1 | #ifndef __FASTJET_TOOLS_PRUNER_HH__ |
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2 | #define __FASTJET_TOOLS_PRUNER_HH__ |
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3 | |
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4 | //STARTHEADER |
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5 | // $Id: Pruner.hh 2616 2011-09-30 18:03:40Z salam $ |
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6 | // |
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7 | // Copyright (c) 2005-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez |
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8 | // |
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9 | //---------------------------------------------------------------------- |
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10 | // This file is part of FastJet. |
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11 | // |
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12 | // FastJet is free software; you can redistribute it and/or modify |
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13 | // it under the terms of the GNU General Public License as published by |
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14 | // the Free Software Foundation; either version 2 of the License, or |
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15 | // (at your option) any later version. |
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16 | // |
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17 | // The algorithms that underlie FastJet have required considerable |
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18 | // development and are described in hep-ph/0512210. If you use |
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19 | // FastJet as part of work towards a scientific publication, please |
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20 | // include a citation to the FastJet paper. |
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21 | // |
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22 | // FastJet is distributed in the hope that it will be useful, |
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23 | // but WITHOUT ANY WARRANTY; without even the implied warranty of |
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24 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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25 | // GNU General Public License for more details. |
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26 | // |
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27 | // You should have received a copy of the GNU General Public License |
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28 | // along with FastJet. If not, see <http://www.gnu.org/licenses/>. |
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29 | //---------------------------------------------------------------------- |
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30 | //ENDHEADER |
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31 | |
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32 | #include "fastjet/ClusterSequence.hh" |
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33 | #include "fastjet/WrappedStructure.hh" |
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34 | #include "fastjet/tools/Transformer.hh" |
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35 | #include <iostream> |
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36 | #include <string> |
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37 | |
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38 | FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh |
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39 | |
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40 | // fwd declarations |
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41 | class Pruner; |
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42 | class PrunerStructure; |
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43 | class PruningRecombiner; |
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44 | class PruningPlugin; |
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45 | |
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46 | //---------------------------------------------------------------------- |
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47 | /// @ingroup tools_generic |
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48 | /// \class Pruner |
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49 | /// Transformer that prunes a jet |
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50 | /// |
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51 | /// This transformer prunes a jet according to the ideas presented in |
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52 | /// arXiv:0903.5081 (S.D. Ellis, C.K. Vermilion and J.R. Walsh). |
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53 | /// |
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54 | /// The jet's constituents are reclustered with a user-specified jet |
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55 | /// definition, with the modification that objects i and j are only |
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56 | /// recombined if at least one of the following two criteria is |
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57 | /// satisfied: |
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58 | /// |
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59 | /// - the geometric distance between i and j is smaller than 'Rcut' |
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60 | /// with Rcut = Rcut_factor*2m/pt (Rcut_factor is a parameter of |
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61 | /// the Pruner and m and pt obtained from the jet being pruned) |
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62 | /// - the transverse momenta of i and j are at least 'zcut' p_t(i+j) |
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63 | /// |
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64 | /// If both these criteria fail, i and j are not recombined, the |
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65 | /// harder of i and j is kept, and the softer is rejected. |
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66 | /// |
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67 | /// Usage: |
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68 | /// \code |
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69 | /// Pruner pruner(jet_def, zcut, Rcut_factor); |
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70 | /// PseudoJet pruned_jet = pruner(jet); |
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71 | /// \endcode |
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72 | /// |
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73 | /// The pruned_jet has a valid associated cluster sequence. In addition |
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74 | /// the subjets of the original jet that have been vetoed by pruning |
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75 | /// (i.e. have been 'pruned away') can be accessed using |
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76 | /// |
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77 | /// \code |
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78 | /// vector<PseudoJet> rejected_subjets = pruned_jet.structure_of<Pruner>().rejected(); |
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79 | /// \endcode |
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80 | /// |
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81 | /// If the re-clustering happens to find more than a single inclusive |
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82 | /// jet (this should normally not happen if the radius of the jet |
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83 | /// definition used for the reclustering was set large enough), |
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84 | /// the hardest of these jets is retured as the result of the |
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85 | /// Pruner. The other jets can be accessed through |
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86 | /// |
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87 | /// \code |
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88 | /// vector<PseudoJet> extra_jets = pruned_jet.structure_of<Pruner>().extra_jets(); |
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89 | /// \endcode |
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90 | /// |
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91 | /// Instead of using Rcut_factor and zcut, one can alternatively |
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92 | /// construct a Pruner by passing two (pointers to) functions of |
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93 | /// PseudoJet that dynamically compute the Rcut and zcut to |
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94 | /// be used for the jet being pruned. |
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95 | /// |
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96 | /// When the jet being pruned has area support and explicit ghosts, |
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97 | /// the resulting pruned jet will likewise have area. |
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98 | /// |
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99 | //---------------------------------------------------------------------- |
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100 | class Pruner : public Transformer{ |
