From 36a102f85de37c4d6ade394eb3f552a1dc1a30b7 Mon Sep 17 00:00:00 2001
From: Lijunhui <1578034415@qq.com>
Date: Wed, 5 Jan 2022 21:49:41 +0800
Subject: [PATCH] optimize elementwise_mul_grad using new interfaces (#37728)

* init commit: new elem_mul_grad

* add template speciallization for complex in multiply

* reply review comments

* correct dx and dy computation when T is complex

* reply review comments

* update to new ReduceRunctor

* mul-output broadcast

* call functions

* call functions with comments

* remove comments
---
 .../elementwise/elementwise_functor.h         | 42 ++++++++
 .../elementwise/elementwise_mul_op.cu         | 95 +++++++------------
 .../elementwise/elementwise_mul_op.h          | 29 ++----
 3 files changed, 86 insertions(+), 80 deletions(-)

diff --git a/paddle/fluid/operators/elementwise/elementwise_functor.h b/paddle/fluid/operators/elementwise/elementwise_functor.h
index b7bebcaa386..a62c531ff07 100644
--- a/paddle/fluid/operators/elementwise/elementwise_functor.h
+++ b/paddle/fluid/operators/elementwise/elementwise_functor.h
@@ -194,5 +194,47 @@ struct FMinFunctor<paddle::platform::float16> {
   }
 };
 
+template <typename T>
+struct MulGradFunctor {
+  inline HOSTDEVICE T operator()(const T& a, const T& b) const { return a * b; }
+};
+template <typename T>
+struct MulGradFunctor<Complex<T>> {
+  inline HOSTDEVICE Complex<T> operator()(const Complex<T>& a,
+                                          const Complex<T>& b) const {
+    Complex<T> b_conj(b.real, -b.imag);
+    return a * b_conj;
+  }
+};
+
+template <typename InT, typename OutT>
+struct MulGradXYFunctor {
+  inline HOSTDEVICE paddle::framework::Array<OutT, 2> operator()(const InT& a,
+                                                                 const InT& b,
+                                                                 const InT& c) {
+    paddle::framework::Array<OutT, 2> outs;
+    // dx = dout * y
+    outs[0] = a * b;
+    // dy = dout * x
+    outs[1] = a * c;
+    return outs;
+  }
+};
+
+template <typename InT, typename OutT>
+struct MulGradXYFunctor<Complex<InT>, Complex<OutT>> {
+  inline HOSTDEVICE paddle::framework::Array<Complex<OutT>, 2> operator()(
+      const Complex<InT>& a, const Complex<InT>& b, const Complex<InT>& c) {
+    paddle::framework::Array<Complex<OutT>, 2> outs;
+    // dx = dout * y
+    Complex<InT> b_conj(b.real, -b.imag);
+    outs[0] = a * b_conj;
+    // dy = dout * x
+    Complex<InT> c_conj(c.real, -c.imag);
+    outs[1] = a * c_conj;
+    return outs;
+  }
+};
+
 }  // namespace operators
 }  // namespace paddle
diff --git a/paddle/fluid/operators/elementwise/elementwise_mul_op.cu b/paddle/fluid/operators/elementwise/elementwise_mul_op.cu
index 12e0062a698..cdf376fd6a8 100644
--- a/paddle/fluid/operators/elementwise/elementwise_mul_op.cu
+++ b/paddle/fluid/operators/elementwise/elementwise_mul_op.cu
@@ -14,6 +14,7 @@ limitations under the License. */
 
 #include "paddle/fluid/operators/elementwise/elementwise_mul_op.h"
 #include "paddle/fluid/operators/elementwise/elementwise_op_broadcast.cu.h"
+#include "paddle/fluid/operators/reduce_ops/reduce_op.cu.h"
 #include "paddle/fluid/platform/complex.h"
 #include "paddle/fluid/platform/float16.h"
 
@@ -68,69 +69,41 @@ class ElementwiseMulKernel<platform::CUDADeviceContext, T>
   }
 };
 
