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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/Definitions/Units.hpp" 0013 #include "Acts/EventData/BoundTrackParameters.hpp" 0014 #include "Acts/Utilities/Result.hpp" 0015 0016 #include <boost/container/flat_map.hpp> // TODO use flat unordered map 0017 #include <boost/functional/hash.hpp> 0018 0019 namespace Acts { 0020 0021 /// @class AdaptiveGridTrackDensity 0022 /// @brief Implements a 1D (no time seeding) / 2D (time seeding) 0023 /// grid that is filled with track densities. 0024 /// Each track is modelled by a 2D / 3D Gaussian distribution in the 0025 /// d0-z0 / d0-z0-t0 plane, which is evaluated at d0=0. Therefore, 0026 /// each track effectively lives in 1D / 2D. 0027 /// The position of the highest track density (of either a single 0028 /// bin or the sum of a certain region) can be determined. 0029 /// Single tracks can be cached and removed from the overall density. 0030 /// Unlike in the GaussianGridTrackDensity, the overall density map 0031 /// grows adaptively when tracks densities are added to the grid. 0032 class AdaptiveGridTrackDensity { 0033 public: 0034 /// The first (second) integer indicates the bin's z (t) position 0035 using Bin = std::pair<std::int32_t, std::int32_t>; 0036 /// Mapping between bins and track densities 0037 using DensityMap = boost::container::flat_map<Bin, float>; 0038 /// Coordinates in the z-t plane; the t value will be set to 0 if time 0039 /// vertex seeding is disabled 0040 using ZTPosition = std::pair<double, double>; 0041 /// z-t position of a maximum and its width 0042 using ZTPositionAndWidth = std::pair<ZTPosition, double>; 0043 /// Optional grid size range 0044 using GridSizeRange = 0045 std::pair<std::optional<std::uint32_t>, std::optional<std::uint32_t>>; 0046 0047 /// The configuration struct 0048 struct Config { 0049 /// Spatial extent of a bin in d0 and z0 direction, should always be set to 0050 /// a positive value 0051 double spatialBinExtent = 15 * UnitConstants::um; 0052 0053 /// Number of standard deviations that the grid covers in z direction 0054 double nSpatialTrkSigmas = 3.0; 0055 0056 /// Temporal extent of a bin, not used if useTime == true 0057 double temporalBinExtent = 19 * UnitConstants::mm; 0058 0059 /// Number of standard deviations that the grid covers in t direction, not 0060 /// used if useTime == true 0061 double nTemporalTrkSigmas = 3.0; 0062 0063 /// Spatial window for filling the density map 0064 std::pair<double, double> spatialWindow = {-250 * UnitConstants::mm, 0065 250 * UnitConstants::mm}; 0066 /// Temporal window for filling the density map 0067 std::pair<double, double> temporalWindow = {-10 * UnitConstants::ns, 0068 10 * UnitConstants::ns}; 0069 0070 /// Optional minimal and maximal number of bins in z direction 0071 GridSizeRange spatialTrkGridSizeRange = {std::nullopt, std::nullopt}; 0072 /// Optional minimal and maximal number of bins in time direction 0073 GridSizeRange temporalTrkGridSizeRange = {std::nullopt, std::nullopt}; 0074 0075 /// Flag indicating whether to use time information in track density 0076 /// calculation 0077 bool useTime = false; 0078 0079 /// Do NOT use just the z-bin with the highest 0080 /// track density, but instead check (up to) 0081 /// first three density maxima (only those that have 0082 /// a maximum relative deviation of 'relativeDensityDev' 0083 /// from the main maximum) and take the z-bin of the 0084 /// maximum with the highest surrounding density sum 0085 bool useHighestSumZPosition = false; 0086 0087 /// The maximum relative density deviation from the main 0088 /// maximum to consider the second and third maximum for 0089 /// the highest-sum approach from above 0090 double maxRelativeDensityDev = 0.01; 0091 }; 0092 0093 /// Constructor 0094 /// @param cfg The configuration parameters 0095 explicit AdaptiveGridTrackDensity(const Config& cfg); 0096 0097 /// @brief Returns the z and t coordinate of maximum (surrounding) 0098 /// track density 0099 /// @note if time vertex seeding is not enabled, the t coordinate 0100 /// will be set to 0. 0101 /// 0102 /// @param densityMap Map between bins and corresponding density 0103 /// values 0104 /// 0105 /// @return The z and t coordinates of maximum track density 0106 Result<ZTPosition> getMaxZTPosition(DensityMap& densityMap) const; 0107 0108 /// @brief Returns the z-t position of maximum track density 0109 /// and the estimated z-width of the maximum 0110 /// 0111 /// @param densityMap Map between bins and corresponding density 0112 /// values 0113 /// 0114 /// @return The z-t position of the maximum track density and 0115 /// its width 0116 Result<ZTPositionAndWidth> getMaxZTPositionAndWidth( 0117 DensityMap& densityMap) const; 0118 0119 /// @brief Adds a single track to the overall grid density 0120 /// 0121 /// @param trk The track to be added 0122 /// @param mainDensityMap Map between bins and corresponding density 0123 /// 0124 /// @return The density map of the track that was added 0125 DensityMap addTrack(const BoundTrackParameters& trk, 0126 DensityMap& mainDensityMap) const; 0127 0128 /// @brief Removes a track from the overall grid density. 