source: HiSusy/trunk/Delphes/Delphes-3.0.9/external/fastjet/ClosestPair2D.cc @ 5

Last change on this file since 5 was 5, checked in by zerwas, 11 years ago

update to Delphes-3.0.9

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1//STARTHEADER
2// $Id: ClosestPair2D.cc 859 2012-11-28 01:49:23Z pavel $
3//
4// Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
5//
6//----------------------------------------------------------------------
7// This file is part of FastJet.
8//
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23//
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26//----------------------------------------------------------------------
27//ENDHEADER
28
29#include "fastjet/internal/ClosestPair2D.hh"
30
31#include<limits>
32#include<iostream>
33#include<iomanip>
34#include<algorithm>
35
36FASTJET_BEGIN_NAMESPACE      // defined in fastjet/internal/base.hh
37
38const unsigned int huge_unsigned = 4294967295U;
39const unsigned int twopow31      = 2147483648U;
40
41using namespace std;
42
43//----------------------------------------------------------------------
44/// takes a point and sets a shuffle with the given shift...
45void ClosestPair2D::_point2shuffle(Point & point, Shuffle & shuffle, 
46                                  unsigned int shift) {
47 
48  Coord2D renorm_point = (point.coord - _left_corner)/_range;
49  // make sure the point is sensible
50  //cerr << point.coord.x <<" "<<point.coord.y<<endl;
51  assert(renorm_point.x >=0);
52  assert(renorm_point.x <=1);
53  assert(renorm_point.y >=0);
54  assert(renorm_point.y <=1);
55 
56  shuffle.x = static_cast<unsigned int>(twopow31 * renorm_point.x) + shift;
57  shuffle.y = static_cast<unsigned int>(twopow31 * renorm_point.y) + shift;
58  shuffle.point = &point;
59}
60
61//----------------------------------------------------------------------
62/// compares this shuffle with the other one
63bool ClosestPair2D::Shuffle::operator<(const Shuffle & q) const {
64
65  if (floor_ln2_less(x ^ q.x, y ^ q.y)) {
66    // i = 2 in Chan's algorithm
67    return (y < q.y);
68  } else {
69    // i = 1 in Chan's algorithm
70    return (x < q.x);
71  }
72}
73
74
75
76//----------------------------------------------------------------------
77void ClosestPair2D::_initialize(const std::vector<Coord2D> & positions, 
78                             const Coord2D & left_corner, 
79                             const Coord2D & right_corner,
80                             unsigned int max_size) {
81
82  unsigned int n_positions = positions.size();
83  assert(max_size >= n_positions);
84
85  //_points(positions.size())
86
87  // allow the points array to grow to the following size
88  _points.resize(max_size);
89  // currently unused points are immediately made available on the
90  // stack
91  for (unsigned int i = n_positions; i < max_size; i++) {
92    _available_points.push(&(_points[i]));
93  }
94
95  _left_corner = left_corner;
96  _range       = max((right_corner.x - left_corner.x),
97                     (right_corner.y - left_corner.y));
98
99  // initialise the coordinates for the points and create the zero-shifted
100  // shuffle array
101  vector<Shuffle> shuffles(n_positions);
102  for (unsigned int i = 0; i < n_positions; i++) {
103    // set up the points
104    _points[i].coord = positions[i];
105    _points[i].neighbour_dist2 = numeric_limits<double>::max();
106    _points[i].review_flag = 0;
107
108    // create shuffle with 0 shift.
109    _point2shuffle(_points[i], shuffles[i], 0);
110  }
111
112  // establish what our shifts will be
113  for (unsigned ishift = 0; ishift < _nshift; ishift++) {
114    // make sure we use double-precision for calculating the shifts
115    // since otherwise we will hit integer overflow.
116   _shifts[ishift] = static_cast<unsigned int>(((twopow31*1.0)*ishift)/_nshift);
117    if (ishift == 0) {_rel_shifts[ishift] = 0;}
118    else {_rel_shifts[ishift] = _shifts[ishift] - _shifts[ishift-1];}
119  }
120  //_shifts[0] = 0;
121  //_shifts[1] = static_cast<unsigned int>((twopow31*1.0)/3.0);
122  //_shifts[2] = static_cast<unsigned int>((twopow31*2.0)/3.0);
123  //_rel_shifts[0] = 0;
124  //_rel_shifts[1] = _shifts[1];
125  //_rel_shifts[2] = _shifts[2]-_shifts[1];
126
127  // and how we will search...
