// 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/fluid/operators/random_routing_op.h"
#include "paddle/fluid/framework/op_registry.h"
#include "paddle/fluid/platform/float16.h"
#include "paddle/phi/backends/gpu/gpu_primitives.h"

namespace paddle {
namespace operators {

#define CEIL(_x_, _y_) (((_x_)-1) / (_y_) + 1)
#define PERTHREAD_EXPERTS 256
#define WARP_SIZE 32

const int CUDA_NUM_THREADS = 512;
static inline int GET_BLOCKS(const int N) {
  return (N + CUDA_NUM_THREADS - 1) / CUDA_NUM_THREADS;
}

template <typename T>
__global__ void random_routing_kernel(int64_t* data,
                                      const int64_t length,
                                      const size_t N,
                                      const size_t D,
                                      const T* prob,
                                      const int64_t* topk_idx,
                                      const T* topk_value) {
  CUDA_KERNEL_LOOP(idx, length) {
    size_t row = idx / D;
    size_t col = idx % D;
    if (col != 1) return;
    if (static_cast<T>(2) * topk_value[idx] < prob[row]) {
      data[idx] = static_cast<int64_t>(-1);
    }
  }
}

template <typename T>
class RandomRoutingOpCUDAKernel : public framework::OpKernel<T> {
 public:
  void Compute(const framework::ExecutionContext& context) const override {
    auto topk_idx = context.Input<phi::DenseTensor>("TopK_Idx");
    auto topk_value = context.Input<phi::DenseTensor>("TopK_Value");
    auto prob = context.Input<phi::DenseTensor>("Prob");
    auto out = context.Output<phi::DenseTensor>("Out");

    auto place = context.GetPlace();
    const auto& dev_ctx = context.template device_context<phi::GPUContext>();
    framework::TensorCopy(*topk_idx, place, out);

    size_t N = topk_idx->dims()[0];
    size_t D = topk_idx->dims()[1];

    int64_t num_idx = topk_idx->numel();

    auto prob_data = prob->data<T>();
    auto topk_value_data = topk_value->data<T>();
    auto topk_idx_data = topk_idx->data<int64_t>();
    auto out_data = out->data<int64_t>();

    random_routing_kernel<T>
        <<<GET_BLOCKS(num_idx), CUDA_NUM_THREADS, 0, dev_ctx.stream()>>>(
            out_data, num_idx, N, D, prob_data, topk_idx_data, topk_value_data);
  }
};

}  // namespace operators
}  // namespace paddle

namespace ops = paddle::operators;
namespace plat = paddle::platform;

REGISTER_OP_CUDA_KERNEL(random_routing,
                        ops::RandomRoutingOpCUDAKernel<float>,
                        ops::RandomRoutingOpCUDAKernel<double>,
                        ops::RandomRoutingOpCUDAKernel<plat::float16>);
