chore: import upstream snapshot with attribution

paddle/phi/kernels/impl/selu_kernel_impl.h

@@ -0,0 +1,92 @@
+// Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+#include <string>
+
+#include "paddle/phi/core/dense_tensor.h"
+#include "paddle/phi/kernels/funcs/for_range.h"
+#include "paddle/phi/kernels/funcs/math.h"
+
+namespace phi {
+
+template <typename T>
+struct SeluFunctor {
+  SeluFunctor(const T* x_data_ptr, float alpha, float scale, T* y_data_ptr)
+      : x_data_ptr_(x_data_ptr),
+        alpha_(alpha),
+        scale_(scale),
+        y_data_ptr_(y_data_ptr) {}
+
+  HOSTDEVICE void operator()(size_t idx) const {
+    T x_ele = x_data_ptr_[idx];
+    if (x_ele <= 0) {
+      x_ele = alpha_ * funcs::real_exp(x_ele) - alpha_;
+    }
+    y_data_ptr_[idx] = scale_ * x_ele;
+  }
+  const T* x_data_ptr_;
+  const float alpha_;
+  const float scale_;
+  T* y_data_ptr_;
+};
+
+template <typename T>
+struct SeluGradFunctor {
+  SeluGradFunctor(const T* y_data_ptr,
+                  const T* dy_data_ptr,
+                  float alpha,
+                  float scale,
+                  T* dx_data_ptr)
+      : y_data_ptr_(y_data_ptr),
+        dy_data_ptr_(dy_data_ptr),
+        alpha_(alpha),
+        scale_(scale),
+        la_(alpha * scale),
+        dx_data_ptr_(dx_data_ptr) {}
+
+  HOSTDEVICE void operator()(size_t idx) const {
+    using MT =
+        typename std::conditional<(sizeof(T) > sizeof(float)), T, float>::type;
+
+    auto y_ele = static_cast<MT>(y_data_ptr_[idx]);
+    auto dy_ele = static_cast<MT>(dy_data_ptr_[idx]);
+
+    auto tmp = static_cast<MT>(scale_);
+    if (y_ele <= 0) {
+      tmp = y_ele + static_cast<MT>(la_);
+    }
+    dx_data_ptr_[idx] = static_cast<T>(dy_ele * tmp);
+  }
+  const T* y_data_ptr_;
+  const T* dy_data_ptr_;
+  const float alpha_;
+  const float scale_;
+  const float la_;
+  T* dx_data_ptr_;
+};
+
+template <typename T, typename Context>
+void SeluKernel(const Context& dev_ctx,
+                const DenseTensor& x,
+                float scale,
+                float alpha,
+                DenseTensor* out) {
+  auto out_ptr = dev_ctx.template Alloc<T>(out);
+  SeluFunctor<T> functor(x.data<T>(), alpha, scale, out_ptr);
+  size_t limit = static_cast<size_t>(x.numel());
+  funcs::ForRange<Context> for_range(dev_ctx, limit);
+  for_range(functor);
+}
+}  // namespace phi