random_acol_init.hpp

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#ifndef MLPACK_METHODS_LMF_RANDOM_ACOL_INIT_HPP
#define MLPACK_METHODS_LMF_RANDOM_ACOL_INIT_HPP

#include <mlpack/prereqs.hpp>
#include <mlpack/core/math/random.hpp>

namespace mlpack {
namespace amf {

template<size_t columnsToAverage = 5>
class RandomAcolInitialization
{
 public:
  // Empty constructor required for the InitializeRule template
  RandomAcolInitialization()
  { }

  template<typename MatType>
  inline static void Initialize(const MatType& V,
                                const size_t r,
                                arma::mat& W,
                                arma::mat& H)
  {
    const size_t n = V.n_rows;
    const size_t m = V.n_cols;

    if (columnsToAverage > m)
    {
      Log::Warn << "Number of random columns (columnsToAverage) is more than "
          << "the number of columns available in the V matrix; weird results "
          << "may ensue!" << std::endl;
    }

    W.zeros(n, r);

    // Initialize W matrix with random columns.
    for (size_t col = 0; col < r; col++)
    {
      for (size_t randCol = 0; randCol < columnsToAverage; randCol++)
      {
        // .col() does not work in this case, as of Armadillo 3.920.
        W.unsafe_col(col) += V.col(math::RandInt(0, m));
      }
    }

    // Now divide by p.
    W /= columnsToAverage;

    // Initialize H to random values.
    H.randu(r, m);
  }

  template<typename Archive>
  void serialize(Archive& /* ar */, const uint32_t /* version */) { }
};

} // namespace amf
} // namespace mlpack

#endif