FPGAActsTrkConverter.cxx

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// Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
 
#include "FPGAActsTrkConverter.h"
#include "TrkEventPrimitives/ParticleHypothesis.h"
#include "Acts/Surfaces/PerigeeSurface.hpp"
#include "ActsGeometry/ATLASSourceLink.h"
#include "Identifier/IdentifierHash.h"
 
#include <format>
#include <sstream>
//Heavily inspired by https://gitlab.cern.ch/atlas/athena/-/blob/main/Tracking/Acts/ActsTrackReconstruction/src/RandomProtoTrackCreator.cxx
 
FPGAActsTrkConverter::FPGAActsTrkConverter(const std::string& type, 
        const std::string& name,
        const IInterface* parent): base_class(type,name,parent) { }
 
 
StatusCode FPGAActsTrkConverter::initialize() {
 
  ATH_MSG_DEBUG("Initializing FPGAActsTrkConverter...");
 
  // Get SCT & pixel Identifier helpers
  ATH_CHECK(detStore()->retrieve(m_pixelId, "PixelID"));
  ATH_CHECK(detStore()->retrieve(m_SCTId, "SCT_ID"));
 
  return StatusCode::SUCCESS;
 
}
 
StatusCode FPGAActsTrkConverter::findProtoTracks(const EventContext& ctx,
                  const xAOD::PixelClusterContainer & pixelContainer,
                  const xAOD::StripClusterContainer & stripContainer,
                  std::vector<ActsTrk::ProtoTrack> & foundProtoTracks,
                  const std::vector<FPGATrackSimRoad>& roads) const {
 
    ATH_MSG_INFO("Creating Acts proto-tracks from FPGA roads...");
 
    if (roads.size() > 0) {
      std::unordered_map<xAOD::DetectorIdentType, const xAOD::PixelCluster*> pixelClusterMap;
      for (const xAOD::PixelCluster* cluster : pixelContainer) {
        pixelClusterMap.emplace(cluster->identifier(), cluster);
      }
 
      std::unordered_map<xAOD::DetectorIdentType, const xAOD::StripCluster*> stripClusterMap;
      for (const xAOD::StripCluster* cluster : stripContainer) {
        stripClusterMap.emplace(cluster->identifier(), cluster);
      
      }
      for (const FPGATrackSimRoad& road : roads) { 
        std::vector<ActsTrk::ATLASUncalibSourceLink> points;
        
        // Process measurements directly from road's shared_ptr hits
        for (size_t l = 0; l < road.getNLayers(); ++l) {
          for (const auto& layerH : road.getHitPtrs(l)) {
            if (!layerH || !layerH->isReal()) continue;
            
            if (layerH->isPixel()) {
              ATH_MSG_DEBUG("Looking for Pixel cluster to match");
              auto it = pixelClusterMap.find(layerH->getRdoIdentifier());
              if (it != pixelClusterMap.end()) {
                ATH_CHECK(matchTrackMeasurements<xAOD::PixelCluster>(ctx, *(it->second), *layerH, points, pixelContainer));
              }
            }
            else if (layerH->isStrip()) {
              ATH_MSG_DEBUG("Looking for Strip cluster to match");
              auto it = stripClusterMap.find(layerH->getRdoIdentifier());
              if (it != stripClusterMap.end()) {
                ATH_CHECK(matchTrackMeasurements<xAOD::StripCluster>(ctx, *(it->second), *layerH, points, stripContainer));
              }
            }
            else {
              ATH_MSG_ERROR("FPGA hit not classified as pixel or strip");
              return StatusCode::FAILURE;
            }
          }
        }
        
        if (points.size()) {
          std::unique_ptr<Acts::BoundTrackParameters> inputPerigee = makeParams(road);
          foundProtoTracks.emplace_back(points, std::move(inputPerigee));
          ATH_MSG_INFO("Made a prototrack with " << points.size() << " measurements");
        }
      }
    }
 
    return StatusCode::SUCCESS;
}
 
StatusCode FPGAActsTrkConverter::findProtoTracks(const EventContext& ctx,
                                                 const xAOD::PixelClusterContainer& pixelContainer,
                                                 const xAOD::StripClusterContainer& stripContainer,
                                                 std::vector<ActsTrk::ProtoTrack>& foundProtoTracks,
                                                 const std::vector<FPGATrackSimTrack>& tracks) const {
 
