Acts::ConstrainedStep Class Reference

A constrained step class for the steppers. More...

#include <Acts/Propagator/ConstrainedStep.hpp>

Public Types
enum class	Type : int { Navigator = 0 , Actor = 1 , User = 2 }
	the types of constraints from navigator - this would be a navigation step from actor - this would be an actor condition from user - this is user given for what reason ever More...

Public Member Functions
constexpr	ConstrainedStep ()=default
constexpr	ConstrainedStep (double v)
	constructor
constexpr double	accuracy () const
	Access the accuracy value.
constexpr void	release (Type type)
	release a certain constraint value
constexpr void	releaseAccuracy ()
	release accuracy
constexpr void	setAccuracy (double v)
	set accuracy
constexpr void	setUser (double v)
	set user
std::ostream &	toStream (std::ostream &os) const
	Stream the constrained step into an output stream.
std::string	toString () const
	Convert the constrained step to a string representation.
constexpr void	update (double v, Type type)
	Update the step size of a certain type.
constexpr double	value () const
	returns the min step size
constexpr double	value (Type type) const
	Access a specific value.

Detailed Description

A constrained step class for the steppers.

This class is symmetrical for forward and backward propagation. The sign of the propagation direction should not enter here but rather be applied the step is actually taken.

As simple as this class looks it hides a few very important details:

• Overstepping handling. The step size sign will flip if we happened to pass our target.
• Convergence handling. Smaller and smaller step sizes have to be used in order to converge on a target.

Because of the points mentioned above, the update function will always prefer negative step sizes. A side effect of this is that we will propagate in the opposite direction if the target is "behind us".

The hierarchy is:

• Overstepping resolution / backpropagation
• Convergence
• Step into the void with std::numeric_limits<double>::max()

Member Enumeration Documentation

Type

enum class Acts::ConstrainedStep::Type : int

strong

the types of constraints from navigator - this would be a navigation step from actor - this would be an actor condition from user - this is user given for what reason ever

Enumerator
Navigator
Actor
User

Constructor & Destructor Documentation

ConstrainedStep() [1/2]

Acts::ConstrainedStep::ConstrainedStep ( )

constexprdefault

ConstrainedStep() [2/2]

Acts::ConstrainedStep::ConstrainedStep ( double v )

explicitconstexpr

constructor

Parameters

v	is the user given initial value

Member Function Documentation

accuracy()

double Acts::ConstrainedStep::accuracy ( ) const

constexpr

Access the accuracy value.

Returns

The step size accuracy constraint

release()

void Acts::ConstrainedStep::release ( Type type )

constexpr

release a certain constraint value

Parameters

type	is the constraint type to be released

releaseAccuracy()

void Acts::ConstrainedStep::releaseAccuracy ( )

constexpr

release accuracy

setAccuracy()

void Acts::ConstrainedStep::setAccuracy ( double v )

constexpr

set accuracy

this will set only the accuracy, as this is the most exposed to the Propagator

Parameters

v	is the new accuracy value

setUser()

void Acts::ConstrainedStep::setUser ( double v )

constexpr

set user

Parameters

v	is the new user value

toStream()

std::ostream & Acts::ConstrainedStep::toStream

(

std::ostream &

os

)

const

Stream the constrained step into an output stream.

Parameters

os	Output stream to write to

Returns

Reference to the output stream for chaining

toString()

std::string Acts::ConstrainedStep::toString

(

)

const

Convert the constrained step to a string representation.

Returns

String representation of the constrained step

update()

void Acts::ConstrainedStep::update ( double v, Type type )

constexpr

Update the step size of a certain type.

Only navigation and target abortion step size updates may change the sign due to overstepping

Parameters

v	is the new value to be updated
type	is the constraint type

value() [1/2]

double Acts::ConstrainedStep::value ( ) const

constexpr

returns the min step size

Returns

The minimum constrained step size considering all constraints

value() [2/2]

double Acts::ConstrainedStep::value ( Type type ) const

constexpr

Access a specific value.

Parameters

type	is the requested parameter type

Returns

The step size for the specified constraint type