nguyen_widrow_init.hpp

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#ifndef MLPACK_METHODS_ANN_INIT_RULES_NGUYEN_WIDROW_INIT_HPP
#define MLPACK_METHODS_ANN_INIT_RULES_NGUYEN_WIDROW_INIT_HPP

#include <mlpack/prereqs.hpp>

#include "init_rules_traits.hpp"
#include "random_init.hpp"

namespace mlpack {
namespace ann  {

class NguyenWidrowInitialization
{
 public:
  NguyenWidrowInitialization(const double lowerBound = -0.5,
                             const double upperBound = 0.5) :
      lowerBound(lowerBound), upperBound(upperBound) { }

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

    double beta = 0.7 * std::pow(cols, 1.0 / rows);
    W *= (beta / arma::norm(W));
  }

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

    double beta = 0.7 * std::pow(W.n_cols, 1.0 / W.n_rows);
    W *= (beta / arma::norm(W));
  }

  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 matrix." << std::endl;

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

 private:
  double lowerBound;

  double upperBound;
}; // class NguyenWidrowInitialization

template<>
class InitTraits<NguyenWidrowInitialization>
{
 public:
  static const bool UseLayer = false;
};


} // namespace ann
} // namespace mlpack

#endif