GaussianSumFitterTool.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include "src/GaussianSumFitterTool.h"
 
// ATHENA
#include "TrkMeasurementBase/MeasurementBase.h"
#include "TrkTrackSummary/TrackSummary.h"
#include "TRT_ReadoutGeometry/TRT_BaseElement.h"
#include "TrkTrack/TrackStateOnSurface.h"
 
// ACTS
#include "Acts/Propagator/MultiEigenStepperLoop.hpp"
#include "Acts/MagneticField/MagneticFieldContext.hpp"
#include "Acts/Surfaces/PerigeeSurface.hpp"
#include "Acts/Utilities/CalibrationContext.hpp"
#include "Acts/Definitions/TrackParametrization.hpp"
#include "Acts/Definitions/Units.hpp"
#include "Acts/Propagator/EigenStepper.hpp"
#include "Acts/Surfaces/Surface.hpp"
#include "Acts/TrackFitting/GsfMixtureReduction.hpp"
#include "Acts/Utilities/Helpers.hpp"
#include "Acts/EventData/VectorMultiTrajectory.hpp"
#include "Acts/EventData/VectorTrackContainer.hpp"
#include "Acts/EventData/TrackParameters.hpp"
#include "Acts/Utilities/Logger.hpp"
#include "Acts/Utilities/CalibrationContext.hpp"
#include "ActsEvent/TrackContainer.h"
 
// PACKAGE
#include "ActsGeometry/ATLASMagneticFieldWrapper.h"
#include "ActsGeometry/ATLASSourceLink.h"
#include "ActsInterop/Logger.h"
#include "ActsGeometry/ActsDetectorElement.h"
#include "ActsGeometryInterfaces/ActsGeometryContext.h"
#include "Acts/Propagator/DirectNavigator.hpp"
#include "src/detail/RefittingCalibrator.h"
 
// STL
#include <vector>
#include <bitset>
#include <type_traits>
#include <system_error>
 
namespace ActsTrk {
 
GaussianSumFitterTool::GaussianSumFitterTool(const std::string& t,
                         const std::string& n,
                         const IInterface* p) :
  base_class(t,n,p)
{}
 
StatusCode GaussianSumFitterTool::initialize() {
  ATH_MSG_DEBUG(name() << "::" << __FUNCTION__);
 
  ATH_CHECK(m_trackingGeometryTool.retrieve());
  ATH_CHECK(m_extrapolationTool.retrieve());
  ATH_CHECK(m_ATLASConverterTool.retrieve());
  if (!m_refitOnly) {
    ATH_CHECK(m_trkSummaryTool.retrieve());
  }else{
    ATH_MSG_INFO("Running GSF without track summary");
  }
 
  m_logger = makeActsAthenaLogger(this, "Acts Gaussian Sum Refit");
 
  auto field = std::make_shared<ATLASMagneticFieldWrapper>();
  Acts::MultiEigenStepperLoop<> stepper(field);
  Acts::Navigator navigator( Acts::Navigator::Config{ m_trackingGeometryTool->trackingGeometry() },
                             logger().cloneWithSuffix("Navigator") );
  Acts::Propagator<Acts::MultiEigenStepperLoop<>, Acts::Navigator> propagator(std::move(stepper), 
                     std::move(navigator),
                     logger().cloneWithSuffix("Prop"));
 
  Acts::AtlasBetheHeitlerApprox<6, 5> bha = Acts::makeDefaultBetheHeitlerApprox();
  m_fitter = std::make_unique<Fitter>(std::move(propagator), std::move(bha),
              logger().cloneWithSuffix("GaussianSumFitter"));
  
  // Direct Fitter
  if( m_useDirectNavigation ){
    Acts::DirectNavigator directNavigator( logger().cloneWithSuffix("DirectNavigator") );
    Acts::MultiEigenStepperLoop<> stepperDirect(field);
    Acts::Propagator<Acts::MultiEigenStepperLoop<>, Acts::DirectNavigator> directPropagator(std::move(stepperDirect),
                                                std::move(directNavigator),
                                                logger().cloneWithSuffix("DirectPropagator"));
    Acts::AtlasBetheHeitlerApprox<6, 5> bhaDirect = Acts::makeDefaultBetheHeitlerApprox();
    m_directFitter = std::make_unique<DirectFitter>(std::move(directPropagator),std::move(bhaDirect),
                            logger().cloneWithSuffix("DirectGaussianSumFitter"));
 
