#ifndef TENSORFLOW_KERNELS_RELU_OP_H_
#define TENSORFLOW_KERNELS_RELU_OP_H_
// Functor definition for ReluOp and ReluGradOp, must be compilable by nvcc.

#include "tensorflow/core/framework/tensor_types.h"
#include "third_party/eigen3/unsupported/Eigen/CXX11/Tensor"

namespace tensorflow {
namespace functor {

// Functor used by ReluOp to do the computations.
template <typename Device, typename T>
struct Relu {
  // Computes Relu activation.
  //
  // features: any shape.
  // activations: same shape as "features".
  void operator()(const Device& d, typename TTypes<T>::ConstTensor features,
                  typename TTypes<T>::Tensor activations) {
    activations.device(d) = features.cwiseMax(static_cast<T>(0));
  }
};

// Functor used by ReluGradOp to do the computations.
template <typename Device, typename T>
struct ReluGrad {
  // Computes ReluGrad backprops.
  //
  // gradients: gradients backpropagated to the Relu op.
  // features: inputs that where passed to the Relu op.
  // backprops: gradients to backpropagate to the Relu inputs.
  void operator()(const Device& d, typename TTypes<T>::ConstTensor gradients,
                  typename TTypes<T>::ConstTensor features,
                  typename TTypes<T>::Tensor backprops) {
    // NOTE: When the activation is exactly zero, we arbitrarily choose to not
    // propagate the associated gradient value.
    backprops.device(d) =
        gradients * (features > features.constant(static_cast<T>(0)));
  }
};

// Functor used by Relu6Op to do the computations.
template <typename Device, typename T>
struct Relu6 {
  // Computes Relu6 activation.
  //
  // features: any shape.
  // activations: same shape as "features".
  void operator()(const Device& d, typename TTypes<T>::ConstTensor features,
                  typename TTypes<T>::Tensor activations) {
    activations.device(d) =
        features.cwiseMax(static_cast<T>(0)).cwiseMin(static_cast<T>(6));
  }
};

// Functor used by ReluGradOp to do the computations.
template <typename Device, typename T>
struct Relu6Grad {
  // Computes Relu6Grad backprops.
  //
  // gradients: gradients backpropagated to the Relu6 op.
  // features: inputs that where passed to the Relu6 op.
  // backprops: gradients to backpropagate to the Relu6 inputs.
  void operator()(const Device& d, typename TTypes<T>::ConstTensor gradients,
                  typename TTypes<T>::ConstTensor features,
                  typename TTypes<T>::Tensor backprops) {
    // NOTE: When the activation is exactly zero or six, we
    // arbitrarily choose to not propagate the associated gradient
    // value.
    backprops.device(d) = gradients *
                          (features > features.constant(static_cast<T>(0))) *
                          (features < features.constant(static_cast<T>(6)));
  }
};

}  // namespace functor
}  // namespace tensorflow

#endif  // TENSORFLOW_KERNELS_RELU_OP_H_