furthest_neighbor_sort.hpp

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#ifndef MLPACK_METHODS_NEIGHBOR_SEARCH_FURTHEST_NEIGHBOR_SORT_HPP
#define MLPACK_METHODS_NEIGHBOR_SEARCH_FURTHEST_NEIGHBOR_SORT_HPP

#include <mlpack/prereqs.hpp>

namespace mlpack {
namespace neighbor {

class FurthestNS
{
 public:
  static inline bool IsBetter(const double value, const double ref)
  {
    return (value >= ref);
  }

  template<typename TreeType>
  static double BestNodeToNodeDistance(const TreeType* queryNode,
                                       const TreeType* referenceNode);

  template<typename TreeType>
  static double BestNodeToNodeDistance(const TreeType* queryNode,
                                       const TreeType* referenceNode,
                                       const double centerToCenterDistance);

  template<typename TreeType>
  static double BestNodeToNodeDistance(const TreeType* queryNode,
                                       const TreeType* referenceNode,
                                       const TreeType* referenceChildNode,
                                       const double centerToCenterDistance);

  template<typename VecType, typename TreeType>
  static double BestPointToNodeDistance(const VecType& queryPoint,
                                        const TreeType* referenceNode);

  template<typename VecType, typename TreeType>
  static double BestPointToNodeDistance(const VecType& queryPoint,
                                        const TreeType* referenceNode,
                                        const double pointToCenterDistance);

  template<typename VecType, typename TreeType>
  static size_t GetBestChild(const VecType& queryPoint, TreeType& referenceNode)
  {
    return referenceNode.GetFurthestChild(queryPoint);
  };

  template<typename TreeType>
  static size_t GetBestChild(const TreeType& queryNode, TreeType& referenceNode)
  {
    return referenceNode.GetFurthestChild(queryNode);
  };

  static inline double WorstDistance() { return 0; }

  static inline double BestDistance() { return DBL_MAX; }

  static inline double CombineBest(const double a, const double b)
  {
    if (a == DBL_MAX || b == DBL_MAX)
      return DBL_MAX;
    return a + b;
  }

  static inline double CombineWorst(const double a, const double b)
  { return std::max(a - b, 0.0); }

  static inline double Relax(const double value, const double epsilon)
  {
    if (value == 0)
      return 0;
    if (value == DBL_MAX || epsilon >= 1)
      return DBL_MAX;
    return (1 / (1 - epsilon)) * value;
  }

  static inline double ConvertToScore(const double distance)
  {
    if (distance == DBL_MAX)
      return 0.0;
    else if (distance == 0.0)
      return DBL_MAX;
    else
      return (1.0 / distance);
  }

  static inline double ConvertToDistance(const double score)
  {
    return ConvertToScore(score);
  }
};

// Due to an internal MinGW compiler bug (string table overflow) we have to
// truncate the class name. For backward compatibility we setup an alias here.
using FurthestNeighborSort = FurthestNS;

} // namespace neighbor
} // namespace mlpack

// Include implementation of templated functions.
#include "furthest_neighbor_sort_impl.hpp"

#endif