DetailedMuonPatternTruthBuilder.cxx

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/*
  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
*/
 
#include "DetailedMuonPatternTruthBuilder.h"
 
#include <algorithm>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <queue>
 
#include "AthContainers/DataVector.h"
#include "AtlasHepMC/GenParticle.h"
#include "AtlasHepMC/GenVertex.h"
#include "GeneratorObjects/HepMcParticleLink.h"
#include "MuonPattern/DetailedMuonPatternTruthCollection.h"
#include "MuonPattern/MuonPattern.h"
#include "MuonPattern/MuonPatternChamberIntersect.h"
#include "MuonPattern/MuonPatternCollection.h"
#include "MuonPattern/MuonPatternCombination.h"
#include "MuonPattern/MuonPatternCombinationCollection.h"
#include "MuonPrepRawData/MMPrepData.h"
#include "MuonPrepRawData/MdtPrepData.h"
#include "MuonPrepRawData/MuonCluster.h"
#include "MuonPrepRawData/sTgcPrepData.h"
#include "MuonRIO_OnTrack/MMClusterOnTrack.h"
#include "MuonRIO_OnTrack/MdtDriftCircleOnTrack.h"
#include "MuonRIO_OnTrack/MuonClusterOnTrack.h"
#include "MuonRecHelperTools/IMuonEDMHelperSvc.h"
#include "MuonRecHelperTools/MuonEDMPrinterTool.h"
#include "MuonRecToolInterfaces/IMdtDriftCircleOnTrackCreator.h"
#include "MuonRecToolInterfaces/IMuonClusterOnTrackCreator.h"
#include "MuonRecToolInterfaces/IMuonCompetingClustersOnTrackCreator.h"
#include "MuonRecToolInterfaces/IMuonTrackToSegmentTool.h"
#include "MuonSegment/MuonSegment.h"
#include "MuonSimData/CscSimDataCollection.h"
#include "MuonSimData/MuonSimData.h"
#include "MuonSimData/MuonSimDataCollection.h"
#include "MuonTrackMakerUtils/SortMeasurementsByPosition.h"
#include "TrackRecord/TrackRecordCollection.h"
#include "TrkCompetingRIOsOnTrack/CompetingRIOsOnTrack.h"
#include "TrkDetElementBase/TrkDetElementBase.h"
#include "TrkExInterfaces/IExtrapolator.h"
#include "TrkFitterInterfaces/ITrackFitter.h"
#include "TrkMeasurementBase/MeasurementBase.h"
#include "TrkParameters/TrackParameters.h"
#include "TrkPrepRawData/PrepRawData.h"
#include "TrkPseudoMeasurementOnTrack/PseudoMeasurementOnTrack.h"
#include "TrkRIO_OnTrack/RIO_OnTrack.h"
#include "TrkSurfaces/PerigeeSurface.h"
#include "TrkTrack/Track.h"
#include "TrkTruthData/DetailedSegmentTruth.h"
#include "TrkTruthData/DetailedTrackTruth.h"
#include "TrkTruthData/TruthTrajectory.h"
 
struct DetectorLayer {
    DetectorLayer() = default;
    Muon::MuonStationIndex::StIndex stIndex{Muon::MuonStationIndex::StIndex::StUnknown};
    bool isEndcap{false};
    double minPos{FLT_MAX};  // flag whether first and second globalpos have been filled
    double maxPos{-FLT_MAX};
    int nnsw{0};
    int nmdtS{0};
    int nmdtL{0};
    int nphi{0};
    Amg::Vector3D first3D{Amg::Vector3D::Zero()};
    Amg::Vector3D last3D{Amg::Vector3D::Zero()};
    std::vector<const Trk::MeasurementBase*> meas;
};
 
namespace {
 
    template <class Map> void printMap(const Map& m) {
        std::cout << "printMap(): [";
        for (typename Map::const_iterator i = m.begin(); i != m.end(); ++i) { std::cout << "(" << i->first << "," << i->second << "), "; }
        std::cout << "]" << std::endl;
    }
 
    struct SubDetPRDs {
        std::array<std::set<Identifier>, SubDetHitStatistics::NUM_SUBDETECTORS>  subDetHits;
    };
 
    SubDetPRDs& operator+=(SubDetPRDs& a, const SubDetPRDs& b) {
        for (unsigned i = 0; i < SubDetHitStatistics::NUM_SUBDETECTORS; i++) {
            const std::set<Identifier>& bset = b.subDetHits[i];
            for (std::set<Identifier>::const_iterator pb = bset.begin(); pb != bset.end(); ++pb) { a.subDetHits[i].insert(*pb); }
        }
        return a;
    }
 
    SubDetHitStatistics makeSubDetHitStatistics(const SubDetPRDs& prds) {
        SubDetHitStatistics res;
        for (unsigned i = 0; i < SubDetHitStatistics::NUM_SUBDETECTORS; i++) {
            res[SubDetHitStatistics::SubDetType(i)] = prds.subDetHits[i].size();
        }
        return res;
    }
 
    // Truth trajectory sprouts
    class Sprout : public std::list<HepMC::ConstGenParticlePtr> {
    public:
        SubDetPRDs stat;
    };
 
}  // namespace
 
namespace Trk {
 
    //================================================================
    DetailedMuonPatternTruthBuilder::DetailedMuonPatternTruthBuilder(const std::string& type, const std::string& name,
                                                                     const IInterface* parent) :
        AthAlgTool(type, name, parent) {
        declareInterface<IDetailedMuonPatternTruthBuilder>(this);
    }
 
    //================================================================
    StatusCode DetailedMuonPatternTruthBuilder::initialize() {
        ATH_CHECK(m_truthTrackBuilder.retrieve());
        ATH_CHECK(m_idHelperSvc.retrieve());
        ATH_CHECK(m_mdtCreator.retrieve());
        ATH_CHECK(m_muonClusterCreator.retrieve());
        return StatusCode::SUCCESS;
    }
 
    //================================================================
    void DetailedMuonPatternTruthBuilder::buildDetailedMuonPatternTruth(DetailedMuonPatternTruthCollection* output,
                                                                        const MuonPatternCombinationCollection& patterns,
                                                                        const std::vector<const PRD_MultiTruthCollection*>& prdTruth) {
        ATH_MSG_VERBOSE("DetailedMuonPatternTruthBuilder::buildDetailedMuonPatternTruth() ");
 
        if (!output) { return; }
 
        //----------------------------------------------------------------
        // The caller can pass PRD truth collections in any order. Sort them out.
 
