optimize elementwise_mul cpu forward

Author: tensor-tang

paddle/fluid/operators/elementwise_mul_op.h

@@ -14,6 +14,7 @@ limitations under the License. */
 
 #pragma once
 #include "paddle/fluid/operators/elementwise_op_function.h"
+#include "paddle/fluid/operators/math/blas.h"
 
 namespace paddle {
 namespace operators {
@@ -23,6 +24,37 @@ struct MulFunctor {
   inline HOSTDEVICE T operator()(T a, T b) const { return a * b; }
 };
 
+template <typename DeviceContext, typename T>
+void default_elementwise_mul(const framework::ExecutionContext& ctx,
+                             const framework::Tensor* x,
+                             const framework::Tensor* y, framework::Tensor* z) {
+  int axis = ctx.Attr<int>("axis");
+  ElementwiseComputeEx<MulFunctor<T>, DeviceContext, T>(ctx, x, y, axis,
+                                                        MulFunctor<T>(), z);
+}
+
+template <typename DeviceContext, typename T>
+typename std::enable_if<
+    std::is_floating_point<T>::value &&
+    std::is_same<DeviceContext, platform::CPUDeviceContext>::value>::type
+elementwise_mul(const framework::ExecutionContext& ctx,
+                const framework::Tensor* x, const framework::Tensor* y,
+                framework::Tensor* z) {
+  auto blas = math::GetBlas<DeviceContext, T>(ctx);
+  blas.VMUL(x->numel(), x->data<T>(), y->data<T>(),
+            z->mutable_data<T>(ctx.GetPlace()));
+}
+
+template <typename DeviceContext, typename T>
+typename std::enable_if<
+    !std::is_floating_point<T>::value ||
+    !std::is_same<DeviceContext, platform::CPUDeviceContext>::value>::type
+elementwise_mul(const framework::ExecutionContext& ctx,
+                const framework::Tensor* x, const framework::Tensor* y,
+                framework::Tensor* z) {
+  default_elementwise_mul<DeviceContext, T>(ctx, x, y, z);
+}
+
 template <typename DeviceContext, typename T>
 class ElementwiseMulKernel : public framework::OpKernel<T> {
  public:
@@ -33,9 +65,11 @@ class ElementwiseMulKernel : public framework::OpKernel<T> {
     auto* y = ctx.Input<Tensor>("Y");
     auto* z = ctx.Output<Tensor>("Out");
     z->mutable_data<T>(ctx.GetPlace());
-    int axis = ctx.Attr<int>("axis");
-    ElementwiseComputeEx<MulFunctor<T>, DeviceContext, T>(ctx, x, y, axis,
-                                                          MulFunctor<T>(), z);
+    if (x->numel() == y->numel()) {
+      elementwise_mul<DeviceContext, T>(ctx, x, y, z);
+    } else {
+      default_elementwise_mul<DeviceContext, T>(ctx, x, y, z);
+    }
   }
 };