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0001 // This file is part of the ACTS project. 0002 // 0003 // Copyright (C) 2016 CERN for the benefit of the ACTS project 0004 // 0005 // This Source Code Form is subject to the terms of the Mozilla Public 0006 // License, v. 2.0. If a copy of the MPL was not distributed with this 0007 // file, You can obtain one at https://mozilla.org/MPL/2.0/. 0008 0009 #pragma once 0010 0011 #include "Acts/Definitions/Algebra.hpp" 0012 #include "Acts/MagneticField/MagneticFieldContext.hpp" 0013 #include "Acts/MagneticField/MagneticFieldProvider.hpp" 0014 #include "Acts/Utilities/Logger.hpp" 0015 #include "Acts/Utilities/Result.hpp" 0016 #include "Acts/Vertexing/FullBilloirVertexFitter.hpp" 0017 #include "Acts/Vertexing/HelicalTrackLinearizer.hpp" 0018 #include "Acts/Vertexing/IVertexFinder.hpp" 0019 #include "Acts/Vertexing/ImpactPointEstimator.hpp" 0020 #include "Acts/Vertexing/TrackLinearizer.hpp" 0021 #include "Acts/Vertexing/Vertex.hpp" 0022 #include "Acts/Vertexing/VertexingOptions.hpp" 0023 0024 #include <functional> 0025 0026 namespace Acts { 0027 0028 /// @class IterativeVertexFinder 0029 /// 0030 /// @brief Implements an iterative vertex finder 0031 /// 0032 //////////////////////////////////////////////////////////// 0033 /// 0034 /// Brief description of the algorithm implemented: 0035 /// Iterative vertex finder which iteratively finds and fits vertices: 0036 /// 1. A list of seed tracks (`seedTracks`, which is the same as the 0037 /// input track list to the finder at the very first iteration) is used 0038 /// to retrieve a single vertex seed using the ZScanVertexFinder. 0039 /// 2. All tracks compatible with the current vertex seed are kept and used 0040 /// for fitting the single vertex. 0041 /// 3.1 If the vertex is a 'good' vertex (i.e. meets requirements) and no 0042 /// track reassignment after first fit is required, go to step 4. If vertex 0043 /// is not a good vertex, remove all tracks in tracksToFit from seedTracks. 0044 /// 3.2 If vertex meets requirements and track reassignment after first fit 0045 /// is required, iterate over all previously found vertices ("old vertex") 0046 /// and over all their tracksAtVertex. Compare compatibility of each track 0047 /// with old vertex and current vertex. If track is more compatible with 0048 /// current vertex, remove track from old vertex, put track back to 0049 /// tracksToFit and refit current vertex with additional track. 0050 /// 4. If good vertex, `removeUsedCompatibleTracks` method is called, which 0051 /// removes all used tracks that are compatible with the fitted vertex 0052 /// from `tracksToFit` and `seedTracks`. It also removes outliers tracks 0053 /// from tracksAtVertex if not compatible. 0054 /// 5. Add vertex to vertexCollection 0055 /// 6. Repeat until no seedTracks are left or max. number of vertices found 0056 class IterativeVertexFinder final : public IVertexFinder { 0057 using VertexFitter = FullBilloirVertexFitter; 0058 0059 public: 0060 /// Configuration struct 0061 struct Config { 0062 /// @brief Config constructor 0063 /// 0064 /// @param fitter Vertex fitter 0065 /// @param sfinder The seed finder 0066 /// @param est ImpactPointEstimator 0067 Config(VertexFitter fitter, std::shared_ptr<IVertexFinder> sfinder, 0068 ImpactPointEstimator est) 0069 : vertexFitter(std::move(fitter)), 0070 seedFinder(std::move(sfinder)), 0071 ipEst(std::move(est)) {} 0072 0073 /// Vertex fitter 0074 VertexFitter vertexFitter; 0075 0076 /// Track linearizer 0077 TrackLinearizer trackLinearizer; 0078 0079 /// Vertex seed finder 0080 std::shared_ptr<IVertexFinder> seedFinder; 0081 0082 /// ImpactPointEstimator 0083 ImpactPointEstimator ipEst; 0084 0085 /// Vertex finder configuration variables. 