        std::vector<const PRD_MultiTruthCollection*> orderedPRD_Truth(SubDetHitStatistics::NUM_SUBDETECTORS);
        PRD_InverseTruth inverseTruth;
 
        for (std::vector<const PRD_MultiTruthCollection*>::const_iterator i = prdTruth.begin(); i != prdTruth.end(); ++i) {
            if (*i) {
                if (!(*i)->empty()) {
                    SubDetHitStatistics::SubDetType subdet = findSubDetType((*i)->begin()->first);
 
                    if (subdet != SubDetHitStatistics::NUM_SUBDETECTORS) {
                        orderedPRD_Truth[subdet] = *i;
                        addToInverseMultiMap(&inverseTruth, **i);
                    } else {
                        ATH_MSG_WARNING("Got unknown SubDetType in prdTruth ");
                    }
                } else {
                    ATH_MSG_DEBUG("Empty truth ???");
                }
            }
        }
 
        //----------------------------------------------------------------
        // Find associated truth for each track
 
        for (unsigned itrack = 0; itrack < patterns.size(); itrack++) {
            ElementLink<DataVector<Muon::MuonPatternCombination> > ptrack(patterns, itrack);
            addTrack(output, ptrack, orderedPRD_Truth, inverseTruth);
        }
 
        // DEBUG
        // FIXME: in normal production jobs that does *a lot of* formatting only to discard the result...
        ATH_MSG_DEBUG(
            "Dumping output collection.\n"
            " Entries with TruthTrajectories of more then one particle shown at the DEBUG level.\n"
            " Use VERBOSE level for complete dump.");
 
        for (DetailedMuonPatternTruthCollection::const_iterator i = output->begin(); i != output->end(); ++i) {
            bool interesting = (i->second.trajectory().size() > 1);
 
            // TODO:  Reinsert the following code once I understand the compile-time error
            //    msg(interesting  ? MSG::DEBUG : MSG::VERBOSE)
            //      <<"out: trk="<<i->first.index()<<" => "<<i->second<<endmsg;
 
            if (interesting) {
                const TruthTrajectory& t = i->second.trajectory();
                msg(MSG::VERBOSE) << "Particles on the trajectory:\n";
                for (unsigned k = 0; k < t.size(); ++k) { msg(MSG::VERBOSE) << t[k] << "\n"; }
                msg(MSG::VERBOSE) << "\n" << endmsg;
            }
        }
    }
 
    //================================================================
 
    void DetailedMuonPatternTruthBuilder::buildDetailedTrackTruth(std::vector<DetailedTrackTruth>* output,
                                                                  const Muon::MuonPatternCombination& pattern,
                                                                  const std::vector<const PRD_MultiTruthCollection*>& prdTruth) {
        ATH_MSG_VERBOSE("DetailedMuonPatternTruthBuilder::buildDetailedTrackTruth() ");
 
        if (!output) { return; }
 
        //----------------------------------------------------------------
        // The caller can pass PRD truth collections in any order. Sort them out.
 
        std::vector<const PRD_MultiTruthCollection*> orderedPRD_Truth(SubDetHitStatistics::NUM_SUBDETECTORS);
        PRD_InverseTruth inverseTruth;
 
        for (std::vector<const PRD_MultiTruthCollection*>::const_iterator i = prdTruth.begin(); i != prdTruth.end(); ++i) {
            if (*i) {
                if (!(*i)->empty()) {
                    SubDetHitStatistics::SubDetType subdet = findSubDetType((*i)->begin()->first);
 
                    if (subdet != SubDetHitStatistics::NUM_SUBDETECTORS) {
                        orderedPRD_Truth[subdet] = *i;
                        addToInverseMultiMap(&inverseTruth, **i);
                    } else {
                        ATH_MSG_WARNING("Got unknown SubDetType in prdTruth ");
                    }
                } else {
                    ATH_MSG_DEBUG("Empty truth ???");
                }
            }
        }
 
        //----------------------------------------------------------------
        // Find associated truth for each track
        addDetailedTrackTruth(output, pattern, orderedPRD_Truth, inverseTruth);
 
        // DEBUG
        // FIXME: in normal production jobs that does *a lot of* formatting only to discard the result...
        ATH_MSG_DEBUG(
            "Dumping output collection.\n"
            " Entries with TruthTrajectories of more then one particle shown at the DEBUG level.\n"
            " Use VERBOSE level for complete dump.");
 
     
    }
    //================================================================
 
    //================================================================
    // Plagiarized from
    // Tracking/TrkTools/TrkTruthCreatorTools/src/TrackTruthMaker.cxx
    // (no way to reuse its private function PrepRawDataCollectionType() )
 
    SubDetHitStatistics::SubDetType DetailedMuonPatternTruthBuilder::findSubDetType(Identifier id) {
        if (!m_idHelperSvc->isMuon(id)) {
            if (m_idHelperSvc->mdtIdHelper().is_pixel(id))
                return SubDetHitStatistics::Pixel;
            else if (m_idHelperSvc->mdtIdHelper().is_sct(id))
                return SubDetHitStatistics::SCT;
            else if (m_idHelperSvc->mdtIdHelper().is_trt(id))
                return SubDetHitStatistics::TRT;
        } else {
            if (m_idHelperSvc->isMdt(id))
                return SubDetHitStatistics::MDT;
            else if (m_idHelperSvc->isRpc(id))
                return SubDetHitStatistics::RPC;
            else if (m_idHelperSvc->isTgc(id))
                return SubDetHitStatistics::TGC;
            else if (m_idHelperSvc->isCsc(id))
                return SubDetHitStatistics::CSC;
            else if (m_idHelperSvc->isMM(id))
                return SubDetHitStatistics::MM;
            else if (m_idHelperSvc->issTgc(id))
                return SubDetHitStatistics::STGC;
        }
 
        ATH_MSG_WARNING("findSubDetType(): UNKNOWN subdet for id=" << id);
 
        return SubDetHitStatistics::NUM_SUBDETECTORS;
    }
 
    //================================================================
    void DetailedMuonPatternTruthBuilder::addTrack(DetailedMuonPatternTruthCollection* output,
                                                   const ElementLink<DataVector<Muon::MuonPatternCombination> >& MuPatternCombo,
                                                   const std::vector<const PRD_MultiTruthCollection*>& orderedPRD_Truth,
                                                   const PRD_InverseTruth& inverseTruth) {
        SubDetHitStatistics trackStat;
        std::map<HepMcParticleLink, SubDetPRDs> pairStat;  // stats for (track,GenParticle) for the current track
 
        // Loop over MuonPatternChamberIntersect
        const std::vector<Muon::MuonPatternChamberIntersect>& MPCIV = (*MuPatternCombo)->chamberData();
        for (unsigned int i_MPCI = 0; i_MPCI < MPCIV.size(); i_MPCI++) {
            if (MPCIV.empty()) continue;
 
            // get the PrepRawData from the MuonPatternChamberIntersect
            std::vector<const Trk::PrepRawData*> PRDV = MPCIV.at(i_MPCI).prepRawDataVec();
 
            // Loop over the PRDV
            for (unsigned int j_PRD = 0; j_PRD < PRDV.size(); j_PRD++) {
                if (PRDV.empty()) continue;
 
