// Copyright (c) 2021 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.

#include <unsupported/Eigen/SpecialFunctions>
#include "paddle/fluid/operators/elementwise/elementwise_op_impl.cu.h"
#include "paddle/fluid/operators/lgamma_op.h"

namespace paddle {
namespace operators {

template <typename T>
struct CudaLgammaFunctor {
  __device__ __forceinline__ T operator()(const T x) const {
    return Eigen::numext::lgamma(x);
  }
};

template <typename T>
class LgammaKernel<platform::CUDADeviceContext, T>
    : public framework::OpKernel<T> {
 public:
  void Compute(const framework::ExecutionContext& context) const override {
    const Tensor* x = context.Input<Tensor>("X");
    Tensor* out = context.Output<Tensor>("Out");
    out->mutable_data<T>(context.GetPlace());

    auto& dev_ctx = context.device_context<platform::CUDADeviceContext>();
    std::vector<const framework::Tensor*> ins = {x};
    std::vector<framework::Tensor*> outs = {out};
    auto functor = CudaLgammaFunctor<T>();
    LaunchSameDimsElementwiseCudaKernel<ElementwiseType::kUnary, T, T>(
        dev_ctx, ins, &outs, functor);
  }
};

}  // namespace operators
}  // namespace paddle

namespace ops = paddle::operators;

REGISTER_OP_CUDA_KERNEL(
    lgamma, ops::LgammaKernel<paddle::platform::CUDADeviceContext, float>,
    ops::LgammaKernel<paddle::platform::CUDADeviceContext, double>);

REGISTER_OP_CUDA_KERNEL(
    lgamma_grad,
    ops::LgammaGradKernel<paddle::platform::CUDADeviceContext, float>,
    ops::LgammaGradKernel<paddle::platform::CUDADeviceContext, double>);