Namespace Acts::Experimental

namespace Experimental

Enums

enum Chi2FitterError

Values:

enumerator NoMeasurementFound

enum GsfError

Values:

enumerator NavigationFailed

enumerator ComponentNumberMismatch

enumerator AllComponentsSteppingError

enumerator NoComponentCreated

enumerator NoStatesCreated

enumerator StartParametersNotOnStartSurface

enumerator PropagationEndedOnWrongSurface

enumerator LastStepParamsContainNan

enumerator SmoothingFailed

Functions

std::error_code make_error_code(Chi2FitterError e)

std::error_code make_error_code(GsfError e)

auto makeDefaultBetheHeitlerApprox()

Creates a AtlasBetheHeitlerApprox object based on an ATLAS configuration, that are stored as static data in the source code.

This may not be an optimal configuration, but should allow to run the GSF without the need to load files

template<int NComponents, int PolyDegree>
class AtlasBetheHeitlerApprox

#include <Acts/TrackFitting/BetheHeitlerApprox.hpp>

This class approximates the Bethe-Heitler distribution as a gaussian mixture.

To enable an approximation for continuous input variables, the weights, means and variances are internally parametrized as a Nth order polynomial.

Public Types

using Data = std::array<PolyData, NComponents>

Public Functions

inline constexpr AtlasBetheHeitlerApprox(const Data &low_data, const Data &high_data, bool low_transform, bool high_transform)

Construct the Bethe-Heitler approximation description.

Additional to the coefficients of the polynomials, the information whether these values need to be transformed beforehand must be given (see ATLAS code).

Parameters

• low_data – data for the lower x/x0 range

• high_data – data for the higher x/x0 range

• low_transform – wether the low data need to be transformed

• high_transform – wether the high data need to be transformed

inline auto mixture(ActsScalar x) const

Generates the mixture from the polynomials and reweights them, so that the sum of all weights is 1.

Parameters

x – pathlength in terms of the radiation length

inline constexpr auto numComponents() const

Returns the number of components the returned mixture will have.

inline constexpr bool validXOverX0(ActsScalar x) const

Checks if an input is valid for the parameterization.

Parameters

x – pathlength in terms of the radiation length

Public Static Functions

static inline auto loadFromFiles(const std::string &low_parameters_path, const std::string &high_parameters_path)

Loads a parameterization from a file according to the Atlas file description.

Parameters

• low_parameters_path – Path to the foo.par file that stores the parameterization for low x/x0

• high_parameters_path – Path to the foo.par file that stores the parameterization for high x/x0

Public Static Attributes

static constexpr double higherLimit = 0.20

static constexpr double lowerLimit = 0.10

static constexpr double noChangeLimit = 0.0001

static constexpr double singleGaussianLimit = 0.002

struct PolyData

#include <Acts/TrackFitting/BetheHeitlerApprox.hpp>

Public Members

std::array<ActsScalar, PolyDegree + 1> meanCoeffs

std::array<ActsScalar, PolyDegree + 1> varCoeffs

std::array<ActsScalar, PolyDegree + 1> weightCoeffs

struct BetheHeitlerApproxSingleCmp

#include <Acts/TrackFitting/BetheHeitlerApprox.hpp>

This class approximates the Bethe-Heitler with only one component.

This is mainly inside AtlasBetheHeitlerApprox, but can also be used as the only component approximation (then probably for debugging)

Public Functions

inline constexpr auto numComponents() const

Returns the number of components the returned mixture will have.

inline constexpr bool validXOverX0(ActsScalar x) const

Checks if an input is valid for the parameterization.

The threshold for x/x0 is 0.002 and orientates on the values used in ATLAS

Public Static Functions

static inline auto mixture(const ActsScalar x)

Returns array with length 1 containing a 1-component-representation of the Bethe-Heitler-Distribution.

Parameters

x – pathlength in terms of the radiation length

template<typename propagator_t, typename traj_t>
class Chi2Fitter

#include <Acts/TrackFitting/Chi2Fitter.hpp>

Chi2 fitter implementation.

Template Parameters

propagator_t – Type of the propagation class

Public Functions

inline Chi2Fitter(propagator_t pPropagator)

template<typename source_link_iterator_t, typename start_parameters_t, typename parameters_t = BoundTrackParameters>
inline Result<Chi2FitterResult<traj_t>> fit(source_link_iterator_t it, source_link_iterator_t end, const start_parameters_t &sParameters, const Chi2FitterOptions<traj_t> &chi2FitterOptions, std::shared_ptr<traj_t> trajectory = {}) const

Fit implementation of the GX2F.

