ActsFatrasSimTool.h

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef ISF_ACTSTOOLS_ACTSFATRASSIMTOOL_H
#define ISF_ACTSTOOLS_ACTSFATRASSIMTOOL_H
 
// Gaudi
#include "GaudiKernel/ServiceHandle.h"
#include "GaudiKernel/ToolHandle.h"
 
// Athena
#include "AthenaKernel/IAthRNGSvc.h"
#include "AthenaKernel/RNGWrapper.h"
#include "CxxUtils/checker_macros.h"
 
// ISF
#include "ISF_Event/ISFParticle.h"
#include "ISF_Interfaces/BaseSimulatorTool.h"
#include "ISF_Interfaces/IParticleFilter.h"
#include "ISF_Interfaces/ITruthSvc.h"
#include "ISF_Interfaces/IEntryLayerTool.h"
#include "ISF_Interfaces/IGeoIDSvc.h"
#include "ActsGeometryInterfaces/IExtrapolationTool.h"
#include "ActsFatrasWriteHandler.h"
 
// ACTS
#include "Acts/Utilities/UnitVectors.hpp"
#include "ActsInterop/Logger.h"
#include "ActsInterop/UnitConverters.h"
#include "Acts/Geometry/GeometryContext.hpp"
#include "Acts/MagneticField/MagneticFieldContext.hpp"
#include "Acts/EventData/BoundTrackParameters.hpp"
#include "Acts/Propagator/Navigator.hpp"
#include "Acts/Propagator/EigenStepper.hpp"
#include "Acts/Propagator/EigenStepperDefaultExtension.hpp"
#include "Acts/Propagator/StraightLineStepper.hpp"
#include "Acts/Propagator/detail/SteppingLogger.hpp"
#include "Acts/Propagator/ActorList.hpp"
#include "Acts/Propagator/Propagator.hpp"
#include "Acts/Definitions/ParticleData.hpp"
#include "ActsFatras/EventData/GenerationProcess.hpp"
#include "ActsFatras/Kernel/InteractionList.hpp"
#include "ActsFatras/Kernel/SingleParticleSimulation.hpp"
#include "ActsFatras/Kernel/SingleParticleSimulationResult.hpp"
#include "ActsFatras/Kernel/MultiParticleSimulation.hpp"
#include "ActsFatras/Physics/Decay/NoDecay.hpp"
#include "ActsFatras/Physics/StandardInteractions.hpp"
#include "ActsFatras/Physics/ElectroMagnetic/PhotonConversion.hpp"
#include "ActsFatras/Selectors/SurfaceSelectors.hpp"
// Tracking
#include "ActsGeometryInterfaces/ITrackingGeometryTool.h"
#include "ActsGeometry/ATLASMagneticFieldWrapper.h"
 
#include <algorithm>
#include <cassert>
#include <vector>
 
class AtlasDetectorID;
 
namespace iFatras {
  class ISimHitCreator;
}
 
namespace ISF {
class IParticleHelper;

 
class ActsFatrasSimTool : public BaseSimulatorTool {
 
 public:
  struct HitSurfaceSelector {
    bool operator()(const Acts::Surface &surface) const {
      return surface.isSensitive();
    }
  };
  // SingleParticleSimulation
  template <typename propagator_t, typename interactions_t,
            typename hit_surface_selector_t, typename decay_t>
  struct SingleParticleSimulation {
    propagator_t propagator;
    decay_t decay;
    interactions_t interactions;
    hit_surface_selector_t selectHitSurface;
    double maxStepSize = 3.0; // leght in m
    double maxStep = 1000;
    double maxRungeKuttaStepTrials = 10000;
    double pathLimit = 100.0; // lenght in cm
    bool   loopProtection = true;
    double loopFraction = 0.5;
    double targetTolerance = 0.0001;
    double stepSizeCutOff = 0.;
    // parameters for densEnv propagator options
    double meanEnergyLoss = true;
    bool   includeGgradient = true;
    double momentumCutOff = 0.;

    std::shared_ptr<const Acts::Logger> localLogger = nullptr;

