scope_->NewVar(inlink);
+      Variable* x = scope_.NewVar(inlink);
       DDim dims =
           make_ddim(std::vector<int>{20 /*batch size*/, 30 /*input dim*/});
       x->GetMutable<Tensor>()->mutable_data<float>(dims, platform::CPUPlace());
     }
 
     LOG(INFO) << "create global variable w";
-    Variable* w = scope_->NewVar("rnn/w");
+    Variable* w = scope_.NewVar("rnn/w");
     w->GetMutable<Tensor>()->mutable_data<float>(
         make_ddim(std::vector<int>{30, 30}), platform::CPUPlace());
 
     for (auto boot : std::vector<std::string>{"x_boot", "h_boot"}) {
       LOG(INFO) << "create global variable " << boot;
-      Variable* h_boot = scope_->NewVar(boot);
+      Variable* h_boot = scope_.NewVar(boot);
       h_boot->GetMutable<Tensor>()->mutable_data<float>(
           make_ddim(std::vector<int>{20 /*batch size*/, 30 /*input dim*/}),
           platform::CPUPlace());
     }
 
     LOG(INFO) << "create variable step_scopes";
-    scope_->NewVar("step_scopes");
+    scope_.NewVar("step_scopes");
 
     LOG(INFO) << "create variable h";
-    scope_->NewVar("h");
+    scope_.NewVar("h");
   }
 
   void CreateRNNOp() {
@@ -150,7 +149,7 @@ protected:
 
   void CreateStepNet() {
     LOG(INFO) << "create variable step_net";
-    Variable* var = scope_->NewVar("step_net");
+    Variable* var = scope_.NewVar("step_net");
     auto net = var->GetMutable<NetOp>();
     // rnn/s is net's input or output?
     net->inputs_ = {"rnn/h@pre", "rnn/w", "rnn/x"};
@@ -164,7 +163,7 @@ protected:
   }
 
   // father scope
-  std::shared_ptr<Scope> scope_;
+  Scope scope_;
   std::shared_ptr<OperatorBase> rnn_op_;
 };
 
@@ -191,66 +190,64 @@ protected:
   virtual void TearDown() override {}
 
   void CreateGlobalVariables() {
-    scope_ = std::make_shared<Scope>();
     // inputs: x
     LOG(INFO) << "create global variable x";
-    Variable* x = scope_->NewVar("x");
+    Variable* x = scope_.NewVar("x");
     DDim dims =
         make_ddim({10 /*sent size*/, 20 /*batch size*/, 30 /*input dim*/});
     x->GetMutable<Tensor>()->mutable_data<float>(dims, platform::CPUPlace());
     // inputs: h_boot
     LOG(INFO) << "create global variable h_boot";
-    Variable* h_boot = scope_->NewVar("h_boot");
+    Variable* h_boot = scope_.NewVar("h_boot");
     h_boot->GetMutable<Tensor>()->mutable_data<float>(
         make_ddim({20 /*batch size*/, 30 /*input dim*/}), platform::CPUPlace());
     // inputs: w
     LOG(INFO) << "create global variable w";
-    Variable* w = scope_->NewVar("rnn/w");
+    Variable* w = scope_.NewVar("rnn/w");
     w->GetMutable<Tensor>()->mutable_data<float>(make_ddim({30, 30}),
                                                  platform::CPUPlace());
     // inputs: h_grad
     LOG(INFO) << "create variable h_grad";
-    Variable* dh = scope_->NewVar("h_grad");
+    Variable* dh = scope_.NewVar("h_grad");
     dh->GetMutable<Tensor>()->mutable_data<float>(make_ddim({10, 20, 30}),
                                                   platform::CPUPlace());
     // inputs: step_scopes
     LOG(INFO) << "create variable step_scopes";
-    scope_->NewVar("step_scopes");
+    scope_.NewVar("step_scopes");
     // inputs: step_net
     LOG(INFO) << "create variable step_net";
-    scope_->NewVar("step_net");
+    scope_.NewVar("step_net");
     // outputs: w_grad
     LOG(INFO) << "create global variable w_grad";
-    scope_->NewVar("rnn/w_grad");
+    scope_.NewVar("rnn/w_grad");
     // outputs: x_grad
     LOG(INFO) << "create global variable x_grad";
-    scope_->NewVar("x_grad");
+    scope_.NewVar("x_grad");
     // outputs: h_boot_grad
     LOG(INFO) << "create global variable h_boot_grad";
-    scope_->NewVar("h_boot_grad");
+    scope_.NewVar("h_boot_grad");
   }
 
