algorithms/fardetectors/FarDetectorLinearTracking.cc

0001 // SPDX-License-Identifier: LGPL-3.0-or-later
0002 // Copyright (C) 2023 - 2025, Simon Gardner
0003
0004 #include <DD4hep/VolumeManager.h>
0005 #include <Evaluator/DD4hepUnits.h>
0006 #include <Math/GenVector/Cartesian3D.h>
0007 #include <Math/GenVector/DisplacementVector3D.h>
0008 #include <algorithms/geo.h>
0009 #include <edm4eic/Cov6f.h>
0010 #include <edm4eic/MCRecoTrackParticleAssociationCollection.h>
0011 #include <edm4eic/MCRecoTrackerHitAssociationCollection.h>
0012 #include <edm4eic/Measurement2DCollection.h>
0013 #include <edm4eic/RawTrackerHit.h>
0014 #include <edm4eic/TrackCollection.h>
0015 #include <edm4eic/TrackerHit.h>
0016 #include <edm4hep/MCParticle.h>
0017 #include <edm4hep/SimTrackerHit.h>
0018 #include <edm4hep/Vector2f.h>
0019 #include <edm4hep/Vector3d.h>
0020 #include <edm4hep/Vector3f.h>
0021 #include <edm4hep/utils/vector_utils.h>
0022 #include <fmt/core.h>
0023 #include <podio/RelationRange.h>
0024 #include <Eigen/Geometry>
0025 #include <Eigen/Householder>
0026 #include <Eigen/Jacobi>
0027 #include <Eigen/SVD>
0028 #include <algorithm>
0029 #include <cmath>
0030 #include <cstddef>
0031 #include <cstdint>
0032 #include <new>
0033 #include <unordered_map>
0034 #include <utility>
0035
0036 #include "FarDetectorLinearTracking.h"
0037 #include "algorithms/fardetectors/FarDetectorLinearTrackingConfig.h"
0038
0039 namespace eicrecon {
0040
0041 void FarDetectorLinearTracking::init() {
0042
0043   // For changing how strongly each layer hit is in contributing to the fit
0044   m_layerWeights = Eigen::VectorXd::Constant(m_cfg.n_layer, 1);
0045
0046   for (std::size_t i = 0; i < std::min(m_cfg.layer_weights.size(), m_cfg.n_layer); i++) {
0047     m_layerWeights(i) = m_cfg.layer_weights[i];
0048   }
0049
0050   // For checking the direction of the track from theta and phi angles
0051   m_optimumDirection = Eigen::Vector3d::UnitZ();
0052   m_optimumDirection =
0053       Eigen::AngleAxisd(m_cfg.optimum_theta, Eigen::Vector3d::UnitY()) * m_optimumDirection;
0054   m_optimumDirection =
0055       Eigen::AngleAxisd(m_cfg.optimum_phi, Eigen::Vector3d::UnitZ()) * m_optimumDirection;
0056
0057   m_cellid_converter = algorithms::GeoSvc::instance().cellIDPositionConverter();
0058 }
0059
0060 void FarDetectorLinearTracking::process(const FarDetectorLinearTracking::Input& input,
0061                                         const FarDetectorLinearTracking::Output& output) const {
0062
0063   const auto [inputhits, assocHits] = input;
0064   auto [outputTracks, assocTracks]  = output;
0065
0066   // Check the number of input collections is correct
0067   std::size_t nCollections = inputhits.size();
0068   if (nCollections != m_cfg.n_layer) {
0069     error("Wrong number of input collections passed to algorithm");
0070     return;
0071   }
0072
0073   std::vector<std::vector<Eigen::Vector3d>> convertedHits;
0074   std::vector<std::vector<edm4hep::MCParticle>> assocParts;
0075
0076   // Check there aren't too many hits in any layer to handle
0077   // Temporary limit of number of hits per layer before Kalman filtering/GNN implemented
0078   // TODO - Implement more sensible solution
0079   for (const auto& layerHits : inputhits) {
0080     if ((*layerHits).size() > m_cfg.layer_hits_max) {
0081       info("Too many hits in layer");
0082       return;
0083     }
0084     if ((*layerHits).empty()) {
0085       trace("No hits in layer");
0086       return;
0087     }
0088     ConvertClusters(*layerHits, *assocHits, convertedHits, assocParts);
0089   }
0090
0091   // Create a matrix to store the hit positions
0092   Eigen::MatrixXd hitMatrix(3, m_cfg.n_layer);
0093
0094   // Create vector to store indexes of hits in the track
0095   std::vector<std::size_t> layerHitIndex(m_cfg.n_layer, 0);
0096
0097   int layer = 0;
0098