                Identifier id = PRDV.at(j_PRD)->identify();
                SubDetHitStatistics::SubDetType subdet = findSubDetType(id);
 
                if (subdet != SubDetHitStatistics::NUM_SUBDETECTORS) {
                    // if PRD truth collection is missing, ignore subdet in track stat calculation as well.
                    if (orderedPRD_Truth[subdet]) {
                        ++trackStat[subdet];
 
                        typedef PRD_MultiTruthCollection::const_iterator iprdt;
                        std::pair<iprdt, iprdt> range = orderedPRD_Truth[subdet]->equal_range(id);
 
                        int n = 0;
                        // Loop over particles contributing to this cluster
                        for (iprdt i = range.first; i != range.second; ++i) {
                            if (!i->second.isValid()) {
                                ATH_MSG_WARNING("Unexpected invalid HepMcParticleLink in PRD_MultiTruthCollection");
                            } else {
                                pairStat[i->second].subDetHits[subdet].insert(id);
                                n += 1;
                                ATH_MSG_VERBOSE("PRD-ID:" << id << " subdet:" << subdet << " number:" << n
                                                          << " particle link:" << i->second);
                            }
                        }
                        if (n == 0) {
                            ATH_MSG_VERBOSE("--> no link, noise ? PRD-ID:" << id << " subdet:" << subdet);
                            // add unique ID 0 to pairs, we like to keep track of fake fakes
                            unsigned int ID(0), EV(0);
                            pairStat[HepMcParticleLink(ID, EV, HepMcParticleLink::IS_POSITION, HepMcParticleLink::IS_ID)].subDetHits[subdet].insert(id);
                        }
                    }  // orderedPRD_Truth[] available
                }      // subdet type check, warning in findSubDetType()
            }
        }
 
        if (msgLvl(MSG::VERBOSE)) {
            msg(MSG::VERBOSE) << "PRD truth particles = ";
            for (std::map<HepMcParticleLink, SubDetPRDs>::const_iterator i = pairStat.begin(); i != pairStat.end(); ++i) {
                msg(MSG::VERBOSE) << i->first << ",";
            }
            msg(MSG::VERBOSE) << endmsg;
        }
 
        //----------------------------------------------------------------
        // The stat structures are ready.
        // Build truth trajectories for the track
        std::set<HepMcParticleLink> seeds;
        for (std::map<HepMcParticleLink, SubDetPRDs>::const_iterator i = pairStat.begin(); i != pairStat.end(); ++i) {
            if (i->first.isValid()) {
                seeds.insert(i->first);
            } else {
                // add uniqueID 0 particles, we like to keep track of fake fakes
                TruthTrajectory traj;
                traj.reserve(1);
                traj.push_back(i->first);
                ATH_MSG_VERBOSE("addTrack(): add barcode 0 hits - noise ?");
 
                // noise/no truth hits on this track
                SubDetHitStatistics noiseStat = makeSubDetHitStatistics(i->second);
 
                // Only valid HepMcParticleLink make it into seeds and then into sprouts, and
                // stored in the loop over sprouts below.
                // Store output for noise/no truth particles here.
                output->insert(std::make_pair(MuPatternCombo, DetailedTrackTruth(traj, noiseStat, trackStat, noiseStat)));
            }
        }
 
        // Grow sprouts from the seeds
        typedef std::map<HepMcParticleLink, Sprout> SproutMap;
        SproutMap sprouts;
 
        while (!seeds.empty()) {
            HepMcParticleLink link = *seeds.begin();
 
            Sprout current_sprout;
            std::queue<HepMC::ConstGenParticlePtr> tmp;
            unsigned eventIndex = link.eventIndex();
#ifdef HEPMC3
            HepMC::ConstGenParticlePtr current = link.scptr();
#else
            const HepMC::GenParticle* current = link.cptr();
#endif
 
            do {
                HepMcParticleLink curlink(HepMC::uniqueID(current), eventIndex, HepMcParticleLink::IS_EVENTNUM, HepMcParticleLink::IS_ID);
 
                // remove the current particle from the list of particles to consider (if it is still there)
                seeds.erase(curlink);
 
                // Have we worked on this particle before?
                SproutMap::iterator p_old = sprouts.find(curlink);
                if (p_old != sprouts.end()) {
                    // merge the old sprout with the current one.
                    current_sprout.splice(current_sprout.end(), p_old->second);
                    current_sprout.stat += p_old->second.stat;
                    // and remove the entry for the old
                    sprouts.erase(p_old);
                    break;  // the do-while(getMother()) loop
                } else {    // No, this is a new particle.  Try to extend the current truth trajectory.
 
                    // Add the particle to the current truth trajectory.
                    // New: with the current stricter cuts on mother-daughter
                    // we don't have to require that ancestors produce hits.
 
                    current_sprout.push_back(current);
 
                    std::map<HepMcParticleLink, SubDetPRDs>::iterator p_newstat = pairStat.find(curlink);
                    if (p_newstat != pairStat.end()) { current_sprout.stat += p_newstat->second; }
                }
            } while ((current = m_truthTrackBuilder->getMother(current)));
 
            // Add the grown sprout to the list
            sprouts.insert(std::make_pair(link, current_sprout));
 
        }  // while(!seeds.empty())
 
        //----------------
        // All seeds have been processed, and the upstream extensions of the
        // sprouts are done.  Extend the sprouts downstream to get the final
        // truth trajectories and store the result.
        //
        // Note: so far the "sprouts" object mapped {last particle ==> sprout}
        // Extending a sprout downstream will break this relationship,
        // but at this point we don't care about it and will only use the
        // value of the map, not the key.
 
        for (SproutMap::iterator s = sprouts.begin(); s != sprouts.end(); ++s) {
            // Attempt to extend the TruthTrajectory sprout to the "outside".
            // This may add only hits that are *not* on the current track.
            // Thus no need to update stats track and stats common.
 
            HepMC::ConstGenParticlePtr current = *s->second.begin();
            while ((current = m_truthTrackBuilder->getDaughter(current))) { s->second.push_front(current); }
 
            // Now we have info to build the final TruthTrajectory.
            // FIXME: what is the current average size?
            TruthTrajectory traj;
            traj.reserve(2);  // The average size is about 1.05.  Hardcode that instead of using slow list::size().
            for (Sprout::const_iterator ppart = s->second.begin(); ppart != s->second.end(); ++ppart) {
                traj.push_back(HepMcParticleLink(HepMC::uniqueID(*ppart), s->first.eventIndex(), HepMcParticleLink::IS_EVENTNUM, HepMcParticleLink::IS_ID));
            }
 
            // Count PRDs on the TruthTrajectory
            std::set<Muon::MuonStationIndex::ChIndex> tempSet;
            SubDetHitStatistics truthStat = countPRDsOnTruth(traj, inverseTruth, tempSet);
 
            ATH_MSG_VERBOSE("addTrack(): sprout length = " << traj.size());
            output->insert(
                std::make_pair(MuPatternCombo, DetailedTrackTruth(traj, makeSubDetHitStatistics(s->second.stat), trackStat, truthStat)));
        }
 
        ATH_MSG_VERBOSE("addTrack(): #sprouts = " << sprouts.size() << ", output->size() = " << output->size());
    }
 
    //================================================================
    SubDetHitStatistics DetailedMuonPatternTruthBuilder::countPRDsOnTruth(const TruthTrajectory& traj, const PRD_InverseTruth& inverseTruth,
                                                                          std::set<Muon::MuonStationIndex::ChIndex> chIndices) {
        // Different particles from the same TruthTrajectory can contribute to the same cluster.
        // We should be careful to avoid double-counting in such cases.
 
