/* Copyright 2017 The TensorFlow 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.
==============================================================================*/
#ifndef TENSORFLOW_CONTRIB_LITE_KERNELS_ACTIVATION_FUNCTOR_H_
#define TENSORFLOW_CONTRIB_LITE_KERNELS_ACTIVATION_FUNCTOR_H_

#include <algorithm>
#include <cmath>
#include <cstdlib>

#include "tensorflow/contrib/lite/c/builtin_op_data.h"

namespace tflite {

// Dynamic (non-fused) activation functor. perhaps it is worth having
// template instantiation?
// TODO(aselle): Make this more efficient by pulling the switch to conv_eval
// using template inlining.
class ActivationFunctor {
 public:
  explicit ActivationFunctor(TfLiteFusedActivation act) : act_(act) {}

  float operator()(float a) const {
    switch (act_) {
      case kTfLiteActNone:
        return a;
      case kTfLiteActRelu:
        return a < 0.f ? 0.f : a;
      case kTfLiteActRelu6:
        return std::max(0.f, std::min(a, 6.f));
      case kTfLiteActTanh:
        return std::tanh(a);
      case kTfLiteActSigmoid:
        return 1.0f / (1.0f + std::exp(-a));
      default:
        // TODO(aselle): More informative fatal error!
        exit(1);
    }
  }

 private:
  TfLiteFusedActivation act_;
};

}  // namespace tflite

#endif  // TENSORFLOW_CONTRIB_LITE_KERNELS_ACTIVATION_FUNCTOR_H_