    SingleParticleSimulation(propagator_t &&propagator_,
                            std::shared_ptr<const Acts::Logger> localLogger_)
        : propagator(propagator_), localLogger(localLogger_) {}

    const Acts::Logger &logger() const { return *localLogger; }

    template <typename generator_t>
    Acts::Result<ActsFatras::SingleParticleSimulationResult> simulate(
        const Acts::GeometryContext &geoCtx,
        const Acts::MagneticFieldContext &magCtx, generator_t &generator,
        const ActsFatras::Particle &particle) const {
      assert(localLogger and "Missing local logger");
      ACTS_VERBOSE("Using ActsFatrasSimTool simulate()");
      // propagator-related additional types
      using SteppingLogger = Acts::detail::SteppingLogger;
      using SimulationActor = ActsFatras::detail::SimulationActor<generator_t, decay_t, interactions_t, hit_surface_selector_t>;
      using Result = typename SimulationActor::result_type;
      using Actions = Acts::ActorList<SteppingLogger, SimulationActor, Acts::EndOfWorldReached>;
      using PropagatorOptions = typename propagator_t::template Options<Actions>;
 
      // Construct per-call options.
      PropagatorOptions options(geoCtx, magCtx);
      // setup the interactor as part of the propagator options
      auto &actor = options.actorList.template get<SimulationActor>();
      actor.generator = &generator;
      actor.decay = decay;
      actor.interactions = interactions;
      actor.selectHitSurface = selectHitSurface;
      actor.initialParticle = particle;
      // use AnyCharge to be able to handle neutral and charged parameters
      Acts::BoundTrackParameters startPoint = Acts::BoundTrackParameters::createCurvilinear(
          particle.fourPosition(), particle.direction(),
          particle.qOverP(), std::nullopt, particle.hypothesis());
      options.pathLimit = pathLimit * Acts::UnitConstants::cm;
      options.loopProtection = loopProtection;
      options.maxSteps = maxStep;
      options.stepping.maxStepSize = maxStepSize * Acts::UnitConstants::m;
      options.direction = Acts::Direction::Forward();
 
      auto result = propagator.propagate(startPoint, options);
      if (not result.ok()) {
        return result.error();
      }
      return result.value().template get<Result>();
    }
  };// end of SingleParticleSimulation
 
  // Standard generator
  using Generator = std::ranlux48;
  // Use default navigator
  using Navigator = Acts::Navigator;
  // Propagate charged particles numerically in the B-field
  using ChargedStepper = Acts::EigenStepper<Acts::EigenStepperDefaultExtension>;
  using ChargedPropagator = Acts::Propagator<ChargedStepper, Navigator>;
  // Propagate neutral particles in straight lines
  using NeutralStepper = Acts::StraightLineStepper;
  using NeutralPropagator = Acts::Propagator<NeutralStepper, Navigator>;
 
  // ===============================
  // Setup ActsFatras simulator types
  // Charged
  using ChargedSelector = ActsFatras::ChargedSelector;
  using ChargedInteractions =
          ActsFatras::StandardChargedElectroMagneticInteractions;
  using ChargedSimulation = SingleParticleSimulation<
          ChargedPropagator, ChargedInteractions, HitSurfaceSelector,
          ActsFatras::NoDecay>;
  // Neutral
  using NeutralSelector = ActsFatras::NeutralSelector;
  using NeutralInteractions = ActsFatras::InteractionList<ActsFatras::PhotonConversion>;
  using NeutralSimulation = SingleParticleSimulation<
          NeutralPropagator, NeutralInteractions, ActsFatras::NoSurface,
          ActsFatras::NoDecay>;
  // Combined
  using Simulation = ActsFatras::MultiParticleSimulation<
          ChargedSelector, ChargedSimulation,
          NeutralSelector, NeutralSimulation>;
  // ===============================
  inline Amg::Vector3D convertMom3FromActs(const Acts::Vector3& actsMom) {
    Amg::Vector3D threeMom{Amg::Vector3D::Zero()};
    threeMom[Amg::x] = ActsTrk::energyToAthena(actsMom[Acts::eMom0]);
    threeMom[Amg::y] = ActsTrk::energyToAthena(actsMom[Acts::eMom1]);
    threeMom[Amg::z] = ActsTrk::energyToAthena(actsMom[Acts::eMom2]);
    return threeMom;
  }
 
