// Copyright 2018 Xiaomi, Inc.  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.

#ifndef MACE_KERNELS_ACTIVATION_H_
#define MACE_KERNELS_ACTIVATION_H_

#include <algorithm>
#include <cmath>
#include <memory>
#include <string>
#include <vector>

#include "mace/core/future.h"
#include "mace/core/tensor.h"
#include "mace/core/types.h"
#include "mace/kernels/kernel.h"

namespace mace {
namespace kernels {

enum ActivationType {
  NOOP = 0,
  RELU = 1,
  RELUX = 2,
  PRELU = 3,
  TANH = 4,
  SIGMOID = 5
};

inline ActivationType StringToActivationType(const std::string type) {
  if (type == "RELU") {
    return ActivationType::RELU;
  } else if (type == "RELUX") {
    return ActivationType::RELUX;
  } else if (type == "PRELU") {
    return ActivationType::PRELU;
  } else if (type == "TANH") {
    return ActivationType::TANH;
  } else if (type == "SIGMOID") {
    return ActivationType::SIGMOID;
  } else if (type == "NOOP") {
    return ActivationType::NOOP;
  } else {
    LOG(FATAL) << "Unknown activation type: " << type;
  }
  return ActivationType::NOOP;
}

template <typename T>
void DoActivation(const T *input_ptr,
                  T *output_ptr,
                  const index_t size,
                  const ActivationType type,
                  const float relux_max_limit) {
  MACE_CHECK(DataTypeToEnum<T>::value != DataType::DT_HALF);

  switch (type) {
    case NOOP:
      break;
    case RELU:
#pragma omp parallel for
      for (index_t i = 0; i < size; ++i) {
        output_ptr[i] = std::max(input_ptr[i], static_cast<T>(0));
      }
      break;
    case RELUX:
#pragma omp parallel for
      for (index_t i = 0; i < size; ++i) {
        output_ptr[i] = std::min(std::max(input_ptr[i], static_cast<T>(0)),
                                 static_cast<T>(relux_max_limit));
      }
      break;
    case TANH:
#pragma omp parallel for
      for (index_t i = 0; i < size; ++i) {
        output_ptr[i] = std::tanh(input_ptr[i]);
      }
      break;
    case SIGMOID:
#pragma omp parallel for
      for (index_t i = 0; i < size; ++i) {
        output_ptr[i] = 1 / (1 + std::exp(-input_ptr[i]));
      }
      break;
    default:
      LOG(FATAL) << "Unknown activation type: " << type;
  }
}

template <typename T>
void PReLUActivation(const T *input_ptr,
                     const index_t outer_size,
                     const index_t input_chan,
                     const index_t inner_size,
                     const T *alpha_ptr,
                     T *output_ptr) {
#pragma omp parallel for collapse(3)
  for (index_t i = 0; i < outer_size; ++i) {
    for (index_t chan_idx = 0; chan_idx < input_chan; ++chan_idx) {
      for (index_t j = 0; j < inner_size; ++j) {
        index_t idx = i * input_chan * inner_size + chan_idx * inner_size + j;
        if (input_ptr[idx] < 0) {
          output_ptr[idx] = input_ptr[idx] * alpha_ptr[chan_idx];
        } else {
          output_ptr[idx] = input_ptr[idx];
        }
      }
    }
  }
}

template <DeviceType D, typename T>
class ActivationFunctor;

template <>
class ActivationFunctor<DeviceType::CPU, float> : OpKernel {
 public:
  ActivationFunctor(OpKernelContext *context,
                    ActivationType type,
                    float relux_max_limit)
      : OpKernel(context),
        activation_(type),
        relux_max_limit_(relux_max_limit) {}

  MaceStatus operator()(const Tensor *input,
                        const Tensor *alpha,
                        Tensor *output,
                        StatsFuture *future) {
    MACE_UNUSED(future);
    const float *input_ptr = input->data<float>();
    float *output_ptr = output->mutable_data<float>();
    if (activation_ == PRELU) {
      MACE_CHECK_NOTNULL(alpha);
      const float *alpha_ptr = alpha->data<float>();
      const index_t outer_size = output->dim(0);
      const index_t inner_size = output->dim(2) * output->dim(3);
      PReLUActivation(input_ptr, outer_size, input->dim(1), inner_size,
                      alpha_ptr, output_ptr);
    } else {
      DoActivation(input_ptr, output_ptr, output->size(), activation_,
                   relux_max_limit_);
    }
    return MACE_SUCCESS;
  }

 private:
  ActivationType activation_;
  float relux_max_limit_;
};

#ifdef MACE_ENABLE_OPENCL
class OpenCLActivationKernel {
 public:
  virtual MaceStatus Compute(
      OpKernelContext *context,
      const Tensor *input,
      const Tensor *alpha,
      Tensor *output,
      StatsFuture *future) = 0;
  MACE_VIRTUAL_EMPTY_DESTRUCTOR(OpenCLActivationKernel);
};
template <typename T>
class ActivationFunctor<DeviceType::GPU, T> : OpKernel {
 public:
  ActivationFunctor(OpKernelContext *context,
                    ActivationType type,
                    T relux_max_limit);

  MaceStatus operator()(const Tensor *input,
                        const Tensor *alpha,
                        Tensor *output,
                        StatsFuture *future);

 private:
  std::unique_ptr<OpenCLActivationKernel> kernel_;
};
#endif  // MACE_ENABLE_OPENCL

}  // namespace kernels
}  // namespace mace

#endif  // MACE_KERNELS_ACTIVATION_H_