Note

The input measurements are given in the form of SourceLink s. It’s the calibrators job to turn them into calibrated measurements used in the fit.

Template Parameters

• source_link_iterator_t – Iterator type used to pass source links

• start_parameters_t – Type of the initial parameters

• parameters_t – Type of parameters used for local parameters

Parameters

• it – Begin iterator for the fittable uncalibrated measurements

• end – End iterator for the fittable uncalibrated measurements

• sParameters – The initial track parameters

• chi2FitterOptions – Chi2FitterOptions steering the fit

• trajectory – Input trajectory storage to append into

Returns

the output as an output track

template<typename traj_t>
struct Chi2FitterExtensions

#include <Acts/TrackFitting/Chi2Fitter.hpp>

Extension struct which holds delegates to customize the GX2F behavior.

Public Types

using Calibrator = Delegate<void(const GeometryContext&, TrackStateProxy)>

using ConstTrackStateProxy = typename MultiTrajectory<traj_t>::ConstTrackStateProxy

using OutlierFinder = Delegate<bool(ConstTrackStateProxy)>

using Parameters = typename TrackStateProxy::Parameters

using TrackStateProxy = typename MultiTrajectory<traj_t>::TrackStateProxy

Public Functions

inline Chi2FitterExtensions()

Default constructor which connects the default void components.

Public Members

Calibrator calibrator

The Calibrator is a dedicated calibration algorithm that allows to calibrate measurements using track information, this could be e.g.

sagging for wires, module deformations, etc.

OutlierFinder outlierFinder

Determines whether a measurement is supposed to be considered as an outlier.

template<typename traj_t>
struct Chi2FitterOptions

#include <Acts/TrackFitting/Chi2Fitter.hpp>

Combined options for the GX2F fitter.

Template Parameters

traj_t – The trajectory type

Public Functions

inline Chi2FitterOptions(const GeometryContext &gctx, const MagneticFieldContext &mctx, std::reference_wrapper<const CalibrationContext> cctx, Chi2FitterExtensions<traj_t> extensions_, LoggerWrapper logger_, const PropagatorPlainOptions &pOptions, bool mScattering = false, bool eLoss = false, int nIter = 1, bool calcFinalChi2_ = true, const FreeToBoundCorrection &freeToBoundCorrection_ = FreeToBoundCorrection(false))

PropagatorOptions with context.

Parameters

• gctx – The goemetry context for this fit

• mctx – The magnetic context for this fit

• cctx – The calibration context for this fit

• extensions_ – The chi2 extensions

• logger_ – The logger wrapper

• pOptions – The plain propagator options

• mScattering – Whether to include multiple scattering

• eLoss – Whether to include energy loss

• nIter – Number of update steps to the parameters

• calcFinalChi2_ – Whether to run additional propagation to calculate final chi2

• freeToBoundCorrection_ – Correction for non-linearity effect during transform from free to bound

Chi2FitterOptions() = delete

Contexts are required and the options must not be default-constructible.

Public Members

bool calcFinalChi2 = true

Whether to do an additional propagation step, just to get the latest chi2 value.

std::reference_wrapper<const CalibrationContext> calibrationContext

context object for the calibration

bool energyLoss = false

Whether to consider energy loss.

Chi2FitterExtensions<traj_t> extensions

FreeToBoundCorrection freeToBoundCorrection

Whether to include non-linear correction during global to local transformation.

std::reference_wrapper<const GeometryContext> geoContext

Context object for the geometry.

LoggerWrapper logger

Logger.

std::reference_wrapper<const MagneticFieldContext> magFieldContext

Context object for the magnetic field.

bool multipleScattering = false

Whether to consider multiple scattering.

int nUpdates = 1

Number of iterations to improve chi2.

PropagatorPlainOptions propagatorPlainOptions

The trivial propagator options.

template<typename traj_t>
struct Chi2FitterResult

#include <Acts/TrackFitting/Chi2Fitter.hpp>

Public Members

ActsScalar chisquare = -1

std::vector<ActsScalar> chisquares

std::vector<ActsScalar> collectorCovariance

BoundVector collectorDerive1Chi2Sum = BoundVector::Zero()

first derivative of chi2 wrt starting track parameters

BoundMatrix collectorDerive2Chi2Sum = BoundMatrix::Zero()

std::vector<ActsScalar> collectorMeasurements

std::vector<ActsScalar> collectorResiduals

ActsDynamicMatrix covariance

bool finished = false

std::optional<BoundTrackParameters> fittedParameters

std::shared_ptr<traj_t> fittedStates

BoundMatrix jacobianFromStart = BoundMatrix::Identity()

size_t lastMeasurementIndex = SIZE_MAX

size_t lastTrackIndex = SIZE_MAX

size_t measurementHoles = 0

size_t measurementStates = 0

std::vector<const Surface*> missedActiveSurfaces

size_t processedStates = 0

ActsDynamicVector residuals

Result<void> result = {Result<void>::success()}

template<typename propagator_t, typename bethe_heitler_approx_t, typename traj_t>
struct GaussianSumFitter

#include <Acts/TrackFitting/GaussianSumFitter.hpp>

Gaussian Sum Fitter implementation.