  ATH_MSG_INFO("Creating Acts proto-tracks from FPGA tracks...");
  // Initialize unordered maps for pixel and strip clusters
  std::unordered_map<xAOD::DetectorIdentType, const xAOD::PixelCluster*> pixelClusterMap;
  for (const xAOD::PixelCluster* cluster : pixelContainer) {
    pixelClusterMap.emplace(cluster->identifier(), cluster);
  }
 
  std::unordered_map<xAOD::DetectorIdentType, const xAOD::StripCluster*> stripClusterMap;
  for (const xAOD::StripCluster* cluster : stripContainer) {
    stripClusterMap.emplace(cluster->identifier(), cluster);
  }
  for (const FPGATrackSimTrack& track : tracks) {
    if (not track.passedOR()) continue;
    std::vector<ActsTrk::ATLASUncalibSourceLink> points;
    const auto& hits = track.getFPGATrackSimHitPtrs();
    for (const auto& hit : hits) {
      if (!hit->isReal()) continue;
      
      if (hit->isPixel()) {
        ATH_MSG_DEBUG("Looking for Pixel cluster to match");
        auto it = pixelClusterMap.find(hit->getRdoIdentifier());
        if (it != pixelClusterMap.end()) {
          ATH_CHECK(matchTrackMeasurements<xAOD::PixelCluster>(ctx, *(it->second), *hit, points, pixelContainer));
        }
      }
      else if (hit->isStrip()) {
        ATH_MSG_DEBUG("Looking for Strip cluster to match");
        auto it = stripClusterMap.find(hit->getRdoIdentifier());
        if (it != stripClusterMap.end()) {
          ATH_CHECK(matchTrackMeasurements<xAOD::StripCluster>(ctx, *(it->second), *hit, points, stripContainer));
        }
      }
      else {
        ATH_MSG_ERROR("FPGA hit not classified as pixel or strip");
        return StatusCode::FAILURE;
      }
    }
    
    if (points.size()) {
      ATH_MSG_DEBUG("\tMaking a proto-track with " << points.size() << " clusters");
      std::unique_ptr<Acts::BoundTrackParameters> inputPerigee = makeParams(track);
      foundProtoTracks.emplace_back(points, std::move(inputPerigee));
    }
  }
  return StatusCode::SUCCESS;
}
 
 
template <typename XAOD_CLUSTER>
StatusCode FPGAActsTrkConverter::matchTrackMeasurements(const EventContext& ctx,
                                                        const XAOD_CLUSTER& cluster,
                                                        const FPGATrackSimHit & trackHit,
                                                        std::vector<ActsTrk::ATLASUncalibSourceLink>& measurements,
                                                        const DataVector<XAOD_CLUSTER>& clusterContainer) const
{
  const Identifier::value_type trackId = (trackHit.getHitType() == HitType::spacepoint) 
                                          ? trackHit.getOriginalHit().getRdoIdentifier() 
                                          : trackHit.getRdoIdentifier();
 
  if(cluster.identifier() == trackId) {
    measurements.emplace_back(ActsTrk::makeATLASUncalibSourceLink(&clusterContainer, cluster.index(), ctx));
    ATH_MSG_DEBUG("Matched FPGATrackSimHit to xAOD cluster");
  }
 
  return StatusCode::SUCCESS;
}
 
std::unique_ptr<Acts::BoundTrackParameters> FPGAActsTrkConverter::makeParams (const FPGATrackSimRoad &road) const{
  using namespace Acts::UnitLiterals;
 
  std::shared_ptr<const Acts::Surface> actsSurface = Acts::Surface::makeShared<Acts::PerigeeSurface>(Acts::Vector3(0., 0., 0.));
  Acts::BoundVector params;
 
  constexpr double GeVToMeV = 1000;
  double d0=0.; //?
  double z0=0.; //?
  double phi=road.getX();
  double eta=0.2;
  double theta=2*std::atan(std::exp(-eta));
  double qop = (std::abs(road.getY()) > 1E-9) ? road.getY()/GeVToMeV : 1E-12;
  double t=0.; //?
  ATH_MSG_DEBUG("\tphi=" <<phi << " eta=" << eta << " qop=" << qop);
 
  params << d0, z0, phi, theta, qop, t; 
 