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101 | public: |
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102 | /// minimal constructor, which takes a jet algorithm, sets the radius |
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103 | /// to JetDefinition::max_allowable_R (practically equivalent to |
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104 | /// infinity) and also tries to use a recombiner based on the one in |
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105 | /// the jet definition of the particular jet being pruned. |
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106 | /// |
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107 | /// \param jet_alg the jet algorithm for the internal clustering |
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108 | /// \param zcut pt-fraction cut in the pruning |
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109 | /// \param Rcut_factor the angular distance cut in the pruning will be |
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110 | /// Rcut_factor * 2m/pt |
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111 | Pruner(const JetAlgorithm jet_alg, double zcut, double Rcut_factor) |
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112 | : _jet_def(jet_alg, JetDefinition::max_allowable_R), |
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113 | _zcut(zcut), _Rcut_factor(Rcut_factor), |
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114 | _zcut_dyn(0), _Rcut_dyn(0), _get_recombiner_from_jet(true) {} |
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115 | |
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116 | |
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117 | /// alternative ctor in which the full reclustering jet definition can |
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118 | /// be specified. |
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119 | /// |
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120 | /// \param jet_def the jet definition for the internal clustering |
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121 | /// \param zcut pt-fraction cut in the pruning |
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122 | /// \param Rcut_factor the angular distance cut in the pruning will be |
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123 | /// Rcut_factor * 2m/pt |
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124 | Pruner(const JetDefinition &jet_def, double zcut, double Rcut_factor) |
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125 | : _jet_def(jet_def), |
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126 | _zcut(zcut), _Rcut_factor(Rcut_factor), |
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127 | _zcut_dyn(0), _Rcut_dyn(0), _get_recombiner_from_jet(false) {} |
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128 | |
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129 | |
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130 | /// alternative ctor in which the pt-fraction cut and angular distance |
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131 | /// cut are functions of the jet being pruned. |
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132 | /// |
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133 | /// \param jet_def the jet definition for the internal clustering |
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134 | /// \param zcut_dyn dynamic pt-fraction cut in the pruning |
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135 | /// \param Rcut_dyn dynamic angular distance cut in the pruning |
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136 | Pruner(const JetDefinition &jet_def, |
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137 | FunctionOfPseudoJet<double> *zcut_dyn, |
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138 | FunctionOfPseudoJet<double> *Rcut_dyn); |
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139 | |
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140 | /// action on a single jet |
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141 | virtual PseudoJet result(const PseudoJet &jet) const; |
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142 | |
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143 | /// description |
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144 | virtual std::string description() const; |
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145 | |
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146 | // the type of the associated structure |
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147 | typedef PrunerStructure StructureType; |
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148 | |
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149 | private: |
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150 | /// check if the jet has explicit_ghosts (knowing that there is an |
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151 | /// area support) |
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152 | bool _check_explicit_ghosts(const PseudoJet &jet) const; |
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153 | |
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154 | /// return a pointer to a "common" recombiner if there is one, |
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155 | /// alternatively a null pointer. |
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156 | const JetDefinition::Recombiner * _get_common_recombiner(const PseudoJet &jet) const; |
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157 | |
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158 | JetDefinition _jet_def; ///< the internal jet definition |
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159 | double _zcut; ///< the pt-fraction cut |
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160 | double _Rcut_factor; ///< the angular separation cut factor |
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161 | FunctionOfPseudoJet<double> *_zcut_dyn; ///< dynamic zcut |
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162 | FunctionOfPseudoJet<double> *_Rcut_dyn; ///< dynamic Rcut |
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163 | bool _get_recombiner_from_jet; ///< true for minimal constructor, |
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164 | ///< causes recombiner to be set equal |
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165 | ///< to that already used in the jet |
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166 | ///< (if it can be deduced) |
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167 | }; |
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168 | |
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169 | |
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170 | //---------------------------------------------------------------------- |
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171 | /// @ingroup tools_generic |
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172 | /// \class PrunerStructure |
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173 | /// The structure associated with a PseudoJet thas has gone through a |
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174 | /// Pruner transformer |
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175 | //---------------------------------------------------------------------- |
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176 | class PrunerStructure : public WrappedStructure{ |
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177 | public: |
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178 | /// default ctor |
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179 | /// \param result_jet the jet for which we have to keep the structure |
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180 | PrunerStructure(const PseudoJet & result_jet) |
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181 | : WrappedStructure(result_jet.structure_shared_ptr()){} |
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182 | |
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183 | /// description |
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184 | virtual std::string description() const{ return "Pruned PseudoJet";} |
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185 | |
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186 | /// return the constituents that have been rejected |
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187 | std::vector<PseudoJet> rejected() const{ |
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188 | return validated_cs()->childless_pseudojets(); |
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189 | } |
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190 | |
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191 | /// return the other jets that may have been found along with the |
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192 | /// result of the pruning |
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193 | /// The resulting vector is sorted in pt |
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194 | std::vector<PseudoJet> extra_jets() const; |
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195 | |
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196 | protected: |
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197 | friend class Pruner; ///< to allow setting the internal information |
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198 | }; |
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199 | |
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200 | //---------------------------------------------------------------------- |