   void CreateStepScopes() {
-    std::vector<std::shared_ptr<Scope>>* step_scopes =
-        scope_->FindVar("step_scopes")
-            ->GetMutable<std::vector<std::shared_ptr<Scope>>>();
+    auto step_scopes =
+        scope_.FindVar("step_scopes")->GetMutable<std::vector<Scope*>>();
     for (int i = 0; i < 10; ++i) {
-      auto scope = std::make_shared<Scope>(scope_);
-      auto pre_t = scope->NewVar("rnn/pre_h")->GetMutable<Tensor>();
-      pre_t->mutable_data<float>(make_ddim({20, 30}), platform::CPUPlace());
-      auto tensor = scope->NewVar("rnn/h")->GetMutable<Tensor>();
-      tensor->mutable_data<float>(make_ddim({20, 30}), platform::CPUPlace());
+      auto& scope = scope_.NewScope();
+      auto pre_t = scope.NewVar("rnn/pre_h")->GetMutable<Tensor>();
+      pre_t->mutable_data<float>({20, 30}, platform::CPUPlace());
+      auto tensor = scope.NewVar("rnn/h")->GetMutable<Tensor>();
+      tensor->mutable_data<float>({20, 30}, platform::CPUPlace());
 
       // for unit test of ConcatOutputs
-      auto xg = scope->NewVar("rnn/x_grad")->GetMutable<Tensor>();
-      xg->mutable_data<float>(make_ddim({20, 30}), platform::CPUPlace());
+      auto xg = scope.NewVar("rnn/x_grad")->GetMutable<Tensor>();
+      xg->mutable_data<float>({20, 30}, platform::CPUPlace());
 
-      step_scopes->push_back(scope);
+      step_scopes->emplace_back(&scope);
     }
 
     // last time step
     auto g = (*step_scopes)[9]->NewVar("rnn/h_pre_grad")->GetMutable<Tensor>();
-    g->mutable_data<float>(make_ddim({20, 30}), platform::CPUPlace());
+    g->mutable_data<float>({20, 30}, platform::CPUPlace());
   }
 
   void CreateRNNGradientAlgorithm() {
@@ -278,7 +275,7 @@ protected:
 
   void CreateStepNet() {
     LOG(INFO) << "create variable step_net";
-    Variable* var = scope_->NewVar("step_net");
+    Variable* var = scope_.NewVar("step_net");
     auto net = var->GetMutable<NetOp>();
     net->AddOp(OpRegistry::CreateOp("mul",
                                     {"rnn/h_pre", "rnn/w", "rnn/s_grad"},
@@ -298,9 +295,8 @@ protected:
     rnn::Link inlink;
     inlink.external = "x";
     inlink.internal = "rnn/x";
-    std::vector<std::shared_ptr<Scope>>* step_scopes =
-        scope_->FindVar("step_scopes")
-            ->GetMutable<std::vector<std::shared_ptr<Scope>>>();
+    auto step_scopes =
+        scope_.FindVar("step_scopes")->GetMutable<std::vector<Scope*>>();
     rnn::SegmentInputs(*step_scopes, std::vector<rnn::Link>{inlink}, 10);
   }
 
@@ -312,15 +308,14 @@ protected:
     mem_attr.boot_var = "boot_h";
     std::vector<rnn::MemoryAttr> memories;
     memories.push_back(mem_attr);
-    std::vector<std::shared_ptr<Scope>>* step_scopes =
-        scope_->FindVar("step_scopes")
-            ->GetMutable<std::vector<std::shared_ptr<Scope>>>();
+    auto step_scopes =
+        scope_.FindVar("step_scopes")->GetMutable<std::vector<Scope*>>();
     for (int i = 1; i < 10; ++i) {
       rnn::LinkMemories(*step_scopes, memories, i, -1);
     }
   }
 
-  std::shared_ptr<Scope> scope_;
+  Scope scope_;
   RecurrentGradientAlgorithm rnn_grad_algo_;
 };
 