  // Covariance - TODO
  Acts::BoundMatrix cov = Acts::BoundMatrix::Identity();
  cov *= (GeVToMeV*GeVToMeV); 
 
  // some ACTS paperwork 
  Trk::ParticleHypothesis hypothesis = Trk::pion;
  float mass = Trk::ParticleMasses::mass[hypothesis] * Acts::UnitConstants::MeV;
  Acts::PdgParticle absPdg = Acts::makeAbsolutePdgParticle(Acts::ePionPlus);
  Acts::ParticleHypothesis actsHypothesis{
    absPdg, mass, Acts::AnyCharge{1.0f}};
 
  return std::make_unique<Acts::BoundTrackParameters>(actsSurface, params,
                                    cov, actsHypothesis);
 
}
 
 
std::unique_ptr<Acts::BoundTrackParameters> FPGAActsTrkConverter::makeParams (const FPGATrackSimTrack &track) const{
 
  using namespace Acts::UnitLiterals;
  std::shared_ptr<const Acts::Surface> actsSurface = Acts::Surface::makeShared<Acts::PerigeeSurface>(Acts::Vector3(0., 0., 0.));
  Acts::BoundVector params;
 
  constexpr double GeVToMeV = 1000.;
  double d0=track.getD0();
  double z0=track.getZ0();
  double phi=track.getPhi();
  double eta=track.getEta();
  double theta=track.getTheta();
  double qopt=track.getQOverPt()*GeVToMeV;
  double pt=track.getPt()/GeVToMeV;
  double px=pt*std::cos(phi);
  double py=pt*std::sin(phi);
  double pz=pt*std::sinh(eta);
  double p=std::sqrt(px*px+py*py+pz*pz);
  double qop=((p > 1e-10) ? (1/p) : 1e10);
  if (qopt < 0) qop *= -1;  
  double t=0.;
 
  params << d0, z0, phi, theta, qop, t;  
  ATH_MSG_DEBUG("\td0= " << d0 << " z0=" <<z0 << " phi=" <<phi << " theta=" << theta<< " qoverp=" << qop);
 
  // Covariance - let's be honest and say we have no clue ;-) 
  Acts::BoundMatrix cov = Acts::BoundMatrix::Identity();
  
  (cov)(0,0) *= 0.16; // d0: 0.4 **2 (conservative)
  (cov)(1,1) *= 25; // z0: 5**2 = 25 (conservative)
  (cov)(2,2) *= 0.0008; // phi: 0.02**2 = 0.0004, increase a bit = double
  (cov)(3,3) *= 0.0008; // width in eta is nearly 0.2, but width in theta = 2*atan(e^-eta) will vary. Take biggest one, which is at eta of 0 when width is 0.02, so get 0.02**2 = 0.0004, increase a bit = double
  (cov)(4,4) *= 0.36; // qop also varies with eta. Error on q/pt conservatively = 0.0003 in mev ^-1, or 0.3 in gev ^-1, double to start giving us 0.6. then square that to get 0.36
 
 
    
  // some ACTS paperwork 
  Trk::ParticleHypothesis hypothesis = Trk::pion;
  float mass = Trk::ParticleMasses::mass[hypothesis] * Acts::UnitConstants::MeV;
  Acts::PdgParticle absPdg = Acts::makeAbsolutePdgParticle(Acts::ePionPlus);
  Acts::ParticleHypothesis actsHypothesis{
    absPdg, mass, Acts::AnyCharge{1.0f}};
 
  return std::make_unique<Acts::BoundTrackParameters>(actsSurface, params,
                                    cov, actsHypothesis);
 
}