/* Copyright (c) 2016 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 <cmath>
#include "paddle/fluid/operators/elementwise/elementwise_op.h"

namespace paddle {
namespace operators {

template <typename DeviceContext, typename T>
class ElementwiseMinKernel : public framework::OpKernel<T> {
 public:
  void Compute(const framework::ExecutionContext& ctx) const override {
    auto* x = ctx.Input<framework::LoDTensor>("X");
    auto* y = ctx.Input<framework::LoDTensor>("Y");
    auto* z = ctx.Output<framework::LoDTensor>("Out");

    z->mutable_data<T>(ctx.GetPlace());
    int axis = ctx.Attr<int>("axis");
    ElementwiseComputeEx<MinFunctor<T>, DeviceContext, T>(ctx, x, y, axis,
                                                          MinFunctor<T>(), z);
  }
};

template <typename T>
struct MinGradDx {
  HOSTDEVICE T operator()(T x, T y, T out, T dout) const {
    return dout * (x < y);
  }
};

template <typename T>
struct MinGradDy {
  HOSTDEVICE T operator()(T x, T y, T out, T dout) const {
    return dout * (x >= y);
  }
};

#ifdef PADDLE_CUDA_FP16
template <>
struct MinGradDx<platform::float16> {
  HOSTDEVICE platform::float16 operator()(platform::float16 x,
                                          platform::float16 y,
                                          platform::float16 out,
                                          platform::float16 dout) const {
    return x < y ? dout : static_cast<platform::float16>(0);
  }
};

template <>
struct MinGradDy<platform::float16> {
  HOSTDEVICE platform::float16 operator()(platform::float16 x,
                                          platform::float16 y,
                                          platform::float16 out,
                                          platform::float16 dout) const {
    return x >= y ? dout : static_cast<platform::float16>(0);
  }
};
#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:
  void Compute(const framework::ExecutionContext& ctx) const override {
    ElemwiseGradKernel<T>::Compute(ctx);
    using Tensor = framework::Tensor;

    auto* x = ctx.Input<Tensor>("X");
    auto* y = ctx.Input<Tensor>("Y");
    auto* dout = ctx.Input<Tensor>(framework::GradVarName("Out"));
    auto* dx = ctx.Output<Tensor>(framework::GradVarName("X"));
    auto* dy = ctx.Output<Tensor>(framework::GradVarName("Y"));
    auto* out = dout;  // Fake out, not used
    ElementwiseMinGrad<DeviceContext, T>(ctx, x, y, out, dout, dx, dy);
  }
};
}  // namespace operators
}  // namespace paddle