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/EDM4eicVersion.h>
0011 #include <edm4eic/MCRecoTrackParticleAssociationCollection.h>
0012 #include <edm4eic/MCRecoTrackerHitAssociationCollection.h>
0013 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0014 #include <edm4eic/MCRecoTrackerHitLinkCollection.h>
0015 #endif
0016 #include <edm4eic/Measurement2DCollection.h>
0017 #include <edm4eic/RawTrackerHit.h>
0018 #include <edm4eic/TrackCollection.h>
0019 #include <edm4eic/TrackerHit.h>
0020 #include <edm4hep/MCParticle.h>
0021 #include <edm4hep/SimTrackerHit.h>
0022 #include <edm4hep/Vector2f.h>
0023 #include <edm4hep/Vector3d.h>
0024 #include <edm4hep/Vector3f.h>
0025 #include <edm4hep/utils/vector_utils.h>
0026 #include <podio/LinkNavigator.h>
0027 #include <podio/RelationRange.h>
0028 #include <podio/detail/Link.h>
0029 #include <Eigen/Geometry>
0030 #include <Eigen/Householder>
0031 #include <Eigen/Jacobi>
0032 #include <Eigen/SVD>
0033 #include <algorithm>
0034 #include <cmath>
0035 #include <cstddef>
0036 #include <cstdint>
0037 #include <memory>
0038 #include <new>
0039 #include <unordered_map>
0040 #include <utility>
0041
0042 #include "FarDetectorLinearTracking.h"
0043 #include "algorithms/fardetectors/FarDetectorLinearTrackingConfig.h"
0044
0045 namespace eicrecon {
0046
0047 void FarDetectorLinearTracking::init() {
0048
0049   // For changing how strongly each layer hit is in contributing to the fit
0050   m_layerWeights = Eigen::VectorXd::Constant(m_cfg.n_layer, 1);
0051
0052   for (std::size_t i = 0; i < std::min(m_cfg.layer_weights.size(), m_cfg.n_layer); i++) {
0053     m_layerWeights(i) = m_cfg.layer_weights[i];
0054   }
0055
0056   // For checking the direction of the track from theta and phi angles
0057   m_optimumDirection = Eigen::Vector3d::UnitZ();
0058   m_optimumDirection =
0059       Eigen::AngleAxisd(m_cfg.optimum_theta, Eigen::Vector3d::UnitY()) * m_optimumDirection;
0060   m_optimumDirection =
0061       Eigen::AngleAxisd(m_cfg.optimum_phi, Eigen::Vector3d::UnitZ()) * m_optimumDirection;
0062
0063   m_cellid_converter = algorithms::GeoSvc::instance().cellIDPositionConverter();
0064 }
0065
0066 void FarDetectorLinearTracking::process(const FarDetectorLinearTracking::Input& input,
0067                                         const FarDetectorLinearTracking::Output& output) const {
0068
0069 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0070   const auto [inputhits, hitLinks, assocHits]  = input;
0071   auto [outputTracks, trackLinks, assocTracks] = output;
0072 #else
0073   const auto [inputhits, assocHits] = input;
0074   auto [outputTracks, assocTracks]  = output;
0075 #endif
0076
0077   // Check the number of input collections is correct
0078   std::size_t nCollections = inputhits.size();
0079   if (nCollections != m_cfg.n_layer) {
0080     error("Wrong number of input collections passed to algorithm");
0081     return;
0082   }
0083
0084 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0085   // Check if truth associations are possible
0086   const bool do_assoc = hitLinks != nullptr && !hitLinks->empty();
0087   if (!do_assoc) {
0088     debug("Provided MCRecoTrackerHitLink collection is empty. No truth associations "
0089           "will be performed.");
0090   }
0091   // Build fast lookup once per event using podio::LinkNavigator
0092   std::optional<podio::LinkNavigator<edm4eic::MCRecoTrackerHitLinkCollection>> link_nav;
0093   if (do_assoc) {
0094     link_nav.emplace(*hitLinks);
0095   }
0096 #else
0097   const bool do_assoc = assocHits != nullptr && !assocHits->empty();
0098   if (!do_assoc) {
0099     debug("Provided MCRecoTrackerHitAssociation collection is empty. No truth associations "
0100           "will be performed.");
0101   }
0102 #endif
0103
0104   std::vector<std::vector<Eigen::Vector3d>> convertedHits;
0105   std::vector<std::vector<edm4hep::MCParticle>> assocParts;
0106
0107   // Check there aren't too many hits in any layer to handle
0108   // Temporary limit of number of hits per layer before Kalman filtering/GNN implemented
0109   // TODO - Implement more sensible solution
0110   for (const auto& layerHits : inputhits) {
0111     if ((*layerHits).size() > m_cfg.layer_hits_max) {
0112       info("Too many hits in layer");
0113       return;
0114     }
0115     if ((*layerHits).empty()) {
0116       trace("No hits in layer");
0117       return;
0118     }
0119 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0120     ConvertClusters(*layerHits, *link_nav, *assocHits, convertedHits, assocParts);
