AdaptiveMultiPriVtxFinderTool.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#include "src/AdaptiveMultiPriVtxFinderTool.h"
 
// ATHENA
#include "GaudiKernel/IInterface.h"
#include "GeoPrimitives/GeoPrimitivesHelpers.h"
#include "TrkParticleBase/LinkToTrackParticleBase.h"
#include "TrkLinks/LinkToXAODTrackParticle.h"
#include "xAODTracking/TrackParticleContainer.h"
 
 
// ACTS
#include "Acts/Propagator/Navigator.hpp"
#include "Acts/Propagator/EigenStepper.hpp"
#include "Acts/Propagator/Propagator.hpp"
#include "Acts/Utilities/AnnealingUtility.hpp"
#include "Acts/Surfaces/PerigeeSurface.hpp"
#include "Acts/Vertexing/TrackAtVertex.hpp"
 
#include "Acts/Vertexing/GaussianGridTrackDensity.hpp"
#include "Acts/Vertexing/GridDensityVertexFinder.hpp"
#include "Acts/Vertexing/GaussianTrackDensity.hpp"
 
 
// STL
#include <iostream>
#include <memory>
 
namespace
{
  // Helper struct for vertex signal compatibility
  struct VertexAndSignalComp {
    xAOD::Vertex* first;
    double second;
    VertexAndSignalComp(xAOD::Vertex* p1, double p2)
    : first(p1), second(p2) {}
    bool
    operator < (const VertexAndSignalComp& other) const
    {return second > other.second;}
  };
} //anonymous namespace
 
StatusCode
ActsTrk::AdaptiveMultiPriVtxFinderTool::initialize()
{
    using namespace std::literals::string_literals;
 
    ATH_CHECK(m_beamSpotKey.initialize());
    ATH_CHECK(m_trkFilter.retrieve());
 
    ATH_CHECK(m_ctxProvider.initialize());
    ATH_MSG_INFO("Initializing ACTS AMVF tool");
    ATH_CHECK( m_trackingGeometrySvc.retrieve() );
    std::shared_ptr<const Acts::TrackingGeometry> trackingGeometry
    = m_trackingGeometrySvc->trackingGeometry();
 
    // Logger
    m_logger = makeActsAthenaLogger(this, "Acts");
    
    Acts::Navigator navigator( Acts::Navigator::Config{ std::move(trackingGeometry) },
                   logger().cloneWithSuffix("Navigator"));
 
    auto bField = std::make_shared<ATLASMagneticFieldWrapper>();
    auto stepper = Acts::EigenStepper<>(bField);
    m_propagator = std::make_shared<Propagator>(std::move(stepper), 
                        std::move(navigator),
                        logger().cloneWithSuffix("Prop"));
 
    // IP Estimator
    Acts::ImpactPointEstimator::Config ipEstCfg(bField, m_propagator);
    ipEstCfg.maxIterations = m_ipEstMaxIterations;
    ipEstCfg.precision = m_ipEstPrecision;
    Acts::ImpactPointEstimator ipEst(ipEstCfg,
                     logger().cloneWithSuffix("ImpactPointEstimator"));
 
    Acts::AnnealingUtility::Config annealingConfig;
    annealingConfig.setOfTemperatures = m_annealingTemps;
    annealingConfig.cutOff = m_annealingCutOff;
    Acts::AnnealingUtility annealingUtility(annealingConfig);
 
    // Linearizer for Acts::BoundParameters type test
    TrackLinearizer::Config ltConfig;
    ltConfig.bField = bField;
    ltConfig.propagator = m_propagator;
    m_linearizer.emplace(ltConfig, logger().cloneWithSuffix("Linearizer"));
 