128  //_cp_search_range = 49;
129  _cp_search_range = 30;
130  _points_under_review.reserve(_nshift * _cp_search_range);
131
132  // now initialise the three trees
133  for (unsigned int ishift = 0; ishift < _nshift; ishift++) {
134
135    // shift the shuffles if need be.
136    if (ishift > 0) {
137      unsigned rel_shift = _rel_shifts[ishift];
138      for (unsigned int i = 0; i < shuffles.size(); i++) {
139        shuffles[i] += rel_shift; }
140    }
141
142    // sort the shuffles
143    sort(shuffles.begin(), shuffles.end());
144
145    // and create the search tree
146    _trees[ishift] = auto_ptr<Tree>(new Tree(shuffles, max_size));
147
148    // now we look for the closest-pair candidates on this tree
149    circulator circ = _trees[ishift]->somewhere(), start=circ;
150    // the actual range in which we search
151    unsigned int CP_range = min(_cp_search_range, n_positions-1);
152    do {
153      Point * this_point = circ->point;
154      //cout << _ID(this_point) << " ";
155      this_point->circ[ishift] = circ;
156      // run over all points within _cp_search_range of this_point on tree
157      circulator other = circ;
158      for (unsigned i=0; i < CP_range; i++) {
159        ++other;
160        double dist2 = this_point->distance2(*other->point);
161        if (dist2 < this_point->neighbour_dist2) {
162          this_point->neighbour_dist2 = dist2;
163          this_point->neighbour       = other->point;
164        }
165      }
166    } while (++circ != start);
167    //cout << endl<<endl;
168  }
169
170  // now initialise the heap object...
171  vector<double> mindists2(n_positions);
172  for (unsigned int i = 0; i < n_positions; i++) {
173    mindists2[i] = _points[i].neighbour_dist2;}
174 
175  _heap = auto_ptr<MinHeap>(new MinHeap(mindists2, max_size));
176}
177
178
179//----------------------------------------------------------------------=
180void ClosestPair2D::closest_pair(unsigned int & ID1, unsigned int & ID2, 
181                                 double & distance2) const {
182  ID1 = _heap->minloc();
183  ID2 = _ID(_points[ID1].neighbour);
184  distance2 = _points[ID1].neighbour_dist2;
185  if (ID1 > ID2) swap(ID1,ID2);
186}
187
188
189//----------------------------------------------------------------------
190inline void ClosestPair2D::_add_label(Point * point, unsigned int review_flag) {
191
192  // if it's not already under review, then put it on the list of
193  // points needing review
194  if (point->review_flag == 0) _points_under_review.push_back(point);
195
196  // OR the point's current flag with the requested review flag
197  point->review_flag |= review_flag;
198}
199
200//----------------------------------------------------------------------
201inline void ClosestPair2D::_set_label(Point * point, unsigned int review_flag) {
202
203  // if it's not already under review, then put it on the list of
204  // points needing review
205  if (point->review_flag == 0) _points_under_review.push_back(point);
206
207  // SET the point's current flag to the requested review flag
208  point->review_flag = review_flag;
209}
210
211//----------------------------------------------------------------------
212void ClosestPair2D::remove(unsigned int ID) {
213
214  //cout << "While removing " << ID <<endl;
215
216  Point * point_to_remove = & (_points[ID]);
217
218  // remove this point from the search tree
219  _remove_from_search_tree(point_to_remove);
220
221  // the above statement labels certain points as needing "review" --
222  // deal with them...
223  _deal_with_points_to_review();
224}
225
226
227//----------------------------------------------------------------------
228void ClosestPair2D::_remove_from_search_tree(Point * point_to_remove) {
229
230  // add this point to the list of "available" points (this is
231  // relevant also from the point of view of determining the range
232  // over which we circulate).
