Complete remove std::shared_ptr

paddle/framework/backward.cc

@@ -15,6 +15,8 @@
 #include "paddle/framework/backward.h"
 
 #include <list>
+#include <memory>
+
 #include "paddle/framework/op_registry.h"
 #include "paddle/operators/net_op.h"
 #include "paddle/operators/recurrent_op.h"
@@ -43,11 +45,11 @@ static bool AllInSet(
   return all_in_set;
 }
 
-static std::shared_ptr<OperatorBase> NOP() {
-  auto net_op = std::make_shared<operators::NetOp>();
+static std::unique_ptr<OperatorBase> NOP() {
+  auto net_op = new operators::NetOp();
   net_op->SetType("@NOP@");
   net_op->CompleteAddOp();
-  return net_op;
+  return std::unique_ptr<OperatorBase>(net_op);
 }
 
 //  Get backward operator from a forward operator, a recursive implementation.
@@ -62,11 +64,7 @@ static std::shared_ptr<OperatorBase> NOP() {
 //  operator, in a complex situation, it maybe a NetOp.
 //
 //  See Backward.h for details
-static std::shared_ptr<OperatorBase> BackwardRecursive(
-    const OperatorBase& forwardOp,
-    std::unordered_set<std::string>& no_grad_names, size_t& uniq_id);
-
-std::shared_ptr<OperatorBase> BackwardRecursive(
+static std::unique_ptr<OperatorBase> BackwardRecursive(
     const OperatorBase& forwardOp,
     std::unordered_set<std::string>& no_grad_names, size_t& uniq_id) {
   //  If all input gradients of forwarding operator do not need to calculate,
@@ -91,7 +89,7 @@ std::shared_ptr<OperatorBase> BackwardRecursive(
   }
 
   // Returned gradient network
-  auto net = std::make_shared<operators::NetOp>();
+  auto net = std::unique_ptr<operators::NetOp>();
 
   if (forwardOp.IsNetOp()) {
     // Because forwardOp is a net op, it can static_cast.
@@ -105,14 +103,14 @@ std::shared_ptr<OperatorBase> BackwardRecursive(
     // reversely travel forwardNet and collect all duplicate outputs.
     for (auto it = forwardNet.ops_.rbegin(); it != forwardNet.ops_.rend();
          ++it, ++local_op_id) {
-      auto fwd = *it;
+      auto& fwd = *it;
       auto bwd = BackwardRecursive(*fwd, no_grad_names, uniq_id);
-      net->AddOp(bwd);
       ForEachVarName(bwd->Outputs(),
                      [&dup_output_ops, local_op_id](const std::string& out) {
                        dup_output_ops[out].emplace_back(local_op_id);
                        return false;
                      });
+      net->AddOp(std::move(bwd));
     }
     // Get unique ID for this method.
     auto uid = uniq_id++;
@@ -122,7 +120,7 @@ std::shared_ptr<OperatorBase> BackwardRecursive(
     // to handle this case. For each duplicate output, rename it to an alias
     // (original name with a offset), append an `add` op for its operator,
     // and finally sum all the alias variable to the final output variable y.
-    using Pos = std::pair<size_t, std::shared_ptr<OperatorBase>>;
+    using Pos = std::pair<size_t, std::unique_ptr<OperatorBase>>;
     std::list<Pos> insert_position;
     for (auto& dup_output_op : dup_output_ops) {
       const std::string& name = dup_output_op.first;
@@ -150,13 +148,13 @@ std::shared_ptr<OperatorBase> BackwardRecursive(
         [](const Pos& l, const Pos& r) { return l.first > r.first; });
 
     for (auto& pos : insert_position) {
-      net->InsertOp(pos.first + 1, pos.second);
+      net->InsertOp(pos.first + 1, std::move(pos.second));
     }
   } else {
-    std::shared_ptr<OperatorBase> grad_op = OpRegistry::CreateGradOp(forwardOp);
+    std::unique_ptr<OperatorBase> grad_op(OpRegistry::CreateGradOp(forwardOp));
 
