Polish code

test=develop

paddle/fluid/imperative/layer.cc

@@ -271,6 +271,22 @@ std::map<std::string, std::vector<VarBase*>> OpBase::ApplyGrad() {
   return input_vars_;
 }
 
+void VarBase::RunBackward() {
+  if (!pre_op_) return;
+
+  VLOG(3) << "start backward";
+  auto grads_t = grads_->var_->GetMutable<framework::LoDTensor>();
+  operators::math::set_constant(
+      *(platform::DeviceContextPool::Instance().Get(
+          var_->GetMutable<framework::LoDTensor>()->place())),
+      grads_t, 1.0);
+
+  PADDLE_ENFORCE(
+      grads_ ==
+      pre_op_->output_vars_[pre_op_out_name_][pre_op_out_idx_]->grads_);
+  Autograd().RunBackward(this);
+}
+
 void PyLayer::RegisterFunc(int func_id, const py::object& py_func) {
   py_funcs_[func_id] = py_func;
 }

paddle/fluid/imperative/layer.h

@@ -140,6 +140,8 @@ class VarBase {
   }
   inline bool IsStopGradient() const { return stop_gradient_; }
 
+  void RunBackward();
+
   void TrackPreOp(OpBase* pre_op, const std::string& pre_op_out_name,
                   int pre_op_out_idx, bool pre_op_stop_gradient) {
     pre_op_ = pre_op;
@@ -150,22 +152,6 @@ class VarBase {
     }
   }
 
-  void RunBackward() {
-    if (!pre_op_) return;
-
-    VLOG(3) << "start backward";
-    auto grads_t = grads_->var_->GetMutable<framework::LoDTensor>();
-    operators::math::set_constant(
-        *(platform::DeviceContextPool::Instance().Get(
-            var_->GetMutable<framework::LoDTensor>()->place())),
-        grads_t, 1.0);
-
-    PADDLE_ENFORCE(
-        grads_ ==
-        pre_op_->output_vars_[pre_op_out_name_][pre_op_out_idx_]->grads_);
-    Autograd().RunBackward(this);
-  }
-
   void ClearGradient() {
     VLOG(1) << "clear gradient of " << var_desc_->Name();
     if (grads_ && grads_->var_ && grads_->var_->IsInitialized()) {