0099   // Iterate over all combinations of measurements in the layers without recursion
0100   while (true) {
0101     hitMatrix.col(layer) << convertedHits[layer][layerHitIndex[layer]];
0102
0103     bool isValid = true;
0104     // Check the last two hits are within a certain angle of the optimum direction
0105     if (layer > 0 && m_cfg.restrict_direction) {
0106       isValid = checkHitPair(hitMatrix.col(layer - 1), hitMatrix.col(layer));
0107     }
0108
0109     // If valid hit combination, move to the next layer or check the combination
0110     if (isValid) {
0111       if (layer == static_cast<long>(m_cfg.n_layer) - 1) {
0112         // Check the combination, if chi2 limit is passed, add the track to the output
0113         checkHitCombination(&hitMatrix, outputTracks, assocTracks, inputhits, assocParts,
0114                             layerHitIndex);
0115       } else {
0116         layer++;
0117         continue;
0118       }
0119     }
0120
0121     // Iterate current layer
0122     layerHitIndex[layer]++;
0123
0124     bool doBreak = false;
0125     // Set up next combination to check
0126     while (layerHitIndex[layer] >= convertedHits[layer].size()) {
0127       layerHitIndex[layer] = 0;
0128       if (layer == 0) {
0129         doBreak = true;
0130         break;
0131       }
0132       layer--;
0133       // Iterate previous layer
0134       layerHitIndex[layer]++;
0135     }
0136     if (doBreak) {
0137       break;
0138     }
0139   }
0140 }
0141
0142 void FarDetectorLinearTracking::checkHitCombination(
0143     Eigen::MatrixXd* hitMatrix, edm4eic::TrackCollection* outputTracks,
0144     edm4eic::MCRecoTrackParticleAssociationCollection* assocTracks,
0145     const std::vector<gsl::not_null<const edm4eic::Measurement2DCollection*>>& inputHits,
0146     const std::vector<std::vector<edm4hep::MCParticle>>& assocParts,
0147     const std::vector<std::size_t>& layerHitIndex) const {
0148
0149   Eigen::Vector3d weightedAnchor = (*hitMatrix) * m_layerWeights / (m_layerWeights.sum());
0150
0151   auto localMatrix = (*hitMatrix).colwise() - weightedAnchor;
0152
0153   Eigen::BDCSVD<Eigen::MatrixXd> svd(localMatrix.transpose(),
0154                                      Eigen::ComputeThinU | Eigen::ComputeThinV);
0155
0156   auto V = svd.matrixV();
0157
0158   // Rotate into principle components and calculate chi2/ndf
0159   auto rotatedMatrix = localMatrix.transpose() * V;
0160   auto residuals     = rotatedMatrix.rightCols(2);
0161   double chi2        = (residuals.array() * residuals.array()).sum() / (2 * m_cfg.n_layer);
0162
0163   if (chi2 > m_cfg.chi2_max) {
0164     return;
0165   }
0166
0167   edm4hep::Vector3d outPos = weightedAnchor.data();
0168   edm4hep::Vector3d outVec = V.col(0).data();
0169
0170   // Make sure fit was pointing in the right direction
0171   if (outVec.z > 0) {
0172     outVec = outVec * -1;
0173   }
0174
0175   int32_t type{0};                                          // Type of track
0176   edm4hep::Vector3f position(outPos.x, outPos.y, outPos.z); // Position of the trajectory point [mm]
0177   edm4hep::Vector3f momentum(outVec.x, outVec.y, outVec.z); // 3-momentum at the point [GeV]
0178   edm4eic::Cov6f positionMomentumCovariance;                // Error on the position
0179   float time{0};                                            // Time at this point [ns]
0180   float timeError{0};                                       // Error on the time at this point
0181   float charge{-1};                                         // Charge of the particle
0182   int32_t ndf{static_cast<int32_t>(m_cfg.n_layer) - 1};     // Number of degrees of freedom
0183   int32_t pdg{11};                                          // PDG code of the particle
0184
0185   // Create the track
0186   auto track = (*outputTracks)
0187                    .create(type, position, momentum, positionMomentumCovariance, time, timeError,
