MsTrackFindingAlg.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#include "MsTrackFindingAlg.h"
 
#include "Acts/Surfaces/PerigeeSurface.hpp"
#include "Acts/Surfaces/PlaneSurface.hpp"
#include "Acts/Surfaces/detail/PlanarHelper.hpp"
 
 
#include "MuonReadoutGeometryR4/MuonDetectorDefs.h"
#include "MuonTrackFindingTools/MsTrackSeeder.h"
#include "ActsCalibBase/CalibrationContext.h"
#include "ActsCalibrators/xAODUncalibMeasCalibrator.h"
#include "xAODMuonPrepData/UtilFunctions.h"
 
#include "GaudiKernel/PhysicalConstants.h"
#include "MuonTruthHelpers/MuonSimHitHelpers.h"
#include "MuonTrackEvent/TrackingHelpers.h"
 
#include "ActsInterop/UnitConverters.h"
#include "GaudiKernel/PhysicalConstants.h"
#include "TruthUtils/HepMCHelpers.h"
#include "MuonVisualizationHelpersR4/ObjVisualizationHelpers.h"
 
#include <system_error>
 
using namespace Acts::UnitLiterals;
using namespace Acts::PlanarHelper;
 
namespace MuonR4{
    StatusCode MsTrackFindingAlg::initialize() {
        ATH_CHECK(m_segmentKey.initialize());
        ATH_CHECK(m_idHelperSvc.retrieve());
        ATH_CHECK(detStore()->retrieve(m_detMgr));
        ATH_CHECK(m_segSelector.retrieve());
        ATH_CHECK(m_msTrkSeedKey.initialize());
 
        ATH_CHECK(m_visualizationTool.retrieve(EnableTool{!m_visualizationTool.empty()}));
        ATH_CHECK(m_trackingGeometryTool.retrieve());
        ATH_CHECK(m_extrapolationTool.retrieve());
        ATH_CHECK(m_trackFitTool.retrieve());
        ATH_CHECK(m_calibTool.retrieve());
        ATH_CHECK(m_writeKey.initialize());
 
        if (m_trackingGeometryTool->trackingGeometry()->geometryVersion() !=
            Acts::TrackingGeometry::GeometryVersion::Gen3){
            ATH_MSG_ERROR("The MS track fit requires the Gen 3 geometry format");
            return StatusCode::FAILURE;
        }
 
        MsTrackSeeder::Config seederCfg{};
        seederCfg.seedHalfLength = m_seedHalfLength;
        seederCfg.selector = m_segSelector.get();
        seederCfg.detMgr = m_detMgr;
 
        m_seeder = std::make_unique<MsTrackSeeder>(name(), std::move(seederCfg));
        return StatusCode::SUCCESS;
    }
 
    MsTrackFindingAlg::~MsTrackFindingAlg() = default;
 
    StatusCode MsTrackFindingAlg::execute(const EventContext& ctx) const {
        ATH_MSG_VERBOSE("Run track finding in event "<<ctx.eventID().event_number());
        
        const xAOD::MuonSegmentContainer* allEventSegs{nullptr};
        ATH_CHECK(SG::get(allEventSegs, m_segmentKey, ctx));
 
        auto seedContainer = findTrackSeeds(ctx, *allEventSegs);
 
        const Acts::GeometryContext tgContext = m_trackingGeometryTool->getGeometryContext(ctx).context();
        const Acts::MagneticFieldContext mfContext = m_extrapolationTool->getMagneticFieldContext(ctx);
        const Acts::CalibrationContext calContext{ActsTrk::getCalibrationContext(ctx)};
        
        
        Acts::VectorTrackContainer trackBackend{};
        Acts::VectorMultiTrajectory trackStateBackend{};
        ActsTrk::MutableTrackContainer cacheTrkContainer{std::move(trackBackend), 
                                                         std::move(trackStateBackend)};
        cacheTrkContainer.addColumn<std::size_t>("parentSeed");
        unsigned seedIdx{0};
        for (const MsTrackSeed& seed : *seedContainer) {
            if (!fitSeedCandidate(tgContext, mfContext, calContext, seed, 
                                  cacheTrkContainer)) {
                ++seedIdx;
                continue;
            }
            auto lastTrack = cacheTrkContainer.getTrack(cacheTrkContainer.size() -1);
            lastTrack.component<std::size_t, Acts::hashString("parentSeed")>() = seedIdx;
            ++seedIdx;
        }
        SG::WriteHandle writeHandleSeed{m_msTrkSeedKey, ctx};
        ATH_CHECK(writeHandleSeed.record(std::move(seedContainer)));
    
        // Constant declination
        Acts::ConstVectorTrackContainer ctrackBackend{std::move(cacheTrkContainer.container())};
        Acts::ConstVectorMultiTrajectory ctrackStateBackend{std::move(cacheTrkContainer.trackStateContainer())};
        auto ctc = std::make_unique<ActsTrk::TrackContainer>(std::move(ctrackBackend),
                                                             std::move(ctrackStateBackend));
  
