// 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.

#include "paddle/phi/backends/gpu/gpu_context.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/funcs/reduce_function.h"
#include "paddle/phi/kernels/gpu/reduce_grad.h"
#include "paddle/phi/kernels/reduce_mean_grad_kernel.h"

namespace phi {

template <typename T, typename Context>
void ReduceMeanGradKernel(const Context& dev_ctx,
                          const DenseTensor& x,
                          const DenseTensor& out_grad,
                          const std::vector<int64_t>& dims,
                          bool keep_dim,
                          bool reduce_all,
                          DenseTensor* x_grad) {
  int dim_size = x.dims().size();
  std::vector<int> reduce_dims =
      funcs::details::GetReduceDim(dims, dim_size, reduce_all);
  int reduce_num = 1;
  for (auto i : reduce_dims) {
    reduce_num *= (x.dims())[i];
  }
  using MPType = typename kps::details::MPTypeTrait<T>::Type;
  ReduceGradKernel<T, T, Context, kps::DivideFunctor<T, MPType>>(
      dev_ctx,
      x,
      out_grad,
      dims,
      keep_dim,
      reduce_all,
      x_grad,
      kps::DivideFunctor<T, MPType>(reduce_num));
}

}  // namespace phi

PD_REGISTER_KERNEL(mean_grad,
                   GPU,
                   ALL_LAYOUT,
                   phi::ReduceMeanGradKernel,
                   bool,
                   float,
                   double,
                   phi::dtype::float16) {}