    // Vertex fitter configuration
    VertexFitter::Config fitterCfg(ipEst);
    fitterCfg.annealingTool = std::move(annealingUtility);
    fitterCfg.maxIterations = m_fitterMaxIterations;
    fitterCfg.maxDistToLinPoint = m_fitterMaxDistToLinPoint;
    fitterCfg.minWeight = m_minWeightFitter;
    fitterCfg.maxRelativeShift = m_fitterMaxRelativeShift;
    fitterCfg.doSmoothing = m_fitterDoSmoothing;
    fitterCfg.extractParameters.connect<&TrackWrapper::extractParameters>();
    fitterCfg.trackLinearizer.connect<&TrackLinearizer::linearizeTrack>(&*m_linearizer);
    VertexFitter fitter(std::move(fitterCfg), logger().cloneWithSuffix("Fitter"));
 
  std::string seederType = m_seederType;
 
    if (seederType == "Grid") {
         int trkGridSize = m_gridTrkGridSize;
         if (trkGridSize % 2 == 0) {
           ATH_MSG_WARNING("GridTrkGridSize=" << m_gridTrkGridSize
                       << " is even; ACTS requires an odd value. Using "
                       << (trkGridSize + 1) << " instead.");
           trkGridSize += 1;
           }
      Acts::GaussianGridTrackDensity::Config trackDensityConfig(
      /*zMinMax_=*/100,
      /*mainGridSize_=*/m_gridMainGridSize,
      /*trkGridSize_=*/trkGridSize);   // <-- changed from m_gridTrkGridSize
      trackDensityConfig.useHighestSumZPosition = m_gridUseHighestSumZPosition;
      Acts::GaussianGridTrackDensity trackDensity(trackDensityConfig);
 
      Acts::GridDensityVertexFinder::Config gridSeedFinderConfig(trackDensity);
      gridSeedFinderConfig.extractParameters.connect<&TrackWrapper::extractParameters>();
      gridSeedFinderConfig.maxD0TrackSignificance = m_gridMaxD0Significance;
      gridSeedFinderConfig.maxZ0TrackSignificance = m_gridMaxZ0Significance;
      gridSeedFinderConfig.d0SignificanceCut = m_gridMaxD0Significance * m_gridMaxD0Significance;
      gridSeedFinderConfig.z0SignificanceCut = m_gridMaxZ0Significance * m_gridMaxZ0Significance;
      ATH_MSG_INFO("Grid seeder: d0SignificanceCut=" << gridSeedFinderConfig.d0SignificanceCut << " z0SignificanceCut=" << gridSeedFinderConfig.z0SignificanceCut);
 
      Acts::GridDensityVertexFinder gridSeedFinder(gridSeedFinderConfig);
 
      VertexFinder::Config finderConfig(
          std::move(fitter),
          std::make_shared<Acts::GridDensityVertexFinder>(gridSeedFinder),
          std::move(ipEst),
          bField
      );
 
      initializeVertexFinder(std::move(finderConfig));
    }
    else if (seederType == "Gaussian") {
      Acts::GaussianTrackDensity::Config trackDensityConfig;
      trackDensityConfig.d0MaxSignificance = m_gaussianMaxD0Significance;
      trackDensityConfig.z0MaxSignificance = m_gaussianMaxZ0Significance;
      trackDensityConfig.extractParameters.connect<&TrackWrapper::extractParameters>();
 
      Acts::GaussianTrackDensity trackDensity(trackDensityConfig);
      VertexSeedFinder::Config seedFinderConfig(trackDensity);
      auto seedFinder = std::make_shared<VertexSeedFinder>(seedFinderConfig);
 
      VertexFinder::Config finderConfig(
          std::move(fitter),
          seedFinder,
          std::move(ipEst),
          bField
      );
 
      initializeVertexFinder(std::move(finderConfig));
    }
    else {
      ATH_MSG_ERROR("Unknown seederType '" << seederType << "'.");
      return StatusCode::FAILURE;
    }
 
