Remove intermediate output's gradient from inputs of grad_op.

paddle/fluid/operators/gru_unit_op.cc

@@ -124,7 +124,7 @@ $$
 
 which is same as one time step of GRU Operator.
 
-@note To implement the complete GRU unit, fully-connected operator must be 
+@note To implement the complete GRU unit, fully-connected operator must be
 used before to feed xu, xr and xc as the Input of GRUUnit operator.
 
 )DOC");
@@ -194,13 +194,45 @@ class GRUUnitGradOp : public framework::OperatorWithKernel {
   }
 };
 
+class GRUUnitGradOpMaker : public framework::SingleGradOpDescMaker {
+ public:
+  using framework::SingleGradOpDescMaker::SingleGradOpDescMaker;
+
+ protected:
+  std::unique_ptr<framework::OpDesc> Apply() const override {
+    auto* op = new framework::OpDesc();
+    op->SetType("gru_unit_grad");
+
+    op->SetInput("Input", Input("Input"));
+    op->SetInput("HiddenPrev", Input("HiddenPrev"));
+    op->SetInput("Weight", Input("Weight"));
+    op->SetInput("Bias", Input("Bias"));
+
+    op->SetInput("Hidden", Output("Hidden"));
+    op->SetInput("Gate", Output("Gate"));
+    op->SetInput("ResetHiddenPrev", Output("ResetHiddenPrev"));
+    op->SetInput(framework::GradVarName("Hidden"), OutputGrad("Hidden"));
+
+    op->SetAttrMap(Attrs());
+
+    op->SetOutput(framework::GradVarName("Input"), InputGrad("Input"));
+    op->SetOutput(framework::GradVarName("HiddenPrev"),
+                  InputGrad("HiddenPrev"));
+    op->SetOutput(framework::GradVarName("Weight"), InputGrad("Weight"));
+    op->SetOutput(framework::GradVarName("Bias"), InputGrad("Bias"));
+    return std::unique_ptr<framework::OpDesc>(op);
+  }
+};
+
 }  // namespace operators
 }  // namespace paddle
 
 namespace ops = paddle::operators;
+
 REGISTER_OPERATOR(gru_unit, ops::GRUUnitOp, ops::GRUUnitOpMaker,
-                  paddle::framework::DefaultGradOpDescMaker<true>)
-REGISTER_OPERATOR(gru_unit_grad, ops::GRUUnitGradOp)
+                  ops::GRUUnitGradOpMaker);
+REGISTER_OPERATOR(gru_unit_grad, ops::GRUUnitGradOp);
+
 REGISTER_OP_CPU_KERNEL(
     gru_unit, ops::GRUUnitKernel<paddle::platform::CPUDeviceContext, float>,
     ops::GRUUnitKernel<paddle::platform::CPUDeviceContext, double>);