oivs_init.hpp

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#ifndef MLPACK_METHODS_ANN_INIT_RULES_OIVS_INIT_HPP
#define MLPACK_METHODS_ANN_INIT_RULES_OIVS_INIT_HPP

#include <mlpack/prereqs.hpp>
#include <mlpack/methods/ann/activation_functions/logistic_function.hpp>

#include "random_init.hpp"

namespace mlpack {
namespace ann  {

template<
    class ActivationFunction = LogisticFunction
>
class OivsInitialization
{
 public:
  OivsInitialization(const double epsilon = 0.1,
                     const int k = 5,
                     const double gamma = 0.9) :
      k(k), gamma(gamma),
      b(std::abs(ActivationFunction::Inv(1 - epsilon) -
                 ActivationFunction::Inv(epsilon)))
  {
  }

  template<typename eT>
  void Initialize(arma::Mat<eT>& W, const size_t rows, const size_t cols)
  {
    RandomInitialization randomInit(-gamma, gamma);
    randomInit.Initialize(W, rows, cols);

    W = (b / (k  * rows)) * arma::sqrt(W + 1);
  }

  template<typename eT>
  void Initialize(arma::Mat<eT>& W)
  {
    RandomInitialization randomInit(-gamma, gamma);
    randomInit.Initialize(W);

    W = (b / (k  * W.n_rows)) * arma::sqrt(W + 1);
  }

  template<typename eT>
  void Initialize(arma::Cube<eT>& W,
                  const size_t rows,
                  const size_t cols,
                  const size_t slices)
  {
    if (W.is_empty())
      W.set_size(rows, cols, slices);

    for (size_t i = 0; i < slices; ++i)
      Initialize(W.slice(i), rows, cols);
  }

  template<typename eT>
  void Initialize(arma::Cube<eT>& W)
  {
    if (W.is_empty())
      Log::Fatal << "Cannot initialize an empty cube." << std::endl;

    for (size_t i = 0; i < W.n_slices; ++i)
      Initialize(W.slice(i));
  }

 private:
  int k;

  double gamma;

  double b;
}; // class OivsInitialization


} // namespace ann
} // namespace mlpack

#endif