// Copyright (c) 2020 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 <thrust/device_vector.h>
#include <thrust/host_vector.h>
#include "paddle/fluid/operators/math/math_function.h"
#include "paddle/fluid/operators/reduce_ops/cub_reduce.h"
#include "paddle/fluid/operators/trace_op.h"

namespace paddle {
namespace operators {

struct IdentityFunctor {
  HOSTDEVICE explicit inline IdentityFunctor() {}

  template <typename U>
  HOSTDEVICE inline U operator()(const U& x) const {
    return x;
  }
};

template <typename DeviceContext, typename T>
class TraceCUDAKernel : public framework::OpKernel<T> {
 public:
  void Compute(const framework::ExecutionContext& context) const override {
    auto* input = context.Input<framework::Tensor>("Input");
    auto* out = context.Output<framework::Tensor>("Out");

    const int64_t offset = context.Attr<int>("offset");
    const int64_t dim1 = context.Attr<int>("axis1");
    const int64_t dim2 = context.Attr<int>("axis2");

    T* out_data = out->mutable_data<T>(context.GetPlace());
    const framework::Tensor diag =
        Diagonal<DeviceContext, T>(context, input, offset, dim1, dim2);
    if (diag.numel() > 0) {
      auto stream = context.cuda_device_context().stream();
      std::vector<int> reduce_dims;
      reduce_dims.push_back(out->dims().size());
      TensorReduce<T, T, cub::Sum, IdentityFunctor>(
          diag, out, reduce_dims, static_cast<T>(0), cub::Sum(),
          IdentityFunctor(), stream);
    } else {
      math::SetConstant<DeviceContext, T> functor;
      functor(context.device_context<DeviceContext>(), out, static_cast<T>(0));
    }
  }
};
}  // namespace operators
}  // namespace paddle

namespace ops = paddle::operators;
namespace platform = paddle::platform;
REGISTER_OP_CUDA_KERNEL(
    trace, ops::TraceCUDAKernel<paddle::platform::CUDADeviceContext, int>,
    ops::TraceCUDAKernel<paddle::platform::CUDADeviceContext, int64_t>,
    ops::TraceCUDAKernel<paddle::platform::CUDADeviceContext,
                         platform::float16>,
    ops::TraceCUDAKernel<paddle::platform::CUDADeviceContext, float>,
    ops::TraceCUDAKernel<paddle::platform::CUDADeviceContext, double>,
    ops::TraceCUDAKernel<paddle::platform::CUDADeviceContext,
                         paddle::platform::complex<float>>,
    ops::TraceCUDAKernel<paddle::platform::CUDADeviceContext,
                         paddle::platform::complex<double>>);
REGISTER_OP_CUDA_KERNEL(
    trace_grad, ops::TraceGradKernel<paddle::platform::CUDADeviceContext, int>,
    ops::TraceGradKernel<paddle::platform::CUDADeviceContext, int64_t>,
    ops::TraceGradKernel<paddle::platform::CUDADeviceContext,
                         platform::float16>,
    ops::TraceGradKernel<paddle::platform::CUDADeviceContext, float>,
    ops::TraceGradKernel<paddle::platform::CUDADeviceContext, double>,
    ops::TraceGradKernel<paddle::platform::CUDADeviceContext,
                         paddle::platform::complex<float>>,
    ops::TraceGradKernel<paddle::platform::CUDADeviceContext,
                         paddle::platform::complex<double>>);