233  _available_points.push(point_to_remove);
234
235  // label it so that it goes from the heap
236  _set_label(point_to_remove, _remove_heap_entry);
237
238  // establish the range over which we search (a) for points that have
239  // acquired a new neighbour and (b) for points which had ID as their
240  // neighbour;
241 
242  unsigned int CP_range = min(_cp_search_range, size()-1);
243
244  // then, for each shift
245  for (unsigned int ishift = 0; ishift < _nshift; ishift++) {
246    //cout << "   ishift = " << ishift <<endl;
247    // get the circulator for the point we'll remove and its successor
248    circulator removed_circ = point_to_remove->circ[ishift];
249    circulator right_end = removed_circ.next();
250    // remove the point
251    _trees[ishift]->remove(removed_circ);
252   
253    // next find the point CP_range points to the left
254    circulator left_end  = right_end, orig_right_end = right_end;
255    for (unsigned int i = 0; i < CP_range; i++) {left_end--;}
256
257    if (size()-1 < _cp_search_range) {
258      // we have a smaller range now than before -- but when seeing who
259      // could have had ID as a neighbour, we still need to use the old
260      // range for seeing how far back we search (but new separation between
261      // points). [cf CCN28-42]
262      left_end--; right_end--;
263    }
264
265    // and then for each left-end point: establish if the removed
266    // point was its neighbour [in which case a new neighbour must be
267    // found], otherwise see if the right-end point is a closer neighbour
268    do {
269      Point * left_point = left_end->point;
270
271      //cout << "    visited " << setw(3)<<_ID(left_point)<<" (its neighbour was "<<    setw(3)<< _ID(left_point->neighbour)<<")"<<endl;
272
273      if (left_point->neighbour == point_to_remove) {
274        // we'll deal with it later...
275        _add_label(left_point, _review_neighbour);
276      } else {
277        // check to see if right point has become its closest neighbour
278        double dist2 = left_point->distance2(*right_end->point);
279        if (dist2 < left_point->neighbour_dist2) {
280          left_point->neighbour = right_end->point;
281          left_point->neighbour_dist2 = dist2;
282          // NB: (LESSER) REVIEW NEEDED HERE TOO...
283          _add_label(left_point, _review_heap_entry);
284        }
285      }
286      ++right_end;
287    } while (++left_end != orig_right_end);
288  } // ishift...
289
290}
291
292
293//----------------------------------------------------------------------
294void ClosestPair2D::_deal_with_points_to_review() {
295
296  // the range in which we carry out searches for new neighbours on
297  // the search tree
298  unsigned int CP_range = min(_cp_search_range, size()-1);
299
300  // now deal with the points that are "under review" in some way
301  // (have lost their neighbour, or need their heap entry updating)
302  while(_points_under_review.size() > 0) {
303    // get the point to be considered
304    Point * this_point = _points_under_review.back();
305    // remove it from the list
306    _points_under_review.pop_back(); 
307   
308    if (this_point->review_flag & _remove_heap_entry) {
309      // make sure no other flags are on (it wouldn't be consistent?)
310      assert(!(this_point->review_flag ^ _remove_heap_entry));
311      _heap->remove(_ID(this_point));
312    } 
313    // check to see if the _review_neighbour flag is on
314    else {
315      if (this_point->review_flag & _review_neighbour) {
316        this_point->neighbour_dist2 = numeric_limits<double>::max();
317        // among all three shifts
318        for (unsigned int ishift = 0; ishift < _nshift; ishift++) {
319          circulator other = this_point->circ[ishift];
320          // among points within CP_range
321          for (unsigned i=0; i < CP_range; i++) {
322            ++other;
323            double dist2 = this_point->distance2(*other->point);
324            if (dist2 < this_point->neighbour_dist2) {
325              this_point->neighbour_dist2 = dist2;
326              this_point->neighbour       = other->point;
327            }
328          }
329        }
330      }
331
332      // for any non-zero review flag we'll have to update the heap
333      _heap->update(_ID(this_point), this_point->neighbour_dist2);
334    }
335
336    // "delabel" the point
337    this_point->review_flag = 0; 
338
339  }
340
341}
342
343//----------------------------------------------------------------------
344unsigned int ClosestPair2D::insert(const Coord2D & new_coord) {
345
346  // get hold of a point
347  assert(_available_points.size() > 0);
348  Point * new_point = _available_points.top();
349  _available_points.pop();
350
351  // set the point's coordinate
352  new_point->coord = new_coord;
353 
354  // now find it's neighbour in the search tree
355  _insert_into_search_tree(new_point);
356
357  // sort out other points that may have been affected by this,
358  // and/or for which the heap needs to be updated
359  _deal_with_points_to_review();
360
361  //
362  return _ID(new_point);
363}
364
365//----------------------------------------------------------------------
366unsigned int ClosestPair2D::replace(unsigned int ID1, unsigned int ID2, 
367                                    const Coord2D & position) {
368 
369  // deletion from tree...