-    ForEachVarName(grad_op->Inputs(), [&no_grad_names, &net,
-                                       grad_op](const std::string& grad_input) {
+    ForEachVarName(grad_op->Inputs(), [&no_grad_names, &net, &grad_op](
+                                          const std::string& grad_input) {
       if (no_grad_names.count(grad_input)) {
         // +1 for \0
         std::string prefix = grad_input.substr(
@@ -190,20 +188,20 @@ std::shared_ptr<OperatorBase> BackwardRecursive(
       const auto& stepnet_op =
           *static_cast<const OperatorBase*>(&rnnop.stepnet());
       // create stepnet's gradient op
-      auto grad_stepnet = BackwardRecursive(stepnet_op, no_grad_names, uniq_id);
       rnn_grad_op->set_stepnet(
-          std::static_pointer_cast<operators::NetOp>(grad_stepnet));
+          BackwardRecursive(stepnet_op, no_grad_names, uniq_id));
     }
 
     if (net->ops_.empty()) {  // Current no aux op is added to network
       return grad_op;
     }
-    net->AddOp(grad_op);
+    net->AddOp(std::move(grad_op));
   }
   net->SetType("@GENERATED_BACKWARD@");
   net->CompleteAddOp();
-  return net;
-}  // namespace framework
+  return std::unique_ptr<OperatorBase>(
+      static_cast<OperatorBase*>(net.release()));
+}
 
 // See header for comments
 std::shared_ptr<OperatorBase> Backward(

paddle/framework/op_registry.h

@@ -174,7 +174,7 @@ class OpRegistry {
     }
   }
 
-  static std::shared_ptr<OperatorBase> CreateOp(const std::string& type,
+  static std::unique_ptr<OperatorBase> CreateOp(const std::string& type,
                                                 const VarNameMap& inputs,
                                                 const VarNameMap& outputs,
                                                 AttributeMap attrs) {
@@ -183,7 +183,7 @@ class OpRegistry {
                    "Operator '%s' has not been registered.", type);
     it->second.checker_->Check(attrs);
     auto op = it->second.creator_(type, inputs, outputs, attrs);
-    return std::shared_ptr<OperatorBase>(op);
+    return std::unique_ptr<OperatorBase>(op);
   }
 
   static VarNameMap ConvertOpDescVarsToVarNameMap(
@@ -199,7 +199,7 @@ class OpRegistry {
     return ret_val;
   }
 
-  static std::shared_ptr<OperatorBase> CreateOp(const OpDesc& op_desc) {
+  static std::unique_ptr<OperatorBase> CreateOp(const OpDesc& op_desc) {
     VarNameMap inputs = ConvertOpDescVarsToVarNameMap(op_desc.inputs());
     VarNameMap outputs = ConvertOpDescVarsToVarNameMap(op_desc.outputs());
     AttributeMap attrs;
@@ -210,11 +210,10 @@ class OpRegistry {
     return CreateOp(op_desc.type(), inputs, outputs, attrs);
   }
 
-  static std::shared_ptr<OperatorBase> CreateGradOp(const OperatorBase& op) {
+  static std::unique_ptr<OperatorBase> CreateGradOp(const OperatorBase& op) {
     PADDLE_ENFORCE(!op.IsNetOp(),
                    "Use framework::Backward to get backward ops");
-    std::shared_ptr<OperatorBase> grad_op(BuildGradOp(&op));
-    return grad_op;
+    return std::unique_ptr<OperatorBase>(BuildGradOp(&op));
   }
 
   static std::unordered_map<std::string, const OpInfo>& op_info_map() {

paddle/framework/op_registry_test.cc

@@ -76,8 +76,7 @@ TEST(OpRegistry, CreateOp) {
   attr->set_type(paddle::framework::AttrType::FLOAT);
   attr->set_f(scale);
 
-  std::shared_ptr<paddle::framework::OperatorBase> op =
-      paddle::framework::OpRegistry::CreateOp(op_desc);
+  auto op = paddle::framework::OpRegistry::CreateOp(op_desc);
   paddle::framework::Scope scope;
   paddle::platform::CPUDeviceContext dev_ctx;
   op->Run(scope, dev_ctx);
@@ -118,8 +117,7 @@ TEST(OpRegistry, DefaultValue) {
 
   ASSERT_TRUE(op_desc.IsInitialized());
 
-  std::shared_ptr<paddle::framework::OperatorBase> op =
-      paddle::framework::OpRegistry::CreateOp(op_desc);
+  auto op = paddle::framework::OpRegistry::CreateOp(op_desc);
   paddle::framework::Scope scope;
   paddle::platform::CPUDeviceContext dev_ctx;
   op->Run(scope, dev_ctx);

paddle/framework/pybind.cc

@@ -207,8 +207,7 @@ All parameter, weight, gradient are variables in Paddle.
       .def(py::init<>())
       .def("__str__", string::to_string<const platform::CPUPlace &>);
 
