// 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/embedding_kernel.h"
#include "paddle/phi/kernels/funcs/embedding_util.h"

#include "paddle/fluid/framework/convert_utils.h"
#include "paddle/fluid/framework/data_type.h"
#include "paddle/phi/backends/gpu/gpu_context.h"
#include "paddle/phi/core/kernel_registry.h"
#include "paddle/phi/kernels/funcs/eigen/eigen_function.h"

namespace phi {

template <typename T,
          typename IdT,
          int BlockDimX,
          int BlockDimY,
          int GridDimX,
          bool PaddingFlag>
__global__ void LookupTableV2(T *output,
                              const T *table,
                              const IdT *ids,
                              const int64_t N,
                              const int64_t K,
                              const int64_t D,
                              const int64_t padding_idx) {
  int idx = threadIdx.x;
  int idy = blockIdx.x + threadIdx.y * GridDimX;

  while (idy < K) {
    auto id = static_cast<int64_t>(ids[idy]);
    T *out = output + idy * D;
    const T *tab = table + id * D;
    for (int i = idx; i < D; i += BlockDimX) {
      if (PaddingFlag) {
        if (id == padding_idx)
          out[i] = static_cast<T>(0);
        else
          out[i] = tab[i];
      } else {
        out[i] = tab[i];
      }
    }
    idy += BlockDimY * GridDimX;
  }
}

template <typename T, typename Context>
struct LookupTableV2CUDAFunctor {
  LookupTableV2CUDAFunctor(const Context &dev_ctx,
                           const DenseTensor &input,
                           const DenseTensor &weight,
                           int64_t padding_idx,
                           DenseTensor *out)
      : dev_ctx_(dev_ctx),
        input_(input),
        weight_(weight),
        out_(out),
        padding_idx_(padding_idx) {}

  template <typename IdT>
  void apply() {
    size_t N = weight_.dims()[0];
    size_t D = weight_.dims()[1];
    size_t K = input_.numel();

    dim3 threads(256, 4);
    dim3 grids(80, 1);

    const auto *table = weight_.template data<T>();
    const auto *ids = input_.template data<IdT>();
    auto *output = out_->template mutable_data<T>(dev_ctx_.GetPlace());
    auto stream = dev_ctx_.stream();

    if (padding_idx_ == -1) {
      LookupTableV2<T, IdT, 256, 4, 80, false><<<grids, threads, 0, stream>>>(
          output, table, ids, N, K, D, padding_idx_);
    } else {
      LookupTableV2<T, IdT, 256, 4, 80, true><<<grids, threads, 0, stream>>>(
          output, table, ids, N, K, D, padding_idx_);
    }
  }

 private:
  const phi::GPUContext &dev_ctx_;
  const DenseTensor &input_;
  const DenseTensor &weight_;
  DenseTensor *out_;
  int64_t padding_idx_;
};

template <typename T, typename Context>
void EmbeddingKernel(const Context &ctx,
                     const DenseTensor &input,
                     const DenseTensor &weight,
                     int64_t padding_idx,
                     DenseTensor *out) {
  LookupTableV2CUDAFunctor<T, Context> functor(
      ctx, input, weight, padding_idx, out);
  paddle::framework::VisitIntDataType(
      paddle::framework::TransToProtoVarType(input.dtype()), functor);
}

}  // namespace phi

PD_REGISTER_KERNEL(embedding,
                   GPU,
                   ALL_LAYOUT,
                   phi::EmbeddingKernel,
                   float,
                   double,
                   phi::dtype::float16) {}