370  Point * point_to_remove = & (_points[ID1]);
371  _remove_from_search_tree(point_to_remove);
372
373  point_to_remove = & (_points[ID2]);
374  _remove_from_search_tree(point_to_remove);
375
376  // insertion into tree
377  // get hold of a point
378  Point * new_point = _available_points.top();
379  _available_points.pop();
380
381  // set the point's coordinate
382  new_point->coord = position;
383 
384  // now find it's neighbour in the search tree
385  _insert_into_search_tree(new_point);
386
387  // the above statement labels certain points as needing "review" --
388  // deal with them...
389  _deal_with_points_to_review();
390
391  //
392  return _ID(new_point);
393
394}
395
396
397//----------------------------------------------------------------------
398void ClosestPair2D::replace_many(
399                  const std::vector<unsigned int> & IDs_to_remove,
400                  const std::vector<Coord2D> & new_positions,
401                  std::vector<unsigned int> & new_IDs) {
402
403  // deletion from tree...
404  for (unsigned int i = 0; i < IDs_to_remove.size(); i++) {
405    _remove_from_search_tree(& (_points[IDs_to_remove[i]]));
406  }
407
408  // insertion into tree
409  new_IDs.resize(0);
410  for (unsigned int i = 0; i < new_positions.size(); i++) {
411    Point * new_point = _available_points.top();
412    _available_points.pop();
413    // set the point's coordinate
414    new_point->coord = new_positions[i];
415    // now find it's neighbour in the search tree
416    _insert_into_search_tree(new_point);
417    // record the ID
418    new_IDs.push_back(_ID(new_point));
419  }
420
421  // the above statement labels certain points as needing "review" --
422  // deal with them...
423  _deal_with_points_to_review();
424
425}
426
427
428//----------------------------------------------------------------------
429void ClosestPair2D::_insert_into_search_tree(Point * new_point) {
430
431  // this point will have to have it's heap entry reviewed...
432  _set_label(new_point, _review_heap_entry);
433
434  // set the current distance to "infinity"
435  new_point->neighbour_dist2 = numeric_limits<double>::max();
436 
437  // establish how far we will be searching;
438  unsigned int CP_range = min(_cp_search_range, size()-1);
439
440  for (unsigned ishift = 0; ishift < _nshift; ishift++) {
441    // create the shuffle
442    Shuffle new_shuffle;
443    _point2shuffle(*new_point, new_shuffle, _shifts[ishift]);
444   
445    // insert it into the tree
446    circulator new_circ = _trees[ishift]->insert(new_shuffle);
447    new_point->circ[ishift] = new_circ;
448
449    // now get hold of the right and left edges of the region we will be
450    // looking at (cf CCN28-43)
451    circulator right_edge = new_circ; right_edge++;
452    circulator left_edge  = new_circ;
453    for (unsigned int i = 0; i < CP_range; i++) {left_edge--;}
454
455    // now
456    do {
457      Point * left_point  = left_edge->point;
458      Point * right_point = right_edge->point;
459
460      // see if the new point is closer to the left-edge than the latter's
461      // current neighbour
462      double new_dist2 = left_point->distance2(*new_point);
463      if (new_dist2 < left_point->neighbour_dist2) {
464        left_point->neighbour_dist2 = new_dist2;
465        left_point->neighbour       = new_point;
466        _add_label(left_point, _review_heap_entry);
467      }
468
469      // see if the right-point is closer to the new point than it's current
470      // neighbour
471      new_dist2 = new_point->distance2(*right_point);
472      if (new_dist2 < new_point->neighbour_dist2) {
473        new_point->neighbour_dist2 = new_dist2;
474        new_point->neighbour = right_point;
475      }
476
477      // if the right-edge point was the left-edge's neighbour, then
478      // then it's just gone off-radar and the left-point will need to
479      // have its neighbour recalculated [actually, this is overdoing
480      // it a little, since right point may be an less "distant"
481      // (circulator distance) in one of the other shifts -- but not
482      // sure how to deal with this...]
483      if (left_point->neighbour == right_point) {
484        _add_label(left_point, _review_neighbour);
485      }
486
487      // shift the left and right edges until left edge hits new_circ
488      right_edge++;
489    } while (++left_edge != new_circ);
490  }
491}
492
493FASTJET_END_NAMESPACE
494
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