-  py::class_<OperatorBase, std::shared_ptr<OperatorBase>> operator_base(
-      m, "Operator");
+  py::class_<OperatorBase> operator_base(m, "Operator");
 
   operator_base.def_static("create", [](py::bytes protobin) {
     OpDesc desc;
@@ -228,25 +227,23 @@ All parameter, weight, gradient are variables in Paddle.
 
   ExposeOperator(operator_base);
 
-  py::class_<operators::NetOp, std::shared_ptr<operators::NetOp>> net(m, "Net");
+  py::class_<operators::NetOp> net(m, "Net");
 
   net.def_static("create",
-                 []() -> std::shared_ptr<operators::NetOp> {
-                   auto retv = std::make_shared<operators::NetOp>();
+                 []() -> operators::NetOp * {
+                   auto *retv = new operators::NetOp;
                    retv->SetType("plain_net");
                    return retv;
                  })
-      .def("add_op", &operators::NetOp::AddOp)
+      .def("add_op", [](operators::NetOp &self,
+                        const OperatorBase &op) { self.AddOp(op); })
       .def("add_op",
-           [](operators::NetOp &self,
-              const std::shared_ptr<operators::NetOp> &net) -> void {
-             self.AddOp(std::static_pointer_cast<OperatorBase>(net));
+           [](operators::NetOp &self, const operators::NetOp &net) -> void {
+             self.AddOp(net);
            })
       .def("add_op",
            [](operators::NetOp &self,
-              const std::shared_ptr<operators::RecurrentOp> &rnn) -> void {
-             self.AddOp(std::static_pointer_cast<OperatorBase>(rnn));
-           })
+              const operators::RecurrentOp &rnn) -> void { self.AddOp(rnn); })
       .def("complete_add_op", &operators::NetOp::CompleteAddOp)
       .def("complete_add_op", [](std::shared_ptr<operators::NetOp> &self) {
         self->CompleteAddOp();
@@ -255,12 +252,11 @@ All parameter, weight, gradient are variables in Paddle.
   ExposeOperator(net);
 
   // recurrent_op
-  py::class_<operators::RecurrentOp, std::shared_ptr<operators::RecurrentOp>>
-      rnn(m, "RecurrentOp");
+  py::class_<operators::RecurrentOp> rnn(m, "RecurrentOp");
 
   rnn.def_static(
          "create",
-         [](py::bytes protobin) -> std::shared_ptr<operators::RecurrentOp> {
+         [](py::bytes protobin) -> operators::RecurrentOp * {
            OpDesc desc;
            PADDLE_ENFORCE(desc.ParsePartialFromString(protobin),
                           "Cannot parse user input to OpDesc");
@@ -268,12 +264,11 @@ All parameter, weight, gradient are variables in Paddle.
                           "User OpDesc is not initialized, reason %s",
                           desc.InitializationErrorString());
            auto rnn_op = OpRegistry::CreateOp(desc);
-           return std::dynamic_pointer_cast<operators::RecurrentOp>(rnn_op);
+           return static_cast<operators::RecurrentOp *>(rnn_op.release());
          })
-      .def("set_stepnet",
-           [](operators::RecurrentOp &self,
-              const std::shared_ptr<operators::NetOp> &net) -> void {
-             self.set_stepnet(net);
+      .def("set_stepnet", [](operators::RecurrentOp &self,
+                             const operators::NetOp &net) -> void {
+        self.set_stepnet(net.Clone());
       });
   ExposeOperator(rnn);
 

paddle/operators/net_op.h

@@ -45,10 +45,10 @@ class NetOp : public framework::OperatorBase {
       : framework::OperatorBase(
             static_cast<const framework::OperatorBase&>(o)) {
     this->ops_.reserve(o.ops_.size());
-    std::transform(o.ops_.begin(), o.ops_.end(), std::back_inserter(this->ops_),
-                   [](const std::shared_ptr<OperatorBase>& op)
-                       -> std::shared_ptr<OperatorBase> {
-                         return std::shared_ptr<OperatorBase>(op->Clone());
+    std::transform(
+        o.ops_.begin(), o.ops_.end(), std::back_inserter(this->ops_),
+        [](const std::unique_ptr<framework::OperatorBase>& op) {
+          return std::unique_ptr<framework::OperatorBase>(op->Clone());
         });
     this->CompleteAddOp();
   }
@@ -86,21 +86,42 @@ class NetOp : public framework::OperatorBase {
     return true;
   }
 