  }
 
  m_gsfExtensions.updater.connect<&ActsTrk::detail::FitterHelperFunctions::gainMatrixUpdate<ActsTrk::MutableTrackStateBackend>>();
  m_calibrator = std::make_unique<ActsTrk::detail::TrkMeasurementCalibrator>(*m_ATLASConverterTool);
  m_gsfExtensions.calibrator.connect<&ActsTrk::detail::TrkMeasurementCalibrator::calibrate<ActsTrk::MutableTrackStateBackend>>(m_calibrator.get());
 
  m_surfaceAccessor.m_converterTool = &(*m_ATLASConverterTool);
  m_gsfExtensions.surfaceAccessor.connect<&ATLASSourceLinkSurfaceAccessor::operator()>(&m_surfaceAccessor);
  m_gsfExtensions.mixtureReducer.connect<&Acts::reduceMixtureWithKLDistance>();
  
  m_outlierFinder.StateChiSquaredPerNumberDoFCut = m_option_outlierChi2Cut;
  m_gsfExtensions.outlierFinder.connect<&ActsTrk::detail::FitterHelperFunctions::ATLASOutlierFinder::operator()<ActsTrk::MutableTrackStateBackend>>(&m_outlierFinder);
  if(m_option_componentMergeMethod == "Mean" ){
    m_componentMergeMethod = Acts::ComponentMergeMethod::eMean;
  }else if(m_option_componentMergeMethod == "MaxWeight"){
    m_componentMergeMethod = Acts::ComponentMergeMethod::eMaxWeight;
  }else{
    throw std::runtime_error("Unknown option for ComponentMergeMethod: " + m_option_componentMergeMethod.value());
  }
  
  ATH_MSG_INFO("ACTS GSF direct nav   " << m_useDirectNavigation.value());
  ATH_MSG_INFO("ACTS GSF max cmps     " << m_maxComponents.value());
  ATH_MSG_INFO("ACTS GSF merge meth   " << m_option_componentMergeMethod.value());
  ATH_MSG_INFO("ACTS GSF weight ctf   " << m_weightCutOff.value());
  ATH_MSG_INFO("ACTS GSF outlier chi2 " << m_option_outlierChi2Cut.value());
  
  return StatusCode::SUCCESS;
}
 
// refit a track
// -------------------------------------------------------
std::unique_ptr<Trk::Track>
GaussianSumFitterTool::fit(const EventContext& ctx,
               const Trk::Track& inputTrack,
               const Trk::RunOutlierRemoval /*runOutlier*/,
               const Trk::ParticleHypothesis /*prtHypothesis*/) const
{
 
  
  std::unique_ptr<Trk::Track> track = nullptr;
  ATH_MSG_VERBOSE ("--> enter GaussianSumFitter::fit(Track,,)    with Track from author = "
       << inputTrack.info().dumpInfo());
 
  // protection against not having measurements on the input track
  if (!inputTrack.measurementsOnTrack() || inputTrack.measurementsOnTrack()->size() < 2) {
    ATH_MSG_DEBUG("called to refit empty track or track with too little information, reject fit");
    return nullptr;
  }
 
  // protection against not having track parameters on the input track
  if (!inputTrack.trackParameters() || inputTrack.trackParameters()->empty()) {
    ATH_MSG_DEBUG("input fails to provide track parameters for seeding the GSF, reject fit");
    return nullptr;
  }
 
  // Construct a perigee surface as the target surface
  std::shared_ptr<Acts::PerigeeSurface> pSurface = Acts::Surface::makeShared<Acts::PerigeeSurface>(
      Acts::Vector3::Zero());
  
  Acts::GeometryContext tgContext = m_trackingGeometryTool->getGeometryContext(ctx).context();
  Acts::MagneticFieldContext mfContext = m_extrapolationTool->getMagneticFieldContext(ctx);
  // CalibrationContext converter not implemented yet.
  Acts::CalibrationContext calContext{};
 
