1 | // -*- C++ -*-
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2 | #ifndef __FASTJET_CLUSTERQUENCE_N2_ICC__
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3 | #define __FASTJET_CLUSTERQUENCE_N2_ICC__
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4 | #include "fastjet/ClusterSequence.hh"
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5 |
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6 | //FJSTARTHEADER
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7 | // $Id: ClusterSequence_N2.cc 1351 2009-01-09 18:03:03Z salam $
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8 | //
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9 | // Copyright (c) 2005-2020, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
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10 | //
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11 | //----------------------------------------------------------------------
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12 | // This file is part of FastJet.
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13 | //
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14 | // FastJet is free software; you can redistribute it and/or modify
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15 | // it under the terms of the GNU General Public License as published by
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16 | // the Free Software Foundation; either version 2 of the License, or
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17 | // (at your option) any later version.
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18 | //
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19 | // The algorithms that underlie FastJet have required considerable
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20 | // development. They are described in the original FastJet paper,
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21 | // hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use
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22 | // FastJet as part of work towards a scientific publication, please
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23 | // quote the version you use and include a citation to the manual and
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24 | // optionally also to hep-ph/0512210.
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25 | //
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26 | // FastJet is distributed in the hope that it will be useful,
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27 | // but WITHOUT ANY WARRANTY; without even the implied warranty of
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28 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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29 | // GNU General Public License for more details.
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30 | //
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31 | // You should have received a copy of the GNU General Public License
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32 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>.
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33 | //----------------------------------------------------------------------
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34 | //FJENDHEADER
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35 |
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36 | //----------------------------------------------------------------------
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37 | /// Order(N^2) clustering
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38 | ///
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39 | /// Works for any class BJ that satisfies certain minimal
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40 | /// requirements (which are ...?)
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41 | ///
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42 | /// - need to have _bj_set_jetinfo
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43 | /// - need to have _bj_dist
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44 | /// - should contain members kt2 (=energy^2), NN, NN_dist, _jets_index
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45 |
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46 | FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
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47 |
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48 | // this should not normally appear in an include file, but we'll make an
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49 | // exception seeing as this is
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50 | //using namespace std;
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51 |
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52 |
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53 | template<class BJ> void ClusterSequence::_simple_N2_cluster() {
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54 | int n = _jets.size();
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55 | BJ * briefjets = new BJ[n];
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56 | BJ * jetA = briefjets, * jetB;
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57 |
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58 | // initialise the basic jet info
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59 | for (int i = 0; i< n; i++) {
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60 | _bj_set_jetinfo(jetA, i);
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61 | jetA++; // move on to next entry of briefjets
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62 | }
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63 | BJ * tail = jetA; // a semaphore for the end of briefjets
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64 | BJ * head = briefjets; // a nicer way of naming start
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65 |
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66 | // now initialise the NN distances: jetA will run from 1..n-1; and
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67 | // jetB from 0..jetA-1
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68 | for (jetA = head + 1; jetA != tail; jetA++) {
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69 | // set NN info for jetA based on jets running from head..jetA-1,
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70 | // checking in the process whether jetA itself is an undiscovered
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71 | // NN of one of those jets.
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72 | _bj_set_NN_crosscheck(jetA, head, jetA);
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73 | }
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74 |
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75 |
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76 | // now create the diJ (where J is i's NN) table -- remember that
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77 | // we differ from standard normalisation here by a factor of R2
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78 | double * diJ = new double[n];
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79 | jetA = head;
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80 | for (int i = 0; i < n; i++) {
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81 | diJ[i] = _bj_diJ(jetA);
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82 | jetA++; // have jetA follow i
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83 | }
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84 |
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85 | // now run the recombination loop
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86 | int history_location = n-1;
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87 | while (tail != head) {
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88 |
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89 | // find the minimum of the diJ on this round
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90 | double diJ_min = diJ[0];
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91 | int diJ_min_jet = 0;
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92 | for (int i = 1; i < n; i++) {
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93 | if (diJ[i] < diJ_min) {diJ_min_jet = i; diJ_min = diJ[i];}
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94 | }
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95 |
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96 | // do the recombination between A and B
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97 | history_location++;
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98 | jetA = & briefjets[diJ_min_jet];
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99 | // GPS mod 2009-02-11
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100 | //jetB = jetA->NN;
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101 | jetB = static_cast<BJ *>(jetA->NN);
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102 | // put the normalisation back in
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103 | diJ_min *= _invR2;
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104 | if (jetB != NULL) {
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105 | // jet-jet recombination
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106 | // If necessary relabel A & B to ensure jetB < jetA, that way if
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107 | // the larger of them == newtail then that ends up being jetA and
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108 | // the new jet that is added as jetB is inserted in a position that
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109 | // has a future!
