File StraightLineStepper.hpp¶
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namespace Acts
Note
This file is foreseen for the
Geometry
module to replaceExtent
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class StraightLineStepper
- #include <Acts/Propagator/StraightLineStepper.hpp>
straight line stepper based on Surface intersection
The straight line stepper is a simple navigation stepper to be used to navigate through the tracking geometry. It can be used for simple material mapping, navigation validation
Public Types
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using BField = NullBField
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using BoundState = std::tuple<BoundTrackParameters, Jacobian, double>
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using Covariance = BoundSymMatrix
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using CurvilinearState = std::tuple<CurvilinearTrackParameters, Jacobian, double>
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using Jacobian = BoundMatrix
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using state_type = State
Always use the same propagation state type, independently of the initial track parameter type and of the target surface.
Public Functions
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StraightLineStepper() = default
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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.
It does not check if the transported state is at the surface, this needs to be guaranteed by the propagator
- Parameters
state – [in] State that will be presented as
BoundState
surface – [in] The surface to which we bind the state
transportCov – [in] Flag steering covariance transport
freeToBoundCorrection – [in] 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 (from last bound)
and the path length (from start - for ordering)
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inline double charge(const State &state) const
Charge access.
- Parameters
state – [in] The stepping state (thread-local cache)
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CurvilinearState curvilinearState(State &state, bool transportCov = true) const
Create and return a curvilinear state at the current position.
This creates a curvilinear state.
- Parameters
state – [in] State that will be presented as
CurvilinearState
transportCov – [in] Flag steering covariance transport
- Returns
A curvilinear state:
the curvilinear parameters at given position
the stepweise jacobian towards it (from last bound)
and the path length (from start - for ordering)
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inline Vector3 direction(const State &state) const
Momentum direction accessor.
- Parameters
state – [in] The stepping state (thread-local cache)
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inline Result<Vector3> getField(State &state, const Vector3 &pos) const
Get the field for the stepping, this gives back a zero field.
- Parameters
state – [inout] is the propagation state associated with the track the magnetic field cell is used (and potentially updated)
pos – [in] is the field position
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inline double 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
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inline double momentum(const State &state) const
Absolute momentum accessor.
- Parameters
state – [in] The stepping state (thread-local cache)
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inline std::string outputStepSize(const State &state) const
Output the Step Size - single component.
- Parameters
state – [in,out] The stepping state (thread-local cache)
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inline double overstepLimit(const State &state) const
Overstep limit.
- Parameters
state – The stepping state (thread-local cache)
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inline Vector3 position(const State &state) const
Global particle position accessor.
- Parameters
state – [in] The stepping state (thread-local cache)
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inline void releaseStepSize(State &state) const
Release the Step size.
- Parameters
state – [in,out] The stepping state (thread-local cache)
Resets the state.
- Parameters
state – [inout] State of the stepper
boundParams – [in] Parameters in bound parametrisation
cov – [in] Covariance matrix
surface – [in] The reset
State
will be on this surfacenavDir – [in] Navigation direction
stepSize – [in] Step size
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inline void setStepSize(State &state, double stepSize, ConstrainedStep::Type stype = ConstrainedStep::actor, bool release = true) const
Set Step size - explicitely with a double.
- Parameters
state – [in,out] The stepping state (thread-local cache)
stepSize – [in] The step size value
stype – [in] The step size type to be set
release – [in] Do we release the step size?
Perform a straight line propagation step.
- Parameters
state – [inout] is the propagation state associated with the track parameters that are being propagated. 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.
- Returns
the step size taken
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inline double time(const State &state) const
Time access.
- Parameters
state – [in] The stepping state (thread-local cache)
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void transportCovarianceToBound(State &state, const Surface &surface, const FreeToBoundCorrection &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 - for the moment a dummy method.
Note
no check is done if the position is actually on the surface
- Template Parameters
surface_t – the surface type - ignored here
- Parameters
state – [inout] The stepper state
surface – [in] is the surface to which the covariance is forwarded to
freeToBoundCorrection – [in] Correction for non-linearity effect during transform from free to bound
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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 - for the moment a dummy method.
- Parameters
state – [inout] State of the stepper
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void update(State &state, const FreeVector &freeParams, const BoundVector &boundParams, const Covariance &covariance, const Surface &surface) const
Method to update a stepper state to the some parameters.
- Parameters
state – [inout] State object that will be updated
freeParams – [in] Free parameters that will be written into
state
boundParams – [in] Corresponding bound parameters used to update jacToGlobal in
state
covariance – [in] Covariance that willl be written into
state
surface – [in] The surface used to update the jacToGlobal
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void update(State &state, const Vector3 &uposition, const Vector3 &udirection, double up, double time) const
Method to update momentum, direction and p.
- Parameters
state – [inout] State object that will be updated
uposition – [in] the updated position
udirection – [in] the updated direction
up – [in] the updated momentum value
time – [in] the updated time value
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template<typename object_intersection_t>
inline void updateStepSize(State &state, const object_intersection_t &oIntersection, bool release = true) 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)
oIntersection – [in] The ObjectIntersection to layer, boundary, etc
release – [in] boolean to trigger step size release
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inline Intersection3D::Status updateSurfaceStatus(State &state, const Surface &surface, const BoundaryCheck &bcheck, const Logger &logger = getDummyLogger()) const
Update surface status.
This method intersects 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
state – [inout] The stepping state (thread-local cache)
surface – [in] The surface provided
bcheck – [in] The boundary check for this status update
logger – [in] A logger instance
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struct State
- #include <Acts/Propagator/StraightLineStepper.hpp>
State for track parameter propagation.
Public Functions
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State() = delete
Constructor from the initial bound track parameters.
Note
the covariance matrix is copied when needed
- Template Parameters
charge_t – Type of the bound parameter charge
- Parameters
gctx – [in] is the context object for the geometry
mctx – [in] is the context object for the magnetic field
par – [in] The track parameters at start
ndir – [in] The navigation direction w.r.t momentum
ssize – [in] is the maximum step size
stolerance – [in] is the stepping tolerance
Public Members
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Covariance cov = Covariance::Zero()
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bool covTransport = false
Boolean to indiciate if you need covariance transport.
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FreeVector derivative = FreeVector::Zero()
The propagation derivative.
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std::reference_wrapper<const GeometryContext> geoContext
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BoundToFreeMatrix jacToGlobal = BoundToFreeMatrix::Zero()
Jacobian from local to the global frame.
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FreeMatrix jacTransport = FreeMatrix::Identity()
Pure transport jacobian part from runge kutta integration.
Navigation direction, this is needed for searching.
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FreeVector pars = FreeVector::Zero()
Internal free vector parameters.
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double pathAccumulated = 0.
accummulated path length state
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double previousStepSize = 0.
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double q = 1.
The charge as the free vector can be 1/p or q/p.
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ConstrainedStep stepSize
adaptive step size of the runge-kutta integration
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double tolerance = s_onSurfaceTolerance
The tolerance for the stepping.
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State() = delete
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using BField = NullBField
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class StraightLineStepper