0086 /// Tracks that are within a distance of 0087 /// 0088 /// significanceCutSeeding * sqrt(sigma(d0)^2+sigma(z0)^2) 0089 /// 0090 /// are considered compatible with the vertex. 0091 double significanceCutSeeding = 10; 0092 /// Maximum chi-squared cut for seeding vertex candidates 0093 double maximumChi2cutForSeeding = 36.; 0094 /// Maximum number of vertices to find per event 0095 int maxVertices = 50; 0096 0097 /// Assign a certain fraction of compatible tracks to a different (so-called 0098 /// split) vertex if boolean is set to true. 0099 bool createSplitVertices = false; 0100 /// Inverse of the fraction of tracks that will be assigned to the split 0101 /// vertex. E.g., if splitVerticesTrkInvFraction = 2, about 50% of 0102 /// compatible tracks will be assigned to the split vertex. 0103 int splitVerticesTrkInvFraction = 2; 0104 /// Flag to enable track reassignment after first vertex fit 0105 bool reassignTracksAfterFirstFit = false; 0106 /// Flag to enable maximum tracks cut per vertex 0107 bool doMaxTracksCut = false; 0108 /// Maximum number of tracks to consider per vertex 0109 int maxTracks = 5000; 0110 /// Minimum track weight threshold for vertex association 0111 double cutOffTrackWeight = 0.01; 0112 /// If `reassignTracksAfterFirstFit` is set this threshold will be used to 0113 /// decide if a track should be checked for reassignment to other vertices 0114 double cutOffTrackWeightReassign = 1; 0115 0116 /// Function to extract parameters from InputTrack 0117 InputTrack::Extractor extractParameters; 0118 0119 /// Magnetic field provider 0120 std::shared_ptr<const MagneticFieldProvider> field; 0121 }; 0122 0123 /// State struct 0124 struct State { 0125 /// Constructor with magnetic field provider and context 0126 /// @param field Magnetic field provider for track extrapolation 0127 /// @param _magContext Magnetic field context for field evaluation 0128 State(const MagneticFieldProvider& field, 0129 const Acts::MagneticFieldContext& _magContext) 0130 : magContext(_magContext), 0131 ipState{field.makeCache(magContext)}, 0132 fieldCache(field.makeCache(magContext)) {} 0133 0134 /// Reference to magnetic field context for vertex finding 0135 std::reference_wrapper<const Acts::MagneticFieldContext> magContext; 0136 0137 /// The IP estimator state 0138 ImpactPointEstimator::State ipState; 0139 0140 /// Cached magnetic field information for efficient access 0141 MagneticFieldProvider::Cache fieldCache; 0142 }; 0143 0144 /// @brief Constructor for user-defined InputTrack type 0145 /// 0146 /// @param cfg Configuration object 0147 /// @param logger The logging instance 0148 explicit IterativeVertexFinder(Config cfg, 0149 std::unique_ptr<const Logger> logger = 0150 getDefaultLogger("IterativeVertexFinder", 0151 Logging::INFO)); 0152 0153 /// @brief Finds vertices corresponding to input trackVector 0154 /// 0155 /// @param trackVector Input tracks 0156 /// @param vertexingOptions Vertexing options 0157 /// @param anyState State for fulfilling interfaces 0158 /// 0159 /// @return Collection of vertices found by finder 0160 Result<std::vector<Vertex>> find( 0161 const std::vector<InputTrack>& trackVector, 0162 const VertexingOptions& vertexingOptions, 0163 IVertexFinder::State& anyState) const override; 0164 0165 IVertexFinder::State makeState( 0166 const MagneticFieldContext& mctx) const override { 0167 return IVertexFinder::State{State{*m_cfg.field, mctx}}; 0168 } 0169 0170 void setTracksToRemove( 0171 IVertexFinder::State& /*anyState*/, 0172 const std::vector<InputTrack>& /*removedTracks*/) const override { 0173 // Nothing to do here 0174 } 0175 0176 private: 0177 /// Configuration object 0178 const Config m_cfg; 0179 0180 /// Logging instance 0181 std::unique_ptr<const Logger> m_logger; 0182 0183 /// Private access to logging instance 0184 const Logger& logger() const { return *m_logger; } 0185 0186 /// @brief Method that