@@ -339,14 +334,14 @@ TEST(RecurrentOp, LinkMemories) {
 
   // create and init step scopes
   int len = 10;
-  std::vector<std::shared_ptr<Scope>> step_scopes;
+  std::vector<Scope*> step_scopes;
   for (int i = 0; i < len; ++i) {
-    auto scope = std::make_shared<Scope>();
+    auto scope = new Scope();
     scope->NewVar("pre_h");
     auto tensor = scope->NewVar("h")->GetMutable<Tensor>();
-    float* data = tensor->mutable_data<float>(make_ddim({15, 20}), CPUPlace());
-    for (int i = 0; i < 15 * 20; ++i) {
-      data[i] = rand() * (1. / (double)RAND_MAX);
+    float* data = tensor->mutable_data<float>({15, 20}, CPUPlace());
+    for (int j = 0; j < 15 * 20; ++j) {
+      data[j] = rand() * (1. / (double)RAND_MAX);
     }
     step_scopes.push_back(scope);
   }
@@ -388,7 +383,17 @@ TEST(RecurrentOp, LinkMemories) {
       ASSERT_FLOAT_EQ(a[i], b[i]);
     }
   }
+
+  for (auto s : step_scopes) {
+    delete s;
+  }
 }
 
 USE_OP(add_two);
 USE_OP(mul);
+
+// int main() {
+//  //! TODO(yuyang18): Temporary disable this unit-test because implementation
+//  //! error.
+//  return 0;
+//}
\ No newline at end of file
diff --git a/paddle/platform/enforce.h b/paddle/platform/enforce.h
index 89a948e495e..ff69a0f8ab9 100644
--- a/paddle/platform/enforce.h
+++ b/paddle/platform/enforce.h
@@ -14,6 +14,7 @@ limitations under the License. */
 
 #pragma once
 
+#include <glog/logging.h>
 #include <paddle/string/printf.h>
 #include <sstream>
 #include <stdexcept>
@@ -127,17 +128,6 @@ inline typename std::enable_if<sizeof...(Args) != 0, void>::type throw_on_error(
 
 #endif  // PADDLE_ONLY_CPU
 
-template <typename T, typename... Args>
-inline typename std::enable_if<std::is_pointer<T>::value, void>::type
-throw_on_error(T stat, const Args&... args) {
-  if (stat == nullptr) {
-    return;
-  } else {
-    throw std::runtime_error("Pointer value is nullptr: " +
-                             string::Sprintf(args...));
-  }
-}
-
 template <typename T>
 inline void throw_on_error(T e) {
   throw_on_error(e, "");
diff --git a/paddle/pybind/pybind.cc b/paddle/pybind/pybind.cc
index eacec91cb29..ee5f675e251 100644
--- a/paddle/pybind/pybind.cc
+++ b/paddle/pybind/pybind.cc
@@ -102,11 +102,18 @@ All parameter, weight, gradient are variables in Paddle.
            },
            py::return_value_policy::reference);
 
-  py::class_<pd::Scope, std::shared_ptr<pd::Scope>>(m, "Scope")
-      .def(py::init<const std::shared_ptr<pd::Scope>&>())
-      .def("get_var", &pd::Scope::FindVar, py::return_value_policy::reference)
-      .def("create_var", &pd::Scope::NewVar, py::return_value_policy::reference)
-      .def("get_var_name", &pd::Scope::FindVarName);
+  py::class_<pd::Scope>(m, "Scope", "")
+      .def("new_var",
+           [](pd::Scope& self, const std::string& name) -> pd::Variable* {
+             return self.NewVar(name);
+           },
+           py::return_value_policy::reference)
+      .def("find_var", &pd::Scope::FindVar, py::return_value_policy::reference)
+      .def(py::init<>())
+      .def("new_scope",
+           [](pd::Scope& self) -> pd::Scope* { return &self.NewScope(); },
+           py::return_value_policy::reference)
+      .def("drop_kids", &pd::Scope::DropKids);
 
   //! @note: Be careful! PyBind will return std::string as an unicode, not
   //! Python str. If you want a str object, you should cast them in Python.
diff --git a/python/paddle/v2/framework/default_scope_funcs.py b/python/paddle/v2/framework/default_scope_funcs.py
index 4e772326c94..1b5580c8b30 100644
--- a/python/paddle/v2/framework/default_scope_funcs.py
+++ b/python/paddle/v2/framework/default_scope_funcs.py
@@ -5,7 +5,7 @@ Default scope function.
 thread-local stack of Scope. Top of that stack is current scope, the bottom 
 of that stack is all scopes' parent. 
 
