mish_function.hpp

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#ifndef MLPACK_METHODS_ANN_ACTIVATION_FUNCTIONS_MISH_FUNCTION_HPP
#define MLPACK_METHODS_ANN_ACTIVATION_FUNCTIONS_MISH_FUNCTION_HPP

#include <mlpack/prereqs.hpp>
#include <algorithm>

namespace mlpack {
namespace ann  {

class MishFunction
{
 public:
  static double Fn(const double x)
  {
    return x * (std::exp(2 * x) + 2 * std::exp(x)) /
           (2 + 2 * std::exp(x) + std::exp(2 * x));
  }

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

  static double Deriv(const double y)
  {
    return std::exp(y) * (4 * (y + 1) + std::exp(y) * (4 * y + 6) +
           4 * std::exp(2 * y) + std::exp(3 * y)) /
           std::pow(std::exp(2 * y) + 2 * std::exp(y) + 2, 2);
  }

  template <typename InputVecType, typename OutputVecType>
  static void Deriv(const InputVecType &y, OutputVecType &x)
  {
    x = arma::exp(y) % (4 * (y + 1) + arma::exp(y) % (4 * y + 6) +
        4 * arma::exp(2 * y) + arma::exp(3 * y)) /
        arma::pow(arma::exp(2 * y) + 2 * arma::exp(y) + 2, 2);
  }
}; // class MishFunction

} // namespace ann
} // namespace mlpack

#endif