        SG::WriteHandle writeHandle{m_writeKey, ctx};
        ATH_CHECK(writeHandle.record(std::move(ctc)));
        return StatusCode::SUCCESS;
    }
 
    std::unique_ptr<MsTrackSeedContainer>  
        MsTrackFindingAlg::findTrackSeeds(const EventContext& ctx,
                                          const xAOD::MuonSegmentContainer& segments) const {
 
        auto seedContainer = m_seeder->findTrackSeeds(ctx, m_trackingGeometryTool->getGeometryContext(ctx), segments);
 
        if (!m_visualizationTool.empty()) {
            m_visualizationTool->displaySeeds(ctx, *m_seeder, segments, *seedContainer);
        }
        return seedContainer;
    }
std::pair<MsTrackFindingAlg::OptBoundPars_t, 
          MsTrackFindingAlg::MeasVec_t>
        MsTrackFindingAlg::prepareFit(const Acts::GeometryContext& tgContext,
                                      const Acts::MagneticFieldContext& mfContext,
                                      const Acts::CalibrationContext& calContext,
                                      const MsTrackSeed& seed) const {
        const EventContext& ctx{*calContext.get<const EventContext*>()};        
        MeasVec_t measurements{};
        measurements.reserve(100);
        const xAOD::MuonSegment* refSeg{nullptr};
        for (const xAOD::MuonSegment* segment : seed.segments()) {
            m_calibTool->stampSignsOnMeasurements(*segment);
            MeasVec_t segMeasurements = collectMeasurements(*segment, /*skipOutlier:*/ true);
            if (msgLvl(MSG::VERBOSE)) {
                std::stringstream sstr{};
                for (const xAOD::UncalibratedMeasurement* m : segMeasurements) {
                    const Acts::Surface& surf{xAOD::muonSurface(m)};
                    sstr<<" ***  "<<m_idHelperSvc->toString(xAOD::identify(m))
                        <<", "<<m->numDimensions()<<", "
                        <<", "<<surf.geometryId()<<" @ "<<Amg::toString(surf.localToGlobalTransform(tgContext))<<std::endl;
                }
                ATH_MSG_VERBOSE("Fetch measurements from segment: "<<Amg::toString(segment->position())
                         <<", direction: "<<Amg::toString(segment->direction())<<"\n"<<sstr.str());
            }
            measurements.insert(measurements.end(), 
                                std::make_move_iterator(segMeasurements.begin()),
                                std::make_move_iterator(segMeasurements.end()));
 
            if (!refSeg && m_segSelector->passSeedingQuality(ctx, *detailedSegment(*segment))) {
                refSeg = segment;
            }
        }
        if (!refSeg || measurements.empty()) {
            ATH_MSG_WARNING(__func__<<"() "<<__LINE__
                            <<" - No reference segment passing seeding quality "<<
                            (refSeg != nullptr)<<" was found. #"<<measurements.size()<<" measurements. ");
            return std::make_pair(Acts::Result<Acts::BoundTrackParameters>::failure(std::make_error_code(std::errc::invalid_argument)),
                                  std::vector<const xAOD::UncalibratedMeasurement_v1*>{});
        }
        ATH_MSG_VERBOSE(__func__<<"() "<<__LINE__<<" - "<<measurements.size()<<" measurements");
        Amg::Vector3D seedPos{refSeg->position()};
        Amg::Vector3D seedDir{refSeg->direction()};
        if (refSeg != seed.segments().front()) {
            const MuonGMR4::SpectrometerSector* innerPlane = m_seeder->envelope(*seed.segments().front());
            const Acts::PlaneSurface& surf = innerPlane->surface();
            const Amg::Transform3D toInnerPlane = surf.localToGlobalTransform(tgContext).inverse();
            const Amg::Vector3D locSeedPos = toInnerPlane * seedPos;
            const Amg::Vector3D locSeedDir = toInnerPlane.linear() * seedDir;
 
            auto seedOnInner = Acts::PlanarHelper::intersectPlane(locSeedPos, locSeedDir,
                                                                  Amg::Vector3D::UnitZ(), 0.);
 
            using enum SegmentFit::ParamDefs;
            SegmentFit::Parameters innerPars = SegmentFit::localSegmentPars(*seed.segments().front());
            innerPars[Acts::toUnderlying(x0)] = seedOnInner.position().x();
            const Amg::Vector3D innerSegDir = 
                    Acts::makeDirectionFromPhiTheta(innerPars[Acts::toUnderlying(phi)],
                                                    innerPars[Acts::toUnderlying(theta)]);
            const Amg::Vector3D combSegDir = 
                    Acts::makeDirectionFromAxisTangents(houghTanAlpha(locSeedDir),
                                                        houghTanBeta(innerSegDir));
            seedPos = surf.localToGlobalTransform(tgContext) * Amg::Vector3D{innerPars[Acts::toUnderlying(x0)],
                                                                             innerPars[Acts::toUnderlying(y0)], 0};
            seedDir = surf.localToGlobalTransform(tgContext).linear() * combSegDir;
        }
        const xAOD::UncalibratedMeasurement* firstVolumeMeas{nullptr};
        const Acts::TrackingVolume* volume{nullptr};
        for (const xAOD::UncalibratedMeasurement* meas : measurements) {
            const Acts::GeometryIdentifier volId = volumeId(xAOD::muonSurface(meas));
            ATH_MSG_VERBOSE(__func__<<"() "<<__LINE__<<" - Check measurement "
                <<m_idHelperSvc->toString(xAOD::identify(meas))<<", "<<xAOD::muonSurface(meas).geometryId());
            volume = m_trackingGeometryTool->trackingGeometry()->findVolume(volId);
            if (volume) {
                firstVolumeMeas = meas;
                break;
            }
        }
 