-Invoking `create_var/get_var`  can `create/get` variable in current scope. 
+Invoking `new_var/find_var`  can `new/find` variable in current scope. 
 Invoking `enter_local_scope/leave_local_scope` can create or destroy local 
 scope. 
 
@@ -19,8 +19,8 @@ import threading
 __tl_scope__ = threading.local()
 
 __all__ = [
-    'get_cur_scope', 'enter_local_scope', 'leave_local_scope', 'create_var',
-    'get_var', 'scoped_function'
+    'get_cur_scope', 'enter_local_scope', 'leave_local_scope', 'new_var',
+    'find_var', 'scoped_function'
 ]
 
 
@@ -33,7 +33,7 @@ def get_cur_scope():
     if cur_scope_stack is None:
         __tl_scope__.cur_scope = list()
     if len(__tl_scope__.cur_scope) == 0:
-        __tl_scope__.cur_scope.append(paddle.v2.framework.core.Scope(None))
+        __tl_scope__.cur_scope.append(paddle.v2.framework.core.Scope())
     return __tl_scope__.cur_scope[-1]
 
 
@@ -42,7 +42,7 @@ def enter_local_scope():
     Enter a new local scope
     """
     cur_scope = get_cur_scope()
-    new_scope = paddle.v2.framework.core.Scope(cur_scope)
+    new_scope = cur_scope.new_scope()
     __tl_scope__.cur_scope.append(new_scope)
 
 
@@ -51,20 +51,21 @@ def leave_local_scope():
     Leave local scope
     """
     __tl_scope__.cur_scope.pop()
+    get_cur_scope().drop_kids()
 
 
-def create_var(name):
+def new_var(name):
     """
     create variable in current scope.
     """
-    return get_cur_scope().create_var(name)
+    return get_cur_scope().new_var(name)
 
 
-def get_var(name):
+def find_var(name):
     """
     get variable in current scope.
     """
-    return get_cur_scope().get_var(name)
+    return get_cur_scope().find_var(name)
 
 
 def scoped_function(func):
diff --git a/python/paddle/v2/framework/network.py b/python/paddle/v2/framework/network.py
index c85e87413ef..cfeb0e3dec0 100644
--- a/python/paddle/v2/framework/network.py
+++ b/python/paddle/v2/framework/network.py
@@ -1,6 +1,6 @@
 import paddle.v2.framework.core as core
 from paddle.v2.framework.create_op_creation_methods import op_creations
-from default_scope_funcs import create_var, get_var, get_cur_scope
+from default_scope_funcs import new_var, find_var, get_cur_scope
 
 __all__ = ['Network']  # Only expose Network
 
@@ -29,12 +29,15 @@ class NetworkFunctor(object):
             if ipt in kwargs:
                 var = kwargs[ipt]
                 if isinstance(var, basestring):
-                    var = create_var(var)
+                    tmp = new_var(var)
+                    self.net.var_names[tmp] = var
+                    var = tmp
+
                 if not isinstance(var, core.Variable):
                     raise TypeError(
                         "Input of op creation must be string or variable")
 
-                kwargs[ipt] = get_cur_scope().get_var_name(var)
+                kwargs[ipt] = self.net.var_names[var]
 
         notemp_outputs = self.func.all_not_temp_output_args
 
@@ -49,17 +52,20 @@ class NetworkFunctor(object):
             if opt in kwargs:
                 var = kwargs[opt]
                 if isinstance(var, basestring):
-                    var = create_var(var)
+                    tmp = new_var(var)
+                    self.net.var_names[tmp] = var
+                    var = tmp
+
                 if not isinstance(var, core.Variable):
                     raise TypeError(
                         "Output of op creation must be string or variable")
-                kwargs[opt] = get_cur_scope().get_var_name(var)
+                kwargs[opt] = self.net.var_names[var]
 
         op = self.func(**kwargs)
 
         self.net.net.add_op(op)
 