  // Set the GaussianSumFitter options
  Acts::GsfOptions<ActsTrk::MutableTrackStateBackend>
    gsfOptions = prepareOptions(tgContext, 
                mfContext, 
                calContext, 
                *pSurface);
  gsfOptions.maxComponents = m_maxComponents;
  gsfOptions.weightCutoff = m_weightCutOff;
  gsfOptions.componentMergeMethod = m_componentMergeMethod;
  
 
  std::vector<Acts::SourceLink> trackSourceLinks = m_ATLASConverterTool->trkTrackToSourceLinks(tgContext,inputTrack);
  const auto& initialParams = m_ATLASConverterTool->trkTrackParametersToActsParameters((*inputTrack.perigeeParameters()), tgContext);
 
  return performFit(ctx, 
            tgContext,
            gsfOptions,
            trackSourceLinks, 
            initialParams);
}
 
// fit a set of MeasurementBase objects
// --------------------------------
std::unique_ptr<Trk::Track>
GaussianSumFitterTool::fit(const EventContext& ctx,
               const Trk::MeasurementSet& inputMeasSet,
               const Trk::TrackParameters& estimatedStartParameters,
               const Trk::RunOutlierRemoval /*runOutlier*/,
               const Trk::ParticleHypothesis /*matEffects*/) const
{
  std::unique_ptr<Trk::Track> track = nullptr;
  // protection against not having measurements on the input track
  if (inputMeasSet.size() < 2) {
    ATH_MSG_DEBUG("called to refit empty measurement set or a measurement set with too little information, reject fit");
    return nullptr;
  }
 
  // Construct a perigee surface as the target surface
  std::shared_ptr<Acts::PerigeeSurface> pSurface = Acts::Surface::makeShared<Acts::PerigeeSurface>(
                                                   Acts::Vector3::Zero());
  
  Acts::GeometryContext tgContext = m_trackingGeometryTool->getGeometryContext(ctx).context();
  Acts::MagneticFieldContext mfContext = m_extrapolationTool->getMagneticFieldContext(ctx);
  // CalibrationContext converter not implemented yet.
  Acts::CalibrationContext calContext{};
 
  // Set the GaussianSumFitter options
  Acts::GsfOptions<ActsTrk::MutableTrackStateBackend>
    gsfOptions = prepareOptions(tgContext, 
                mfContext, 
                calContext, 
                *pSurface);
 
  // Set abortOnError to false, else the refitting crashes if no forward propagation is done. Here, we just skip the event and continue.
  gsfOptions.abortOnError = false;
  
  std::vector< Acts::SourceLink > trackSourceLinks;
  trackSourceLinks.reserve(inputMeasSet.size());
 
  for (auto* measSet : inputMeasSet) {
    trackSourceLinks.push_back(m_ATLASConverterTool->trkMeasurementToSourceLink(tgContext, *measSet));
  }
 
  const auto& initialParams = m_ATLASConverterTool->trkTrackParametersToActsParameters(estimatedStartParameters, tgContext);
  
  if(m_useDirectNavigation){
    
    std::vector<const Acts::Surface*> surfaces;
    surfaces.reserve(inputMeasSet.size());
    for (auto* measSet : inputMeasSet) {
      const auto& slink = m_ATLASConverterTool->trkMeasurementToSourceLink(tgContext, *measSet);
      const auto& sl = slink.get<ATLASSourceLink>();
      const auto& trkSrf = sl->associatedSurface();
      const auto& actsSrf = m_ATLASConverterTool->trkSurfaceToActsSurface(trkSrf);
      surfaces.push_back(&actsSrf);
    }
    
    return performDirectFit(ctx,
                tgContext,
                gsfOptions,
                trackSourceLinks,
                initialParams,
                surfaces);
  }else{
    return performFit(ctx,
              tgContext,
              gsfOptions,
              trackSourceLinks,
              initialParams);
  }
}
 
// fit a set of PrepRawData objects
// --------------------------------
std::unique_ptr<Trk::Track>
GaussianSumFitterTool::fit(const EventContext& /*ctx*/,
               const Trk::PrepRawDataSet& /*inputPRDColl*/,
               const Trk::TrackParameters& /*estimatedStartParameters*/,
               const Trk::RunOutlierRemoval /*runOutlier*/,
               const Trk::ParticleHypothesis /*prtHypothesis*/) const
{
  ATH_MSG_DEBUG("Fit of PrepRawDataSet not yet implemented");
  return nullptr;
}
 