0188                            charge, chi2, ndf, pdg);
0189
0190   // Add Measurement2D relations and count occurrence of particles contributing to the track
0191   std::unordered_map<const edm4hep::MCParticle*, int> particleCount;
0192   for (std::size_t layer = 0; layer < layerHitIndex.size(); layer++) {
0193     track.addToMeasurements((*inputHits[layer])[layerHitIndex[layer]]);
0194     const auto& assocParticle = assocParts[layer][layerHitIndex[layer]];
0195     particleCount[&assocParticle]++;
0196   }
0197
0198   // Create track associations for each particle
0199   for (const auto& [particle, count] : particleCount) {
0200     auto trackAssoc = assocTracks->create();
0201     trackAssoc.setRec(track);
0202     trackAssoc.setSim(*particle);
0203     trackAssoc.setWeight(count / static_cast<double>(m_cfg.n_layer));
0204   }
0205 }
0206
0207 // Check if a pair of hits lies close to the optimum direction
0208 bool FarDetectorLinearTracking::checkHitPair(const Eigen::Vector3d& hit1,
0209                                              const Eigen::Vector3d& hit2) const {
0210
0211   Eigen::Vector3d hitDiff = hit2 - hit1;
0212   hitDiff.normalize();
0213
0214   double angle = std::acos(hitDiff.dot(m_optimumDirection));
0215
0216   debug("Vector: x={}, y={}, z={}", hitDiff.x(), hitDiff.y(), hitDiff.z());
0217   debug("Optimum: x={}, y={}, z={}", m_optimumDirection.x(), m_optimumDirection.y(),
0218         m_optimumDirection.z());
0219   debug("Angle: {}, Tolerance {}", angle, m_cfg.step_angle_tolerance);
0220
0221   return angle <= m_cfg.step_angle_tolerance;
0222 }
0223
0224 // Convert measurements into global coordinates
0225 void FarDetectorLinearTracking::ConvertClusters(
0226     const edm4eic::Measurement2DCollection& clusters,
0227     const edm4eic::MCRecoTrackerHitAssociationCollection& assoc_hits,
0228     std::vector<std::vector<Eigen::Vector3d>>& pointPositions,
0229     std::vector<std::vector<edm4hep::MCParticle>>& assoc_parts) const {
0230
0231   // Get context of first hit
0232   const dd4hep::VolumeManagerContext* context =
0233       m_cellid_converter->findContext(clusters[0].getSurface());
0234
0235   std::vector<Eigen::Vector3d> layerPositions;
0236   std::vector<edm4hep::MCParticle> assocParticles;
0237
0238   for (auto cluster : clusters) {
0239
0240     auto globalPos = context->localToWorld({cluster.getLoc()[0], cluster.getLoc()[1], 0});
0241     layerPositions.emplace_back(globalPos.x() / dd4hep::mm, globalPos.y() / dd4hep::mm,
0242                                 globalPos.z() / dd4hep::mm);
0243
0244     // Determine the MCParticle associated with this measurement based on the weights
0245     // Get hit in measurement with max weight
0246     float maxWeight      = 0;
0247     std::size_t maxIndex = cluster.getWeights().size();
0248     for (std::size_t i = 0; i < cluster.getWeights().size(); ++i) {
0249       if (cluster.getWeights()[i] > maxWeight) {
0250         maxWeight = cluster.getWeights()[i];
0251         maxIndex  = i;
0252       }
0253     }
0254     if (maxIndex == cluster.getWeights().size()) {
0255       // no maximum found (e.g. all weights zero, cluster size zero)
0256       continue;
0257     }
0258     auto maxHit = cluster.getHits()[maxIndex];
0259     // Get associated raw hit
0260     auto rawHit = maxHit.getRawHit();
0261
0262     // Loop over the hit associations to find the associated MCParticle
0263     for (const auto& hit_assoc : assoc_hits) {
0264       if (hit_assoc.getRawHit() == rawHit) {
0265         auto particle = hit_assoc.getSimHit().getParticle();
0266         assocParticles.push_back(particle);
0267         break;
0268       }
0269     }
0270   }
0271
0272   pointPositions.push_back(layerPositions);
0273   assoc_parts.push_back(assocParticles);
0274 }
0275
0276 } // namespace eicrecon