average_init.hpp

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#ifndef MLPACK_METHODS_AMF_AVERAGE_INIT_HPP
#define MLPACK_METHODS_AMF_AVERAGE_INIT_HPP

#include <mlpack/prereqs.hpp>

namespace mlpack {
namespace amf {

class AverageInitialization
{
 public:
  // Empty constructor required for the InitializeRule template
  AverageInitialization() { }

  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;

    double avgV = 0;
    size_t count = 0;
    double min = DBL_MAX;

    // Iterate over all elements in the matrix (for sparse matrices, this only
    // iterates over nonzeros).
    for (typename MatType::const_row_col_iterator it = V.begin();
        it != V.end(); ++it)
    {
      ++count;
      avgV += *it;
      // Track the minimum value.
      if (*it < min)
        min = *it;
    }

    avgV = sqrt(((avgV / (n * m)) - min) / r);

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

    W = W + avgV;
    H = H + avgV;
  }

  template<typename Archive>
  void Serialize(Archive& /* ar */, const unsigned int /* version */) { }
};

} // namespace amf
} // namespace mlpack

#endif