optimize elementwise_min_grad using new reduce interface (#38236)

* ini commit

* multi-outputs init commit

* optimize code

* remove inplace

paddle/fluid/operators/elementwise/elementwise_functor.h

@@ -233,6 +233,32 @@ struct FMinFunctor<int64_t> {
   }
 };
 
+template <typename T>
+struct MinGradXFunctor {
+  inline HOSTDEVICE T operator()(const T& x, const T& y, const T& dout) const {
+    return dout * static_cast<T>(x < y);
+  }
+};
+template <typename T>
+struct MinGradYFunctor {
+  inline HOSTDEVICE T operator()(const T& x, const T& y, const T& dout) const {
+    return dout * static_cast<T>(x >= y);
+  }
+};
+
+template <typename InT, typename OutT>
+struct MinGradXYFunctor {
+  inline HOSTDEVICE paddle::framework::Array<OutT, 2> operator()(
+      const InT& x, const InT& y, const InT& dout) {
+    paddle::framework::Array<OutT, 2> outs;
+    // dx = dout * (x < y)
+    outs[0] = static_cast<OutT>(dout * static_cast<InT>(x < y));
+    // dy = dout * (x >= y)
+    outs[1] = static_cast<OutT>(dout * static_cast<InT>(x >= y));
+    return outs;
+  }
+};
+
 template <typename T>
 struct MulGradFunctor {
   inline HOSTDEVICE T operator()(const T& a, const T& b) const { return a * b; }

paddle/fluid/operators/elementwise/elementwise_min_op.cu

@@ -24,15 +24,41 @@ class ElementwiseMinKernel<platform::CUDADeviceContext, T>
   void Compute(const framework::ExecutionContext& ctx) const override {
     std::vector<const framework::Tensor*> ins;
     std::vector<framework::Tensor*> outs;
-    const auto& cuda_ctx =
+    const auto& dev_ctx =
         ctx.template device_context<platform::CUDADeviceContext>();
 
     int axis = PackTensorsIntoVector<T>(ctx, &ins, &outs);
     LaunchElementwiseCudaKernel<ElementwiseType::kBinary, T, T>(
-        cuda_ctx, ins, &outs, axis, MinFunctor<T>());
+        dev_ctx, ins, &outs, axis, MinFunctor<T>());
   }
 };
 
+template <typename DeviceContext, typename T>
+typename std::enable_if<
+    std::is_same<DeviceContext, platform::CUDADeviceContext>::value>::type
+ElementwiseMinGrad(const framework::ExecutionContext& ctx,
+                   const framework::Tensor* x, const framework::Tensor* y,
+                   const framework::Tensor* out, const framework::Tensor* dout,
+                   framework::Tensor* dx, framework::Tensor* dy) {
+  int axis = ctx.Attr<int>("axis");
+  const auto& dev_ctx =
+      ctx.template device_context<platform::CUDADeviceContext>();
+  const auto place = ctx.GetPlace();
+  if (dx != nullptr && dy != nullptr) {
+    std::vector<const framework::Tensor*> ins = {x, y, dout};
+    GetGradXAndYOut<ElementwiseType::kTernary, T>(
+        dev_ctx, place, axis, ins, dout, dx, dy, MinGradXYFunctor<T, T>());
+  } else if (dx != nullptr && dy == nullptr) {
+    std::vector<const framework::Tensor*> ins = {x, y, dout};
+    GetGradXOrYOut<ElementwiseType::kTernary, T>(
+        dev_ctx, place, axis, ins, dout, dx, MinGradXFunctor<T>());
+  } else if (dx == nullptr && dy != nullptr) {
+    std::vector<const framework::Tensor*> ins = {x, y, dout};
+    GetGradXOrYOut<ElementwiseType::kTernary, T>(
+        dev_ctx, place, axis, ins, dout, dy, MinGradYFunctor<T>());
+  }
+}
+
 }  // namespace operators
 }  // namespace paddle
 

paddle/fluid/operators/elementwise/elementwise_min_op.h

@@ -86,6 +86,28 @@ struct MinGradDy<platform::float16> {
 };
 #endif
 
+template <typename DeviceContext, typename T>
+typename std::enable_if<
+    std::is_same<DeviceContext, platform::CPUDeviceContext>::value>::type
+ElementwiseMinGrad(const framework::ExecutionContext& ctx,
+                   const framework::Tensor* x, const framework::Tensor* y,
+                   const framework::Tensor* out, const framework::Tensor* dout,
+                   framework::Tensor* dx, framework::Tensor* dy) {
+  int axis = ctx.Attr<int>("axis");
+  ElemwiseGradCompute<DeviceContext, T, MinGradDx<T>, MinGradDy<T>>(
+      ctx, *x, *y, *out, *dout, axis, dx, dy, MinGradDx<T>(), MinGradDy<T>());
+}
+
+#if defined(PADDLE_WITH_CUDA) || defined(PADDLE_WITH_HIP)
+template <typename DeviceContext, typename T>
+typename std::enable_if<
+    std::is_same<DeviceContext, platform::CUDADeviceContext>::value>::type
+ElementwiseMinGrad(const framework::ExecutionContext& ctx,
+                   const framework::Tensor* x, const framework::Tensor* y,
+                   const framework::Tensor* out, const framework::Tensor* dout,
+                   framework::Tensor* dx, framework::Tensor* dy);
+#endif
+
 template <typename DeviceContext, typename T>
 class ElementwiseMinGradKernel : public ElemwiseGradKernel<T> {
  public:
@@ -99,9 +121,7 @@ class ElementwiseMinGradKernel : public ElemwiseGradKernel<T> {
     auto* dx = ctx.Output<Tensor>(framework::GradVarName("X"));
     auto* dy = ctx.Output<Tensor>(framework::GradVarName("Y"));
     auto* out = dout;  // Fake out, not used
-    int axis = ctx.Attr<int>("axis");
-    ElemwiseGradCompute<DeviceContext, T, MinGradDx<T>, MinGradDy<T>>(
-        ctx, *x, *y, *out, *dout, axis, dx, dy, MinGradDx<T>(), MinGradDy<T>());
+    ElementwiseMinGrad<DeviceContext, T>(ctx, x, y, out, dout, dx, dy);
   }
 };