select_impl.hpp

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#ifndef MLPACK_METHODS_ANN_LAYER_SELECT_IMPL_HPP
#define MLPACK_METHODS_ANN_LAYER_SELECT_IMPL_HPP

// In case it hasn't yet been included.
#include "constant.hpp"

namespace mlpack {
namespace ann  {

template<typename InputDataType, typename OutputDataType>
Select<InputDataType, OutputDataType>::Select(
    const size_t index,
    const size_t elements) :
    index(index),
    elements(elements)
  {
    // Nothing to do here.
  }

template<typename InputDataType, typename OutputDataType>
template<typename eT>
void Select<InputDataType, OutputDataType>::Forward(
    const arma::Mat<eT>& input, arma::Mat<eT>& output)
{
  if (elements == 0)
  {
    output = input.col(index);
  }
  else
  {
    output = input.submat(0, index, elements - 1, index);
  }
}

template<typename InputDataType, typename OutputDataType>
template<typename eT>
void Select<InputDataType, OutputDataType>::Backward(
    const arma::Mat<eT>& /* input */,
    const arma::Mat<eT>& gy,
    arma::Mat<eT>& g)
{
  if (elements == 0)
  {
    g = gy;
  }
  else
  {
    g = gy.submat(0, 0, elements - 1, 0);
  }
}

template<typename InputDataType, typename OutputDataType>
template<typename Archive>
void Select<InputDataType, OutputDataType>::serialize(
    Archive& ar, const uint32_t /* version */)
{
  ar(CEREAL_NVP(index));
  ar(CEREAL_NVP(elements));
}

} // namespace ann
} // namespace mlpack

#endif