0121 #else
0122     ConvertClusters(*layerHits, *assocHits, convertedHits, assocParts);
0123 #endif
0124   }
0125
0126   // Create a matrix to store the hit positions
0127   Eigen::MatrixXd hitMatrix(3, m_cfg.n_layer);
0128
0129   // Create vector to store indexes of hits in the track
0130   std::vector<std::size_t> layerHitIndex(m_cfg.n_layer, 0);
0131
0132   int layer = 0;
0133
0134   // Iterate over all combinations of measurements in the layers without recursion
0135   while (true) {
0136     hitMatrix.col(layer) << convertedHits[layer][layerHitIndex[layer]];
0137
0138     bool isValid = true;
0139     // Check the last two hits are within a certain angle of the optimum direction
0140     if (layer > 0 && m_cfg.restrict_direction) {
0141       isValid = checkHitPair(hitMatrix.col(layer - 1), hitMatrix.col(layer));
0142     }
0143
0144     // If valid hit combination, move to the next layer or check the combination
0145     if (isValid) {
0146       if (layer == static_cast<long>(m_cfg.n_layer) - 1) {
0147         // Check the combination, if chi2 limit is passed, add the track to the output
0148         checkHitCombination(&hitMatrix, outputTracks,
0149 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0150                             trackLinks,
0151 #endif
0152                             assocTracks, inputhits, assocParts, layerHitIndex);
0153       } else {
0154         layer++;
0155         continue;
0156       }
0157     }
0158
0159     // Iterate current layer
0160     layerHitIndex[layer]++;
0161
0162     bool doBreak = false;
0163     // Set up next combination to check
0164     while (layerHitIndex[layer] >= convertedHits[layer].size()) {
0165       layerHitIndex[layer] = 0;
0166       if (layer == 0) {
0167         doBreak = true;
0168         break;
0169       }
0170       layer--;
0171       // Iterate previous layer
0172       layerHitIndex[layer]++;
0173     }
0174     if (doBreak) {
0175       break;
0176     }
0177   }
0178 }
0179
0180 void FarDetectorLinearTracking::checkHitCombination(
0181     Eigen::MatrixXd* hitMatrix, edm4eic::TrackCollection* outputTracks,
0182 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0183     edm4eic::MCRecoTrackParticleLinkCollection* trackLinks,
0184 #endif
0185     edm4eic::MCRecoTrackParticleAssociationCollection* assocTracks,
0186     const std::vector<gsl::not_null<const edm4eic::Measurement2DCollection*>>& inputHits,
0187     const std::vector<std::vector<edm4hep::MCParticle>>& assocParts,
0188     const std::vector<std::size_t>& layerHitIndex) const {
0189
0190   Eigen::Vector3d weightedAnchor = (*hitMatrix) * m_layerWeights / (m_layerWeights.sum());
0191
0192   auto localMatrix = (*hitMatrix).colwise() - weightedAnchor;
0193
0194   Eigen::BDCSVD<Eigen::MatrixXd> svd(localMatrix.transpose(),
0195                                      Eigen::ComputeThinU | Eigen::ComputeThinV);
0196
0197   auto V = svd.matrixV();
0198
0199   // Rotate into principle components and calculate chi2/ndf
0200   auto rotatedMatrix = localMatrix.transpose() * V;
0201   auto residuals     = rotatedMatrix.rightCols(2);
0202   double chi2        = (residuals.array() * residuals.array()).sum() / (2 * m_cfg.n_layer);
0203
0204   if (chi2 > m_cfg.chi2_max) {
0205     return;
0206   }
0207
0208   edm4hep::Vector3d outPos = weightedAnchor.data();
0209   edm4hep::Vector3d outVec = V.col(0).data();
0210
0211   // Make sure fit was pointing in the right direction
0212   if (outVec.z > 0) {
0213     outVec = outVec * -1;
0214   }
0215
0216   int32_t type{0};                                          // Type of track
0217   edm4hep::Vector3f position(outPos.x, outPos.y, outPos.z); // Position of the trajectory point [mm]
0218   edm4hep::Vector3f momentum(outVec.x, outVec.y, outVec.z); // 3-momentum at the point [GeV]
0219   edm4eic::Cov6f positionMomentumCovariance;                // Error on the position
0220   float time{0};                                            // Time at this point [ns]
0221   float timeError{0};                                       // Error on the time at this point
0222   float charge{-1};                                         // Charge of the particle
0223   int32_t ndf{static_cast<int32_t>(m_cfg.n_layer) - 1};     // Number of degrees of freedom
0224   int32_t pdg{11};                                          // PDG code of the particle
0225
0226   // Create the track
0227   auto track = (*outputTracks)
0228                    .create(type, position, momentum, positionMomentumCovariance, time, timeError,
