inverse_quadratic_function.hpp

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#ifndef MLPACK_METHODS_ANN_ACTIVATION_FUNCTIONS_INVERSE_QUAD_FUNCTION_HPP
#define MLPACK_METHODS_ANN_ACTIVATION_FUNCTIONS_INVERSE_QUAD_FUNCTION_HPP

#include <mlpack/prereqs.hpp>

namespace mlpack {
namespace ann  {

class InvQuadFunction
{
 public:
  static double Fn(const double x)
  {
    return 1 / ( 1 + x * x);
  }

  template<typename InputVecType, typename OutputVecType>
  static void Fn(const InputVecType& x, OutputVecType& y)
  {
    y = 1 / (1 + arma::pow(x, 2));
  }

  static double Deriv(const double y)
  {
    return  - 2 * y / std::pow(1 + std::pow(y, 2), 2);
  }

  template<typename InputVecType, typename OutputVecType>
  static void Deriv(const InputVecType& x, OutputVecType& y)
  {
    y = - 2 * x / arma::pow(1 + arma::pow(x, 2), 2);
  }
}; // class InvQuadFunction

} // namespace ann
} // namespace mlpack

#endif