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0001 // This file is part of the Acts project. 0002 // 0003 // Copyright (C) 2020-2023 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 http://mozilla.org/MPL/2.0/. 0008 0009 #pragma once 0010 #include "Acts/Definitions/Algebra.hpp" 0011 #include "Acts/EventData/TrackParameters.hpp" 0012 #include "Acts/Utilities/Result.hpp" 0013 0014 #include <boost/container/flat_map.hpp> // TODO use flat unordered map 0015 #include <boost/functional/hash.hpp> 0016 0017 namespace Acts { 0018 0019 /// @class AdaptiveGridTrackDensity 0020 /// @brief Implements a 1D (no time seeding) / 2D (time seeding) 0021 /// grid that is filled with track densities. 0022 /// Each track is modelled by a 2D / 3D Gaussian distribution in the 0023 /// d0-z0 / d0-z0-t0 plane, which is evaluated at d0=0. Therefore, 0024 /// each track effectively lives in 1D / 2D. 0025 /// The position of the highest track density (of either a single 0026 /// bin or the sum of a certain region) can be determined. 0027 /// Single tracks can be cached and removed from the overall density. 0028 /// Unlike in the GaussianGridTrackDensity, the overall density map 0029 /// grows adaptively when tracks densities are added to the grid. 0030 class AdaptiveGridTrackDensity { 0031 public: 0032 /// The first (second) integer indicates the bin's z (t) position 0033 using Bin = std::pair<std::int32_t, std::int32_t>; 0034 /// Mapping between bins and track densities 0035 using DensityMap = boost::container::flat_map<Bin, float>; 0036 /// Coordinates in the z-t plane; the t value will be set to 0 if time 0037 /// vertex seeding is disabled 0038 using ZTPosition = std::pair<double, double>; 0039 /// z-t position of a maximum and its width 0040 using ZTPositionAndWidth = std::pair<ZTPosition, double>; 0041 /// Optional grid size range 0042 using GridSizeRange = 0043 std::pair<std::optional<std::uint32_t>, std::optional<std::uint32_t>>; 0044 0045 /// The configuration struct 0046 struct Config { 0047 /// Spatial extent of a bin in d0 and z0 direction, should always be set to 0048 /// a positive value 0049 double spatialBinExtent = 15 * UnitConstants::um; 0050 0051 /// Number of standard deviations that the grid covers in z direction 0052 double nSpatialTrkSigmas = 3.0; 0053 0054 /// Temporal extent of a bin, not used if useTime == true 0055 double temporalBinExtent = 19 * UnitConstants::mm; 0056 0057 /// Number of standard deviations that the grid covers in t direction, not 0058 /// used if useTime == true 0059 double nTemporalTrkSigmas = 3.0; 0060 0061 /// Spatial window for filling the density map 0062 std::pair<double, double> spatialWindow = {-250 * UnitConstants::mm, 0063 250 * UnitConstants::mm}; 0064 /// Temporal window for filling the density map 0065 std::pair<double, double> temporalWindow = {-10 * UnitConstants::ns, 0066 10 * UnitConstants::ns}; 0067 0068 /// Optional minimal and maximal number of bins in z direction 0069 GridSizeRange spatialTrkGridSizeRange = {std::nullopt, std::nullopt}; 0070 /// Optional minimal and maximal number of bins in time direction 0071 GridSizeRange temporalTrkGridSizeRange = {std::nullopt, std::nullopt}; 0072 0073 bool useTime = false; 0074 0075 /// Do NOT use just the z-bin with the highest 0076 /// track density, but instead check (up to) 0077 /// first three density maxima (only those that have 0078 /// a maximum relative deviation of 'relativeDensityDev' 0079 /// from the main maximum) and take the z-bin of the 0080 /// maximum with the highest surrounding density sum 0081 bool useHighestSumZPosition = false; 0082 0083 /// The maximum relative density deviation from the main 0084 /// maximum to consider the second and third maximum for 0085 /// the highest-sum approach from above 0086 double maxRelativeDensityDev = 0.01; 0087 }; 0088 0089 AdaptiveGridTrackDensity(const Config& cfg); 0090 0091 /// @brief Returns the z and t coordinate of maximum (surrounding) 0092 /// track density 0093 /// @note if time vertex seeding is not enabled, the t coordinate 0094 /// will be set to 0. 0095 /// 0096 /// @param densityMap Map between bins and corresponding density 0097 /// values 0098 /// 0099 /// @return The z and t coordinates of maximum track density 0100 Result<ZTPosition> getMaxZTPosition(DensityMap& densityMap) const; 0101 0102 /// @brief Returns the z-t position of maximum track density 0103 /// and the estimated z-width of the maximum 0104 /// 0105 /// @param densityMap Map between bins and corresponding density 0106 /// values 0107 /// 0108 /// @return The z-t position of the maximum track density and 0109 /// its width 0110 Result<ZTPositionAndWidth> getMaxZTPositionAndWidth( 0111 DensityMap& densityMap) const; 0112 0113 /// @brief Adds a single track to the overall grid density 0114 /// 0115 /// @param trk The track to be added 0116 /// @param mainDensityMap Map between bins and corresponding density 0117 /// 0118 /// @return The density map of the track that was added 0119 DensityMap addTrack(const BoundTrackParameters& trk, 0120 DensityMap& mainDensityMap) const; 0121 0122 /// @brief Removes a track from the overall grid density. 