-        lst = [get_var(kwargs[opt]) for opt in notemp_outputs]
+        lst = [find_var(kwargs[opt]) for opt in notemp_outputs]
         if len(lst) == 1:
             return lst[0]
         elif len(lst) == 0:
@@ -89,6 +95,7 @@ class Network(object):
         self.net = core.Net.create()
         funcs = (func_name for func_name in dir(op_creations)
                  if not func_name.startswith("__"))
+        self.var_names = dict()
 
         # TODO(yuyang18): This code can work, but do not generate a good
         # docstring, try to give a better way generate function in runtime
diff --git a/python/paddle/v2/framework/tests/op_test_util.py b/python/paddle/v2/framework/tests/op_test_util.py
index 7b62313f8ac..99085c36722 100644
--- a/python/paddle/v2/framework/tests/op_test_util.py
+++ b/python/paddle/v2/framework/tests/op_test_util.py
@@ -24,13 +24,13 @@ class OpTestMeta(type):
             func = getattr(creation.op_creations, self.type, None)
             self.assertIsNotNone(func)
 
-            scope = core.Scope(None)
+            scope = core.Scope()
             kwargs = dict()
 
             for in_name in func.all_input_args:
                 if hasattr(self, in_name):
                     kwargs[in_name] = in_name
-                    var = scope.create_var(in_name).get_tensor()
+                    var = scope.new_var(in_name).get_tensor()
                     arr = getattr(self, in_name)
                     var.set_dims(arr.shape)
                     var.set(arr)
@@ -40,7 +40,7 @@ class OpTestMeta(type):
             for out_name in func.all_output_args:
                 if hasattr(self, out_name):
                     kwargs[out_name] = out_name
-                    scope.create_var(out_name).get_tensor()
+                    scope.new_var(out_name).get_tensor()
 
             for attr_name in func.all_attr_args:
                 if hasattr(self, attr_name):
@@ -54,7 +54,7 @@ class OpTestMeta(type):
             op.run(scope, ctx)
 
             for out_name in func.all_output_args:
-                actual = numpy.array(scope.get_var(out_name).get_tensor())
+                actual = numpy.array(scope.find_var(out_name).get_tensor())
                 expect = getattr(self, out_name)
                 # TODO(qijun) The default decimal is 7, but numpy.dot and eigen.mul
                 # has some diff, and could not pass unittest. So I set decimal 3 here.
diff --git a/python/paddle/v2/framework/tests/test_default_scope_funcs.py b/python/paddle/v2/framework/tests/test_default_scope_funcs.py
index 81033deb154..495863c4562 100644
--- a/python/paddle/v2/framework/tests/test_default_scope_funcs.py
+++ b/python/paddle/v2/framework/tests/test_default_scope_funcs.py
@@ -7,19 +7,19 @@ class TestDefaultScopeFuncs(unittest.TestCase):
         self.assertIsNotNone(get_cur_scope())
 
     def test_none_variable(self):
-        self.assertIsNone(get_var("test"))
+        self.assertIsNone(find_var("test"))
 
     def test_create_var_get_var(self):
-        var_a = create_var("var_a")
+        var_a = new_var("var_a")
         self.assertIsNotNone(var_a)
-        self.assertIsNotNone(get_cur_scope().get_var('var_a'))
+        self.assertIsNotNone(get_cur_scope().find_var('var_a'))
         enter_local_scope()
-        self.assertIsNotNone(get_cur_scope().get_var('var_a'))
+        self.assertIsNotNone(get_cur_scope().find_var('var_a'))
         leave_local_scope()
 
     def test_var_get_int(self):
         def __new_scope__():
-            i = create_var("var_i")
+            i = new_var("var_i")
             self.assertFalse(i.is_int())
             i.set_int(10)
             self.assertTrue(i.is_int())
diff --git a/python/paddle/v2/framework/tests/test_fc_op.py b/python/paddle/v2/framework/tests/test_fc_op.py
index 59e7e61249e..43931aac406 100644
--- a/python/paddle/v2/framework/tests/test_fc_op.py
+++ b/python/paddle/v2/framework/tests/test_fc_op.py
@@ -6,13 +6,13 @@ import paddle.v2.framework.create_op_creation_methods as creation
 
 class TestFc(unittest.TestCase):
     def test_fc(self):
-        scope = core.Scope(None)
-        x = scope.create_var("X")
+        scope = core.Scope()
+        x = scope.new_var("X")
         x_tensor = x.get_tensor()
         x_tensor.set_dims([1000, 784])
         x_tensor.alloc_float()
 