        SubDetPRDs prds;
        for (TruthTrajectory::const_iterator p = traj.begin(); p != traj.end(); ++p) {
            typedef PRD_InverseTruth::const_iterator iter;
            std::pair<iter, iter> range = inverseTruth.equal_range(*p);
            for (iter i = range.first; i != range.second; ++i) {
                if (chIndices.find(m_idHelperSvc->chamberIndex(i->second)) != chIndices.end()) {
                    SubDetHitStatistics::SubDetType subdet = findSubDetType(i->second);
                    if (subdet == SubDetHitStatistics::NUM_SUBDETECTORS) continue;
                    prds.subDetHits[subdet].insert(i->second);
                }
            }
        }
 
        return makeSubDetHitStatistics(prds);
    }
 
    //================================================================
    Amg::Vector3D DetailedMuonPatternTruthBuilder::getPRDTruthPosition(const Muon::MuonSegment& segment,
                                                                       std::list<HepMC::ConstGenParticlePtr> genPartList, int truthPos,
                                                                       std::set<Muon::MuonStationIndex::ChIndex> chIndices) {
        double minPos = 2e8, maxPos = 0;
        Amg::Vector3D first3D(0, 0, 0), last3D(0, 0, 0);
 
        if (genPartList.empty()) {
            ATH_MSG_WARNING("No GenParticles associated to this PRD_TruthTrajectory. Exiting segment creation.");
            return Amg::Vector3D(0, 0, 0);
        }
 
        const MuonSimDataCollection* mdtSimDataMap = retrieveTruthCollection("MDT_SDO");
        if (!mdtSimDataMap) {
            ATH_MSG_WARNING(" failed to retrieve MuonSimDataCollection: "
                            << "MDT_SDO");
            return Amg::Vector3D(0, 0, 0);
        }
        const MuonSimDataCollection* mmSimDataMap = retrieveTruthCollection("MM_SDO");
        if (!mmSimDataMap) {
            ATH_MSG_WARNING(" failed to retrieve MuonSimDataCollection: "
                            << "MM_SDO");
            return Amg::Vector3D(0, 0, 0);
        }
        const MuonSimDataCollection* stgcSimDataMap = retrieveTruthCollection("sTGC_SDO");
        if (!stgcSimDataMap) {
            ATH_MSG_WARNING(" failed to retrieve MuonSimDataCollection: "
                            << "sTGC_SDO");
            return Amg::Vector3D(0, 0, 0);
        }
 
        // First sort the hits per detector layer
        std::map<Muon::MuonStationIndex::StIndex, DetectorLayer> hitsPerLayer;
        std::map<const Trk::TrkDetElementBase*, std::pair<std::list<const Trk::PrepRawData*>, std::list<const Trk::PrepRawData*> > >
            clustersPerDetEl;
 
        // Loop over containedROTs in segment
        for (unsigned int i_cROTv = 0; i_cROTv < segment.numberOfContainedROTs(); i_cROTv++) {
            const Trk::RIO_OnTrack* rot = segment.rioOnTrack(i_cROTv);
 
            // get the PrepRawData from the ROT
            const Trk::PrepRawData* prd = rot->prepRawData();
 
            Identifier id = prd->identify();
 
            Muon::MuonStationIndex::StIndex stIndex = m_idHelperSvc->stationIndex(id);
            bool isEndcap = m_idHelperSvc->isEndcap(id);
 
            if (chIndices.find(m_idHelperSvc->chamberIndex(id)) == chIndices.end()) {
                ATH_MSG_DEBUG("Muon station doesn't match segment.  Continuing");
                continue;
            }
 
            // some patches until MuonIdHelper is updated
            const Muon::MMPrepData* mm = dynamic_cast<const Muon::MMPrepData*>(prd);
            if (mm) {
                isEndcap = true;
                stIndex = Muon::MuonStationIndex::StIndex::EI;
            }
            const Muon::sTgcPrepData* stgc = dynamic_cast<const Muon::sTgcPrepData*>(prd);
            if (stgc) {
                isEndcap = true;
                stIndex = Muon::MuonStationIndex::StIndex::EI;
            }
            // BEGIN NEW WORK
 
            DetectorLayer& detLayer = hitsPerLayer[stIndex];
            detLayer.isEndcap = isEndcap;
            detLayer.stIndex = stIndex;
 
            // const Trk::MeasurementBase* meas = 0;
            if (m_idHelperSvc->isMdt(id)) {
                const Muon::MdtPrepData* mprd = dynamic_cast<const Muon::MdtPrepData*>(prd);
                if (!mprd) {
                    ATH_MSG_WARNING(" MDT PRD not of type MdtPrepData " << m_idHelperSvc->toString(id));
                    continue;
                }
 
                const MuonSimData::Deposit* deposit = nullptr;
                for (auto it = genPartList.begin(); it != genPartList.end() && !deposit; ++it) {
                    deposit = getDeposit(*mdtSimDataMap, *it, id);
                }
                if (!deposit) {
                    ATH_MSG_WARNING(" Deposit for GenParticle not found " << m_idHelperSvc->toString(id));
                    continue;
                }
 
                Amg::Vector2D lp(deposit->second.firstEntry(), deposit->second.secondEntry());
                const Amg::Vector3D gpos = prd->detectorElement()->surface(id).localToGlobal(lp);
 
                double val = isEndcap ? fabs(gpos.z()) : gpos.perp();
 
