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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/EventData/TrackParameters.hpp" 0013 #include "Acts/Utilities/Result.hpp" 0014 0015 #include <boost/container/flat_map.hpp> // TODO use flat unordered map 0016 #include <boost/functional/hash.hpp> 0017 0018 namespace Acts { 0019 0020 /// @class AdaptiveGridTrackDensity 0021 /// @brief Implements a 1D (no time seeding) / 2D (time seeding) 0022 /// grid that is filled with track densities. 0023 /// Each track is modelled by a 2D / 3D Gaussian distribution in the 0024 /// d0-z0 / d0-z0-t0 plane, which is evaluated at d0=0. Therefore, 0025 /// each track effectively lives in 1D / 2D. 0026 /// The position of the highest track density (of either a single 0027 /// bin or the sum of a certain region) can be determined. 0028 /// Single tracks can be cached and removed from the overall density. 0029 /// Unlike in the GaussianGridTrackDensity, the overall density map 0030 /// grows adaptively when tracks densities are added to the grid. 0031 class AdaptiveGridTrackDensity { 0032 public: 0033 /// The first (second) integer indicates the bin's z (t) position 0034 using Bin = std::pair<std::int32_t, std::int32_t>; 0035 /// Mapping between bins and track densities 0036 using DensityMap = boost::container::flat_map<Bin, float>; 0037 /// Coordinates in the z-t plane; the t value will be set to 0 if time 0038 /// vertex seeding is disabled 0039 using ZTPosition = std::pair<double, double>; 0040 /// z-t position of a maximum and its width 0041 using ZTPositionAndWidth = std::pair<ZTPosition, double>; 0042 /// Optional grid size range 0043 using GridSizeRange = 0044 std::pair<std::optional<std::uint32_t>, std::optional<std::uint32_t>>; 0045 0046 /// The configuration struct 0047 struct Config { 0048 /// Spatial extent of a bin in d0 and z0 direction, should always be set to 0049 /// a positive value 0050 double spatialBinExtent = 15 * UnitConstants::um; 0051 0052 /// Number of standard deviations that the grid covers in z direction 0053 double nSpatialTrkSigmas = 3.0; 0054 0055 /// Temporal extent of a bin, not used if useTime == true 0056 double temporalBinExtent = 19 * UnitConstants::mm; 0057 0058 /// Number of standard deviations that the grid covers in t direction, not 0059 /// used if useTime == true 0060 double nTemporalTrkSigmas = 3.0; 0061 0062 /// Spatial window for filling the density map 0063 std::pair<double, double> spatialWindow = {-250 * UnitConstants::mm, 0064 250 * UnitConstants::mm}; 0065 /// Temporal window for filling the density map 0066 std::pair<double, double> temporalWindow = {-10 * UnitConstants::ns, 0067 10 * UnitConstants::ns}; 0068 0069 /// Optional minimal and maximal number of bins in z direction 0070 GridSizeRange spatialTrkGridSizeRange = {std::nullopt, std::nullopt}; 0071 /// Optional minimal and maximal number of bins in time direction 0072 GridSizeRange temporalTrkGridSizeRange = {std::nullopt, std::nullopt}; 0073 0074 /// Flag indicating whether to use time information in track density 0075 /// calculation 0076 bool useTime = false; 0077 0078 /// Do NOT use just the z-bin with the highest 0079 /// track density, but instead check (up to) 0080 /// first three density maxima (only those that have 0081 /// a maximum relative deviation of 'relativeDensityDev' 0082 /// from the main maximum) and take the z-bin of the 0083 /// maximum with the highest surrounding density sum 0084 bool useHighestSumZPosition = false; 0085 0086 /// The maximum relative density deviation from the main 0087 /// maximum to consider the second and third maximum for 0088 /// the highest-sum approach from above 0089 double maxRelativeDensityDev = 0.01; 0090 }; 0091 0092 /// Constructor 0093 /// @param cfg The configuration parameters 0094 explicit AdaptiveGridTrackDensity(const Config& cfg); 0095 0096 /// @brief Returns the z and t coordinate of maximum (surrounding) 0097 /// track density 0098 /// @note if time vertex seeding is not enabled, the t coordinate 0099 /// will be set to 0. 0100 /// 0101 /// @param densityMap Map between bins and corresponding density 0102 /// values 0103 /// 0104 /// @return The z and t coordinates of maximum track density 0105 Result<ZTPosition> getMaxZTPosition(DensityMap& densityMap) const; 0106 0107 /// @brief Returns the z-t position of maximum track density 0108 /// and the estimated z-width of the maximum 0109 /// 0110 /// @param densityMap Map between bins and corresponding density 0111 /// values 0112 /// 0113 /// @return The z-t position of the maximum track density and 0114 /// its width 0115 Result<ZTPositionAndWidth> getMaxZTPositionAndWidth( 0116 DensityMap& densityMap) const; 0117 0118 /// @brief Adds a single track to the overall grid density 0119 /// 0120 /// @param trk The track to be added 0121 /// @param mainDensityMap Map between bins and corresponding density 0122 /// 0123 /// @return The density map of the track that was added 0124 DensityMap addTrack(const BoundTrackParameters& trk, 0125 DensityMap& mainDensityMap) const; 0126 0127 /// @brief Removes a track from the overall grid density. 