similarity_interpolation.hpp

Go to the documentation of this file.

#ifndef MLPACK_METHODS_CF_SIMILARITY_INTERPOLATION_HPP
#define MLPACK_METHODS_CF_SIMILARITY_INTERPOLATION_HPP

#include <mlpack/prereqs.hpp>

namespace mlpack {
namespace cf {

class SimilarityInterpolation
{
 public:
  // Empty onstructor.
  SimilarityInterpolation() { }

  SimilarityInterpolation(const arma::sp_mat& /* cleanedData */) { }

  template <typename VectorType,
            typename DecompositionPolicy>
  void GetWeights(VectorType&& weights,
                  const DecompositionPolicy& /* decomposition */,
                  const size_t /* queryUser */,
                  const arma::Col<size_t>& neighbors,
                  const arma::vec& similarities,
                  const arma::sp_mat& /* cleanedData */)
  {
    if (similarities.n_elem == 0)
    {
      Log::Fatal << "Require: similarities.n_elem > 0. There should be at "
          << "least one neighbor!" << std::endl;
    }

    if (weights.n_elem != neighbors.n_elem)
    {
      Log::Fatal << "The size of the first parameter (weights) should "
          << "be set to the number of neighbors before calling GetWeights()."
          << std::endl;
    }

    double similaritiesSum = arma::sum(similarities);
    if (std::fabs(similaritiesSum) < 1e-14)
    {
      weights.fill(1.0 / similarities.n_elem);
    }
    else
    {
      weights = similarities / similaritiesSum;
    }
  }
};

} // namespace cf
} // namespace mlpack

#endif