-        w = scope.create_var("W")
+        w = scope.new_var("W")
         w_tensor = w.get_tensor()
         w_tensor.set_dims([784, 100])
         w_tensor.alloc_float()
@@ -25,10 +25,10 @@ class TestFc(unittest.TestCase):
         op = creation.op_creations.fc(X="X", Y="Y", W="W")
 
         for out in op.outputs():
-            if scope.get_var(out) is None:
-                scope.create_var(out).get_tensor()
+            if scope.find_var(out) is None:
+                scope.new_var(out).get_tensor()
 
-        tensor = scope.get_var("Y").get_tensor()
+        tensor = scope.find_var("Y").get_tensor()
         op.infer_shape(scope)
         self.assertEqual([1000, 100], tensor.shape())
 
diff --git a/python/paddle/v2/framework/tests/test_scope.py b/python/paddle/v2/framework/tests/test_scope.py
index f0ee45cfc75..1ce9454067f 100644
--- a/python/paddle/v2/framework/tests/test_scope.py
+++ b/python/paddle/v2/framework/tests/test_scope.py
@@ -5,29 +5,29 @@ import unittest
 class TestScope(unittest.TestCase):
     def test_create_destroy(self):
         paddle_c = paddle.v2.framework.core
-        scope = paddle_c.Scope(None)
+        scope = paddle_c.Scope()
         self.assertIsNotNone(scope)
-        scope_with_parent = paddle_c.Scope(scope)
+        scope_with_parent = scope.new_scope()
         self.assertIsNotNone(scope_with_parent)
 
     def test_none_variable(self):
         paddle_c = paddle.v2.framework.core
-        scope = paddle_c.Scope(None)
-        self.assertIsNone(scope.get_var("test"))
+        scope = paddle_c.Scope()
+        self.assertIsNone(scope.find_var("test"))
 
     def test_create_var_get_var(self):
         paddle_c = paddle.v2.framework.core
-        scope = paddle_c.Scope(None)
-        var_a = scope.create_var("var_a")
+        scope = paddle_c.Scope()
+        var_a = scope.new_var("var_a")
         self.assertIsNotNone(var_a)
-        self.assertIsNotNone(scope.get_var('var_a'))
-        scope2 = paddle_c.Scope(scope)
-        self.assertIsNotNone(scope2.get_var('var_a'))
+        self.assertIsNotNone(scope.find_var('var_a'))
+        scope2 = scope.new_scope()
+        self.assertIsNotNone(scope2.find_var('var_a'))
 
     def test_var_get_int(self):
         paddle_c = paddle.v2.framework.core
-        scope = paddle_c.Scope(None)
-        var = scope.create_var("test_int")
+        scope = paddle_c.Scope()
+        var = scope.new_var("test_int")
         var.set_int(10)
         self.assertTrue(var.is_int())
         self.assertEqual(10, var.get_int())
diff --git a/python/paddle/v2/framework/tests/test_tensor.py b/python/paddle/v2/framework/tests/test_tensor.py
index b72aff3b9cd..6d59863cea2 100644
--- a/python/paddle/v2/framework/tests/test_tensor.py
+++ b/python/paddle/v2/framework/tests/test_tensor.py
@@ -5,8 +5,8 @@ import numpy
 
 class TestScope(unittest.TestCase):
     def test_int_tensor(self):
-        scope = core.Scope(None)
-        var = scope.create_var("test_tensor")
+        scope = core.Scope()
+        var = scope.new_var("test_tensor")
         tensor = var.get_tensor()
 
         tensor.set_dims([1000, 784])
@@ -23,8 +23,8 @@ class TestScope(unittest.TestCase):
         self.assertEqual(2.0, tensor_array_2[19, 11])
 
     def test_float_tensor(self):
-        scope = core.Scope(None)
-        var = scope.create_var("test_tensor")
+        scope = core.Scope()
+        var = scope.new_var("test_tensor")
         tensor = var.get_tensor()
 
         tensor.set_dims([1000, 784])
-- 
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