// extend a track fit to include an additional set of MeasurementBase objects
// re-implements the TrkFitterUtils/TrackFitter.cxx general code in a more
// mem efficient and stable way
// --------------------------------
std::unique_ptr<Trk::Track>
GaussianSumFitterTool::fit(const EventContext& ctx,
               const Trk::Track& inputTrack,
               const Trk::MeasurementSet& addMeasColl,
               const Trk::RunOutlierRemoval /*runOutlier*/,
               const Trk::ParticleHypothesis /*matEffects*/) const
{
  ATH_MSG_VERBOSE ("--> enter GaussianSumFitter::fit(Track,Meas'BaseSet,,)");
  ATH_MSG_VERBOSE ("    with Track from author = " << inputTrack.info().dumpInfo());
 
  // protection, if empty MeasurementSet
  if (addMeasColl.empty()) {
    ATH_MSG_DEBUG( "client tries to add an empty MeasurementSet to the track fit." );
    return fit(ctx,inputTrack);
  }
 
  // protection against not having measurements on the input track
  if (!inputTrack.measurementsOnTrack() || (inputTrack.measurementsOnTrack()->size() < 2 && addMeasColl.empty())) {
    ATH_MSG_DEBUG("called to refit empty track or track with too little information, reject fit");
    return nullptr;
  }
 
  // protection against not having track parameters on the input track
  if (!inputTrack.trackParameters() || inputTrack.trackParameters()->empty()) {
    ATH_MSG_DEBUG("input fails to provide track parameters for seeding the GSF, reject fit");
    return nullptr;
  }
 
  std::unique_ptr<Trk::Track> track = nullptr;
 
  // Construct a perigee surface as the target surface
  std::shared_ptr<Acts::PerigeeSurface> pSurface = Acts::Surface::makeShared<Acts::PerigeeSurface>(Acts::Vector3::Zero());
  
  Acts::GeometryContext tgContext = m_trackingGeometryTool->getGeometryContext(ctx).context();
  Acts::MagneticFieldContext mfContext = m_extrapolationTool->getMagneticFieldContext(ctx);
  // CalibrationContext converter not implemented yet.
  Acts::CalibrationContext calContext{};
 
  // Set the GaussianSumFitter options
  Acts::GsfOptions<ActsTrk::MutableTrackStateBackend>
    gsfOptions = prepareOptions(tgContext, 
                mfContext, 
                calContext,
                *pSurface);
 
  std::vector<Acts::SourceLink> trackSourceLinks = m_ATLASConverterTool->trkTrackToSourceLinks(tgContext, inputTrack);
  const auto& initialParams = m_ATLASConverterTool->trkTrackParametersToActsParameters(*(inputTrack.perigeeParameters()), tgContext);
 
  for (auto* meas : addMeasColl)  {
    trackSourceLinks.push_back(m_ATLASConverterTool->trkMeasurementToSourceLink(tgContext, *meas));
  }
 
  return performFit(ctx,
            tgContext,
            gsfOptions,
                    trackSourceLinks,
                    initialParams);
}
 
// extend a track fit to include an additional set of PrepRawData objects
// --------------------------------
std::unique_ptr<Trk::Track>
GaussianSumFitterTool::fit(const EventContext& /*ctx*/,
               const Trk::Track& /*inputTrack*/,
               const Trk::PrepRawDataSet& /*addPrdColl*/,
               const Trk::RunOutlierRemoval /*runOutlier*/,
               const Trk::ParticleHypothesis /*matEffects*/) const
{
 
  ATH_MSG_DEBUG("Fit of Track with additional PrepRawDataSet not yet implemented");
  return nullptr;
}
 
// combined fit of two tracks
// --------------------------------
std::unique_ptr<Trk::Track>
GaussianSumFitterTool::fit(const EventContext& ctx,
               const Trk::Track& intrk1,
               const Trk::Track& intrk2,
               const Trk::RunOutlierRemoval /*runOutlier*/,
               const Trk::ParticleHypothesis /*matEffects*/) const
{ 
  ATH_MSG_VERBOSE ("--> enter GaussianSumFitter::fit(Track,Track,)");
  ATH_MSG_VERBOSE ("    with Tracks from #1 = " << intrk1.info().dumpInfo()
                   << " and #2 = " << intrk2.info().dumpInfo());
 