    ATH_MSG_INFO("ACTS AMVF tool successfully initialized");
    return StatusCode::SUCCESS;
  }
 
  void
  ActsTrk::AdaptiveMultiPriVtxFinderTool::initializeVertexFinder(VertexFinder::Config&& finderConfig)
  {
 
  finderConfig.tracksMaxZinterval          = m_tracksMaxZinterval;
  finderConfig.tracksMaxSignificance       = m_tracksMaxSignificance;
  finderConfig.maxVertexChi2               = m_maxVertexChi2;
  finderConfig.doRealMultiVertex           = m_doRealMultiVertex;
  finderConfig.useFastCompatibility        = m_useFastCompatibility;
  finderConfig.maxMergeVertexSignificance  = m_maxMergeVertexSignificance;
  finderConfig.minWeight                   = m_minWeight;
  finderConfig.maxIterations               = m_maxIterations;
  finderConfig.addSingleTrackVertices      = m_addSingleTrackVertices;
  finderConfig.doFullSplitting             = m_doFullSplitting;
  finderConfig.maximumVertexContamination  = m_maximumVertexContamination;
  finderConfig.initialVariances            = Acts::Vector4::Constant(m_looseConstrValue);
  finderConfig.useVertexCovForIPEstimation = m_useVertexCovForIPEstimation;
  finderConfig.useSeedConstraint           = m_useSeedConstraint;
 
  finderConfig.extractParameters.connect<&TrackWrapper::extractParameters>();
 
  m_vertexFinder = std::make_shared<VertexFinder>(
      std::move(finderConfig),
      logger().cloneWithSuffix("Finder"));
}
 
std::pair<xAOD::VertexContainer*, xAOD::VertexAuxContainer*>
ActsTrk::AdaptiveMultiPriVtxFinderTool::findVertex(const EventContext& ctx,
                                                   const TrackCollection* trackTES) const
{
  SG::ReadCondHandle<InDet::BeamSpotData> beamSpotHandle { m_beamSpotKey, ctx};
  const Trk::RecVertex& beamposition(beamSpotHandle->beamVtx());
 
  std::vector<std::unique_ptr<Trk::ITrackLink>> selectedTracks;
 
  typedef DataVector<Trk::Track>::const_iterator TrackDataVecIter;
 
  bool selectionPassed;
  for (TrackDataVecIter itr = (*trackTES).begin(); itr != (*trackTES).end(); ++itr) {
    if (m_useBeamConstraint) {
      selectionPassed = static_cast<bool>(m_trkFilter->accept(**itr, &beamposition));
    } else {
        Trk::Vertex null(Amg::Vector3D(0, 0, 0));
        selectionPassed = static_cast<bool>(m_trkFilter->accept(**itr, &null));
    }
    if (selectionPassed) {
        ElementLink<TrackCollection> link;
        link.setElement(*itr);
        auto trkPtr = std::make_unique<Trk::LinkToTrack>(link);
        trkPtr->setStorableObject(*trackTES);
        selectedTracks.push_back(std::move(trkPtr));
    }
  }
 
  std::pair<xAOD::VertexContainer*, xAOD::VertexAuxContainer*> returnContainers = findVertex(ctx, std::move(selectedTracks));
 
  return returnContainers;
}
 
std::pair<xAOD::VertexContainer*, xAOD::VertexAuxContainer*>
ActsTrk::AdaptiveMultiPriVtxFinderTool::findVertex(const EventContext& ctx,
                                                   const xAOD::TrackParticleContainer* trackParticles) const
{
 
  std::vector<std::unique_ptr<Trk::ITrackLink>> selectedTracks;
  SG::ReadCondHandle<InDet::BeamSpotData> beamSpotHandle { m_beamSpotKey, ctx};
  xAOD::Vertex beamposition;
  beamposition.makePrivateStore();
  beamposition.setPosition(beamSpotHandle->beamVtx().position());
  beamposition.setCovariancePosition(beamSpotHandle->beamVtx().covariancePosition());
 
  typedef DataVector<xAOD::TrackParticle>::const_iterator TrackParticleDataVecIter;
 
  bool selectionPassed;
  for (TrackParticleDataVecIter itr = (*trackParticles).begin(); itr != (*trackParticles).end(); ++itr) {
    if (m_useBeamConstraint) {
      selectionPassed = static_cast<bool>(m_trkFilter->accept(**itr, &beamposition));
    } else {
        xAOD::Vertex null;
        null.makePrivateStore();
        null.setPosition(Amg::Vector3D(0, 0, 0));
        AmgSymMatrix(3) vertexError;
        vertexError.setZero();
        null.setCovariancePosition(vertexError);
        selectionPassed = static_cast<bool>(m_trkFilter->accept(**itr, &null));
    }
 
