Package org.hipparchus.ode.events

Class AbstractODEDetector<T extends AbstractODEDetector<T>>

java.lang.Object

org.hipparchus.ode.events.AbstractODEDetector<T>

Type Parameters:

T - type of the detector

All Implemented Interfaces:

ODEEventDetector

Direct Known Subclasses:

EventSlopeFilter

public abstract class AbstractODEDetector<T extends AbstractODEDetector<T>>
extends Object
implements ODEEventDetector

Base class for #@link ODEEventDetector.

Since:

3.0

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_MAX_ITER	Default maximum number of iterations in the event time search.
static final double	DEFAULT_MAXCHECK	Default maximum checking interval (s).
static final double	DEFAULT_THRESHOLD	Default convergence threshold (s).

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractODEDetector(AdaptableInterval maxCheck, int maxIter, BracketedUnivariateSolver<UnivariateFunction> solver, ODEEventHandler handler)	Build a new instance.

Method Summary

Modifier and Type	Method	Description
protected abstract T	create(AdaptableInterval newMaxCheck, int newmaxIter, BracketedUnivariateSolver<UnivariateFunction> newSolver, ODEEventHandler newHandler)	Build a new instance.
abstract double	g(ODEStateAndDerivative s)	Compute the value of the switching function.
ODEEventHandler	getHandler()	Get the underlying event handler.
AdaptableInterval	getMaxCheckInterval()	Get the maximal time interval between events handler checks.
int	getMaxIterationCount()	Get the upper limit in the iteration count for event localization.
BracketedUnivariateSolver<UnivariateFunction>	getSolver()	Get the root-finding algorithm to use to detect state events.
void	init(ODEStateAndDerivative s0, double t)	Initialize event handler at the start of an ODE integration.
boolean	isForward()	Check if the current propagation is forward or backward.
T	withHandler(ODEEventHandler newHandler)	Setup the event handler to call at event occurrences.
T	withMaxCheck(double newMaxCheck)	Setup the maximum checking interval.
T	withMaxCheck(AdaptableInterval newMaxCheck)	Setup the maximum checking interval.
T	withMaxIter(int newMaxIter)	Setup the maximum number of iterations in the event time search.
T	withSolver(BracketedUnivariateSolver<UnivariateFunction> newSolver)	Setup the root-finding algorithm to use to detect state events.
T	withThreshold(double newThreshold)	Setup the convergence threshold.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DEFAULT_MAXCHECK

public static final double DEFAULT_MAXCHECK

Default maximum checking interval (s).

See Also:

• Constant Field Values

DEFAULT_THRESHOLD

public static final double DEFAULT_THRESHOLD

Default convergence threshold (s).

See Also:

• Constant Field Values

DEFAULT_MAX_ITER

public static final int DEFAULT_MAX_ITER

Default maximum number of iterations in the event time search.

See Also:

• Constant Field Values

Constructor Details

AbstractODEDetector

protected AbstractODEDetector(AdaptableInterval maxCheck,
 int maxIter,
 BracketedUnivariateSolver<UnivariateFunction> solver,
 ODEEventHandler handler)

Build a new instance.

Parameters:

maxCheck - maximum checking interval, must be strictly positive (s)

maxIter - maximum number of iterations in the event time search

solver - root-finding algorithm to use to detect state events

handler - event handler to call at event occurrences

Method Details

init

public void init(ODEStateAndDerivative s0,
 double t)

Initialize event handler at the start of an ODE integration.

This method is called once at the start of the integration. It may be used by the event handler to initialize some internal data if needed.

The default implementation does nothing

This implementation sets the direction of integration and initializes the event handler. If a subclass overrides this method it should call super.init(s0, t).

Specified by:

init in interface ODEEventDetector

Parameters:

s0 - initial time, state vector and derivative

t - target time for the integration

g

public abstract double g(ODEStateAndDerivative s)

Compute the value of the switching function.

The discrete events are generated when the sign of this switching function changes. The integrator will take care to change the stepsize in such a way these events occur exactly at step boundaries. The switching function must be continuous in its roots neighborhood (but not necessarily smooth), as the integrator will need to find its roots to locate precisely the events.

Also note that for the integrator to detect an event the sign of the switching function must have opposite signs just before and after the event. If this consistency is not preserved the integrator may not detect any events.