  // protection, if empty track2
  if (!intrk2.measurementsOnTrack()) {
    ATH_MSG_DEBUG( "input #2 is empty try to fit track 1 alone" );
    return fit(ctx,intrk1);
  }
 
  // protection, if empty track1
  if (!intrk1.measurementsOnTrack()) {
    ATH_MSG_DEBUG( "input #1 is empty try to fit track 2 alone" );
    return fit(ctx,intrk2);
  }
 
  // protection against not having track parameters on the input track
  if (!intrk1.trackParameters() || intrk1.trackParameters()->empty()) {
    ATH_MSG_DEBUG("input #1 fails to provide track parameters for seeding the GSF, reject fit");
    return nullptr;
  }
 
   std::unique_ptr<Trk::Track> track = nullptr;
 
  // Construct a perigee surface as the target surface
   std::shared_ptr<Acts::PerigeeSurface> pSurface = Acts::Surface::makeShared<Acts::PerigeeSurface>(
      Acts::Vector3::Zero());
  
  Acts::GeometryContext tgContext = m_trackingGeometryTool->getGeometryContext(ctx).context();
  Acts::MagneticFieldContext mfContext = m_extrapolationTool->getMagneticFieldContext(ctx);
  // CalibrationContext converter not implemented yet.
  Acts::CalibrationContext calContext{};
 
  // Set the GaussianSumFitter options
  Acts::GsfOptions<ActsTrk::MutableTrackStateBackend>
    gsfOptions = prepareOptions(tgContext, 
                mfContext, 
                calContext,
                *pSurface);
 
  std::vector<Acts::SourceLink> trackSourceLinks = m_ATLASConverterTool->trkTrackToSourceLinks(tgContext, intrk1);
  std::vector<Acts::SourceLink> trackSourceLinks2 = m_ATLASConverterTool->trkTrackToSourceLinks(tgContext, intrk2);
  trackSourceLinks.insert(trackSourceLinks.end(), trackSourceLinks2.begin(), trackSourceLinks2.end());
  const auto &initialParams = m_ATLASConverterTool->trkTrackParametersToActsParameters(*(intrk1.perigeeParameters()), tgContext);
 
  return performFit(ctx,
            tgContext,
            gsfOptions,
                    trackSourceLinks,
                    initialParams);
}
 
// Acts track refit
std::unique_ptr< ActsTrk::MutableTrackContainer >
GaussianSumFitterTool::fit(const EventContext& /*ctx*/,
        const ActsTrk::Seed & /*seed*/,
        const Acts::BoundTrackParameters& /*initialParams*/,
        const Acts::GeometryContext& /*tgContext*/,
        const Acts::MagneticFieldContext& /*mfContext*/,
        const Acts::CalibrationContext& /*calContext*/,
        const DetectorElementToActsGeometryIdMap & /*detectorElementToGeometryIdMap*/) const
{
  ATH_MSG_VERBOSE("ACTS seed refit is not implemented in GaussianSumFitterTool");
  return nullptr;
}
 
std::unique_ptr< ActsTrk::MutableTrackContainer >
GaussianSumFitterTool::fit(const EventContext& /*ctx*/,
         const std::vector< ActsTrk::ATLASUncalibSourceLink> & /*clusterList*/,
         const Acts::BoundTrackParameters& /*initialParams*/,
         const Acts::GeometryContext& /*tgContext*/,
         const Acts::MagneticFieldContext& /*mfContext*/,
         const Acts::CalibrationContext& /*calContext*/,
         const DetectorElementToActsGeometryIdMap & /*detectorElementToGeometryIdMap*/,
         const Acts::Surface* /*targetSurface*/) const
{
  ATH_MSG_VERBOSE("ACTS uncalib slink refit is not implemented in GaussianSumFitterTool");  
  return nullptr;
}
 
