cover_tree.hpp

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#ifndef MLPACK_CORE_TREE_COVER_TREE_COVER_TREE_HPP
#define MLPACK_CORE_TREE_COVER_TREE_COVER_TREE_HPP

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

#include "../statistic.hpp"
#include "first_point_is_root.hpp"

namespace mlpack {
namespace tree {

template<typename MetricType = metric::LMetric<2, true>,
         typename StatisticType = EmptyStatistic,
         typename MatType = arma::mat,
         typename RootPointPolicy = FirstPointIsRoot>
class CoverTree
{
 public:
  typedef MatType Mat;
  typedef typename MatType::elem_type ElemType;

  CoverTree(const MatType& dataset,
            const ElemType base = 2.0,
            MetricType* metric = NULL);

  CoverTree(const MatType& dataset,
            MetricType& metric,
            const ElemType base = 2.0);

  CoverTree(MatType&& dataset,
            const ElemType base = 2.0);

  CoverTree(MatType&& dataset,
            MetricType& metric,
            const ElemType base = 2.0);

  CoverTree(const MatType& dataset,
            const ElemType base,
            const size_t pointIndex,
            const int scale,
            CoverTree* parent,
            const ElemType parentDistance,
            arma::Col<size_t>& indices,
            arma::vec& distances,
            size_t nearSetSize,
            size_t& farSetSize,
            size_t& usedSetSize,
            MetricType& metric = NULL);

  CoverTree(const MatType& dataset,
            const ElemType base,
            const size_t pointIndex,
            const int scale,
            CoverTree* parent,
            const ElemType parentDistance,
            const ElemType furthestDescendantDistance,
            MetricType* metric = NULL);

  CoverTree(const CoverTree& other);

  CoverTree(CoverTree&& other);

  CoverTree& operator=(const CoverTree& other);

  CoverTree& operator=(CoverTree&& other);

  template<typename Archive>
  CoverTree(
      Archive& ar,
      const typename std::enable_if_t<cereal::is_loading<Archive>()>* = 0);

  ~CoverTree();

  template<typename RuleType>
  class SingleTreeTraverser;

  template<typename RuleType>
  class DualTreeTraverser;

  template<typename RuleType>
  using BreadthFirstDualTreeTraverser = DualTreeTraverser<RuleType>;

  const MatType& Dataset() const { return *dataset; }

  size_t Point() const { return point; }
  size_t Point(const size_t) const { return point; }

  bool IsLeaf() const { return (children.size() == 0); }
  size_t NumPoints() const { return 1; }

  const CoverTree& Child(const size_t index) const { return *children[index]; }
  CoverTree& Child(const size_t index) { return *children[index]; }

  CoverTree*& ChildPtr(const size_t index) { return children[index]; }

  size_t NumChildren() const { return children.size(); }

  const std::vector<CoverTree*>& Children() const { return children; }
  std::vector<CoverTree*>& Children() { return children; }

  size_t NumDescendants() const;

  size_t Descendant(const size_t index) const;

  int Scale() const { return scale; }
  int& Scale() { return scale; }

  ElemType Base() const { return base; }
  ElemType& Base() { return base; }

  const StatisticType& Stat() const { return stat; }
  StatisticType& Stat() { return stat; }

  template<typename VecType>
  size_t GetNearestChild(
      const VecType& point,
      typename std::enable_if_t<IsVector<VecType>::value>* = 0);

  template<typename VecType>
  size_t GetFurthestChild(
      const VecType& point,
      typename std::enable_if_t<IsVector<VecType>::value>* = 0);

  size_t GetNearestChild(const CoverTree& queryNode);

  size_t GetFurthestChild(const CoverTree& queryNode);

  ElemType MinDistance(const CoverTree& other) const;

  ElemType MinDistance(const CoverTree& other, const ElemType distance) const;

  ElemType MinDistance(const arma::vec& other) const;

  ElemType MinDistance(const arma::vec& other, const ElemType distance) const;

  ElemType MaxDistance(const CoverTree& other) const;

  ElemType MaxDistance(const CoverTree& other, const ElemType distance) const;

  ElemType MaxDistance(const arma::vec& other) const;

  ElemType MaxDistance(const arma::vec& other, const ElemType distance) const;

  math::RangeType<ElemType> RangeDistance(const CoverTree& other) const;

  math::RangeType<ElemType> RangeDistance(const CoverTree& other,
                                          const ElemType distance) const;

  math::RangeType<ElemType> RangeDistance(const arma::vec& other) const;

  math::RangeType<ElemType> RangeDistance(const arma::vec& other,
                                          const ElemType distance) const;

  CoverTree* Parent() const { return parent; }
  CoverTree*& Parent() { return parent; }

  ElemType ParentDistance() const { return parentDistance; }
  ElemType& ParentDistance() { return parentDistance; }

  ElemType FurthestPointDistance() const { return 0.0; }

  ElemType FurthestDescendantDistance() const
  { return furthestDescendantDistance; }
  ElemType& FurthestDescendantDistance() { return furthestDescendantDistance; }

  ElemType MinimumBoundDistance() const { return furthestDescendantDistance; }

  void Center(arma::vec& center) const
  {
    center = arma::vec(dataset->col(point));
  }

  MetricType& Metric() const { return *metric; }

 private:
  const MatType* dataset;
  size_t point;
  std::vector<CoverTree*> children;
  int scale;
  ElemType base;
  StatisticType stat;
  size_t numDescendants;
  CoverTree* parent;
  ElemType parentDistance;
  ElemType furthestDescendantDistance;
  bool localMetric;
  bool localDataset;
  MetricType* metric;

  void CreateChildren(arma::Col<size_t>& indices,
                      arma::vec& distances,
                      size_t nearSetSize,
                      size_t& farSetSize,
                      size_t& usedSetSize);

  void ComputeDistances(const size_t pointIndex,
                        const arma::Col<size_t>& indices,
                        arma::vec& distances,
                        const size_t pointSetSize);
  size_t SplitNearFar(arma::Col<size_t>& indices,
                      arma::vec& distances,
                      const ElemType bound,
                      const size_t pointSetSize);

  size_t SortPointSet(arma::Col<size_t>& indices,
                      arma::vec& distances,
                      const size_t childFarSetSize,
                      const size_t childUsedSetSize,
                      const size_t farSetSize);

  void MoveToUsedSet(arma::Col<size_t>& indices,
                     arma::vec& distances,
                     size_t& nearSetSize,
                     size_t& farSetSize,
                     size_t& usedSetSize,
                     arma::Col<size_t>& childIndices,
                     const size_t childFarSetSize,
                     const size_t childUsedSetSize);
  size_t PruneFarSet(arma::Col<size_t>& indices,
                     arma::vec& distances,
                     const ElemType bound,
                     const size_t nearSetSize,
                     const size_t pointSetSize);

  void RemoveNewImplicitNodes();

 protected:
  CoverTree();

  friend class cereal::access;

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

  size_t DistanceComps() const { return distanceComps; }
  size_t& DistanceComps() { return distanceComps; }

 private:
  size_t distanceComps;
};

} // namespace tree
} // namespace mlpack

// Include implementation.
#include "cover_tree_impl.hpp"

// Include the rest of the pieces, if necessary.
#include "../cover_tree.hpp"

#endif