0129 /// 0130 /// @param trackDensityMap Map between bins and corresponding density 0131 /// @note The track density comes from a single track 0132 /// @param mainDensityMap Map between bins and corresponding density 0133 /// @note The track density comes from an arbitrary number of tracks 0134 void subtractTrack(const DensityMap& trackDensityMap, 0135 DensityMap& mainDensityMap) const; 0136 0137 // TODO this should not be public 0138 /// @brief Calculates the bin center from the bin number 0139 /// @param bin Bin number 0140 /// @param binExtent Bin extent 0141 /// @return Bin center 0142 static double getBinCenter(std::int32_t bin, double binExtent); 0143 0144 private: 0145 Config m_cfg; 0146 0147 /// @brief Calculates the bin number corresponding to a d, z, or time value 0148 /// @param value d, z, or time value 0149 /// @param binExtent Bin extent 0150 /// @return Bin number 0151 static std::int32_t getBin(double value, double binExtent); 0152 0153 /// @brief Calculates the grid size in z or time direction 0154 /// @param sigma Standard deviation of the track density 0155 /// @param trkSigmas Number of standard deviations that the grid 0156 /// covers in z or time direction 0157 /// @param binExtent Bin extent 0158 /// @param trkGridSizeRange Optional minimal and maximal number of bins 0159 /// in z or time direction 0160 /// @return Grid size 0161 static std::uint32_t getTrkGridSize(double sigma, double trkSigmas, 0162 double binExtent, 0163 const GridSizeRange& trkGridSizeRange); 0164 0165 /// @brief Calculates the bin number corresponding to a z value 0166 /// @param value z value 0167 /// @return Bin number 0168 std::int32_t getSpatialBin(double value) const; 0169 /// @brief Calculates the bin number corresponding to a time value 0170 /// @param value Time value 0171 /// @return Bin number 0172 std::int32_t getTemporalBin(double value) const; 0173 0174 /// @brief Calculates the spatial bin center corresponding to a bin number 0175 /// @param bin Bin number 0176 /// @return Bin center 0177 double getSpatialBinCenter(std::int32_t bin) const; 0178 /// @brief Calculates the temporal bin center corresponding to a bin number 0179 /// @param bin Bin number 0180 /// @return Bin center 0181 double getTemporalBinCenter(std::int32_t bin) const; 0182 0183 /// @brief Calculates the grid size in z direction 0184 /// @param sigma Standard deviation of the track density 0185 /// @return Grid size 0186 std::uint32_t getSpatialTrkGridSize(double sigma) const; 0187 /// @brief Calculates the grid size in time direction 0188 /// @param sigma Standard deviation of the track density 0189 /// @return Grid size 0190 std::uint32_t getTemporalTrkGridSize(double sigma) const; 0191 0192 /// @brief Finds the maximum density of a DensityMap 0193 /// @param densityMap Map between bins and corresponding density 0194 /// values 0195 /// @return Iterator of the map entry with the highest density 0196 DensityMap::const_iterator highestDensityEntry( 0197 const DensityMap& densityMap) const; 0198 0199 /// @brief Function that creates a track density map, i.e., a map from bins 0200 /// to the corresponding density values for a single track. 0201 /// 0202 /// @param impactParams vector containing d0, z0, and t0 of the track 0203 /// @param centralBin Central z and t bin of the track (where its 0204 /// density is the highest) 0205 /// @param cov 3x3 impact parameter covariance matrix 0206 /// @param spatialTrkGridSize Number of bins in z direction 0207 /// @param temporalTrkGridSize Number of bins in time direction 0208 /// 0209 /// @return The track density map 0210 DensityMap createTrackGrid(const Acts::Vector3& impactParams, 0211 const Bin& centralBin, 0212 const Acts::SquareMatrix3& cov, 0213 std::uint32_t spatialTrkGridSize, 0214 std::uint32_t temporalTrkGridSize) const; 0215 0216 /// @brief Function that estimates the seed width in z direction based 0217 /// on the full width at half maximum (FWHM) of the maximum density peak 0218 /// @note This only works if the maximum is sufficiently isolated since 0219 /// overlapping neighboring peaks might lead to an overestimation of the 0220 /// seed width. 0221 /// 0222 /// @param densityMap Map from bins to corresponding track density 0223 /// @param maxZT z-t position of the maximum density value 0224 /// 0225 /// @return The width 0226 Result<double> estimateSeedWidth(const DensityMap& densityMap, 0227 const ZTPosition& maxZT) const; 0228 0229 /// @brief Checks (up to) first three density maxima that have a 0230 /// maximum relative deviation of 'relativeDensityDev' from the 0231 /// global maximum. Returns the bin of the maximum that has the 0232 /// highest surrounding density in z direction. 0233 /// 0234 /// @param densityMap Map between bins and corresponding density values 0235 /// 0236 /// @return The bin corresponding to the highest surrounding density 0237 Bin highestDensitySumBin(DensityMap& densityMap) const; 0238 0239 /// @brief Calculates the density sum of a bin and its two neighboring bins 0240 /// in z direction 0241 /// 0242 /// @param densityMap Map between bins and corresponding density values 0243 /// @param bin Bin whose neighbors in z we want to sum up 0244 /// 0245 /// @return The density sum 0246 double getDensitySum(const DensityMap& densityMap, const Bin& bin) const; 0247 }; 0248 0249 } // namespace Acts
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