the AtlasStepper implementation for the More...

#include <Acts/Propagator/AtlasStepper.hpp>

Classes
struct	Config
struct	Options
struct	State
	Nested State struct for the local caching. More...

Public Types
using	BoundState = std::tuple<BoundTrackParameters, Jacobian, double>
	Type alias for bound state (parameters, jacobian, path length).
using	Covariance = BoundSquareMatrix
	Type alias for covariance matrix.
using	Jacobian = BoundMatrix
	Type alias for Jacobian matrix.

Public Member Functions
	AtlasStepper (const Config &config)
	Construct AtlasStepper with configuration.
	AtlasStepper (std::shared_ptr< const MagneticFieldProvider > bField)
	Construct AtlasStepper with magnetic field provider.
double	absoluteMomentum (const State &state) const
	Absolute momentum accessor.
Result< BoundState >	boundState (State &state, const Surface &surface, bool transportCov=true, const FreeToBoundCorrection &freeToBoundCorrection=FreeToBoundCorrection(false)) const
	Create and return the bound state at the current position.
double	charge (const State &state) const
	Charge access.
BoundState	curvilinearState (State &state, bool transportCov=true) const
	Create and return a curvilinear state at the current position.
Vector3	direction (const State &state) const
	Get particle direction from stepper state.
Result< Vector3 >	getField (State &state, const Vector3 &pos) const
	Get the field for the stepping It checks first if the access is still within the Cell, and updates the cell if necessary, then it takes the field from the cell.
double	getStepSize (const State &state, ConstrainedStep::Type stype) const
	Get the step size.
void	initialize (State &state, const BoundTrackParameters &par) const
	Initialize stepper state from bound track parameters.
void	initialize (State &state, const BoundVector &boundParams, const std::optional< BoundMatrix > &cov, ParticleHypothesis particleHypothesis, const Surface &surface) const
	Initialize stepper state from individual parameters.
State	makeState (const Options &options) const
	Create stepper state with given options.
Vector3	momentum (const State &state) const
	Get 3D momentum vector from stepper state.
std::string	outputStepSize (const State &state) const
	Output the Step Size - single component.
double	overstepLimit (const State &) const
	Overstep limit.
const ParticleHypothesis &	particleHypothesis (const State &state) const
	Particle hypothesis.
Vector3	position (const State &state) const
	Get particle position from stepper state.
bool	prepareCurvilinearState (State &state) const
	If necessary fill additional members needed for curvilinearState.
double	qOverP (const State &state) const
	Get charge over momentum from stepper state.
void	releaseStepSize (State &state, ConstrainedStep::Type stype) const
	Release the Step size.
void	setIdentityJacobian (State &state) const
	Method that reset the Jacobian to the Identity for when no bound state are available.
Result< double >	step (State &state, Direction propDir, const IVolumeMaterial *material) const
	Perform the actual step on the state.
double	time (const State &state) const
	Time access.
void	transportCovarianceToBound (State &state, const Surface &surface, const FreeToBoundCorrection &=FreeToBoundCorrection(false)) const
	Method for on-demand transport of the covariance to a new curvilinear frame at current position, or direction of the state.
void	transportCovarianceToCurvilinear (State &state) const
	Method for on-demand transport of the covariance to a new curvilinear frame at current position, or direction of the state.
void	update (State &state, const FreeVector &parameters, const BoundVector &boundParams, const Covariance &covariance, const Surface &surface) const
	The state update method.
void	update (State &state, const Vector3 &uposition, const Vector3 &udirection, double qop, double time) const
	Method to update momentum, direction and p.
void	updateStepSize (State &state, const NavigationTarget &target, Direction direction, ConstrainedStep::Type stype) const
	Update step size.
void	updateStepSize (State &state, double stepSize, ConstrainedStep::Type stype) const
	Update step size - explicitly with a double.
IntersectionStatus	updateSurfaceStatus (State &state, const Surface &surface, std::uint8_t index, Direction navDir, const BoundaryTolerance &boundaryTolerance, double surfaceTolerance, ConstrainedStep::Type stype, const Logger &logger=getDummyLogger()) const
	Update surface status.