 
StatusCode GaussianSumFitterTool::fit(
  const EventContext& ctx,  
  const ActsTrk::TrackContainer::ConstTrackProxy& track,          
  ActsTrk::MutableTrackContainer& trackContainer) const {
  ATH_MSG_VERBOSE("GaussianSumFitterTool::fit(TrackProxy) called");
 
  const Acts::BoundTrackParameters initialParams = track.createParametersAtReference();
  std::vector<Acts::SourceLink> sourceLinks;
  std::vector<const Acts::Surface*> surfSequence;
 
  for (auto ts : track.trackStatesReversed()) {
    surfSequence.push_back(&ts.referenceSurface());
    if (!ts.hasCalibrated()) {
      continue;
    }
    
    if (ts.typeFlags().test(Acts::TrackStateFlag::MeasurementFlag)) {
      sourceLinks.push_back(Acts::SourceLink{detail::RefittingCalibrator::RefittingSourceLink(ts)});
    }
  }
 
  if (sourceLinks.size() < 2) {
    ATH_MSG_DEBUG("called to refit 0 or 1 sourceLink with too little information, reject fit");
    return StatusCode::SUCCESS;
  }
 
  // Construct a perigee surface as the target surface
  std::shared_ptr<Acts::PerigeeSurface> pSurface = Acts::Surface::makeShared<Acts::PerigeeSurface>(Acts::Vector3::Zero());
 
  Acts::GeometryContext tgContext = m_trackingGeometryTool->getGeometryContext(ctx).context();
  Acts::MagneticFieldContext mfContext = m_extrapolationTool->getMagneticFieldContext(ctx);
  Acts::CalibrationContext calContext{};
 
  Acts::GsfOptions<ActsTrk::MutableTrackStateBackend> gsfOptions = prepareOptions(tgContext, mfContext, calContext, *pSurface);
  const Acts::TrackingGeometry* actsTrackingGeometry = m_trackingGeometryTool->trackingGeometry().get();
 
  if (!actsTrackingGeometry) {
    ATH_MSG_ERROR("No Acts tracking geometry.");
    return StatusCode::FAILURE;
  }
 
  detail::RefittingCalibrator calibrator;
 
  auto gsfExtensions = m_gsfExtensions;
  gsfExtensions.calibrator.connect<&detail::RefittingCalibrator::calibrate>(&calibrator);
  gsfExtensions.surfaceAccessor.connect<&detail::RefittingCalibrator::accessSurface>();
  gsfOptions.extensions = gsfExtensions;
  gsfOptions.abortOnError = false;
 
  if (m_useDirectNavigation) {
    m_directFitter->fit(sourceLinks.begin(), sourceLinks.end(), initialParams, gsfOptions, surfSequence, trackContainer);
  } else {
    m_fitter->fit(sourceLinks.begin(), sourceLinks.end(), initialParams, gsfOptions, trackContainer);
  }
 
  return StatusCode::SUCCESS;
}
 
std::unique_ptr<Trk::Track>
GaussianSumFitterTool::makeTrack(const EventContext& ctx,
                 const Acts::GeometryContext& tgContext,
                 ActsTrk::MutableTrackContainer& tracks,
                 Acts::Result<typename ActsTrk::MutableTrackContainer::TrackProxy, std::error_code>& fitResult) const
{
  if (not fitResult.ok()) 
    return nullptr;
 
  std::unique_ptr<Trk::Track> newtrack = nullptr;
  // Get the fit output object
  const auto& acts_track = fitResult.value();
  auto finalTrajectory = std::make_unique<Trk::TrackStates>();
  // initialise the number of dead Pixel and Acts strip
  int numberOfDeadPixel = 0;
  int numberOfDeadSCT = 0;
 
  std::vector<std::unique_ptr<const Acts::BoundTrackParameters>> actsSmoothedParam;
  // Loop over all the output state to create track state
  tracks.trackStateContainer().visitBackwards(acts_track.tipIndex(), 
                [&] (const auto &state) -> void
  {
    // First only concider state with an associated detector element not in the TRT
    auto flag = state.typeFlags();
    const auto* associatedDetEl = state.referenceSurface().associatedDetectorElement();
    if (not associatedDetEl) 
      return;
    
    const auto* actsElement = dynamic_cast<const ActsDetectorElement*>(associatedDetEl);
    if (not actsElement) 
      return;
 
    const auto* upstreamDetEl = actsElement->upstreamDetectorElement();
    if (not upstreamDetEl) 
      return;
 