    if (selectionPassed) {
        ElementLink<xAOD::TrackParticleContainer> link;
        link.setElement(*itr);
        auto trkPtr = std::make_unique<Trk::LinkToXAODTrackParticle>(link);
        trkPtr->setStorableObject(*trackParticles);
        selectedTracks.push_back(std::move(trkPtr));
    }
  }
 
  std::pair<xAOD::VertexContainer*, xAOD::VertexAuxContainer*> returnContainers = findVertex(ctx, std::move(selectedTracks));
 
  return returnContainers;
}
 
 
std::pair<xAOD::VertexContainer*, xAOD::VertexAuxContainer*> 
ActsTrk::AdaptiveMultiPriVtxFinderTool::findVertex(const EventContext& ctx,
                                                   const std::vector<std::unique_ptr<Trk::ITrackLink>>& trackVector) const
{
    using namespace Acts::UnitLiterals; // !!!
    
    const InDet::BeamSpotData* beamSpotHandle{};
    if (!SG::get(beamSpotHandle, m_beamSpotKey, ctx).isSuccess()) {
      return {};
    }
    const Acts::Vector3& beamSpotPos = beamSpotHandle->beamVtx().position();
    Acts::Vertex beamSpotConstraintVtx(beamSpotPos);
    beamSpotConstraintVtx.setCovariance(beamSpotHandle->beamVtx().covariancePosition());
 
    // Get the magnetic field context
    const Acts::MagneticFieldContext magFieldContext = m_ctxProvider.getMagneticFieldContext(ctx);
    const Acts::GeometryContext geoContext = m_ctxProvider.getGeometryContext(ctx);
 
    // The output vertex containers
    xAOD::VertexContainer* theVertexContainer = new xAOD::VertexContainer;
    xAOD::VertexAuxContainer* theVertexAuxContainer = new xAOD::VertexAuxContainer;
    theVertexContainer->setStore(theVertexAuxContainer);
 
    if(trackVector.empty()){
      xAOD::Vertex* dummyxAODVertex = new xAOD::Vertex;
      theVertexContainer->push_back(dummyxAODVertex);
      dummyxAODVertex->setPosition(beamSpotHandle->beamVtx().position());
      dummyxAODVertex->setCovariancePosition(beamSpotHandle->beamVtx().covariancePosition());
      dummyxAODVertex->setVertexType(xAOD::VxType::NoVtx);
 
      return std::make_pair(theVertexContainer, theVertexAuxContainer);
    }
 
    std::shared_ptr<Acts::PerigeeSurface> perigeeSurface =
      Acts::Surface::makeShared<Acts::PerigeeSurface>(
        Amg::toIsometry3D((trackVector[0])->parameters()->associatedSurface().transform()));
 
    // Convert tracks to Acts::BoundParameters
    std::vector<TrackWrapper> allTracks;
 
    for (const auto& trk : trackVector) {
      const auto& trkParams = trk->parameters();
      const auto& params = trkParams->parameters();
 
      Acts::BoundVector actsParams;
      actsParams << params(0), params(1), params(2), params(3), params(4)*1./(1_MeV), 0.;
 
      if(trkParams->covariance() == nullptr){
          continue;
      }
 
      auto cov = *(trkParams->covariance());
      
      // TODO: check if the following works as well:
      // cov->col(4) *= 1./1_MeV;
      // cov->row(4) *= 1./1_MeV;
      Acts::BoundMatrix covMat;
      covMat << cov(0,0) , cov(0,1) , cov(0,2) , cov(0,3) , cov(0,4) *1./(1_MeV), 0      
      , cov(1,0) , cov(1,1) , cov(1,2) , cov(1,3) , cov(1,4) *1./(1_MeV) , 0
      , cov(2,0) , cov(2,1) , cov(2,2) , cov(2,3) , cov(2,4) *1./(1_MeV) , 0
      , cov(3,0) , cov(3,1) , cov(3,2) , cov(3,3) , cov(3,4) *1./(1_MeV) , 0 
      , cov(4,0) *1./(1_MeV) , cov(4,1) *1./(1_MeV) , cov(4,2) *1./(1_MeV) , cov(4,3) *1./(1_MeV) , cov(4,4) *1./(1_MeV*1_MeV), 0
      , 0. , 0. , 0. , 0., 0., 1.;
      