This need for consistency is sometimes tricky to achieve. A typical example is using an event to model a ball bouncing on the floor. The first idea to represent this would be to have g(state) = h(state) where h is the height above the floor at time state.getTime(). When g(state) reaches 0, the ball is on the floor, so it should bounce and the typical way to do this is to reverse its vertical velocity. However, this would mean that before the event g(state) was decreasing from positive values to 0, and after the event g(state) would be increasing from 0 to positive values again. Consistency is broken here! The solution here is to have g(state) = sign * h(state), where sign is a variable with initial value set to +1. Each time eventOccurred is called, sign is reset to -sign. This allows the g(state) function to remain continuous (and even smooth) even across events, despite h(state) is not. Basically, the event is used to fold h(state) at bounce points, and sign is used to unfold it back, so the solvers sees a g(state) function which behaves smoothly even across events.

This method is idempotent, that is calling this multiple times with the same state will result in the same value, with two exceptions. First, the definition of the g function may change when an event occurs on the handler, as in the above example. Second, the definition of the g function may change when the eventOccurred method of any other event handler in the same integrator returns Action.RESET_EVENTS, Action.RESET_DERIVATIVES, or Action.RESET_STATE.

Specified by:

g in interface ODEEventDetector

Parameters:

s - current value of the independent time variable, state vector and derivative

Returns:

value of the g switching function

See Also:

• org.hipparchus.ode.events

getMaxCheckInterval

public AdaptableInterval getMaxCheckInterval()

Get the maximal time interval between events handler checks.

Specified by:

getMaxCheckInterval in interface ODEEventDetector

Returns:

maximal time interval between events handler checks

getMaxIterationCount

public int getMaxIterationCount()

Get the upper limit in the iteration count for event localization.

Specified by:

getMaxIterationCount in interface ODEEventDetector

Returns:

upper limit in the iteration count for event localization

getSolver

public BracketedUnivariateSolver<UnivariateFunction> getSolver()

Get the root-finding algorithm to use to detect state events.

Specified by:

getSolver in interface ODEEventDetector

Returns:

root-finding algorithm to use to detect state events

withMaxCheck

public T withMaxCheck(double newMaxCheck)

Setup the maximum checking interval.

This will override a maximum checking interval if it has been configured previously.

Parameters:

newMaxCheck - maximum checking interval

Returns:

a new detector with updated configuration (the instance is not changed)

withMaxCheck

public T withMaxCheck(AdaptableInterval newMaxCheck)

Setup the maximum checking interval.

This will override a maximum checking interval if it has been configured previously.

Parameters:

newMaxCheck - maximum checking interval

Returns:

a new detector with updated configuration (the instance is not changed)

Since:

3.0

withMaxIter

public T withMaxIter(int newMaxIter)

Setup the maximum number of iterations in the event time search.

This will override a number of iterations if it has been configured previously.

Parameters:

newMaxIter - maximum number of iterations in the event time search

Returns:

a new detector with updated configuration (the instance is not changed)

withThreshold

public T withThreshold(double newThreshold)

Setup the convergence threshold.

This is equivalent to call withSolver(new BracketingNthOrderBrentSolver(0, newThreshold, 0, 5)), so it will override a solver if one has been configured previously.

Parameters:

newThreshold - convergence threshold

Returns:

a new detector with updated configuration (the instance is not changed)

See Also:

• withSolver(BracketedUnivariateSolver)

withSolver

public T withSolver(BracketedUnivariateSolver<UnivariateFunction> newSolver)

Setup the root-finding algorithm to use to detect state events.

This will override a solver if it has been configured previously.

Parameters:

newSolver - root-finding algorithm to use to detect state events

Returns:

a new detector with updated configuration (the instance is not changed)

See Also:

• withThreshold(double)

withHandler

public T withHandler(ODEEventHandler newHandler)

Setup the event handler to call at event occurrences.

This will override a handler if it has been configured previously.

Parameters:

newHandler - event handler to call at event occurrences

Returns:

a new detector with updated configuration (the instance is not changed)

getHandler

public ODEEventHandler getHandler()

Get the underlying event handler.

Specified by:

getHandler in interface ODEEventDetector

Returns:

underlying event handler

create

protected abstract T create(AdaptableInterval newMaxCheck,
 int newmaxIter,
 BracketedUnivariateSolver<UnivariateFunction> newSolver,
 ODEEventHandler newHandler)

Build a new instance.

Parameters:

newMaxCheck - maximum checking interval

newmaxIter - maximum number of iterations in the event time search

newSolver - root-finding algorithm to use to detect state events

newHandler - event handler to call at event occurrences

Returns:

a new instance of the appropriate sub-type

isForward

public boolean isForward()

Check if the current propagation is forward or backward.

Returns:

true if the current propagation is forward