                // nasty comparisons to figure out which MDT hit comes first
                if (val < detLayer.minPos) {
                    if (detLayer.maxPos < -1e8 && detLayer.minPos < 1e8) {
                        detLayer.last3D = detLayer.first3D;
                        detLayer.maxPos = detLayer.minPos;
                    }
                    detLayer.first3D = gpos;
                    detLayer.minPos = val;
                } else if (val > detLayer.maxPos) {
                    detLayer.last3D = gpos;
                    detLayer.maxPos = val;
                }
 
                if (val < minPos) {
                    if (maxPos < -1e8 && minPos < 1e8) {
                        last3D = first3D;
                        maxPos = minPos;
                    }
                    minPos = val;
                    first3D = gpos;
                } else if (val > maxPos) {
                    maxPos = val;
                    last3D = gpos;
                }
 
                const Muon::MdtDriftCircleOnTrack* mdt = m_mdtCreator->createRIO_OnTrack(*mprd, gpos);
                if (!mdt) {
                    ATH_MSG_WARNING(" ROT creation failed " << m_idHelperSvc->toString(id));
                    continue;
                }
                Trk::DriftCircleSide side = deposit->second.firstEntry() < 0 ? Trk::LEFT : Trk::RIGHT;
                m_mdtCreator->updateSign(*const_cast<Muon::MdtDriftCircleOnTrack*>(mdt), side);
                double pull = (mdt->driftRadius() - deposit->second.firstEntry()) / mdt->localCovariance()(Trk::locR);
                ATH_MSG_VERBOSE(" new MDT    " << m_idHelperSvc->toString(id) << " radius " << mdt->driftRadius() << " true radius "
                                               << deposit->second.firstEntry() << " pull " << pull);
                if (fabs(pull) > 3.) ATH_MSG_VERBOSE(" hit with large pull ");
                detLayer.meas.push_back(mdt);
                if (m_idHelperSvc->isSmallChamber(id))
                    ++detLayer.nmdtS;
                else
                    ++detLayer.nmdtL;
                // meas = mdt;
            } else if (mm) {
                const MuonSimData::Deposit* deposit = nullptr;
                for (auto it = genPartList.begin(); it != genPartList.end() && !deposit; ++it) {
                    deposit = getDeposit(*mmSimDataMap, *it, id);
                }
                if (!deposit) {
                    ATH_MSG_WARNING(" Deposit for GenParticle not found " << m_idHelperSvc->toString(id));
                    continue;
                }
 
                Amg::Vector2D lp(deposit->second.firstEntry(), deposit->second.secondEntry());
                const Amg::Vector3D gpos = prd->detectorElement()->surface(id).localToGlobal(lp);
 
                // double val = isEndcap ? fabs(gpos->z()) : gpos->perp();
                // micormegas are always endcap
                double val = fabs(gpos.z());
                // nasty comparisons to figure out which MDT hit comes first
                if (val < detLayer.minPos) {
                    if (detLayer.maxPos < -1e8 && detLayer.minPos < 1e8) {
                        detLayer.last3D = detLayer.first3D;
                        detLayer.maxPos = detLayer.minPos;
                    }
                    detLayer.first3D = gpos;
                    detLayer.minPos = val;
                } else if (val > detLayer.maxPos) {
                    detLayer.last3D = gpos;
                    detLayer.maxPos = val;
                }
 
                if (val < minPos) {
                    if (maxPos < -1e8 && detLayer.minPos < 1e8) {
                        last3D = first3D;
                        maxPos = minPos;
                    }
                    minPos = val;
                    first3D = gpos;
                } else if (val > maxPos) {
                    maxPos = val;
                    last3D = gpos;
                }
 
                const Muon::MuonClusterOnTrack* rot = m_muonClusterCreator->createRIO_OnTrack(*mm, gpos);
                if (!rot) {
                    ATH_MSG_WARNING(" ROT creation failed " << m_idHelperSvc->toString(id));
                    continue;
                }
                double residual = rot->localParameters().get(Trk::locX) - lp.x();
                double pull = residual / rot->localCovariance()(Trk::locX);
                ATH_MSG_DEBUG("Adding r " << gpos.perp() << " z " << gpos.z() << "  " << m_idHelperSvc->toString(id) << " " << residual
                                          << " pull " << pull);
                detLayer.meas.push_back(rot);
                // meas = rot;
                ++detLayer.nnsw;
 
            } else if (stgc) {
                // skip pads in outer most two chambers as here the wires are more precise
                if (m_idHelperSvc->stgcIdHelper().channelType(id) == 0 && abs(m_idHelperSvc->stationEta(id)) > 2) continue;
 
                // there is already a check for this at the beginning of the method
                // if( !stgcSimDataMap ) continue;
 
                const MuonSimData::Deposit* deposit = nullptr;
                for (auto it = genPartList.begin(); it != genPartList.end() && !deposit; ++it) {
                    deposit = getDeposit(*stgcSimDataMap, *it, id);
                }
                if (!deposit) {
                    ATH_MSG_WARNING(" Deposit for GenParticle not found " << m_idHelperSvc->toString(id));
                    continue;
                }
 
                Amg::Vector2D lp(deposit->second.firstEntry(), deposit->second.secondEntry());
                const Amg::Vector3D gpos = prd->detectorElement()->surface(id).localToGlobal(lp);
 
                // double val = isEndcap ? fabs(gpos->z()) : gpos->perp();
                // stgcs are always endcap
                double val = fabs(gpos.z());
                // // nasty comparisons to figure out which STGC hit comes first
                if (val < detLayer.minPos) {
                    if (detLayer.maxPos < -1e8 && detLayer.minPos < 1e8) {
                        detLayer.last3D = detLayer.first3D;
                        detLayer.maxPos = detLayer.minPos;
                    }
                    detLayer.first3D = gpos;
                    detLayer.minPos = val;
                } else if (val > detLayer.maxPos) {
                    detLayer.last3D = gpos;
                    detLayer.maxPos = val;
                }
 
                if (val < minPos) {
                    if (maxPos < -1e8 && minPos < 1e8) {
                        last3D = first3D;
                        maxPos = minPos;
                    }
                    minPos = val;
                    first3D = gpos;
                } else if (val > maxPos) {
                    maxPos = val;
                    last3D = gpos;
                }
 
                const Muon::MuonClusterOnTrack* rot = m_muonClusterCreator->createRIO_OnTrack(*stgc, gpos);
                if (!rot) {
                    ATH_MSG_WARNING(" ROT creation failed " << m_idHelperSvc->toString(id));
                    continue;
                }
                double residual = rot->localParameters().get(Trk::locX) - lp.x();
                double pull = residual / rot->localCovariance()(Trk::locX);
                ATH_MSG_DEBUG("Adding r " << gpos.perp() << " z " << gpos.z() << "  " << m_idHelperSvc->toString(id) << " " << residual
                                          << " pull " << pull);
                detLayer.meas.push_back(rot);
                // meas = rot;
                ++detLayer.nnsw;
            }
        }
 
        // END NEW WORK
        if (minPos == 2e8 || maxPos == 0) {
            ATH_MSG_WARNING("Min and max positions not found.  Filling with meaningless position");
            return Amg::Vector3D(-15000, -15000, -15000);
        }
 
        if (truthPos)
            return (first3D + last3D) / 2;
        else {
            // else truth direction
            return (last3D - first3D);
        }
    }
 