  inline Amg::Vector3D convertPos3FromActs(const Acts::Vector3& actsPos) {
    Amg::Vector3D pos{Amg::Vector3D::Zero()};
    pos[Amg::x] = ActsTrk::lengthToAthena(actsPos[Acts::ePos0]);
    pos[Amg::y] = ActsTrk::lengthToAthena(actsPos[Acts::ePos1]);
    pos[Amg::z] = ActsTrk::lengthToAthena(actsPos[Acts::ePos2]);
    return pos;
  }
 
  ActsFatrasSimTool(const std::string& type, const std::string& name,
                    const IInterface* parent);
  virtual ~ActsFatrasSimTool();
 
  // ISF BaseSimulatorTool Interface methods
  virtual StatusCode initialize() override;
  virtual StatusCode simulate(const EventContext& ctx, ISFParticle& isp, ISFParticleContainer&,
                              McEventCollection*) override;
  virtual StatusCode simulateVector(
            const EventContext& ctx,
            const ISFParticleVector& particles,
            ISFParticleContainer& secondaries,
            McEventCollection* mcEventCollection, McEventCollection *shadowTruth=nullptr) override;
  virtual StatusCode setupEvent(const EventContext&) override {
    ATH_CHECK(m_truthRecordSvc->initializeTruthCollection());
    m_pixelSiHits.Clear();
    m_sctSiHits.Clear();
    return StatusCode::SUCCESS; };
  virtual StatusCode releaseEvent(const EventContext& ctx) override {
    std::vector<SiHitCollection> hitcolls;
    hitcolls.push_back(m_pixelSiHits);
    hitcolls.push_back(m_sctSiHits);
    ATH_CHECK(m_ActsFatrasWriteHandler->WriteHits(hitcolls,ctx));
    ATH_CHECK(m_truthRecordSvc->releaseEvent());
    return StatusCode::SUCCESS; };
  virtual ISF::SimulationFlavor simFlavor() const override{
    return ISF::Fatras; };
 
  virtual Acts::MagneticFieldContext getMagneticFieldContext(
    const EventContext&) const;
 
 private:
  // For sihit creation
  SiHitCollection m_pixelSiHits;
  SiHitCollection m_sctSiHits;
  // Templated tool retrieval
  template <class T>
  StatusCode retrieveTool(ToolHandle<T>& thandle) {
    if (!thandle.empty() && thandle.retrieve().isFailure()) {
      ATH_MSG_FATAL("Cannot retrieve " << thandle << ". Abort.");
      return StatusCode::FAILURE;
    } else ATH_MSG_DEBUG("Successfully retrieved " << thandle);
    return StatusCode::SUCCESS;
  }
 
  bool checkStartSurface(const Acts::MagneticFieldContext& mctx,
                          const Acts::GeometryContext& anygctx,
                          const ChargedPropagator& chargedPropagator,
                          const Acts::BoundTrackParameters& startParameters,
                          Acts::Direction navDir = Acts::Direction::Forward(),
                          double pathLimit = std::numeric_limits<double>::max()) const;
 
  // Random number service
  ServiceHandle<IAthRNGSvc> m_rngSvc{this, "RNGService", "AthRNGSvc"};
  ATHRNG::RNGWrapper* m_randomEngine ATLAS_THREAD_SAFE {};
  Gaudi::Property<std::string> m_randomEngineName{this, "RandomEngineName",
    "RandomEngineName", "Name of random number stream"};
 
  // GeoID service
  ServiceHandle<ISF::IGeoIDSvc> m_geoIDSvc{this, "GeoIDSvc", "ISF::GeoIDSvc"};
 
  // ACTS Extrapolator
  PublicToolHandle<ActsTrk::IExtrapolationTool> m_extrapolationTool{this, "ExtrapolationTool", "ActsExtrapolationTool"};
 
