1 | //STARTHEADER |
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2 | // $Id: MinHeap.cc 859 2012-11-28 01:49:23Z pavel $ |
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3 | // |
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4 | // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez |
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5 | // |
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6 | //---------------------------------------------------------------------- |
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7 | // This file is part of FastJet. |
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8 | // |
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9 | // FastJet is free software; you can redistribute it and/or modify |
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10 | // it under the terms of the GNU General Public License as published by |
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11 | // the Free Software Foundation; either version 2 of the License, or |
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12 | // (at your option) any later version. |
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13 | // |
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14 | // The algorithms that underlie FastJet have required considerable |
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15 | // development and are described in hep-ph/0512210. If you use |
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16 | // FastJet as part of work towards a scientific publication, please |
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17 | // include a citation to the FastJet paper. |
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18 | // |
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19 | // FastJet is distributed in the hope that it will be useful, |
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20 | // but WITHOUT ANY WARRANTY; without even the implied warranty of |
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21 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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22 | // GNU General Public License for more details. |
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23 | // |
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24 | // You should have received a copy of the GNU General Public License |
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25 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>. |
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26 | //---------------------------------------------------------------------- |
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27 | //ENDHEADER |
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28 | |
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29 | #include "fastjet/internal/MinHeap.hh" |
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30 | #include<iostream> |
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31 | #include<cmath> |
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32 | #include<limits> |
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33 | |
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34 | FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh |
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35 | |
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36 | using namespace std; |
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37 | |
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38 | //---------------------------------------------------------------------- |
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39 | /// construct the MinHeap; structure will be as follows: |
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40 | /// . _heap[0].minloc points to globally smallest entry |
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41 | /// _heap[1].minloc points to smallest entry in one half of heap |
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42 | /// _heap[2].minloc points to smallest entry in other half of heap |
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43 | /// |
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44 | /// . for _heap[i], the "parent" is to be found at (i-1)/2 |
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45 | void MinHeap::_initialise(const std::vector<double> & values){ |
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46 | |
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47 | // fill the high-range of the heap with the largest possible value |
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48 | // (minloc of each entry is itself) |
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49 | for (unsigned i = values.size(); i < _heap.size(); i++) { |
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50 | _heap[i].value = std::numeric_limits<double>::max(); |
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51 | _heap[i].minloc = &(_heap[i]); |
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52 | } |
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53 | |
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54 | // fill the rest of the heap with the actual values |
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55 | // (minloc of each entry is itself) |
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56 | for (unsigned i = 0; i < values.size(); i++) { |
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57 | _heap[i].value = values[i]; |
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58 | _heap[i].minloc = &(_heap[i]); |
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59 | } |
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60 | |
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61 | // now adjust the minlocs so that everything is OK... |
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62 | for (unsigned i = _heap.size()-1; i > 0; i--) { |
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63 | ValueLoc * parent = &(_heap[(i-1)/2]); |
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64 | ValueLoc * here = &(_heap[i]); |
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65 | if (here->minloc->value < parent->minloc->value) { |
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66 | parent->minloc = here->minloc; |
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67 | } |
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68 | } |
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69 | //cout << minloc() << " "<<sqrt(minval())<<endl; |
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70 | //cout << sqrt(_heap[47].value)<<endl; |
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71 | //cout << sqrt(_heap[48].value)<<endl; |
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72 | //cout << sqrt(_heap[25].value)<<endl; |
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73 | } |
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74 | |
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75 | |
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76 | //---------------------------------------------------------------------- |
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77 | void MinHeap::update(unsigned int loc, double new_value) { |
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78 | |
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79 | |
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80 | assert(loc < _heap.size()); |
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81 | ValueLoc * start = &(_heap[loc]); |
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82 | |
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83 | // if the minloc is somewhere below us and our value is no smaller |
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84 | // than the previous value, we can't possibly change the minloc |
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85 | if (start->minloc != start && !(new_value < start->minloc->value)) { |
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86 | start->value = new_value; |
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87 | //std::cout << " had easy exit\n"; |
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88 | return; |
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89 | } |
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90 | |
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91 | // update the value and put a temporary location |
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92 | start->value = new_value; |
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93 | start->minloc = start; |
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94 | // warn that a change has been made at this place |
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95 | bool change_made = true; |
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96 | // to make sure we don't go off edge... |
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97 | ValueLoc * heap_end = (&(_heap[0])) + _heap.size(); |
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98 | |
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99 | // now work our way up the heap |
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100 | while(change_made) { |
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101 | ValueLoc * here = &(_heap[loc]); |
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102 | change_made = false; |
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103 | |
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104 | // if we were pointing to start, then we must re-initialise things |
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105 | if (here->minloc == start) { |
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106 | here->minloc = here; change_made = true; |
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107 | } |
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108 | |
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109 | // now compare current location to children (at 2*loc+1, 2*loc+2) |
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110 | ValueLoc * child = &(_heap[2*loc+1]); |
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111 | if (child < heap_end && child->minloc->value < here->minloc->value ) { |
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112 | here->minloc = child->minloc; |
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113 | change_made = true;} |
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114 | child++; |
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115 | if (child < heap_end && child->minloc->value < here->minloc->value ) { |
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116 | here->minloc = child->minloc; |
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117 | change_made = true;} |
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118 | |
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119 | // then we move up (loc ->(loc-1)/2) if there's anywhere to go |
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120 | if (loc == 0) {break;} |
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121 | loc = (loc-1)/2; |
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122 | } |
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123 | |
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124 | } |
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125 | |
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126 | FASTJET_END_NAMESPACE |
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127 | |
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