FastJet  3.3.3
ClosestPair2D.hh
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30 
31 #ifndef __FASTJET_CLOSESTPAIR2D__HH__
32 #define __FASTJET_CLOSESTPAIR2D__HH__
33 
34 #include<vector>
35 #include<stack>
36 #include<iostream>
37 #include "fastjet/internal/ClosestPair2DBase.hh"
38 #include "fastjet/internal/SearchTree.hh"
39 #include "fastjet/internal/MinHeap.hh"
40 #include "fastjet/SharedPtr.hh"
41 
42 FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
43 
44 //----------------------------------------------------------------------
45 /// \if internal_doc
46 /// @ingroup internal
47 /// \class ClosestPair2D
48 /// concrete implementation for finding closest pairs in 2D -- will
49 /// use Chan's (hopefully efficient) shuffle based structures
50 /// \endif
51 class ClosestPair2D : public ClosestPair2DBase {
52 public:
53  /// constructor from a vector of 2D positions -- number of objects
54  /// after insertion and deletion must never exceed positions.size();
55  /// objects are given IDs that correspond to their index in the vector
56  /// of positions
57  ClosestPair2D(const std::vector<Coord2D> & positions,
58  const Coord2D & left_corner, const Coord2D & right_corner) {
59  _initialize(positions, left_corner, right_corner, positions.size());
60  };
61 
62  /// constructor which allows structure to grow beyond positions.size(), up
63  /// to max_size
64  ClosestPair2D(const std::vector<Coord2D> & positions,
65  const Coord2D & left_corner, const Coord2D & right_corner,
66  const unsigned int max_size) {
67  _initialize(positions, left_corner, right_corner, max_size);
68  };
69 
70  /// provides the IDs of the closest pair as well as the distance between
71  /// them
72  void closest_pair(unsigned int & ID1, unsigned int & ID2,
73  double & distance2) const;
74 
75  /// removes the entry labelled by ID from the object;
76  void remove(unsigned int ID);
77 
78  /// inserts the position into the closest pair structure and returns the
79  /// ID that has been allocated for the object.
80  unsigned int insert(const Coord2D &);
81 
82  /// removes ID1 and ID2 and inserts position, returning the ID
83  /// corresponding to position...
84  virtual unsigned int replace(unsigned int ID1, unsigned int ID2,
85  const Coord2D & position);
86 
87  /// replaces IDs_to_remove with points at the new_positions
88  /// indicating the IDs allocated to the new points in new_IDs
89  virtual void replace_many(const std::vector<unsigned int> & IDs_to_remove,
90  const std::vector<Coord2D> & new_positions,
91  std::vector<unsigned int> & new_IDs);
92 
93  // mostly for checking how things are working...
94  inline void print_tree_depths(std::ostream & outdev) const {
95  outdev << _trees[0]->max_depth() << " "
96  << _trees[1]->max_depth() << " "
97  << _trees[2]->max_depth() << "\n";
98  };
99 
100  unsigned int size();
101 
102 private:
103 
104  void _initialize(const std::vector<Coord2D> & positions,
105  const Coord2D & left_corner, const Coord2D & right_corner,
106  const unsigned int max_size);
107 
108  static const unsigned int _nshift = 3;
109 
110  class Point; // will be defined below
111 
112  /// since sets of three objects will crop up repeatedly, useful
113  /// to have a triplet class?