Detailed Description

the AtlasStepper implementation for the

This is based original stepper code from the ATLAS RungeKuttaPropagator

Member Typedef Documentation

◆ BoundState

using Acts::AtlasStepper::BoundState = std::tuple<BoundTrackParameters, Jacobian, double>

Type alias for bound state (parameters, jacobian, path length).

◆ Covariance

using Acts::AtlasStepper::Covariance = BoundSquareMatrix

Type alias for covariance matrix.

◆ Jacobian

using Acts::AtlasStepper::Jacobian = BoundMatrix

Type alias for Jacobian matrix.

Constructor & Destructor Documentation

◆ AtlasStepper() [1/2]

Acts::AtlasStepper::AtlasStepper ( std::shared_ptr< const MagneticFieldProvider > bField )

explicit

Construct AtlasStepper with magnetic field provider.

Parameters

bField Shared pointer to magnetic field provider

◆ AtlasStepper() [2/2]

Acts::AtlasStepper::AtlasStepper ( const Config & config )

explicit

Construct AtlasStepper with configuration.

Parameters

config Configuration containing magnetic field provider and other settings

Member Function Documentation

◆ absoluteMomentum()

double Acts::AtlasStepper::absoluteMomentum ( const State & state ) const

Absolute momentum accessor.

Parameters

state [in] The stepping state (thread-local cache)

Returns: Absolute momentum magnitude

◆ boundState()

Result< BoundState > Acts::AtlasStepper::boundState	(	State &	state,
		const Surface &	surface,
		bool	transportCov = true,
		const FreeToBoundCorrection &	freeToBoundCorrection = FreeToBoundCorrection(false) ) const

Create and return the bound state at the current position.

Parameters

[in]	state	State that will be presented as `BoundState`
[in]	surface	The surface to which we bind the state
[in]	transportCov	Flag steering covariance transport
[in]	freeToBoundCorrection	Correction for non-linearity effect during transform from free to bound

Returns

A bound state:

the parameters at the surface
the stepwise jacobian towards it
and the path length (from start - for ordering)

◆ charge()

double Acts::AtlasStepper::charge ( const State & state ) const

Charge access.

Parameters

state [in] The stepping state (thread-local cache)

Returns: Electric charge of the particle

◆ curvilinearState()

BoundState Acts::AtlasStepper::curvilinearState	(	State &	state,
		bool	transportCov = true ) const

Create and return a curvilinear state at the current position.

Parameters

[in]	state	State that will be presented as `CurvilinearState`
[in]	transportCov	Flag steering covariance transport

Returns

A curvilinear state:

the curvilinear parameters at given position
the stepweise jacobian towards it
and the path length (from start - for ordering)

◆ direction()

Vector3 Acts::AtlasStepper::direction ( const State & state ) const

Get particle direction from stepper state.

Parameters

state Stepper state containing track information

Returns: 3D unit direction vector

◆ getField()

Result< Vector3 > Acts::AtlasStepper::getField	(	State &	state,
		const Vector3 &	pos ) const

Get the field for the stepping It checks first if the access is still within the Cell, and updates the cell if necessary, then it takes the field from the cell.

Parameters

[in,out]	state	is the stepper state associated with the track the magnetic field cell is used (and potentially updated)
[in]	pos	is the field position

Returns: Magnetic field vector at the given position or error

◆ getStepSize()

double Acts::AtlasStepper::getStepSize	(	const State &	state,
		ConstrainedStep::Type	stype ) const

Get the step size.

Parameters

state	[in] The stepping state (thread-local cache)
stype	[in] The step size type to be returned

Returns: Current step size for the specified constraint type

◆ initialize() [1/2]

void Acts::AtlasStepper::initialize	(	State &	state,
		const BoundTrackParameters &	par ) const

Initialize stepper state from bound track parameters.