    ATH_MSG_VERBOSE("Try casting to TRT for if");
    if (dynamic_cast<const InDetDD::TRT_BaseElement*>(upstreamDetEl))
      return;
 
    const auto* trkDetElem = dynamic_cast<const Trk::TrkDetElementBase*>(upstreamDetEl);
    if (not trkDetElem)
      return;
 
    ATH_MSG_VERBOSE("trkDetElem type: " << static_cast<std::underlying_type_t<Trk::DetectorElemType>>(trkDetElem->detectorType()));
 
    ATH_MSG_VERBOSE("Try casting to SiDetectorElement");
    const auto* detElem = dynamic_cast<const InDetDD::SiDetectorElement*>(upstreamDetEl);
    if (not detElem)
      return;
    ATH_MSG_VERBOSE("detElem = " << detElem);
 
    // We need to determine the type of state 
    std::bitset<Trk::TrackStateOnSurface::NumberOfTrackStateOnSurfaceTypes> typePattern;
    std::unique_ptr<Trk::TrackParameters> parm;
 
    // State is a hole (no associated measurement), use predicted parameters      
    if (flag.test(Acts::TrackStateFlag::HoleFlag)){
      ATH_MSG_VERBOSE("State is a hole (no associated measurement), use predicted parameters");
      const Acts::BoundTrackParameters actsParam(state.referenceSurface().getSharedPtr(),
             state.predicted(),
             state.predictedCovariance(),
             acts_track.particleHypothesis());
      parm = m_ATLASConverterTool->actsTrackParametersToTrkParameters(actsParam, tgContext);
      auto boundaryCheck = m_boundaryCheckTool->boundaryCheck(*parm);
      // Check if this is a hole, a dead sensors or a state outside the sensor boundary
      ATH_MSG_VERBOSE("Check if this is a hole, a dead sensors or a state outside the sensor boundary");
      if(boundaryCheck == Trk::BoundaryCheckResult::DeadElement){
  if (detElem->isPixel()) {
    ++numberOfDeadPixel;
  }
  else if (detElem->isSCT()) {
    ++numberOfDeadSCT;
  }
  // Dead sensors states are not stored              
  return;
      } else if (boundaryCheck != Trk::BoundaryCheckResult::Candidate){
  // States outside the sensor boundary are ignored
  return;
      }
      typePattern.set(Trk::TrackStateOnSurface::Hole);
    }
    // The state was tagged as an outlier or was missed in the reverse filtering, use filtered parameters
    else if (flag.test(Acts::TrackStateFlag::OutlierFlag) or not state.hasSmoothed()) {
      ATH_MSG_VERBOSE("The state was tagged as an outlier or was missed in the reverse filtering, use filtered parameters");
      const Acts::BoundTrackParameters actsParam(state.referenceSurface().getSharedPtr(),
             state.filtered(),
             state.filteredCovariance(),
             acts_track.particleHypothesis());
      parm = m_ATLASConverterTool->actsTrackParametersToTrkParameters(actsParam, tgContext);
      typePattern.set(Trk::TrackStateOnSurface::Outlier);
    }
    // The state is a measurement state, use smoothed parameters 
    else{
      ATH_MSG_VERBOSE("The state is a measurement state, use smoothed parameters");
 
      const Acts::BoundTrackParameters actsParam(state.referenceSurface().getSharedPtr(),
             state.smoothed(),
             state.smoothedCovariance(),
             acts_track.particleHypothesis());
      
      actsSmoothedParam.push_back(std::make_unique<const Acts::BoundTrackParameters>(Acts::BoundTrackParameters(actsParam)));
      parm = m_ATLASConverterTool->actsTrackParametersToTrkParameters(actsParam, tgContext);
      typePattern.set(Trk::TrackStateOnSurface::Measurement);
    }
 
    std::unique_ptr<Trk::MeasurementBase> measState;
    if (state.hasUncalibratedSourceLink()){
      auto sl = state.getUncalibratedSourceLink().template get<ATLASSourceLink>();
      assert(sl);
      measState = sl->uniqueClone();
    }
    double nDoF = state.calibratedSize();
    auto quality =Trk::FitQualityOnSurface(state.chi2(), nDoF);
    const Trk::TrackStateOnSurface *perState = new Trk::TrackStateOnSurface(quality, std::move(measState), std::move(parm), nullptr, typePattern);
    // If a state was succesfully created add it to the trajectory 
    if (perState) {
      ATH_MSG_VERBOSE("State succesfully creates, adding it to the trajectory");
      finalTrajectory->insert(finalTrajectory->begin(), perState);
    }
  });
  
