// 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/kernels/gather_nd_grad_kernel.h"

#include "paddle/phi/backends/cpu/cpu_context.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/funcs/eigen/eigen_function.h"
#include "paddle/phi/kernels/funcs/scatter.h"

namespace phi {

template <typename T, typename Context>
void GatherNdGradKernel(const Context &ctx,
                        const DenseTensor &x UNUSED,
                        const DenseTensor &index,
                        const DenseTensor &out_grad,
                        DenseTensor *x_grad) {
  ctx.template Alloc<T>(x_grad);
  auto dxt = phi::EigenVector<T>::Flatten(*x_grad);
  auto &place = *ctx.eigen_device();
  dxt.device(place) = dxt.constant(static_cast<T>(0));
  if (out_grad.numel() == 0) return;

  auto index_type = index.dtype();
  bool index_type_match =
      index_type == phi::DataType::INT32 || index_type == phi::DataType::INT64;
  PADDLE_ENFORCE_EQ(
      index_type_match,
      true,
      phi::errors::InvalidArgument("Index holds the wrong type, it holds [%s],"
                                   "but desires to be [%s] or [%s]",
                                   index_type,
                                   phi::DataType::INT32,
                                   phi::DataType::INT64));

  if (index_type == phi::DataType::INT32) {
    phi::funcs::ScatterNdAdd<T, int32_t>(ctx, out_grad, index, x_grad);
  } else if (index_type == phi::DataType::INT64) {
    phi::funcs::ScatterNdAdd<T, int64_t>(ctx, out_grad, index, x_grad);
  }
}

}  // namespace phi

PD_REGISTER_KERNEL(gather_nd_grad,
                   CPU,
                   ALL_LAYOUT,
                   phi::GatherNdGradKernel,
                   float,
                   double,
                   int64_t,
                   int,
                   uint8_t) {}