      allTracks.emplace_back(trk.get(),Acts::BoundTrackParameters(perigeeSurface, actsParams, covMat, Acts::ParticleHypothesis::pion()));
    }
 
    std::vector<Acts::InputTrack> allTrackPtrs;
    allTrackPtrs.reserve(allTracks.size());
    
    for(const auto& trk : allTracks){
      allTrackPtrs.emplace_back(&trk);
    }
 
    Acts::VertexingOptions vertexingOptions( geoContext, magFieldContext );
 
    if(!m_useBeamConstraint){
      beamSpotConstraintVtx.setPosition(Acts::Vector3::Zero());
      Amg::MatrixX looseConstraintCovariance(3, 3);
      looseConstraintCovariance.setIdentity();
      looseConstraintCovariance = looseConstraintCovariance * 1e+8;
      beamSpotConstraintVtx.setCovariance(looseConstraintCovariance);
    }
 
    vertexingOptions.useConstraintInFit = m_useBeamConstraint;
    vertexingOptions.constraint = std::move(beamSpotConstraintVtx);
 
    auto finderState = m_vertexFinder->makeState(magFieldContext);
 
    auto findResult = m_vertexFinder->find(allTrackPtrs, vertexingOptions, finderState);
    
    if(!findResult.ok()){
      xAOD::Vertex* dummyxAODVertex = new xAOD::Vertex;
      theVertexContainer->push_back(dummyxAODVertex);
      dummyxAODVertex->setPosition(beamSpotHandle->beamVtx().position());
      dummyxAODVertex->setCovariancePosition(beamSpotHandle->beamVtx().covariancePosition());
      dummyxAODVertex->setVertexType(xAOD::VxType::NoVtx);
      return std::make_pair(theVertexContainer, theVertexAuxContainer);
    }
 
    std::vector<Acts::Vertex> allVertices = *findResult;
 
    std::vector<VertexAndSignalComp> vtxList;
    
    // Reserve memory for all vertices
    vtxList.reserve(allVertices.size());
 
    for(const auto& vtx : allVertices){
      //skip the vertex with negative covariance
      if(vtx.covariance()(0,0)<0||vtx.covariance()(1,1)<0||vtx.covariance()(2,2)<0)
    continue;
      xAOD::Vertex* xAODVtx = new xAOD::Vertex;
      xAODVtx->makePrivateStore();
      xAODVtx->setPosition(vtx.position());
      xAODVtx->setCovariancePosition(vtx.covariance());
      xAODVtx->setFitQuality(vtx.fitQuality().first, vtx.fitQuality().second);
 
      const auto& tracks = vtx.tracks();
      std::vector<Trk::VxTrackAtVertex>* trkAtVtxVec = &(xAODVtx->vxTrackAtVertex());
      for(const auto& trk : tracks){
 
        // Clean up incompatible tracks
        if ((trk.vertexCompatibility > m_maxVertexChi2 && m_useFastCompatibility) ||
          ((trk.trackWeight < m_minWeight
            || trk.chi2Track > m_maxVertexChi2)
          && !m_useFastCompatibility)) {
          continue;
        }
 
        const TrackWrapper* originalParams = trk.originalParams.template as<TrackWrapper>();
 
        Trk::Perigee* fittedPerigee = actsBoundToTrkPerigee(trk.fittedParams, beamSpotPos);
        Trk::VxTrackAtVertex trkAtVtx(originalParams->trackLink()->clone());
        trkAtVtx.setPerigeeAtVertex(fittedPerigee);
        trkAtVtx.setTrackQuality(Trk::FitQuality(trk.chi2Track, trk.ndf));
        trkAtVtx.setVtxCompatibility(trk.vertexCompatibility);
        trkAtVtx.setWeight(trk.trackWeight);
        trkAtVtxVec->push_back(std::move(trkAtVtx));
 
