//   Copyright (c) 2018 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/framework/details/scale_loss_grad_op_handle.h"

namespace paddle {
namespace framework {
namespace details {
ScaleLossGradOpHandle::ScaleLossGradOpHandle(size_t num_dev, Scope *scope,
                                             platform::Place place,
                                             platform::DeviceContext *dev_ctx)
    : coeff_(static_cast<float>(1.0 / num_dev)), scope_(scope), place_(place) {
  dev_ctxes_[place_] = dev_ctx;
}

ScaleLossGradOpHandle::~ScaleLossGradOpHandle() {}

void ScaleLossGradOpHandle::RunImpl() {
  std::string var_name = static_cast<VarHandle *>(this->outputs_[0])->name_;

  float *tmp =
      scope_->FindVar(var_name)->GetMutable<LoDTensor>()->mutable_data<float>(
          make_ddim({1}), place_);

  if (platform::is_cpu_place(place_)) {
    *tmp = coeff_;
  } else {
#ifdef PADDLE_WITH_CUDA
    auto stream =
        static_cast<platform::CUDADeviceContext *>(this->dev_ctxes_[place_])
            ->stream();
    memory::Copy(boost::get<platform::CUDAPlace>(place_), tmp,
                 platform::CPUPlace(), &coeff_, sizeof(float), stream);
#endif
  }
}

std::string ScaleLossGradOpHandle::Name() const { return "Scale LossGrad"; }
}  // namespace details
}  // namespace framework
}  // namespace paddle