Note

This GSF implementation tries to be as compatible to the KalmanFitter as possible. However, there are certain differences at the moment:

• There is always a backward pass during fitting.

• There are only measurement states in the result

• Passed-again-surfaces is always empty at the moment

• Probably some more differences which I don’t think of at the moment.

Template Parameters

• propagator_t – The propagator type on which the algorithm is built on

• bethe_heitler_approx_t – The type of the Bethe-Heitler-Approximation

• traj_t – The MultiTrajectory type (backend)

Public Types

using GsfActor = detail::GsfActor<bethe_heitler_approx_t, traj_t>

The actor type.

using GsfNavigator = typename propagator_t::Navigator

The navigator type.

Public Functions

inline GaussianSumFitter(propagator_t &&propagator, bethe_heitler_approx_t &&bha)

template<typename source_link_it_t, typename start_parameters_t>
inline Acts::Result<Acts::KalmanFitterResult<traj_t>> fit(source_link_it_t begin, source_link_it_t end, const start_parameters_t &sParameters, const GsfOptions<traj_t> &options, const std::vector<const Surface*> &sSequence, std::shared_ptr<traj_t> trajectory = {}) const

The fit function for the Direct navigator.

template<typename source_link_it_t, typename start_parameters_t>
inline Acts::Result<Acts::KalmanFitterResult<traj_t>> fit(source_link_it_t begin, source_link_it_t end, const start_parameters_t &sParameters, const GsfOptions<traj_t> &options, std::shared_ptr<traj_t> trajectory = {}) const

The fit function for the standard navigator.

template<typename source_link_it_t, typename start_parameters_t, typename fwd_prop_initializer_t, typename bwd_prop_initializer_t>
inline Acts::Result<Acts::KalmanFitterResult<traj_t>> fit_impl(source_link_it_t begin, source_link_it_t end, const start_parameters_t &sParameters, const GsfOptions<traj_t> &options, const fwd_prop_initializer_t &fwdPropInitializer, const bwd_prop_initializer_t &bwdPropInitializer, std::shared_ptr<traj_t> trajectory) const

The generic implementation of the fit function.

TODO check what this function does with the referenceSurface is e.g. the first measuerementSurface

Public Members

bethe_heitler_approx_t m_bethe_heitler_approx

The fitter holds the instance of the bethe heitler approx.

propagator_t m_propagator

The propagator instance used by the fit function.

template<typename traj_t>
struct GsfExtensions

#include <Acts/TrackFitting/GsfOptions.hpp>

The extensions needed for the GSF.

Public Types

using Calibrator = Delegate<void(const GeometryContext&, TrackStateProxy)>

using ConstTrackStateProxy = typename MultiTrajectory<traj_t>::ConstTrackStateProxy

using OutlierFinder = Delegate<bool(ConstTrackStateProxy)>

using TrackStateProxy = typename MultiTrajectory<traj_t>::TrackStateProxy

using Updater = Delegate<Result<void>(const GeometryContext&, TrackStateProxy, NavigationDirection, LoggerWrapper)>

Public Functions

inline GsfExtensions()

Default constructor which connects the default void components.

Public Members

Calibrator calibrator

The Calibrator is a dedicated calibration algorithm that allows to calibrate measurements using track information, this could be e.g.

sagging for wires, module deformations, etc.

OutlierFinder outlierFinder

Determines whether a measurement is supposed to be considered as an outlier.

Updater updater

The updater incorporates measurement information into the track parameters.

template<typename traj_t>
struct GsfOptions

#include <Acts/TrackFitting/GsfOptions.hpp>

Public Members

bool abortOnError = true

std::reference_wrapper<const CalibrationContext> calibrationContext

bool disableAllMaterialHandling = false

GsfExtensions<traj_t> extensions

std::reference_wrapper<const GeometryContext> geoContext

LoggerWrapper logger

std::reference_wrapper<const MagneticFieldContext> magFieldContext

std::size_t maxComponents = 4

PropagatorPlainOptions propagatorPlainOptions

const Surface *referenceSurface = nullptr