    //================================================================
    void DetailedMuonPatternTruthBuilder::addDetailedTrackTruth(std::vector<DetailedTrackTruth>* output,
                                                                const Muon::MuonPatternCombination& pattern,
                                                                const std::vector<const PRD_MultiTruthCollection*>& orderedPRD_Truth,
                                                                const PRD_InverseTruth& inverseTruth) {
        SubDetHitStatistics trackStat;
        std::map<HepMcParticleLink, SubDetPRDs> pairStat;  // stats for (track,GenParticle) for the current track
 
        // Loop over MuonPatternChamberIntersect
        const std::vector<Muon::MuonPatternChamberIntersect>& MPCIV = pattern.chamberData();
        for (unsigned int i_MPCI = 0; i_MPCI < MPCIV.size(); i_MPCI++) {
            if (MPCIV.empty()) continue;
 
            // get the PrepRawData from the MuonPatternChamberIntersect
            std::vector<const Trk::PrepRawData*> PRDV = MPCIV.at(i_MPCI).prepRawDataVec();
 
            // Loop over the PRDV
            for (unsigned int j_PRD = 0; j_PRD < PRDV.size(); j_PRD++) {
                if (PRDV.empty()) continue;
 
                Identifier id = PRDV.at(j_PRD)->identify();
                SubDetHitStatistics::SubDetType subdet = findSubDetType(id);
 
                if (subdet != SubDetHitStatistics::NUM_SUBDETECTORS) {
                    // if PRD truth collection is missing, ignore subdet in track stat calculation as well.
                    if (orderedPRD_Truth[subdet]) {
                        ++trackStat[subdet];
 
                        typedef PRD_MultiTruthCollection::const_iterator iprdt;
                        std::pair<iprdt, iprdt> range = orderedPRD_Truth[subdet]->equal_range(id);
 
                        int n = 0;
                        // Loop over particles contributing to this cluster
                        for (iprdt i = range.first; i != range.second; ++i) {
                            if (!i->second.isValid()) {
                                ATH_MSG_WARNING("Unexpected invalid HepMcParticleLink in PRD_MultiTruthCollection");
                            } else {
                                pairStat[i->second].subDetHits[subdet].insert(id);
                                n += 1;
                                ATH_MSG_VERBOSE("PRD-ID:" << id << " subdet:" << subdet << " number:" << n
                                                          << " particle link:" << i->second);
                            }
                        }
                        if (n == 0) {
                            ATH_MSG_VERBOSE("--> no link, noise ? PRD-ID:" << id << " subdet:" << subdet);
                            // add uniqueID 0 to pairs, we like to keep track of fake fakes
                            unsigned int ID(0), EV(0);
                            pairStat[HepMcParticleLink(ID, EV, HepMcParticleLink::IS_POSITION, HepMcParticleLink::IS_ID)].subDetHits[subdet].insert(id);
                        }
                    }  // orderedPRD_Truth[] available
                }      // subdet type check, warning in findSubDetType()
            }
        }
 
        if (msgLvl(MSG::VERBOSE)) {
            msg(MSG::VERBOSE) << "PRD truth particles = ";
            for (std::map<HepMcParticleLink, SubDetPRDs>::const_iterator i = pairStat.begin(); i != pairStat.end(); ++i) {
                msg(MSG::VERBOSE) << i->first << ",";
            }
            msg(MSG::VERBOSE) << endmsg;
        }
 
        //----------------------------------------------------------------
        // The stat structures are ready.
        // Build truth trajectories for the track
 
        std::set<HepMcParticleLink> seeds;
        for (std::map<HepMcParticleLink, SubDetPRDs>::const_iterator i = pairStat.begin(); i != pairStat.end(); ++i) {
            if (i->first.isValid()) {
                seeds.insert(i->first);
            } else {
                // add uniqueID 0 particles, we like to keep track of fake fakes
                TruthTrajectory traj;
                traj.reserve(1);
                traj.push_back(i->first);
                ATH_MSG_VERBOSE("addTrack(): add barcode 0 hits - noise ?");
 
                // noise/no truth hits on this track
                SubDetHitStatistics noiseStat = makeSubDetHitStatistics(i->second);
 
                // Only valid HepMcParticleLink make it into seeds and then into sprouts, and
                // stored in the loop over sprouts below.
                // Store output for noise/no truth particles here.
                output->push_back(DetailedTrackTruth(traj, noiseStat, trackStat, noiseStat));
            }
        }
 
        // Grow sprouts from the seeds
        typedef std::map<HepMcParticleLink, Sprout> SproutMap;
        SproutMap sprouts;
 
        while (!seeds.empty()) {
            HepMcParticleLink link = *seeds.begin();
 
            Sprout current_sprout;
            std::queue<HepMC::ConstGenParticlePtr> tmp;
            unsigned eventIndex = link.eventIndex();
#ifdef HEPMC3
            HepMC::ConstGenParticlePtr current = link.scptr();
#else
            const HepMC::GenParticle* current = link.cptr();
#endif
 
            do {
                HepMcParticleLink curlink(HepMC::uniqueID(current), eventIndex, HepMcParticleLink::IS_EVENTNUM, HepMcParticleLink::IS_ID);
 
                // remove the current particle from the list of particles to consider (if it is still there)
                seeds.erase(curlink);
 
                // Have we worked on this particle before?
                SproutMap::iterator p_old = sprouts.find(curlink);
                if (p_old != sprouts.end()) {
                    // merge the old sprout with the current one.
                    current_sprout.splice(current_sprout.end(), p_old->second);
                    current_sprout.stat += p_old->second.stat;
                    // and remove the entry for the old
                    sprouts.erase(p_old);
                    break;  // the do-while(getMother()) loop
                } else {    // No, this is a new particle.  Try to extend the current truth trajectory.
 
                    // Add the particle to the current truth trajectory.
                    // New: with the current stricter cuts on mother-daughter
                    // we don't have to require that ancestors produce hits.
 
                    current_sprout.push_back(current);
 
                    std::map<HepMcParticleLink, SubDetPRDs>::iterator p_newstat = pairStat.find(curlink);
                    if (p_newstat != pairStat.end()) { current_sprout.stat += p_newstat->second; }
                }
            } while ((current = m_truthTrackBuilder->getMother(current)));
 
            // Add the grown sprout to the list
            sprouts.insert(std::make_pair(link, current_sprout));
 
        }  // while(!seeds.empty())
 
        //----------------
        // All seeds have been processed, and the upstream extensions of the
        // sprouts are done.  Extend the sprouts downstream to get the final
        // truth trajectories and store the result.
        //
        // Note: so far the "sprouts" object mapped {last particle ==> sprout}
        // Extending a sprout downstream will break this relationship,
        // but at this point we don't care about it and will only use the
        // value of the map, not the key.
        for (SproutMap::iterator s = sprouts.begin(); s != sprouts.end(); ++s) {
            // Attempt to extend the TruthTrajectory sprout to the "outside".
            // This may add only hits that are *not* on the current track.
            // Thus no need to update stats track and stats common.
 