0128 /// 0129 /// @param trackDensityMap Map between bins and corresponding density 0130 /// @note The track density comes from a single track 0131 /// @param mainDensityMap Map between bins and corresponding density 0132 /// @note The track density comes from an arbitrary number of tracks 0133 void subtractTrack(const DensityMap& trackDensityMap, 0134 DensityMap& mainDensityMap) const; 0135 0136 // TODO this should not be public 0137 /// @brief Calculates the bin center from the bin number 0138 /// @param bin Bin number 0139 /// @param binExtent Bin extent 0140 /// @return Bin center 0141 static double getBinCenter(std::int32_t bin, double binExtent); 0142 0143 private: 0144 Config m_cfg; 0145 0146 /// @brief Calculates the bin number corresponding to a d, z, or time value 0147 /// @param value d, z, or time value 0148 /// @param binExtent Bin extent 0149 /// @return Bin number 0150 static std::int32_t getBin(double value, double binExtent); 0151 0152 /// @brief Calculates the grid size in z or time direction 0153 /// @param sigma Standard deviation of the track density 0154 /// @param trkSigmas Number of standard deviations that the grid 0155 /// covers in z or time direction 0156 /// @param binExtent Bin extent 0157 /// @param trkGridSizeRange Optional minimal and maximal number of bins 0158 /// in z or time direction 0159 /// @return Grid size 0160 static std::uint32_t getTrkGridSize(double sigma, double trkSigmas, 0161 double binExtent, 0162 const GridSizeRange& trkGridSizeRange); 0163 0164 /// @brief Calculates the bin number corresponding to a z value 0165 /// @param value z value 0166 /// @return Bin number 0167 std::int32_t getSpatialBin(double value) const; 0168 /// @brief Calculates the bin number corresponding to a time value 0169 /// @param value Time value 0170 /// @return Bin number 0171 std::int32_t getTemporalBin(double value) const; 0172 0173 /// @brief Calculates the spatial bin center corresponding to a bin number 0174 /// @param bin Bin number 0175 /// @return Bin center 0176 double getSpatialBinCenter(std::int32_t bin) const; 0177 /// @brief Calculates the temporal bin center corresponding to a bin number 0178 /// @param bin Bin number 0179 /// @return Bin center 0180 double getTemporalBinCenter(std::int32_t bin) const; 0181 0182 /// @brief Calculates the grid size in z direction 0183 /// @param sigma Standard deviation of the track density 0184 /// @return Grid size 0185 std::uint32_t getSpatialTrkGridSize(double sigma) const; 0186 /// @brief Calculates the grid size in time direction 0187 /// @param sigma Standard deviation of the track density 0188 /// @return Grid size 0189 std::uint32_t getTemporalTrkGridSize(double sigma) const; 0190 0191 /// @brief Finds the maximum density of a DensityMap 0192 /// @param densityMap Map between bins and corresponding density 0193 /// values 0194 /// @return Iterator of the map entry with the highest density 0195 DensityMap::const_iterator highestDensityEntry( 0196 const DensityMap& densityMap) const; 0197 0198 /// @brief Function that creates a track density map, i.e., a map from bins 0199 /// to the corresponding density values for a single track. 0200 /// 0201 /// @param impactParams vector containing d0, z0, and t0 of the track 0202 /// @param centralBin Central z and t bin of the track (where its 0203 /// density is the highest) 0204 /// @param cov 3x3 impact parameter covariance matrix 0205 /// @param spatialTrkGridSize Number of bins in z direction 0206 /// @param temporalTrkGridSize Number of bins in time direction 0207 /// 0208 /// @return The track density map 0209 DensityMap createTrackGrid(const Acts::Vector3& impactParams, 0210 const Bin& centralBin, 0211 const Acts::SquareMatrix3& cov, 0212 std::uint32_t spatialTrkGridSize, 0213 std::uint32_t temporalTrkGridSize) const; 0214 0215 /// @brief Function that estimates the seed width in z direction based 0216 /// on the full width at half maximum (FWHM) of the maximum density peak 0217 /// @note This only works if the maximum is sufficiently isolated since 0218 /// overlapping neighboring peaks might lead to an overestimation of the 0219 /// seed width. 0220 /// 0221 /// @param densityMap Map from bins to corresponding track density 0222 /// @param maxZT z-t position of the maximum density value 0223 /// 0224 /// @return The width 0225 Result<double> estimateSeedWidth(const DensityMap& densityMap, 0226 const ZTPosition& maxZT) const; 0227 0228 /// @brief Checks (up to) first three density maxima that have a 0229 /// maximum relative deviation of 'relativeDensityDev' from the 0230 /// global maximum. Returns the bin of the maximum that has the 0231 /// highest surrounding density in z direction. 0232 /// 0233 /// @param densityMap Map between bins and corresponding density values 0234 /// 0235 /// @return The bin corresponding to the highest surrounding density 0236 Bin highestDensitySumBin(DensityMap& densityMap) const; 0237 0238 /// @brief Calculates the density sum of a bin and its two neighboring bins 0239 /// in z direction 0240 /// 0241 /// @param densityMap Map between bins and corresponding density values 0242 /// @param bin Bin whose neighbors in z we want to sum up 0243 /// 0244 /// @return The density sum 0245 double getDensitySum(const DensityMap& densityMap, const Bin& bin) const; 0246 }; 0247 0248 } // namespace Acts
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