Merge pull request #3180 from reyoung/feature/MeanOpGrad

Add Gradient Operator for mean

paddle/operators/mean_op.cc

@@ -33,13 +33,23 @@ public:
   MeanOpMaker(OpProto *proto, OpAttrChecker *op_checker)
       : OpProtoAndCheckerMaker(proto, op_checker) {
     AddInput("X", "The input of mean op");
-    AddOutput("Out", "The output of mean op");
+    AddOutput("Out", "The output of mean op").IgnoreGradient();
     AddComment("Mean Operator");
   }
 };
 
+class MeanGradOp : public OperatorWithKernel {
+protected:
+  void InferShape(const InferShapeContext &ctx) const override {
+    ctx.Output<Tensor>("X" + GRAD_VAR_SUFFIX())
+        ->Resize(ctx.Input<Tensor>("X")->dims());
+  }
+};
+
 }  // namespace operators
 }  // namespace paddle
 
 REGISTER_OP(mean, ops::MeanOp, ops::MeanOpMaker);
 REGISTER_OP_CPU_KERNEL(mean, ops::MeanKernel<ops::CPUPlace, float>);
+REGISTER_GRADIENT_OP(mean, mean_grad, ops::MeanGradOp);
+REGISTER_OP_CPU_KERNEL(mean_grad, ops::MeanGradKernel<ops::CPUPlace, float>);

paddle/operators/mean_op.cu

@@ -3,3 +3,4 @@
 #include "paddle/operators/mean_op.h"
 
 REGISTER_OP_GPU_KERNEL(mean, ops::MeanKernel<ops::GPUPlace, float>);
+REGISTER_OP_GPU_KERNEL(mean_grad, ops::MeanGradKernel<ops::GPUPlace, float>);
\ No newline at end of file

paddle/operators/mean_op.h

@@ -35,5 +35,22 @@ public:
   }
 };
 
+template <typename Place, typename T>
+class MeanGradKernel : public OpKernel {
+public:
+  void Compute(const ExecutionContext& context) const override {
+    auto OG = context.Input<Tensor>("Out" + OperatorBase::GRAD_VAR_SUFFIX());
+    PADDLE_ENFORCE(framework::product(OG->dims()) == 1,
+                   "Mean Gradient should be scalar");
+    auto IG = context.Output<Tensor>("X" + OperatorBase::GRAD_VAR_SUFFIX());
+    IG->mutable_data<T>(context.GetPlace());
+
+    T ig_size = (T)framework::product(IG->dims());
+
+    EigenVector<T>::Flatten(*IG).device(*(context.GetEigenDevice<Place>())) =
+        EigenScalar<T>::From(*OG) / ig_size;
+  }
+};
+
 }  // namespace operators
 }  // namespace paddle

paddle/operators/type_alias.h

@@ -51,6 +51,7 @@ using CPUPlace = platform::CPUPlace;
 using GPUPlace = platform::GPUPlace;
 using NetOp = framework::NetOp;
 using OpRegistry = framework::OpRegistry;
+using OperatorBase = framework::OperatorBase;
 }  // namespace operators
 }  // namespace paddle