0229                            charge, chi2, ndf, pdg);
0230
0231   // Add Measurement2D relations and count occurrence of particles contributing to the track
0232   std::unordered_map<const edm4hep::MCParticle*, int> particleCount;
0233   for (std::size_t layer = 0; layer < layerHitIndex.size(); layer++) {
0234     track.addToMeasurements((*inputHits[layer])[layerHitIndex[layer]]);
0235     const auto& assocParticle = assocParts[layer][layerHitIndex[layer]];
0236     particleCount[&assocParticle]++;
0237   }
0238
0239   // Create track associations for each particle
0240   for (const auto& [particle, count] : particleCount) {
0241 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0242     auto trackLink = trackLinks->create();
0243     trackLink.setFrom(track);
0244     trackLink.setTo(*particle);
0245     trackLink.setWeight(count / static_cast<double>(m_cfg.n_layer));
0246 #endif
0247     auto trackAssoc = assocTracks->create();
0248     trackAssoc.setRec(track);
0249     trackAssoc.setSim(*particle);
0250     trackAssoc.setWeight(count / static_cast<double>(m_cfg.n_layer));
0251   }
0252 }
0253
0254 // Check if a pair of hits lies close to the optimum direction
0255 bool FarDetectorLinearTracking::checkHitPair(const Eigen::Vector3d& hit1,
0256                                              const Eigen::Vector3d& hit2) const {
0257
0258   Eigen::Vector3d hitDiff = hit2 - hit1;
0259   hitDiff.normalize();
0260
0261   double angle = std::acos(hitDiff.dot(m_optimumDirection));
0262
0263   debug("Vector: x={}, y={}, z={}", hitDiff.x(), hitDiff.y(), hitDiff.z());
0264   debug("Optimum: x={}, y={}, z={}", m_optimumDirection.x(), m_optimumDirection.y(),
0265         m_optimumDirection.z());
0266   debug("Angle: {}, Tolerance {}", angle, m_cfg.step_angle_tolerance);
0267
0268   return angle <= m_cfg.step_angle_tolerance;
0269 }
0270
0271 // Convert measurements into global coordinates
0272 void FarDetectorLinearTracking::ConvertClusters(
0273     const edm4eic::Measurement2DCollection& clusters,
0274 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0275     const podio::LinkNavigator<edm4eic::MCRecoTrackerHitLinkCollection>& link_nav,
0276 #endif
0277     [[maybe_unused]] const edm4eic::MCRecoTrackerHitAssociationCollection& assoc_hits,
0278     std::vector<std::vector<Eigen::Vector3d>>& pointPositions,
0279     std::vector<std::vector<edm4hep::MCParticle>>& assoc_parts) const {
0280
0281   // Get context of first hit
0282   const dd4hep::VolumeManagerContext* context =
0283       m_cellid_converter->findContext(clusters[0].getSurface());
0284
0285   std::vector<Eigen::Vector3d> layerPositions;
0286   std::vector<edm4hep::MCParticle> assocParticles;
0287
0288   for (auto cluster : clusters) {
0289
0290     auto globalPos = context->localToWorld({cluster.getLoc()[0], cluster.getLoc()[1], 0});
0291     layerPositions.emplace_back(globalPos.x() / dd4hep::mm, globalPos.y() / dd4hep::mm,
0292                                 globalPos.z() / dd4hep::mm);
0293
0294     // Determine the MCParticle associated with this measurement based on the weights
0295     // Get hit in measurement with max weight
0296     float maxWeight      = 0;
0297     std::size_t maxIndex = cluster.getWeights().size();
0298     for (std::size_t i = 0; i < cluster.getWeights().size(); ++i) {
0299       if (cluster.getWeights()[i] > maxWeight) {
0300         maxWeight = cluster.getWeights()[i];
0301         maxIndex  = i;
0302       }
0303     }
0304     if (maxIndex == cluster.getWeights().size()) {
0305       // no maximum found (e.g. all weights zero, cluster size zero)
0306       continue;
0307     }
0308     auto maxHit = cluster.getHits()[maxIndex];
0309     // Get associated raw hit
0310     auto rawHit = maxHit.getRawHit();
0311
0312 #if EDM4EIC_BUILD_VERSION >= EDM4EIC_VERSION(8, 7, 0)
0313     const auto sim_hits = link_nav.getLinked(rawHit);
0314     if (!sim_hits.empty()) {
0315       auto particle = sim_hits[0].o.getParticle();
0316       assocParticles.push_back(particle);
0317     }
0318 #else
0319     // Fallback: linear search through associations
0320     for (const auto& assoc : assoc_hits) {
0321       if (assoc.getRawHit() == rawHit) {
0322         auto particle = assoc.getSimHit().getParticle();
0323         assocParticles.push_back(particle);
0324         break;
0325       }
0326     }
0327 #endif
0328   }
0329
0330   pointPositions.push_back(layerPositions);
0331   assoc_parts.push_back(assocParticles);
0332 }
0333
0334 } // namespace eicrecon