+  void AddOp(const framework::OperatorBase& op) { AddOp(op.Clone()); }
+
   /**
    * @brief Add an operator by ptr
    */
-  void AddOp(const std::shared_ptr<OperatorBase>& op) {
+  void AddOp(framework::OperatorBase* op, bool own) {
     PADDLE_ENFORCE(!add_op_done_, "Cannot AddOp when this network is sealed");
     PADDLE_ENFORCE_NOT_NULL(op, "Cannot Insert Null op");
-    ops_.push_back(op);
+    if (!own) {
+      op = op->Clone().release();
+    }
+    ops_.emplace_back(op);
   }
 
-  void InsertOp(size_t pos, const std::shared_ptr<OperatorBase>& op) {
+  void AddOp(std::unique_ptr<framework::OperatorBase>&& op) {
+    AddOp(op.release(), true);
+  }
+
+  void InsertOp(size_t pos, framework::OperatorBase* op, bool own) {
     PADDLE_ENFORCE(!add_op_done_,
                    "Cannot InsertOp when this network is sealed");
     PADDLE_ENFORCE_NOT_NULL(op, "Cannot Insert Null op");
     PADDLE_ENFORCE_LE(pos, ops_.size(), "Out of range");
-    ops_.insert(ops_.begin() + pos, op);
+    if (!own) {
+      op = op->Clone().release();
+    }
+    ops_.insert(ops_.begin() + pos,
+                std::unique_ptr<framework::OperatorBase>(op));
+  }
+
+  void InsertOp(size_t pos, std::unique_ptr<framework::OperatorBase>&& op) {
+    InsertOp(pos, op.release(), true);
+  }
+
+  void InsertOp(size_t pos, const framework::OperatorBase& op) {
+    InsertOp(pos, op.Clone());
   }
 
   void CompleteAddOp(bool calculate = true);
@@ -112,7 +133,7 @@ class NetOp : public framework::OperatorBase {
 
   std::unique_ptr<framework::OperatorBase> Clone() const override;
 
-  std::vector<std::shared_ptr<OperatorBase>> ops_;
+  std::vector<std::unique_ptr<framework::OperatorBase>> ops_;
 
  private:
   bool add_op_done_{false};

paddle/operators/net_op_test.cc

@@ -38,15 +38,12 @@ TEST(OpKernel, all) {
   auto net = std::make_shared<NetOp>();
   ASSERT_NE(net, nullptr);
 
-  auto op1 = std::shared_ptr<TestOp>(
+  net->AddOp(std::unique_ptr<TestOp>(
       new TestOp("test", {{"X", {"x"}}, {"W", {"w1"}}, {"b", {"b1"}}},
-                 {{"Out", {"y"}}}, {}));
-  net->AddOp(op1);
-
-  auto op2 = std::shared_ptr<TestOp>(
+                 {{"Out", {"y"}}}, {})));
+  net->AddOp(std::unique_ptr<TestOp>(
       new TestOp("test", {{"X", {"y"}}, {"W", {"w2"}}, {"b", {"b2"}}},
-                 {{"Out", {"z"}}}, {}));
-  net->AddOp(op2);
+                 {{"Out", {"z"}}}, {})));
 
   net->CompleteAddOp();
   AssertSameVectorWithoutOrder({"x", "w1", "b1", "w2", "b2"},
@@ -61,21 +58,21 @@ TEST(OpKernel, all) {
 
 TEST(NetOp, insert_op) {
   NetOp net;
-  auto op1 = std::shared_ptr<framework::NOP>(
+  auto op1 = std::unique_ptr<framework::NOP>(
       new framework::NOP("empty", {{"X", {"x"}}, {"W", {"w1"}}, {"b", {"b1"}}},
                          {{"Out", {"y"}}}, {}));
-  net.AddOp(op1);
-  net.InsertOp(0, op1);
+  net.AddOp(*op1);
+  net.InsertOp(0, *op1);
   ASSERT_EQ(2UL, net.ops_.size());
-  net.InsertOp(2, op1);
+  net.InsertOp(2, std::move(op1));
   ASSERT_EQ(3UL, net.ops_.size());
 }
 