114  template<class T> class triplet {
115  public:
116  inline const T & operator[](unsigned int i) const {return _contents[i];};
117  inline T & operator[](unsigned int i) {return _contents[i];};
118  private:
119  T _contents[_nshift];
120  };
121 
122 
123  /// class that will take care of ordering of shuffles for us
124  class Shuffle {
125  public:
126  unsigned int x, y;
127  Point * point;
128  bool operator<(const Shuffle &) const;
129  void operator+=(unsigned int shift) {x += shift; y+= shift;};
130  };
131 
132  typedef SearchTree<Shuffle> Tree;
133  typedef Tree::circulator circulator;
134  typedef Tree::const_circulator const_circulator;
135 
136 
137  triplet<SharedPtr<Tree> > _trees;
138  SharedPtr<MinHeap> _heap;
139  std::vector<Point> _points;
140  std::stack<Point *> _available_points;
141 
142  /// points that are "under review" in some way
143  std::vector<Point *> _points_under_review;
144 
145  // different statuses for review
146  static const unsigned int _remove_heap_entry = 1;
147  static const unsigned int _review_heap_entry = 2;
148  static const unsigned int _review_neighbour = 4;
149 
150  /// add a label to a point as to the nature of review needed
151  /// (includes adding it to list of points needing review) [doesn't
152  /// affect other labels already set for the point]
153  void _add_label(Point * point, unsigned int review_flag);
154 
155  /// sets the label for the point to be exclusively this
156  /// review flag (and adds it to list of points needing review
157  /// if not already there)
158  void _set_label(Point * point, unsigned int review_flag);
159 
160  /// for all entries of the _points_under_review[] vector, carry out
161  /// the actions indicated by its review flag; the points are
162  /// then removed from _points_under_review[] and their flags
163  /// set to zero
164  void _deal_with_points_to_review();
165 
166  /// carry out the search-tree related operations of point removal
167  void _remove_from_search_tree(Point * point_to_remove);
168 
169  /// carry out the search-tree related operations of point insertion
170  void _insert_into_search_tree(Point * new_point);
171 
172  /// takes a point and creates a shuffle with the given shift
173  void _point2shuffle(Point & , Shuffle & , unsigned int shift);
174 
175  /// pieces needed for converting coordinates to integer
176  Coord2D _left_corner;
177  double _range;
178 
179  int _ID(const Point *) const;
180 
181  triplet<unsigned int> _shifts; // absolute shifts
182  triplet<unsigned int> _rel_shifts; // shifts relative to previous shift
183 
184  unsigned int _cp_search_range;
185 };
186 
187 
188 //----------------------------------------------------------------------
189 /// \if internal_doc
190 /// @ingroup internal
191 /// \class ClosestPair2D::Point
192 /// class for representing all info needed about a point
193 /// \endif
194 class ClosestPair2D::Point {
195 public:
196  /// the point's coordinates
197  Coord2D coord;
198  /// a pointer to its closest neighbour in our structure
199  Point * neighbour;
200  /// the corresponding squared distance
201  double neighbour_dist2;
202  /// circulators for each of the shifts of the shuffles
203  triplet<circulator> circ;
204 
205  /// indicates that something special is currently happening to this point
206  unsigned int review_flag;
207 
208  /// returns the distance between two of these objects
209  double distance2(const Point & other) const {
210  return coord.distance2(other.coord);
211  };
212 
213  /// creates a shuffle for us with a given shift
214  //void set_shuffle(Shuffle & shuffle);
215 };
216 
217 
218 //----------------------------------------------------------------------
219 /// returns true if floor(ln_base2(x)) < floor(ln_base2(y)), using
220 /// Chan's neat trick...
221 inline bool floor_ln2_less(unsigned x, unsigned y) {
222  if (x>y) return false;
223  return (x < (x^y)); // beware of operator precedence...
224 }
225 
226 
227 //----------------------------------------------------------------------
228 /// returns the ID for the specified point...
229 inline int ClosestPair2D::_ID(const Point * point) const {
230  return point - &(_points[0]);
231 }
232 
233 
234 //
235 inline unsigned int ClosestPair2D::size() {
236  return _points.size() - _available_points.size();
237 }
238 
239 
240 
241 FASTJET_END_NAMESPACE
242 
243 #endif // __FASTJET_CLOSESTPAIR2D__HH__
bool floor_ln2_less(unsigned x, unsigned y)
returns true if floor(ln_base2(x)) < floor(ln_base2(y)), using Chan&#39;s neat trick...
bool operator<(SharedPtr< T > const &t, SharedPtr< U > const &u)
comparison: orgering
Definition: SharedPtr.hh:390