  // Convert the perigee state and add it to the trajectory
  const Acts::BoundTrackParameters actsPer(acts_track.referenceSurface().getSharedPtr(), 
                 acts_track.parameters(), 
                 acts_track.covariance(),
                 acts_track.particleHypothesis());
  std::unique_ptr<Trk::TrackParameters> per = m_ATLASConverterTool->actsTrackParametersToTrkParameters(actsPer, tgContext);
  std::bitset<Trk::TrackStateOnSurface::NumberOfTrackStateOnSurfaceTypes> typePattern;
  typePattern.set(Trk::TrackStateOnSurface::Perigee);
  const Trk::TrackStateOnSurface *perState = new Trk::TrackStateOnSurface(nullptr, std::move(per), nullptr, typePattern);
  if (perState) finalTrajectory->insert(finalTrajectory->begin(), perState);
 
  // Create the track using the states
  Trk::TrackInfo newInfo(Trk::TrackInfo::TrackFitter::GaussianSumFilter, Trk::noHypothesis);
  newInfo.setTrackFitter(Trk::TrackInfo::TrackFitter::GaussianSumFilter); //Mark the fitter as GaussianSumFilter
  newtrack = std::make_unique<Trk::Track>(newInfo, std::move(finalTrajectory), nullptr);
  if (newtrack && !m_refitOnly) {
    // Create the track summary and update the holes information
    if (!newtrack->trackSummary()) {
      newtrack->setTrackSummary(std::make_unique<Trk::TrackSummary>());
      newtrack->trackSummary()->update(Trk::numberOfPixelHoles, 0);
      newtrack->trackSummary()->update(Trk::numberOfSCTHoles, 0);
      newtrack->trackSummary()->update(Trk::numberOfTRTHoles, 0);
      newtrack->trackSummary()->update(Trk::numberOfPixelDeadSensors, numberOfDeadPixel);
      newtrack->trackSummary()->update(Trk::numberOfSCTDeadSensors, numberOfDeadSCT);
    }
    m_trkSummaryTool->updateTrackSummary(ctx, *newtrack, true);
  }
  
  return newtrack;
}
 
const Acts::GsfExtensions<typename ActsTrk::MutableTrackStateBackend>& 
GaussianSumFitterTool::getExtensions() const 
{ 
  return m_gsfExtensions;
}
 
const Acts::Logger& 
GaussianSumFitterTool::logger() const 
{ 
  return *m_logger;
}
 
Acts::GsfOptions<typename ActsTrk::MutableTrackStateBackend> 
GaussianSumFitterTool::prepareOptions(const Acts::GeometryContext& tgContext,
                      const Acts::MagneticFieldContext& mfContext,
                      const Acts::CalibrationContext& calContext,
                      const Acts::PerigeeSurface& surface) const
{
  Acts::PropagatorPlainOptions propagationOption(tgContext, mfContext);
  propagationOption.maxSteps = m_option_maxPropagationStep;
 
  Acts::GsfOptions<typename ActsTrk::MutableTrackStateBackend> gsfOptions(tgContext, mfContext, calContext);
  gsfOptions.extensions=m_gsfExtensions;
  gsfOptions.propagatorPlainOptions=propagationOption;
  gsfOptions.referenceSurface = &surface;
 
  // Set abortOnError to false, else the refitting crashes if no forward propagation is done. Here, we just skip the event and continue.
  gsfOptions.abortOnError = false;
  gsfOptions.maxComponents = m_maxComponents;
  gsfOptions.weightCutoff = m_weightCutOff;
  gsfOptions.componentMergeMethod = m_componentMergeMethod;
 
  return gsfOptions;
}
 
}