[5] | 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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