Parameters

state	Stepper state to initialize
par	Bound track parameters containing initial conditions

◆ initialize() [2/2]

void Acts::AtlasStepper::initialize	(	State &	state,
		const BoundVector &	boundParams,
		const std::optional< BoundMatrix > &	cov,
		ParticleHypothesis	particleHypothesis,
		const Surface &	surface ) const

Initialize stepper state from individual parameters.

Parameters

state	Stepper state to initialize
boundParams	Bound track parameter vector
cov	Optional covariance matrix
particleHypothesis	Particle hypothesis (mass, charge)
surface	Reference surface for bound parameters

◆ makeState()

State Acts::AtlasStepper::makeState ( const Options & options ) const

Create stepper state with given options.

Parameters

options Stepper options including magnetic field context

Returns: Stepper state initialized with options and magnetic field cache

◆ momentum()

Vector3 Acts::AtlasStepper::momentum ( const State & state ) const

Get 3D momentum vector from stepper state.

Parameters

state Stepper state containing track information

Returns: 3D momentum vector

◆ outputStepSize()

std::string Acts::AtlasStepper::outputStepSize ( const State & state ) const

Output the Step Size - single component.

Parameters

[in,out] state The stepping state (thread-local cache)

Returns: String representation of the current step size

◆ overstepLimit()

double Acts::AtlasStepper::overstepLimit ( const State & ) const

Overstep limit.

Returns: Overstep limit for this stepper (negative value)

◆ particleHypothesis()

const ParticleHypothesis & Acts::AtlasStepper::particleHypothesis ( const State & state ) const

Particle hypothesis.

Parameters

state [in] The stepping state (thread-local cache)

Returns: Reference to the particle hypothesis used

◆ position()

Vector3 Acts::AtlasStepper::position ( const State & state ) const

Get particle position from stepper state.

Parameters

state Stepper state containing track information

Returns: 3D position vector

◆ prepareCurvilinearState()

bool Acts::AtlasStepper::prepareCurvilinearState ( State & state ) const

If necessary fill additional members needed for curvilinearState.

Compute path length derivatives in case they have not been computed yet, which is the case if no step has been executed yet.

Parameters

[in,out] state The stepping state (thread-local cache)

Returns: true if nothing is missing after this call, false otherwise.

◆ qOverP()

double Acts::AtlasStepper::qOverP ( const State & state ) const

Get charge over momentum from stepper state.

Parameters

state Stepper state containing track information

Returns: Charge over momentum (q/p)

◆ releaseStepSize()

void Acts::AtlasStepper::releaseStepSize	(	State &	state,
		ConstrainedStep::Type	stype ) const

Release the Step size.

Parameters

[in,out]	state	The stepping state (thread-local cache)
[in]	stype	The step size type to be released

◆ setIdentityJacobian()

void Acts::AtlasStepper::setIdentityJacobian ( State & state ) const

Method that reset the Jacobian to the Identity for when no bound state are available.

Parameters

[in,out] state State of the stepper

◆ step()

Result< double > Acts::AtlasStepper::step	(	State &	state,
		Direction	propDir,
		const IVolumeMaterial *	material ) const

Perform the actual step on the state.

Parameters

[in,out]	state	State of the stepper
	propDir	is the direction of propagation
	material	is the optional volume material we are stepping through.

Returns: the result of the step

Note: The state contains the desired step size. It can be negative during backwards track propagation, and since we're using an adaptive algorithm, it can be modified by the stepper class during propagation.

◆ time()

double Acts::AtlasStepper::time ( const State & state ) const

Time access.

Parameters

state The stepping state to get time from

Returns: Current time coordinate

◆ transportCovarianceToBound()

void Acts::AtlasStepper::transportCovarianceToBound	(	State &	state,
		const Surface &	surface,
		const FreeToBoundCorrection &	= FreeToBoundCorrection(false) ) const

Method for on-demand transport of the covariance to a new curvilinear frame at current position, or direction of the state.