 TEST(NetOp, Clone) {
   NetOp net;
   net.AddOp(
-      std::shared_ptr<framework::NOP>(new framework::NOP{"empty", {}, {}, {}}));
-  net.AddOp(std::shared_ptr<framework::NOP>(
+      std::unique_ptr<framework::NOP>(new framework::NOP{"empty", {}, {}, {}}));
+  net.AddOp(std::unique_ptr<framework::NOP>(
       new framework::NOP{"empty2", {}, {}, {}}));
   net.CompleteAddOp(true);
   auto new_net_op = net.Clone();

paddle/operators/recurrent_op.cc

@@ -42,7 +42,7 @@ void RecurrentAlgorithm::InferShape(const Scope& scope) const {
       rnn::LinkMemories(step_scopes, arg_->memories, i, -1,
                         true /*infer_shape_mode*/);
     }
-    (*stepnet_)->InferShape(*step_scopes[i]);
+    stepnet_->InferShape(*step_scopes[i]);
   }
   rnn::ConcatOutputs(step_scopes, arg_->outlinks, seq_len_,
                      true /*infer_shape_mode*/);
@@ -61,7 +61,7 @@ void RecurrentAlgorithm::Run(const Scope& scope,
       rnn::LinkMemories(step_scopes, arg_->memories, step_id, -1,
                         false /*infer_shape_mode*/);
     }
-    (*stepnet_)->Run(*step_scopes[step_id], dev_ctx);
+    stepnet_->Run(*step_scopes[step_id], dev_ctx);
   }
   rnn::ConcatOutputs(step_scopes, arg_->outlinks, seq_len_,
                      false /*infer_shape_mode*/);
@@ -76,15 +76,15 @@ void RecurrentAlgorithm::CreateScopes(const Scope& scope) const {
 
   // Now all variables in scope must be created outside of op.
   PADDLE_ENFORCE_NOT_NULL(stepnet_);
-  PADDLE_ENFORCE(!(*stepnet_)->Outputs().empty(), "stepnet_ op has no outputs");
-  PADDLE_ENFORCE(!(*stepnet_)->Outputs().empty(), "net_op has no outputs");
+  PADDLE_ENFORCE(!stepnet_->Outputs().empty(), "stepnet_ op has no outputs");
+  PADDLE_ENFORCE(!stepnet_->Outputs().empty(), "net_op has no outputs");
 
   if (seq_len_ > step_scopes->size()) {
     for (size_t i = step_scopes->size(); i < seq_len_; ++i) {
       auto& step_scope = scope.NewScope();
 
       // create step net's temp inputs
-      for (auto& input : (*stepnet_)->Inputs()) {
+      for (auto& input : stepnet_->Inputs()) {
         // the weight are located in parent scope
         for (auto& var_name : input.second) {
           if (!step_scope.FindVar(var_name)) {
@@ -93,7 +93,7 @@ void RecurrentAlgorithm::CreateScopes(const Scope& scope) const {
         }
       }
       // create stepnet's outputs
-      for (const auto& output : (*stepnet_)->Outputs()) {
+      for (const auto& output : stepnet_->Outputs()) {
         for (auto& var_name : output.second) {
           step_scope.NewVar(var_name);
         }
@@ -136,7 +136,7 @@ RecurrentOp::RecurrentOp(const std::string& type,
                          const framework::AttributeMap& attrs)
     : OperatorBase(type, inputs, outputs, attrs) {
   rnn::InitArgument(kArgName, &arg_, *this);
-  alg_.Init(&arg_, &stepnet_);
+  alg_.Init(&arg_, stepnet_.get());
 }
 
