identity_function.hpp

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#ifndef MLPACK_METHODS_ANN_ACTIVATION_FUNCTIONS_IDENTITY_FUNCTION_HPP
#define MLPACK_METHODS_ANN_ACTIVATION_FUNCTIONS_IDENTITY_FUNCTION_HPP

#include <mlpack/prereqs.hpp>

namespace mlpack {
namespace ann  {

class IdentityFunction
{
 public:
  static double fn(const double x)
  {
    return x;
  }

  template<typename InputVecType, typename OutputVecType>
  static void fn(const InputVecType& x, OutputVecType& y)
  {
    y = x;
  }

  static double deriv(const double /* unused */)
  {
    return 1.0;
  }

  template<typename InputVecType, typename OutputVecType>
  static void deriv(const InputVecType& y, OutputVecType& x)
  {
    x.ones(y.n_elem);
  }

  template<typename eT>
  static void deriv(const arma::Cube<eT>& y, arma::Cube<eT>& x)
  {
    x.ones(y.n_rows, y.n_cols, y.n_slices);
  }


}; // class IdentityFunction

} // namespace ann
} // namespace mlpack

#endif