  // Tracking geometry
  PublicToolHandle<ActsTrk::ITrackingGeometryTool> m_trackingGeometryTool{
      this, "TrackingGeometryTool", "ActsTrackingGeometryTool"};
  std::shared_ptr<const Acts::TrackingGeometry> m_trackingGeometry;
 
  // Magnetic field
  SG::ReadCondHandleKey<AtlasFieldCacheCondObj> m_fieldCacheCondObjInputKey {this, "AtlasFieldCacheCondObj", "fieldCondObj", "Name of the Magnetic Field conditions object key"};
 
  // Logging
  std::shared_ptr<const Acts::Logger> m_logger{nullptr};
 
  // ISF Tools
  PublicToolHandle<ISF::IParticleFilter> m_particleFilter{
      this, "ParticleFilter", "", "Particle filter kinematic cuts, etc."};
 
  ServiceHandle<ISF::ITruthSvc> m_truthRecordSvc{this, "TruthRecordService", "ISF_TruthRecordSvc", ""};
 
  // ActsFatrasHitConvtTool
  ToolHandle<ActsFatrasWriteHandler> m_ActsFatrasWriteHandler{
      this, "ActsFatrasWriteHandler", "ActsFatrasWriteHandler"};
 
  Gaudi::Property<double> m_interact_minPt{this, "Interact_MinPt", 50.0,
      "Min pT of the interactions (MeV)"};
 
  // DensEnviroment Propergator option
  Gaudi::Property<bool> m_meanEnergyLoss{this, "MeanEnergyLoss", true, "Toggle between mean and mode evaluation of energy loss"};
  Gaudi::Property<bool> m_includeGgradient{this, "IncludeGgradient", true, "Boolean flag for inclusion of d(dEds)d(q/p) into energy loss"};
  Gaudi::Property<double> m_momentumCutOff{this, "MomentumCutOff", 0., "Cut-off value for the momentum in SI units"};
  // Propergator option
  Gaudi::Property<double> m_maxStep{this, "MaxSteps", 1000,
       "Max number of steps"};
  Gaudi::Property<double> m_maxRungeKuttaStepTrials{this, "MaxRungeKuttaStepTrials", 10000,
       "Maximum number of Runge-Kutta steps for the stepper step call"};
  Gaudi::Property<double> m_maxStepSize{this, "MaxStepSize", 3.0,
      "Max step size (converted to Acts::UnitConstants::m)"};
  Gaudi::Property<double> m_pathLimit{this, "PathLimit", 100.0,
      "Track path limit (converted to Acts::UnitConstants::cm)"};
  Gaudi::Property<bool> m_loopProtection{this, "LoopProtection", true,
      "Loop protection, it adapts the pathLimit"};
  Gaudi::Property<double> m_loopFraction{this, "LoopFraction", 0.5,
      "Allowed loop fraction, 1 is a full loop"};
  Gaudi::Property<double> m_tolerance{this, "Tolerance", 0.0001,
       "Tolerance for the error of the integration"};
  Gaudi::Property<double> m_stepSizeCutOff{this, "StepSizeCutOff", 0.,
       "Cut-off value for the step size"};
 
  // https://vmc-project.github.io/geant4_vmc/g4vmc_html/TG4ProcessMapPhysics_8cxx_source.html#:~:text=155%20pMap%2D%3EAdd(DECAY,);%20//%20G4%20value:%20231
  Gaudi::Property<std::map<int,int>> m_processTypeMap{this, "ProcessTypeMap",
      {{0,0}, {1,201}, {2,14}, {3,3}, {4,121}}, "proessType map <ActsFatras,G4>"};
      //{{ActsFatras::GenerationProcess::eUndefined,0}, {ActsFatras::GenerationProcess::eDecay,201}, {ActsFatras::GenerationProcess::ePhotonConversion,14}, {ActsFatras::GenerationProcess::eBremsstrahlung,3}, {ActsFatras::GenerationProcess::eNuclearInteraction,121}}
  inline int getATLASProcessCode(ActsFatras::GenerationProcess actspt){return m_processTypeMap[static_cast<uint32_t>(actspt)];};
};
 
}  // namespace ISF
 
#endif