calls seed finder to retrieve a vertex seed 0187 /// 0188 /// @param state The state object 0189 /// @param seedTracks Seeding tracks 0190 /// @param vertexingOptions Vertexing options 0191 /// 0192 /// @return Vertex seed 0193 Result<std::optional<Vertex>> getVertexSeed( 0194 State& state, const std::vector<InputTrack>& seedTracks, 0195 const VertexingOptions& vertexingOptions) const; 0196 0197 /// @brief Removes all tracks in tracksToRemove from seedTracks 0198 /// 0199 /// @param tracksToRemove Tracks to be removed from seedTracks 0200 /// @param seedTracks List to remove tracks from 0201 void removeTracks(const std::vector<InputTrack>& tracksToRemove, 0202 std::vector<InputTrack>& seedTracks) const; 0203 0204 /// @brief Function for calculating how compatible 0205 /// a given track is to a given vertex 0206 /// 0207 /// @param params Track parameters 0208 /// @param vertex The vertex 0209 /// @param perigeeSurface The perigee surface at vertex position 0210 /// @param vertexingOptions Vertexing options 0211 /// @param state The state object 0212 Result<double> getCompatibility(const BoundTrackParameters& params, 0213 const Vertex& vertex, 0214 const Surface& perigeeSurface, 0215 const VertexingOptions& vertexingOptions, 0216 State& state) const; 0217 0218 /// @brief Function that removes used tracks compatible with 0219 /// current vertex (`vertex`) from `tracksToFit` and `seedTracks` 0220 /// as well as outliers from vertex.tracksAtVertex 0221 /// 0222 /// @param vertex Current vertex 0223 /// @param tracksToFit Tracks used to fit `vertex` 0224 /// @param seedTracks Tracks used for vertex seeding 0225 /// @param vertexingOptions Vertexing options 0226 /// @param state The state object 0227 Result<void> removeUsedCompatibleTracks( 0228 Vertex& vertex, std::vector<InputTrack>& tracksToFit, 0229 std::vector<InputTrack>& seedTracks, 0230 const VertexingOptions& vertexingOptions, State& state) const; 0231 0232 /// @brief Function that fills vector with tracks compatible with seed vertex 0233 /// 0234 /// @param seedTracks List of all available tracks used for seeding 0235 /// @param seedVertex Seed vertex 0236 /// @param tracksToFitOut Tracks to fit 0237 /// @param tracksToFitSplitVertexOut Tracks to fit to split vertex 0238 /// @param vertexingOptions Vertexing options 0239 /// @param state The state object 0240 Result<void> fillTracksToFit( 0241 const std::vector<InputTrack>& seedTracks, const Vertex& seedVertex, 0242 std::vector<InputTrack>& tracksToFitOut, 0243 std::vector<InputTrack>& tracksToFitSplitVertexOut, 0244 const VertexingOptions& vertexingOptions, State& state) const; 0245 0246 /// @brief Function that reassigns tracks from other vertices 0247 /// to the current vertex if they are more compatible 0248 /// 0249 /// @param vertexCollection Collection of vertices 0250 /// @param currentVertex Current vertex to assign tracks to 0251 /// @param tracksToFit Tracks to fit vector 0252 /// @param seedTracks Seed tracks vector 0253 /// @param origTracks Vector of original track objects 0254 /// @param vertexingOptions Vertexing options 0255 /// @param state The state object 0256 /// 0257 /// @return Bool if currentVertex is still a good vertex 0258 Result<bool> reassignTracksToNewVertex( 0259 std::vector<Vertex>& vertexCollection, Vertex& currentVertex, 0260 std::vector<InputTrack>& tracksToFit, std::vector<InputTrack>& seedTracks, 0261 const std::vector<InputTrack>& origTracks, 0262 const VertexingOptions& vertexingOptions, State& state) const; 0263 0264 /// @brief Counts all tracks that are significant for a vertex 0265 /// 0266 /// @param vtx The vertex 0267 /// 0268 /// @return Number of significant tracks 0269 int countSignificantTracks(const Vertex& vtx) const; 0270 }; 0271 0272 } // namespace Acts
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