            HepMC::ConstGenParticlePtr current = *s->second.begin();
            while ((current = m_truthTrackBuilder->getDaughter(current))) { s->second.push_front(current); }
 
            // Now we have info to build the final TruthTrajectory.
            // FIXME: what is the current average size?
            TruthTrajectory traj;
            traj.reserve(2);  // The average size is about 1.05.  Hardcode that instead of using slow list::size().
            for (Sprout::const_iterator ppart = s->second.begin(); ppart != s->second.end(); ++ppart) {
                traj.push_back(HepMcParticleLink(HepMC::uniqueID(*ppart), s->first.eventIndex(), HepMcParticleLink::IS_EVENTNUM, HepMcParticleLink::IS_ID));
            }
 
            // Count PRDs on the TruthTrajectory
            std::set<Muon::MuonStationIndex::ChIndex> tempSet;
            SubDetHitStatistics truthStat = countPRDsOnTruth(traj, inverseTruth, tempSet);
 
            ATH_MSG_VERBOSE("addTrack(): sprout length = " << traj.size());
            output->push_back(DetailedTrackTruth(traj, makeSubDetHitStatistics(s->second.stat), trackStat, truthStat));
        }
 
        ATH_MSG_VERBOSE("addTrack(): #sprouts = " << sprouts.size() << ", output->size() = " << output->size());
    }
 
    void DetailedMuonPatternTruthBuilder::buildDetailedTrackTruthFromSegments(
        std::vector<DetailedSegmentTruth>* output, const Muon::MuonSegment& segment,
        const std::vector<const PRD_MultiTruthCollection*>& prdTruth) {
        ATH_MSG_VERBOSE("DetailedMuonPatternTruthBuilder::buildDetailedTrackTruthFromSegments() ");
 
        if (!output) { return; }
 
        //----------------------------------------------------------------
        // The caller can pass PRD truth collections in any order. Sort them out.
 
        std::vector<const PRD_MultiTruthCollection*> orderedPRD_Truth(SubDetHitStatistics::NUM_SUBDETECTORS);
        PRD_InverseTruth inverseTruth;
 
        for (std::vector<const PRD_MultiTruthCollection*>::const_iterator i = prdTruth.begin(); i != prdTruth.end(); ++i) {
            if (*i) {
                if (!(*i)->empty()) {
                    SubDetHitStatistics::SubDetType subdet = findSubDetType((*i)->begin()->first);
 
                    if (subdet != SubDetHitStatistics::NUM_SUBDETECTORS) {
                        orderedPRD_Truth[subdet] = *i;
                        addToInverseMultiMap(&inverseTruth, **i);
                    } else {
                        ATH_MSG_WARNING("Got unknown SubDetType in prdTruth ");
                    }
                } else {
                    ATH_MSG_DEBUG("Empty truth ???");
                }
            }
        }
 
        //----------------------------------------------------------------
        // Find associated truth for each track
        addDetailedTrackTruthFromSegment(output, segment, orderedPRD_Truth, inverseTruth);
 
        // DEBUG
        // FIXME: in normal production jobs that does *a lot of* formatting only to discard the result...
        ATH_MSG_DEBUG(
            "Dumping output collection.\n"
            " Entries with TruthTrajectories of more then one particle shown at the DEBUG level.\n"
            " Use VERBOSE level for complete dump.");
    }
 
    //================================================================
    void DetailedMuonPatternTruthBuilder::addDetailedTrackTruthFromSegment(
        std::vector<DetailedSegmentTruth>* output, const Muon::MuonSegment& segment,
        const std::vector<const PRD_MultiTruthCollection*>& orderedPRD_Truth, const PRD_InverseTruth& inverseTruth) {
        SubDetHitStatistics trackStat;
        std::map<HepMcParticleLink, SubDetPRDs> pairStat;  // stats for (track,GenParticle) for the current track
 
        std::set<Muon::MuonStationIndex::ChIndex> chIndices;
 
        // Loop over containedROTs in segment
        for (unsigned int i_cROTv = 0; i_cROTv < segment.numberOfContainedROTs(); i_cROTv++) {
            const Trk::RIO_OnTrack* rot = segment.rioOnTrack(i_cROTv);
 
            // get the PrepRawData from the ROT
            const Trk::PrepRawData* prd = rot->prepRawData();
 
            Identifier id = prd->identify();
            chIndices.insert(m_idHelperSvc->chamberIndex(id));
 
            SubDetHitStatistics::SubDetType subdet = findSubDetType(id);
 
            if (subdet != SubDetHitStatistics::NUM_SUBDETECTORS) {
                // if PRD truth collection is missing, ignore subdet in track stat calculation as well.
                if (orderedPRD_Truth[subdet]) {
                    ++trackStat[subdet];
 
                    typedef PRD_MultiTruthCollection::const_iterator iprdt;
                    std::pair<iprdt, iprdt> range = orderedPRD_Truth[subdet]->equal_range(id);
 
                    int n = 0;
                    // Loop over particles contributing to this cluster
                    for (iprdt i = range.first; i != range.second; ++i) {
                        if (!i->second.isValid()) {
                            ATH_MSG_WARNING("Unexpected invalid HepMcParticleLink in PRD_MultiTruthCollection");
                        } else {
                            pairStat[i->second].subDetHits[subdet].insert(id);
                            n += 1;
                            ATH_MSG_VERBOSE("PRD-ID:" << id << " subdet:" << subdet << " number:" << n << " particle link:" << i->second);
                        }
                    }
                    if (n == 0) {
                        ATH_MSG_VERBOSE("--> no link, noise ? PRD-ID:" << id << " subdet:" << subdet);
                        // add uniqueID 0 to pairs, we like to keep track of fake fakes
                        unsigned int ID(0), EV(0);
                        pairStat[HepMcParticleLink(ID, EV, HepMcParticleLink::IS_POSITION, HepMcParticleLink::IS_ID)].subDetHits[subdet].insert(id);
                    }
                }  // orderedPRD_Truth[] available
            }      // subdet type check, warning in findSubDetType()
        }
 
        if (msgLvl(MSG::VERBOSE)) {
            msg(MSG::VERBOSE) << "PRD truth particles = ";
            for (std::map<HepMcParticleLink, SubDetPRDs>::const_iterator i = pairStat.begin(); i != pairStat.end(); ++i) {
                msg(MSG::VERBOSE) << i->first << ",";
            }
            msg(MSG::VERBOSE) << endmsg;
        }
 
        //----------------------------------------------------------------
        // The stat structures are ready.
        // Build truth trajectories for the track
 
        std::set<HepMcParticleLink> seeds;
        for (std::map<HepMcParticleLink, SubDetPRDs>::const_iterator i = pairStat.begin(); i != pairStat.end(); ++i) {
            if (i->first.isValid()) {
                seeds.insert(i->first);
            } else {
                // add uniqueID 0 particles, we like to keep track of fake fakes
                TruthTrajectory traj;
                traj.reserve(1);
                traj.push_back(i->first);
                ATH_MSG_VERBOSE("addTrack(): add barcode 0 hits - noise ?");
 