        const Trk::LinkToXAODTrackParticle* linkToXAODTP =
        dynamic_cast<const Trk::LinkToXAODTrackParticle*>(originalParams->trackLink());
        if (linkToXAODTP) {
          xAODVtx->addTrackAtVertex(*linkToXAODTP, trk.trackWeight);
        }
      }
      // Find signal compatibility
      double sigComp = estimateSignalCompatibility(xAODVtx);
            // Insert vertex at correct position according to sigComp value
      VertexAndSignalComp vertexAndSig(xAODVtx, sigComp);
      auto it = std::lower_bound( vtxList.begin(), vtxList.end(), vertexAndSig );
      vtxList.insert( it, vertexAndSig );
    }
  
    for(unsigned int i = 0; i < vtxList.size(); i++){
      auto vtx = vtxList[i].first;
      theVertexContainer->push_back(vtx);
      if(i == 0){
    vtx->setVertexType(xAOD::VxType::PriVtx);
      }
      else{
    vtx->setVertexType(xAOD::VxType::PileUp);
      }
    }
 
    // Add dummy vertex to collection
    xAOD::Vertex* dummyxAODVertex = new xAOD::Vertex;
    theVertexContainer->push_back(dummyxAODVertex);
 
    if(!vtxList.empty()){
      // If HS vertex exists, create dummy with same position/covariance
      xAOD::Vertex* primaryVtx = theVertexContainer->front();
      dummyxAODVertex->setPosition(primaryVtx->position());
      dummyxAODVertex->setCovariancePosition(primaryVtx->covariancePosition());
      dummyxAODVertex->setVertexType(xAOD::VxType::NoVtx);
    }
    else{
      dummyxAODVertex->setPosition(beamSpotHandle->beamVtx().position());
      dummyxAODVertex->setCovariancePosition(beamSpotHandle->beamVtx().covariancePosition());
      dummyxAODVertex->setVertexType(xAOD::VxType::NoVtx);
    }
 
    return std::make_pair(theVertexContainer, theVertexAuxContainer);
}
 
 
Trk::Perigee*
ActsTrk::AdaptiveMultiPriVtxFinderTool::actsBoundToTrkPerigee(const Acts::BoundTrackParameters& bound,
                                                              const Acts::Vector3& surfCenter) const
{
  using namespace Acts::UnitLiterals;
  AmgSymMatrix(5) cov =  AmgSymMatrix(5)(bound.covariance()->block<5,5>(0,0));
  cov.col(Trk::qOverP) *= 1_MeV;
  cov.row(Trk::qOverP) *= 1_MeV;
  Acts::Vector<5> params = bound.parameters().head<5>();
  params[Trk::qOverP] *= 1_MeV;
 
  return new Trk::Perigee(params, Trk::PerigeeSurface(surfCenter), std::move(cov));
}
 
double
ActsTrk::AdaptiveMultiPriVtxFinderTool::estimateSignalCompatibility(xAOD::Vertex* vtx) const
{
  double totalPt2 = 0;
  unsigned int nTracks = 0;
 
  for(const auto& trk : vtx->vxTrackAtVertex()){
    if ((trk.vtxCompatibility() < m_finalCutMaxVertexChi2 && m_useFastCompatibility) ||
      (trk.weight() > m_minWeight
         && trk.trackQuality().chiSquared() < m_finalCutMaxVertexChi2
         && !m_useFastCompatibility)) {
      const Trk::TrackParameters* perigee = nullptr;
      if (trk.perigeeAtVertex() != nullptr) {
          perigee = trk.perigeeAtVertex();
      } else {
          ATH_MSG_VERBOSE("Only initialPerigee is available");
          perigee = trk.initialPerigee();
      }
      if (perigee == nullptr) {
          ATH_MSG_ERROR("Neutrals are not supported. Skipping track in pT calculation...");
          continue;
      }
      totalPt2 +=
      std::pow(std::fabs(1. / perigee->parameters()[Trk::qOverP]) * std::sin(perigee->parameters()[Trk::theta]), 2);
      nTracks += 1;
    }
  }
  return totalPt2 * std::sqrt((double) nTracks);
}