        if (!volume) {
            ATH_MSG_WARNING(__func__<<"() "<<__LINE__
                            <<" - Failed to find tracking volume for any seed measurement");
            return std::make_pair(Acts::Result<Acts::BoundTrackParameters>::failure(std::make_error_code(std::errc::invalid_argument)),
                                  std::vector<const xAOD::UncalibratedMeasurement_v1*>{});
        }
        ATH_MSG_VERBOSE(__func__<<"() "<<__LINE__<<" - Using seed measurement " 
                        << m_idHelperSvc->toString(xAOD::identify(firstVolumeMeas))
                        << " with volume id " << volumeId(xAOD::muonSurface(firstVolumeMeas)));
 
        auto boundSurf = MuonGMR4::bottomBoundary(*volume);
        if (!boundSurf) {
            ATH_MSG_WARNING(__func__<<"() "<<__LINE__<<" - Failed to find boundary surface for tracking volume");
            return std::make_pair(Acts::Result<Acts::BoundTrackParameters>::failure(std::make_error_code(std::errc::invalid_argument)),
                                  std::vector<const xAOD::UncalibratedMeasurement_v1*>{});
        }
        auto targetSurf = boundSurf->getSharedPtr();
        using namespace Acts::PlanarHelper;
 
        auto pIsect = intersectPlane(seedPos, seedDir, 
                                     targetSurf->localToGlobalTransform(tgContext).linear().col(2), 
                                     targetSurf->center(tgContext));
        
        auto fourPos = ActsTrk::convertPosToActs(pIsect.position(), pIsect.position().mag() / Gaudi::Units::c_light);
        const double qOverP = 1./ m_seeder->estimateQtimesP(*tgContext.get<const ActsTrk::GeometryContext*>(),
                                                            *mfContext.get<const AtlasFieldCacheCondObj*>(), seed);
        auto initialPars = Acts::BoundTrackParameters::create(tgContext, targetSurf, fourPos, 
                                                              seedDir, ActsTrk::energyToActs(qOverP),
                                                              Acts::BoundMatrix::Identity(), 
                                                              Acts::ParticleHypothesis::muon());
        return std::make_pair(std::move(initialPars),  std::move(measurements));
 
    }
    bool MsTrackFindingAlg::fitSeedCandidate(const Acts::GeometryContext& tgContext,
                                             const Acts::MagneticFieldContext& mfContext,
                                             const Acts::CalibrationContext& calContext,
                                             const MsTrackSeed& seed,
                                             ActsTrk::MutableTrackContainer& outContainer) const {
        
        ATH_MSG_DEBUG(__func__<<"() "<<__LINE__<<" - Attempt to fit a new track seed \n"<<seed);
        const EventContext& ctx{*calContext.get<const EventContext*>()};
        const auto [initialPars, measurements] = prepareFit(tgContext, mfContext, calContext, seed);
        
        if (!initialPars.ok()) {
            ATH_MSG_WARNING(__func__<<"() "<<__LINE__<<" - Failed to construct valid parameters for seed \n"<<seed);
            if (m_visualizationTool.isEnabled()) {
                m_visualizationTool->displayTrackSeedObj(ctx, seed, initialPars, "FailedStartPars");
            }
            return false;
        }
        auto fitTraject = m_trackFitTool->fit(measurements, *initialPars, 
                                              tgContext, mfContext, calContext, 
                                              &(*initialPars).referenceSurface());
        if (!fitTraject || fitTraject->size() == 0) {
            ATH_MSG_DEBUG(__func__<<"() "<<__LINE__<<" - Fit failed ");
            if (m_visualizationTool.isEnabled()) {
                m_visualizationTool->displayTrackSeedObj(ctx, seed, initialPars, "FailedFit");
            }
            return false;
        }
        {
            fitTraject->addColumn<std::vector<const xAOD::MuonSegment*>>("muonSegLinks");
            fitTraject->getTrack(0).component<std::vector<const xAOD::MuonSegment*>>("muonSegLinks") = seed.segments();
        }
        outContainer.ensureDynamicColumns(*fitTraject);
        auto destProxy = outContainer.getTrack(outContainer.addTrack());
        destProxy.copyFrom(fitTraject->getTrack(0));
        ATH_MSG_DEBUG(__func__<<"() "<<__LINE__<<" - Good track fit...");
        if (m_visualizationTool.isEnabled()) {
            m_visualizationTool->displayTrackSeedObj(ctx, seed, 
                destProxy.createParametersAtReference(), "GoodFit");
        }
        return true;
    }
    
}