                // noise/no truth hits on this track
                SubDetHitStatistics noiseStat = makeSubDetHitStatistics(i->second);
 
                // Only valid HepMcParticleLink make it into seeds and then into sprouts, and
                // stored in the loop over sprouts below.
                // Store output for noise/no truth particles here.
                output->push_back(
                    DetailedSegmentTruth(traj, noiseStat, trackStat, noiseStat, Amg::Vector3D(0, 0, 0), Amg::Vector3D(0, 0, 0)));
            }
        }
 
        // Grow sprouts from the seeds
        typedef std::map<HepMcParticleLink, Sprout> SproutMap;
        SproutMap sprouts;
 
        while (!seeds.empty()) {
            HepMcParticleLink link = *seeds.begin();
 
            Sprout current_sprout;
            std::queue<HepMC::ConstGenParticlePtr> tmp;
            unsigned eventIndex = link.eventIndex();
#ifdef HEPMC3
            HepMC::ConstGenParticlePtr current = link.scptr();
#else
            const HepMC::GenParticle* current = link.cptr();
#endif
 
            do {
                HepMcParticleLink curlink(HepMC::uniqueID(current), eventIndex, HepMcParticleLink::IS_EVENTNUM, HepMcParticleLink::IS_ID);
 
                // remove the current particle from the list of particles to consider (if it is still there)
                seeds.erase(curlink);
 
                // Have we worked on this particle before?
                SproutMap::iterator p_old = sprouts.find(curlink);
                if (p_old != sprouts.end()) {
                    // merge the old sprout with the current one.
                    current_sprout.splice(current_sprout.end(), p_old->second);
                    current_sprout.stat += p_old->second.stat;
                    // and remove the entry for the old
                    sprouts.erase(p_old);
                    break;  // the do-while(getMother()) loop
                } else {    // No, this is a new particle.  Try to extend the current truth trajectory.
 
                    // Add the particle to the current truth trajectory.
                    // New: with the current stricter cuts on mother-daughter
                    // we don't have to require that ancestors produce hits.
 
                    current_sprout.push_back(current);
 
                    std::map<HepMcParticleLink, SubDetPRDs>::iterator p_newstat = pairStat.find(curlink);
                    if (p_newstat != pairStat.end()) { current_sprout.stat += p_newstat->second; }
                }
            } while ((current = m_truthTrackBuilder->getMother(current)));
 
            // Add the grown sprout to the list
            sprouts.insert(std::make_pair(link, current_sprout));
 
        }  // while(!seeds.empty())
 
        //----------------
        // All seeds have been processed, and the upstream extensions of the
        // sprouts are done.  Extend the sprouts downstream to get the final
        // truth trajectories and store the result.
        //
        // Note: so far the "sprouts" object mapped {last particle ==> sprout}
        // Extending a sprout downstream will break this relationship,
        // but at this point we don't care about it and will only use the
        // value of the map, not the key.
        for (SproutMap::iterator s = sprouts.begin(); s != sprouts.end(); ++s) {
            // Attempt to extend the TruthTrajectory sprout to the "outside".
            // This may add only hits that are *not* on the current track.
            // Thus no need to update stats track and stats common.
 
            HepMC::ConstGenParticlePtr current = *s->second.begin();
            while ((current = m_truthTrackBuilder->getDaughter(current))) { s->second.push_front(current); }
 
            // Now we have info to build the final TruthTrajectory.
            // FIXME: what is the current average size?
            TruthTrajectory traj;
            traj.reserve(2);  // The average size is about 1.05.  Hardcode that instead of using slow list::size().
            for (Sprout::const_iterator ppart = s->second.begin(); ppart != s->second.end(); ++ppart) {
                traj.push_back(HepMcParticleLink(HepMC::uniqueID(*ppart), s->first.eventIndex(), HepMcParticleLink::IS_EVENTNUM, HepMcParticleLink::IS_ID));
            }
 
            // Count PRDs on the TruthTrajectory
            SubDetHitStatistics truthStat = countPRDsOnTruth(traj, inverseTruth, chIndices);
            Amg::Vector3D pos = getPRDTruthPosition(segment, s->second, 1, chIndices);
            Amg::Vector3D dir = getPRDTruthPosition(segment, s->second, 0, chIndices);
 
            ATH_MSG_VERBOSE("addTrack(): sprout length = " << traj.size());
            output->push_back(DetailedSegmentTruth(traj, makeSubDetHitStatistics(s->second.stat), trackStat, truthStat, pos, dir));
        }
 
        ATH_MSG_VERBOSE("addTrack(): #sprouts = " << sprouts.size() << ", output->size() = " << output->size());
    }
 
    // AV Note: MuonSimData::Deposit  typedef std::pair<HepMcParticleLink, MuonMCData> Deposit;
    const MuonSimData::Deposit* DetailedMuonPatternTruthBuilder::getDeposit(const MuonSimDataCollection& simCol,
                                                                            const HepMC::ConstGenParticlePtr& genPart, const Identifier& id) {
        MuonSimDataCollection::const_iterator it = simCol.find(id);
        if (it == simCol.end()) {
            ATH_MSG_WARNING(" Truth PRD not found in simdata collection: " << m_idHelperSvc->toString(id));
            return nullptr;
        }
 
        const MuonSimData& simData = it->second;
        const MuonSimData::Deposit* deposit = nullptr;
        std::vector<MuonSimData::Deposit>::const_iterator dit = simData.getdeposits().begin();
        std::vector<MuonSimData::Deposit>::const_iterator dit_end = simData.getdeposits().end();
        for (; dit != dit_end; ++dit) {
#ifdef HEPMC3
            HepMC::ConstGenParticlePtr gp = dit->first.scptr();
#else
            const HepMC::GenParticle* gp = dit->first;
#endif
            if (gp == genPart) {
                deposit = &*dit;
                break;
            }
 
        }
        return deposit;
    }
 
    const MuonSimDataCollection* DetailedMuonPatternTruthBuilder::retrieveTruthCollection(const std::string& colName) {
        // Retrieve SDO map for this event
        if (!evtStore()->contains<MuonSimDataCollection>(colName)) return nullptr;
 
        const MuonSimDataCollection* truthCol(nullptr);
        if (!evtStore()->retrieve(truthCol, colName).isSuccess()) {
            ATH_MSG_VERBOSE("Could NOT find the MuonSimDataMap map key = " << colName);
        } else {
            ATH_MSG_VERBOSE("Retrieved MuonSimDataCollection for key = " << colName);
        }
        return truthCol;
    }
 
}  // namespace Trk