"fix return net error"

paddle/framework/backward_test.cc

@@ -60,6 +60,16 @@ class SigmoidOpMaker : public OpProtoAndCheckerMaker {
   }
 };
 
+class NoGradOpMaker : public OpProtoAndCheckerMaker {
+ public:
+  NoGradOpMaker(OpProto *proto, OpAttrChecker *op_checker)
+      : OpProtoAndCheckerMaker(proto, op_checker) {
+    AddInput("X", "X input");
+    AddOutput("Y", "Y output");
+    AddComment("NoGradOp, same input output. no Grad");
+  }
+};
+
 class FcOp : public NetOp {
  public:
   void Init() override {
@@ -139,6 +149,7 @@ REGISTER_OP(mul, f::EmptyOp, f::MulOpMaker);
 REGISTER_GRADIENT_OP(mul, mul_grad, f::EmptyOp);
 REGISTER_OP(sigmoid, f::EmptyOp, f::SigmoidOpMaker);
 REGISTER_GRADIENT_OP(sigmoid, sigmoid_grad, f::EmptyOp);
+REGISTER_OP(nograd, f::EmptyOp, f::NoGradOpMaker);
 REGISTER_OP(fill_zeros_like, f::EmptyOp, f::FillZeroOpMaker);
 REGISTER_OP(add, f::EmptyOp, f::AddOpMaker);
 REGISTER_GRADIENT_OP(add, add_grad, f::EmptyOp);
@@ -266,9 +277,11 @@ TEST(Backward, net_shared_weight) {
 }
 
 TEST(Backward, op_register_grad_not_for_network) {
-  auto fwd =
-      f::OpRegistry::CreateOp("fc", {"X", "W", "b"}, {"Out", "tmp_out"},
-                              {{"temporary_index", std::vector<int>{1}}});
+  // auto fwd =
+  //     f::OpRegistry::CreateOp("fc", {"X", "W", "b"}, {"Out", "tmp_out"},
+  //                             {{"temporary_index", std::vector<int>{1}}});
+
+  auto fwd = f::OpRegistry::CreateOp("nograd", {"x"}, {"x"}, {});
   ASSERT_THROW(f::OpRegistry::CreateGradOp(*fwd), EnforceNotMet);
 }
 
@@ -316,11 +329,7 @@ TEST(Backward, op_part_of_output_are_not_need) {
 TEST(Backward, op_part_of_input_are_not_need) {
   auto fwd = f::OpRegistry::CreateOp("mul", {"a", "b"}, {"out"}, {});
   auto backward = f::Backward(*fwd, {"a"});
-  ASSERT_FALSE(backward->IsNetOp());
-  auto net = static_cast<f::NetOp *>(backward.get());
-  ASSERT_EQ(net->ops_.size(), 1UL);
-
-  auto &grad_mul = *net->ops_[0];
+  auto &grad_mul = *backward;
   ASSERT_EQ(grad_mul.type_, "mul_grad");
   ASSERT_EQ(grad_mul.inputs_.size(), 2UL + 1UL + 1UL);
   ASSERT_EQ(grad_mul.outputs_.size(), 2UL);