-template <typename T>
-static __global__ void SimpleElemwiseMulGradCUDAKernel(const T* x, const T* y,
-                                                       const T* out,
-                                                       const T* dout,
-                                                       int64_t size, T* dx,
-                                                       T* dy) {
-  int col = blockIdx.x * blockDim.x + threadIdx.x;
-
-  while (col < size) {
-    T o = dout[col];
-    dx[col] = y[col] * o;
-    dy[col] = x[col] * o;
-    col += blockDim.x * gridDim.x;
-  }
-}
-
-template <>
-__global__ void SimpleElemwiseMulGradCUDAKernel<plat::complex<float>>(
-    const plat::complex<float>* x, const plat::complex<float>* y,
-    const plat::complex<float>* out, const plat::complex<float>* dout,
-    int64_t size, plat::complex<float>* dx, plat::complex<float>* dy) {
-  int col = blockIdx.x * blockDim.x + threadIdx.x;
-
-  while (col < size) {
-    plat::complex<float> o = dout[col];
-    dx[col] = plat::complex<float>(y[col].real, -y[col].imag) * o;
-    dy[col] = plat::complex<float>(x[col].real, -x[col].imag) * o;
-    col += blockDim.x * gridDim.x;
-  }
-}
-
-template <>
-__global__ void SimpleElemwiseMulGradCUDAKernel<plat::complex<double>>(
-    const plat::complex<double>* x, const plat::complex<double>* y,
-    const plat::complex<double>* out, const plat::complex<double>* dout,
-    int64_t size, plat::complex<double>* dx, plat::complex<double>* dy) {
-  int col = blockIdx.x * blockDim.x + threadIdx.x;
-
-  while (col < size) {
-    plat::complex<double> o = dout[col];
-    dx[col] = plat::complex<double>(y[col].real, -y[col].imag) * o;
-    dy[col] = plat::complex<double>(x[col].real, -x[col].imag) * o;
-    col += blockDim.x * gridDim.x;
-  }
-}
-
 template <typename DeviceContext, typename T>
 typename std::enable_if<
-    std::is_same<DeviceContext, plat::CUDADeviceContext>::value>::type
-elementwise_mul_grad(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) {
-  dim3 block_size = dim3(ELEMENTWISE_BLOCK_SIZE, 1);
-  auto size = x->numel();
-  dim3 grid_size =
-      dim3((size + ELEMENTWISE_BLOCK_SIZE - 1) / ELEMENTWISE_BLOCK_SIZE, 1);
-  SimpleElemwiseMulGradCUDAKernel<
-      T><<<grid_size, block_size, 0,
-           ctx.template device_context<plat::CUDADeviceContext>().stream()>>>(
-      x->data<T>(), y->data<T>(), out->data<T>(), dout->data<T>(), size,
-      dx->mutable_data<T>(ctx.GetPlace()), dy->mutable_data<T>(ctx.GetPlace()));
+    std::is_same<DeviceContext, platform::CUDADeviceContext>::value>::type
+ElementwiseMulGrad(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) {
+    dx->mutable_data<T>(place);
+    if (dx->IsSharedBufferWith(*dout)) {
+      dx->clear();
+      dx->mutable_data<T>(x->dims(), place);
+    }
+    std::vector<const framework::Tensor*> ins = {dout, y, x};
+    GetGradXAndYOut<ElementwiseType::kBinary, T>(
+        dev_ctx, place, axis, ins, dout, dx, dy, MulGradXYFunctor<T, T>());
+  } else if (dx != nullptr && dy == nullptr) {
+    dx->mutable_data<T>(place);
+    if (dx->IsSharedBufferWith(*dout)) {
+      dx->clear();
+      dx->mutable_data<T>(x->dims(), place);
+    }
+    std::vector<const framework::Tensor*> ins = {dout, y};
+    GetGradXOrYOut<ElementwiseType::kBinary, T>(dev_ctx, place, axis, ins, dout,
+                                                dx, MulGradFunctor<T>());
+  } else if (dx == nullptr && dy != nullptr) {
+    std::vector<const framework::Tensor*> ins = {dout, x};
+    GetGradXOrYOut<ElementwiseType::kBinary, T>(dev_ctx, place, axis, ins, dout,
+                                                dy, MulGradFunctor<T>());
+  }
 }
 
 }  // namespace operators
diff --git a/paddle/fluid/operators/elementwise/elementwise_mul_op.h b/paddle/fluid/operators/elementwise/elementwise_mul_op.h
index 3b0f0725722..5cff3173e81 100644
--- a/paddle/fluid/operators/elementwise/elementwise_mul_op.h
+++ b/paddle/fluid/operators/elementwise/elementwise_mul_op.h
@@ -174,26 +174,23 @@ struct MulGradDY<paddle::platform::complex<T>> {
 template <typename DeviceContext, typename T>
 typename std::enable_if<
     std::is_same<DeviceContext, platform::CPUDeviceContext>::value>::type
-elementwise_mul_grad(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) {
+ElementwiseMulGrad(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, MulGradDX<T>, MulGradDY<T>>(
       ctx, *x, *y, *out, *dout, axis, dx, dy, MulGradDX<T>(), MulGradDY<T>());
 }
 
 #if defined(PADDLE_WITH_CUDA) || defined(PADDLE_WITH_HIP)
-// cuda definition
 template <typename DeviceContext, typename T>
 typename std::enable_if<
     std::is_same<DeviceContext, platform::CUDADeviceContext>::value>::type
-elementwise_mul_grad(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);
+ElementwiseMulGrad(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>
@@ -209,14 +206,8 @@ class ElementwiseMulGradKernel : public ElemwiseGradKernel<T> {
     auto* out = dout;  // out is not necessary
     auto* dx = ctx.Output<Tensor>(framework::GradVarName("X"));
     auto* dy = ctx.Output<Tensor>(framework::GradVarName("Y"));
-    int axis = ctx.Attr<int>("axis");
-    if (dx != nullptr && dy != nullptr && (dx->dims() == dy->dims())) {
-      elementwise_mul_grad<DeviceContext, T>(ctx, x, y, out, dout, dx, dy);
-    } else {
-      ElemwiseGradCompute<DeviceContext, T, MulGradDX<T>, MulGradDY<T>>(
-          ctx, *x, *y, *out, *dout, axis, dx, dy, MulGradDX<T>(),
-          MulGradDY<T>());
-    }
+
+    ElementwiseMulGrad<DeviceContext, T>(ctx, x, y, out, dout, dx, dy);
   }
 };
 
-- 
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