ClosestPair2D.hh

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//STARTHEADER
// $Id: ClosestPair2D.hh 293 2006-08-17 19:38:38Z salam $
//
// Copyright (c) 2005-2006, Matteo Cacciari and Gavin Salam
//
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// This file is part of FastJet.
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#ifndef __FASTJET_CLOSESTPAIR2D__HH__
#define __FASTJET_CLOSESTPAIR2D__HH__

#include<vector>
#include<stack>
#include<iostream>
#include "fastjet/internal/ClosestPair2DBase.hh"
#include "fastjet/internal/SearchTree.hh"
#include "fastjet/internal/MinHeap.hh"

FASTJET_BEGIN_NAMESPACE      // defined in fastjet/internal/base.hh

//----------------------------------------------------------------------
class ClosestPair2D : public ClosestPair2DBase {
public:
  ClosestPair2D(const std::vector<Coord2D> & positions, 
                const Coord2D & left_corner, const Coord2D & right_corner) {
    _initialize(positions, left_corner, right_corner, positions.size());
  };

  ClosestPair2D(const std::vector<Coord2D> & positions, 
                const Coord2D & left_corner, const Coord2D & right_corner,
                const unsigned int max_size) {
    _initialize(positions, left_corner, right_corner, max_size);
  };

  void closest_pair(unsigned int & ID1, unsigned int & ID2, 
                    double & distance2) const;

  void remove(unsigned int ID);
 
  unsigned int insert(const Coord2D &);

  virtual unsigned int replace(unsigned int ID1, unsigned int ID2, 
                               const Coord2D & position);

  virtual void replace_many(const std::vector<unsigned int> & IDs_to_remove,
                            const std::vector<Coord2D> & new_positions,
                            std::vector<unsigned int> & new_IDs);

  // mostly for checking how things are working...
  inline void print_tree_depths(std::ostream & outdev) const {
    outdev    << _trees[0]->max_depth() << " "
              << _trees[1]->max_depth() << " "
              << _trees[2]->max_depth() << "\n";
  };

  unsigned int size();

private:
  
  void _initialize(const std::vector<Coord2D> & positions, 
              const Coord2D & left_corner, const Coord2D & right_corner,
              const unsigned int max_size);

  static const unsigned int _nshift = 3;

  class Point; // will be defined below

  template<class T> class triplet {
  public:
    inline const T & operator[](unsigned int i) const {return _contents[i];};
    inline       T & operator[](unsigned int i)       {return _contents[i];};
  private:
    T _contents[_nshift];
  };


  class Shuffle {
  public:
    unsigned int x, y;
    Point * point;
    bool operator<(const Shuffle &) const;
    void operator+=(unsigned int shift) {x += shift; y+= shift;};
  };

  typedef SearchTree<Shuffle>     Tree;
  typedef Tree::circulator        circulator;
  typedef Tree::const_circulator  const_circulator;


  triplet<std::auto_ptr<Tree> >  _trees;
  std::auto_ptr<MinHeap> _heap;
  std::vector<Point>     _points;
  std::stack<Point *>    _available_points;

  std::vector<Point *>   _points_under_review;

  // different statuses for review
  static const unsigned int _remove_heap_entry = 1;
  static const unsigned int _review_heap_entry = 2;
  static const unsigned int _review_neighbour  = 4;

  void _add_label(Point * point, unsigned int review_flag);

  void _set_label(Point * point, unsigned int review_flag);

  void _deal_with_points_to_review();

  void _remove_from_search_tree(Point * point_to_remove);

  void _insert_into_search_tree(Point * new_point);

  void _point2shuffle(Point & , Shuffle & , unsigned int shift);

  Coord2D _left_corner;
  double _range;

  int _ID(const Point *) const;

  triplet<unsigned int> _shifts;     // absolute shifts
  triplet<unsigned int> _rel_shifts; // shifts relative to previous shift

  unsigned int _cp_search_range;
};


//----------------------------------------------------------------------
class ClosestPair2D::Point {
public:
  Coord2D coord;
  Point * neighbour;
  double  neighbour_dist2;
  triplet<circulator> circ;

  unsigned int review_flag;

  double distance2(const Point & other) const {
    return coord.distance2(other.coord);
  };

  //void set_shuffle(Shuffle & shuffle);
};


//----------------------------------------------------------------------
inline bool floor_ln2_less(unsigned x, unsigned y) {
  if (x>y) return false;
  return (x < (x^y)); // beware of operator precedence...
}


//----------------------------------------------------------------------
inline int ClosestPair2D::_ID(const Point * point) const {
  return point - &(_points[0]);
}


//
inline unsigned int ClosestPair2D::size() {
  return _points.size() - _available_points.size();
}



FASTJET_END_NAMESPACE

#endif // __FASTJET_CLOSESTPAIR2D__HH__