 class RecurrentAlgorithmProtoAndCheckerMaker
@@ -178,7 +178,7 @@ void RecurrentGradientAlgorithm::Run(
       rnn::LinkMemories(step_scopes, arg_->memories, step_id, 1,
                         false /*infer_shape_mode*/);
     }
-    (*stepnet_)->Run(*step_scopes[step_id], dev_ctx);
+    stepnet_->Run(*step_scopes[step_id], dev_ctx);
   }
   LinkBootMemoryGradients(step_scopes[0], false);
   rnn::ConcatOutputs(step_scopes, arg_->outlinks, seq_len_,
@@ -215,7 +215,7 @@ void RecurrentGradientAlgorithm::InferShape(const Scope& scope) const {
       rnn::LinkMemories(step_scopes, arg_->memories, step_id, 1,
                         true /*infer_shape_mode*/);
     }
-    (*stepnet_)->InferShape(*step_scopes[step_id]);
+    stepnet_->InferShape(*step_scopes[step_id]);
   }
   rnn::ConcatOutputs(step_scopes, arg_->outlinks, seq_len_,
                      true /*infer_shape_mode*/);
@@ -228,7 +228,7 @@ RecurrentGradientOp::RecurrentGradientOp(
     const framework::AttributeMap& attrs)
     : OperatorBase(type, inputs, outputs, attrs) {
   rnn::InitArgument(kArgName, &arg_, *this);
-  alg_.Init(&arg_, &stepnet_);
+  alg_.Init(&arg_, stepnet_.get());
 }
 
 }  // namespace operators

paddle/operators/recurrent_op.h

@@ -34,7 +34,7 @@ class RecurrentAlgorithm {
   void Run(const framework::Scope& scope,
            const platform::DeviceContext& dev_ctx) const;
 
-  void Init(rnn::Argument* arg, std::shared_ptr<NetOp>* stepnet) {
+  void Init(rnn::Argument* arg, framework::OperatorBase* stepnet) {
     PADDLE_ENFORCE_NOT_NULL(stepnet, "stepnet should be set before.");
     arg_ = arg;
     stepnet_ = stepnet;
@@ -63,7 +63,7 @@ class RecurrentAlgorithm {
   void InitMemories(framework::Scope* step_scopes, bool infer_shape_mode) const;
 
  private:
-  std::shared_ptr<NetOp>* stepnet_;
+  framework::OperatorBase* stepnet_;
   rnn::Argument* arg_;
   mutable size_t seq_len_;
 };
@@ -80,7 +80,7 @@ class RecurrentGradientAlgorithm {
    * operator.
    */
  public:
-  void Init(rnn::Argument* arg, std::shared_ptr<NetOp>* stepnet) {
+  void Init(rnn::Argument* arg, framework::OperatorBase* stepnet) {
     PADDLE_ENFORCE_NOT_NULL(stepnet, "stepnet should be set before.");
     arg_ = std::move(arg);
     stepnet_ = stepnet;
@@ -107,7 +107,7 @@ class RecurrentGradientAlgorithm {
  private:
   rnn::Argument* arg_;
   mutable size_t seq_len_;
-  std::shared_ptr<NetOp>* stepnet_;
+  framework::OperatorBase* stepnet_;
 };
 
 class RecurrentOp : public framework::OperatorBase {
@@ -133,15 +133,17 @@ class RecurrentOp : public framework::OperatorBase {
     alg_.Run(scope, dev_ctx);
   }
 
-  void set_stepnet(std::shared_ptr<NetOp> net) { stepnet_ = net; }
-  const NetOp& stepnet() const { return *stepnet_; }
+  void set_stepnet(std::unique_ptr<OperatorBase> net) {
+    stepnet_ = std::move(net);
+  }
+  const OperatorBase& stepnet() const { return *stepnet_; }
 
   static const rnn::ArgumentName kArgName;
 
  private:
   RecurrentAlgorithm alg_;
   rnn::Argument arg_;
-  std::shared_ptr<NetOp> stepnet_;
+  std::unique_ptr<OperatorBase> stepnet_;
 };
 
 class RecurrentGradientOp : public framework::OperatorBase {
@@ -171,12 +173,14 @@ class RecurrentGradientOp : public framework::OperatorBase {
 
   static const rnn::ArgumentName kArgName;
 
-  void set_stepnet(const std::shared_ptr<NetOp>& net) { stepnet_ = net; }
-  const NetOp& stepnet() const { return *stepnet_; }
+  void set_stepnet(std::unique_ptr<OperatorBase> net) {
+    stepnet_ = std::move(net);
+  }
+  const OperatorBase& stepnet() const { return *stepnet_; }
 
  private:
   RecurrentGradientAlgorithm alg_;
-  std::shared_ptr<NetOp> stepnet_;
+  std::unique_ptr<OperatorBase> stepnet_;
   rnn::Argument arg_;
 };