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201 | /// \if internal_doc |
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202 | /// @ingroup internal |
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203 | /// \class PruningRecombiner |
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204 | /// recombines the objects that are not vetoed by pruning |
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205 | /// |
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206 | /// This recombiner only recombines, using the provided 'recombiner', |
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207 | /// objects (i and j) that pass at least one of the following two criteria: |
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208 | /// |
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209 | /// - the geometric distance between i and j is smaller than 'Rcut' |
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210 | /// - the transverse momenta of i and j are at least 'zcut' p_t(i+j) |
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211 | /// |
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212 | /// If both these criteria fail, the hardest of i and j is kept and |
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213 | /// the softest is rejected. |
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214 | /// |
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215 | /// Note that this in not meant for standalone use [in particular |
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216 | /// because it could lead to memory issues due to the rejected indices |
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217 | /// stored internally]. |
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218 | /// |
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219 | /// \endif |
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220 | class PruningRecombiner : public JetDefinition::Recombiner{ |
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221 | public: |
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222 | /// ctor |
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223 | /// \param zcut transverse momentum fraction cut |
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224 | /// \param Rcut angular separation cut |
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225 | /// \param recomb pointer to a recombiner to use to cluster pairs |
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226 | PruningRecombiner(double zcut, double Rcut, |
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227 | const JetDefinition::Recombiner *recombiner) |
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228 | : _zcut2(zcut*zcut), _Rcut2(Rcut*Rcut), |
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229 | _recombiner(recombiner){} |
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230 | |
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231 | /// perform a recombination taking into account the pruning |
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232 | /// conditions |
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233 | virtual void recombine(const PseudoJet &pa, |
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234 | const PseudoJet &pb, |
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235 | PseudoJet &pab) const; |
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236 | |
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237 | /// returns the description of the recombiner |
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238 | virtual std::string description() const; |
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239 | |
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240 | /// return the history indices that have been pruned away |
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241 | const std::vector<unsigned int> & rejected() const{ return _rejected;} |
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242 | |
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243 | /// clears the list of rejected indices |
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244 | /// |
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245 | /// If one decides to use this recombiner standalone, one has to |
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246 | /// call this after each clustering in order for the rejected() vector |
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247 | /// to remain sensible and not grow to infinite size. |
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248 | void clear_rejected(){ _rejected.clear();} |
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249 | |
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250 | private: |
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251 | double _zcut2; ///< transverse momentum fraction cut (squared) |
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252 | double _Rcut2; ///< angular separation cut (squared) |
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253 | const JetDefinition::Recombiner *_recombiner; ///< the underlying recombiner to use |
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254 | mutable std::vector<unsigned int> _rejected; ///< list of rejected history indices |
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255 | }; |
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256 | |
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257 | |
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258 | //---------------------------------------------------------------------- |
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259 | /// \if internal_doc |
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260 | /// @ingroup internal |
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261 | /// \class PruningPlugin |
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262 | /// FastJet internal plugin that clusters the particles using the |
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263 | /// PruningRecombiner. |
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264 | /// |
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265 | /// See PruningRecombiner for a description of what pruning does. |
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266 | /// |
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267 | /// Note that this is an internal FastJet class used by the Pruner |
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268 | /// transformer and it is not meant to be used as a standalone clustering |
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269 | /// tool. |
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270 | /// |
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271 | /// \endif |
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272 | //---------------------------------------------------------------------- |
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273 | class PruningPlugin : public JetDefinition::Plugin{ |
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274 | public: |
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275 | /// ctor |
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276 | /// \param jet_def the jet definition to be used for the |
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277 | /// internal clustering |
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278 | /// \param zcut transverse momentum fraction cut |
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279 | /// \param Rcut angular separation cut |
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280 | PruningPlugin(const JetDefinition &jet_def, double zcut, double Rcut) |
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281 | : _jet_def(jet_def), _zcut(zcut), _Rcut(Rcut){} |
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282 | |
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283 | /// the actual clustering work for the plugin |
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284 | virtual void run_clustering(ClusterSequence &input_cs) const; |
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285 | |
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286 | /// description of the plugin |
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287 | virtual std::string description() const; |
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288 | |
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289 | /// returns the radius |
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290 | virtual double R() const {return _jet_def.R();} |
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291 | |
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292 | private: |
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293 | JetDefinition _jet_def; ///< the internal jet definition |
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294 | double _zcut; ///< transverse momentum fraction cut |
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295 | double _Rcut; ///< angular separation cut |
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296 | }; |
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297 | |
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298 | |
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299 | |
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300 | FASTJET_END_NAMESPACE // defined in fastjet/internal/base.hh |
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301 | |
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302 | #endif // __FASTJET_TOOLS_PRUNER_HH__ |
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