Parameters

[in,out]	state	State of the stepper
[in]	surface	is the surface to which the covariance is forwarded to

◆ transportCovarianceToCurvilinear()

void Acts::AtlasStepper::transportCovarianceToCurvilinear ( State & state ) const

Method for on-demand transport of the covariance to a new curvilinear frame at current position, or direction of the state.

Parameters

[in,out] state State of the stepper

◆ update() [1/2]

void Acts::AtlasStepper::update	(	State &	state,
		const FreeVector &	parameters,
		const BoundVector &	boundParams,
		const Covariance &	covariance,
		const Surface &	surface ) const

The state update method.

Parameters

[in,out]	state	The stepper state for
[in]	parameters	The new free track parameters at start
[in]	boundParams	Corresponding bound parameters
[in]	covariance	The updated covariance matrix
[in]	surface	The surface used to update the pVector

◆ update() [2/2]

void Acts::AtlasStepper::update	(	State &	state,
		const Vector3 &	uposition,
		const Vector3 &	udirection,
		double	qop,
		double	time ) const

Method to update momentum, direction and p.

Parameters

state	The state object
uposition	the updated position
udirection	the updated direction
qop	the updated momentum value
time	the update time

◆ updateStepSize() [1/2]

void Acts::AtlasStepper::updateStepSize	(	State &	state,
		const NavigationTarget &	target,
		Direction	direction,
		ConstrainedStep::Type	stype ) const

Update step size.

It checks the status to the reference surface & updates the step size accordingly

Parameters

state	[in,out] The stepping state (thread-local cache)
target	[in] The NavigationTarget
direction	[in] The propagation direction
stype	[in] The step size type to be set

◆ updateStepSize() [2/2]

void Acts::AtlasStepper::updateStepSize	(	State &	state,
		double	stepSize,
		ConstrainedStep::Type	stype ) const

Update step size - explicitly with a double.

Parameters

[in,out]	state	The stepping state (thread-local cache)
[in]	stepSize	The step size value
[in]	stype	The step size type to be set

◆ updateSurfaceStatus()

IntersectionStatus Acts::AtlasStepper::updateSurfaceStatus	(	State &	state,
		const Surface &	surface,
		std::uint8_t	index,
		Direction	navDir,
		const BoundaryTolerance &	boundaryTolerance,
		double	surfaceTolerance,
		ConstrainedStep::Type	stype,
		const Logger &	logger = getDummyLogger() ) const

Update surface status.

This method intersect the provided surface and update the navigation step estimation accordingly (hence it changes the state). It also returns the status of the intersection to trigger onSurface in case the surface is reached.

Parameters

[in,out]	state	The stepping state (thread-local cache)
[in]	surface	The surface provided
[in]	index	The surface intersection index
[in]	navDir	The navigation direction
[in]	boundaryTolerance	The boundary check for this status update
[in]	surfaceTolerance	Surface tolerance used for intersection
[in]	stype	The step size type to be set
[in]	logger	Logger instance to use

Returns: IntersectionStatus indicating how the surface was encountered

Classes

Public Types

Public Member Functions

Detailed Description

Member Typedef Documentation

◆ BoundState

◆ Covariance

◆ Jacobian

Constructor & Destructor Documentation

◆ AtlasStepper() [1/2]

◆ AtlasStepper() [2/2]

Member Function Documentation

◆ absoluteMomentum()

◆ boundState()

◆ charge()

◆ curvilinearState()

◆ direction()

◆ getField()

◆ getStepSize()

◆ initialize() [1/2]

◆ initialize() [2/2]

◆ makeState()

◆ momentum()

◆ outputStepSize()

◆ overstepLimit()

◆ particleHypothesis()

◆ position()

◆ prepareCurvilinearState()

◆ qOverP()

◆ releaseStepSize()

◆ setIdentityJacobian()

◆ step()

◆ time()

◆ transportCovarianceToBound()

◆ transportCovarianceToCurvilinear()

◆ update() [1/2]

◆ update() [2/2]

◆ updateStepSize() [1/2]

◆ updateStepSize() [2/2]

◆ updateSurfaceStatus()