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110 | if (jetA < jetB) {std::swap(jetA,jetB);}
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111 |
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112 | int nn; // new jet index
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113 | _do_ij_recombination_step(jetA->_jets_index, jetB->_jets_index, diJ_min, nn);
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114 |
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115 | // what was jetB will now become the new jet
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116 | _bj_set_jetinfo(jetB, nn);
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117 |
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118 | } else {
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119 | // jet-beam recombination
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120 | _do_iB_recombination_step(jetA->_jets_index, diJ_min);
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121 | }
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122 |
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123 | // now update our nearest neighbour info and diJ table
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124 | // first reduce size of table
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125 | tail--; n--;
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126 | // Copy last jet contents and diJ info into position of jetA
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127 | *jetA = *tail;
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128 | diJ[jetA - head] = diJ[tail-head];
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129 |
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130 | // Initialise jetB's NN distance as well as updating it for
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131 | // other particles.
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132 | // NB: by having different loops for jetB == or != NULL we could
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133 | // perhaps save a few percent (usually avoid one if inside loop),
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134 | // but will not do it for now because on laptop fluctuations are
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135 | // too large to reliably measure a few percent difference...
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136 | for (BJ * jetI = head; jetI != tail; jetI++) {
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137 | // see if jetI had jetA or jetB as a NN -- if so recalculate the NN
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138 | if (jetI->NN == jetA || jetI->NN == jetB) {
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139 | _bj_set_NN_nocross(jetI, head, tail);
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140 | diJ[jetI-head] = _bj_diJ(jetI); // update diJ
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141 | }
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142 | // check whether new jetB is closer than jetI's current NN and
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143 | // if need be update things
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144 | if (jetB != NULL) {
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145 | double dist = _bj_dist(jetI,jetB);
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146 | if (dist < jetI->NN_dist) {
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147 | if (jetI != jetB) {
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148 | jetI->NN_dist = dist;
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149 | jetI->NN = jetB;
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150 | diJ[jetI-head] = _bj_diJ(jetI); // update diJ...
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151 | }
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152 | }
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153 | if (dist < jetB->NN_dist) {
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154 | if (jetI != jetB) {
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155 | jetB->NN_dist = dist;
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156 | jetB->NN = jetI;}
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157 | }
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158 | }
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159 | // if jetI's NN is the new tail then relabel it so that it becomes jetA
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160 | if (jetI->NN == tail) {jetI->NN = jetA;}
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161 | }
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162 |
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163 |
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164 | if (jetB != NULL) {diJ[jetB-head] = _bj_diJ(jetB);}
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165 |
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166 |
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167 | }
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168 |
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169 |
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170 | // final cleaning up;
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171 | delete[] diJ;
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172 | delete[] briefjets;
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173 | }
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174 |
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175 |
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176 |
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177 | // //----------------------------------------------------------------------
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178 | // // initialises a GenBriefJet
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179 | // template<> inline void ClusterSequence::_bj_set_jetinfo(
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180 | // GenBriefJet * const jetA, const int _jets_index) const {
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181 | //
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182 | // jetA->init(_jets[_jets_index]);
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183 | // jetA->_jets_index = _jets_index;
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184 | //
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185 | // }
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186 | //
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187 | //
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188 | // //----------------------------------------------------------------------
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189 | // // returns the distance between two GenBriefJets
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190 | // template<> double ClusterSequence::_bj_dist(
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191 | // const GenBriefJet * const jeta,
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192 | // const GenBriefJet * const jetb) const {
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193 | // return jeta->geom_ij(jetb);
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194 | // }
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195 |
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196 | FASTJET_END_NAMESPACE
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197 |
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198 | #endif // __FASTJET_CLUSTERQUENCE_N2_ICC__
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199 |
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200 |
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