0123 /// 0124 /// @param trackDensityMap Map between bins and corresponding density 0125 /// @note The track density comes from a single track 0126 /// @param mainDensityMap Map between bins and corresponding density 0127 /// @note The track density comes from an arbitrary number of tracks 0128 void subtractTrack(const DensityMap& trackDensityMap, 0129 DensityMap& mainDensityMap) const; 0130 0131 // TODO this should not be public 0132 /// @brief Calculates the bin center from the bin number 0133 /// @param bin Bin number 0134 /// @param binExtent Bin extent 0135 /// @return Bin center 0136 static double getBinCenter(std::int32_t bin, double binExtent); 0137 0138 private: 0139 Config m_cfg; 0140 0141 /// @brief Calculates the bin number corresponding to a d, z, or time value 0142 /// @param value d, z, or time value 0143 /// @param binExtent Bin extent 0144 /// @return Bin number 0145 static std::int32_t getBin(double value, double binExtent); 0146 0147 /// @brief Calculates the grid size in z or time direction 0148 /// @param sigma Standard deviation of the track density 0149 /// @param trkSigmas Number of standard deviations that the grid 0150 /// covers in z or time direction 0151 /// @param binExtent Bin extent 0152 /// @param trkGridSizeRange Optional minimal and maximal number of bins 0153 /// in z or time direction 0154 /// @return Grid size 0155 static std::uint32_t getTrkGridSize(double sigma, double trkSigmas, 0156 double binExtent, 0157 const GridSizeRange& trkGridSizeRange); 0158 0159 /// @brief Calculates the bin number corresponding to a z value 0160 /// @param value z value 0161 /// @return Bin number 0162 std::int32_t getSpatialBin(double value) const; 0163 /// @brief Calculates the bin number corresponding to a time value 0164 /// @param value Time value 0165 /// @return Bin number 0166 std::int32_t getTemporalBin(double value) const; 0167 0168 /// @brief Calculates the spatial bin center corresponding to a bin number 0169 /// @param bin Bin number 0170 /// @return Bin center 0171 double getSpatialBinCenter(std::int32_t bin) const; 0172 /// @brief Calculates the temporal bin center corresponding to a bin number 0173 /// @param bin Bin number 0174 /// @return Bin center 0175 double getTemporalBinCenter(std::int32_t bin) const; 0176 0177 /// @brief Calculates the grid size in z direction 0178 /// @param sigma Standard deviation of the track density 0179 /// @return Grid size 0180 std::uint32_t getSpatialTrkGridSize(double sigma) const; 0181 /// @brief Calculates the grid size in time direction 0182 /// @param sigma Standard deviation of the track density 0183 /// @return Grid size 0184 std::uint32_t getTemporalTrkGridSize(double sigma) const; 0185 0186 /// @brief Finds the maximum density of a DensityMap 0187 /// @param densityMap Map between bins and corresponding density 0188 /// values 0189 /// @return Iterator of the map entry with the highest density 0190 DensityMap::const_iterator highestDensityEntry( 0191 const DensityMap& densityMap) const; 0192 0193 /// @brief Function that creates a track density map, i.e., a map from bins 0194 /// to the corresponding density values for a single track. 0195 /// 0196 /// @param impactParams vector containing d0, z0, and t0 of the track 0197 /// @param centralBin Central z and t bin of the track (where its 0198 /// density is the highest) 0199 /// @param cov 3x3 impact parameter covariance matrix 0200 /// @param spatialTrkGridSize Number of bins in z direction 0201 /// @param temporalTrkGridSize Number of bins in time direction 0202 /// 0203 /// @return The track density map 0204 DensityMap createTrackGrid(const Acts::Vector3& impactParams, 0205 const Bin& centralBin, 0206 const Acts::SquareMatrix3& cov, 0207 std::uint32_t spatialTrkGridSize, 0208 std::uint32_t temporalTrkGridSize) const; 0209 0210 /// @brief Function that estimates the seed width in z direction based 0211 /// on the full width at half maximum (FWHM) of the maximum density peak 0212 /// @note This only works if the maximum is sufficiently isolated since 0213 /// overlapping neighboring peaks might lead to an overestimation of the 0214 /// seed width. 0215 /// 0216 /// @param densityMap Map from bins to corresponding track density 0217 /// @param maxZT z-t position of the maximum density value 0218 /// 0219 /// @return The width 0220 Result<double> estimateSeedWidth(const DensityMap& densityMap, 0221 const ZTPosition& maxZT) const; 0222 0223 /// @brief Checks (up to) first three density maxima that have a 0224 /// maximum relative deviation of 'relativeDensityDev' from the 0225 /// global maximum. Returns the bin of the maximum that has the 0226 /// highest surrounding density in z direction. 0227 /// 0228 /// @param densityMap Map between bins and corresponding density values 0229 /// 0230 /// @return The bin corresponding to the highest surrounding density 0231 Bin highestDensitySumBin(DensityMap& densityMap) const; 0232 0233 /// @brief Calculates the density sum of a bin and its two neighboring bins 0234 /// in z direction 0235 /// 0236 /// @param densityMap Map between bins and corresponding density values 0237 /// @param bin Bin whose neighbors in z we want to sum up 0238 /// 0239 /// @return The density sum 0240 double getDensitySum(const DensityMap& densityMap, const Bin& bin) const; 0241 }; 0242 0243 } // namespace Acts
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