mahalanobis_distance.hpp

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/***
 * @file mahalanobis_distance.hpp
 * @author Ryan Curtin
 *
 * The Mahalanobis distance.
 *
 * mlpack is free software; you may redistribute it and/or modify it under the
 * terms of the 3-clause BSD license.  You should have received a copy of the
 * 3-clause BSD license along with mlpack.  If not, see
 * http://www.opensource.org/licenses/BSD-3-Clause for more information.
 */
#ifndef MLPACK_CORE_METRICS_MAHALANOBIS_DISTANCE_HPP
#define MLPACK_CORE_METRICS_MAHALANOBIS_DISTANCE_HPP

#include <mlpack/prereqs.hpp>

namespace mlpack {
namespace metric {

template<bool TakeRoot = true>
class MahalanobisDistance
{
 public:
  MahalanobisDistance() { }

  MahalanobisDistance(const size_t dimensionality) :
      covariance(arma::eye<arma::mat>(dimensionality, dimensionality)) { }

  MahalanobisDistance(arma::mat covariance) :
      covariance(std::move(covariance)) { }

  template<typename VecTypeA, typename VecTypeB>
  double Evaluate(const VecTypeA& a, const VecTypeB& b);

  const arma::mat& Covariance() const { return covariance; }

  arma::mat& Covariance() { return covariance; }

  template<typename Archive>
  void serialize(Archive& ar, const unsigned int version);

 private:
  arma::mat covariance;
};

} // namespace metric
} // namespace mlpack

#include "mahalanobis_distance_impl.hpp"

#endif