org.apache.commons.math.ode
Class AbstractIntegrator

java.lang.Object
  org.apache.commons.math.ode.AbstractIntegrator

All Implemented Interfaces:

FirstOrderIntegrator, ODEIntegrator

Direct Known Subclasses:

AdaptiveStepsizeIntegrator, RungeKuttaIntegrator

public abstract class AbstractIntegrator
extends Object
implements FirstOrderIntegrator

Base class managing common boilerplate for all integrators.

Since:

2.0

Version:

$Revision: 1073267 $ $Date: 2011-02-22 10:06:20 +0100 (mar. 22 févr. 2011) $

Field Summary

protected boolean	isLastStep Indicator for last step.
protected boolean	resetOccurred Indicator that a state or derivative reset was triggered by some event.
protected Collection<StepHandler>	stepHandlers Step handler.
protected double	stepSize Current stepsize.
protected double	stepStart Current step start time.

Constructor Summary

protected	AbstractIntegrator() Build an instance with a null name.
	AbstractIntegrator(String name) Build an instance.

Method Summary

protected double	acceptStep(AbstractStepInterpolator interpolator, double[] y, double[] yDot, double tEnd) Accept a step, triggering events and step handlers.
protected CombinedEventsManager	addEndTimeChecker(double startTime, double endTime, CombinedEventsManager manager) Deprecated. as of 2.2, this method is not used any more
void	addEventHandler(EventHandler handler, double maxCheckInterval, double convergence, int maxIterationCount) Add an event handler to the integrator.
void	addStepHandler(StepHandler handler) Add a step handler to this integrator.
void	clearEventHandlers() Remove all the event handlers that have been added to the integrator.
void	clearStepHandlers() Remove all the step handlers that have been added to the integrator.
void	computeDerivatives(double t, double[] y, double[] yDot) Compute the derivatives and check the number of evaluations.
double	getCurrentSignedStepsize() Get the current signed value of the integration stepsize.
double	getCurrentStepStart() Get the current value of the step start time ti.
int	getEvaluations() Get the number of evaluations of the differential equations function.
Collection<EventHandler>	getEventHandlers() Get all the event handlers that have been added to the integrator.
int	getMaxEvaluations() Get the maximal number of functions evaluations.
String	getName() Get the name of the method.
Collection<StepHandler>	getStepHandlers() Get all the step handlers that have been added to the integrator.
protected boolean	requiresDenseOutput() Check if dense output is needed.
protected void	resetEvaluations() Reset the number of evaluations to zero.
protected void	sanityChecks(FirstOrderDifferentialEquations ode, double t0, double[] y0, double t, double[] y) Perform some sanity checks on the integration parameters.
protected void	setEquations(FirstOrderDifferentialEquations equations) Set the differential equations.
void	setMaxEvaluations(int maxEvaluations) Set the maximal number of differential equations function evaluations.
protected void	setStateInitialized(boolean stateInitialized) Set the stateInitialized flag.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.commons.math.ode.FirstOrderIntegrator

integrate

Field Detail

stepHandlers

protected Collection<StepHandler> stepHandlers

Step handler.

stepStart

protected double stepStart

Current step start time.

stepSize

protected double stepSize

Current stepsize.

isLastStep

protected boolean isLastStep

Indicator for last step.

resetOccurred

protected boolean resetOccurred

Indicator that a state or derivative reset was triggered by some event.

Constructor Detail

AbstractIntegrator

public AbstractIntegrator(String name)

Build an instance.

Parameters:

name - name of the method

AbstractIntegrator

protected AbstractIntegrator()

Build an instance with a null name.

Method Detail

getName

public String getName()

Get the name of the method.

Specified by:

getName in interface ODEIntegrator

Returns:

name of the method

addStepHandler

public void addStepHandler(StepHandler handler)

Add a step handler to this integrator.

The handler will be called by the integrator for each accepted step.

Specified by:

addStepHandler in interface ODEIntegrator

Parameters:

handler - handler for the accepted steps

See Also:

ODEIntegrator.getStepHandlers(), ODEIntegrator.clearStepHandlers()

getStepHandlers

public Collection<StepHandler> getStepHandlers()

Get all the step handlers that have been added to the integrator.

Specified by:

getStepHandlers in interface ODEIntegrator

Returns:

an unmodifiable collection of the added events handlers

See Also:

ODEIntegrator.addStepHandler(StepHandler), ODEIntegrator.clearStepHandlers()

clearStepHandlers

public void clearStepHandlers()

Remove all the step handlers that have been added to the integrator.

Specified by:

clearStepHandlers in interface ODEIntegrator

See Also:

ODEIntegrator.addStepHandler(StepHandler), ODEIntegrator.getStepHandlers()

addEventHandler

public void addEventHandler(EventHandler handler,
                            double maxCheckInterval,
                            double convergence,
                            int maxIterationCount)

Add an event handler to the integrator.

Specified by:

addEventHandler in interface ODEIntegrator

Parameters:

handler - event handler

maxCheckInterval - maximal time interval between switching function checks (this interval prevents missing sign changes in case the integration steps becomes very large)

convergence - convergence threshold in the event time search

maxIterationCount - upper limit of the iteration count in the event time search

See Also:

ODEIntegrator.getEventHandlers(), ODEIntegrator.clearEventHandlers()

getEventHandlers

public Collection<EventHandler> getEventHandlers()

Get all the event handlers that have been added to the integrator.

Specified by:

getEventHandlers in interface ODEIntegrator

Returns:

an unmodifiable collection of the added events handlers

See Also:

ODEIntegrator.addEventHandler(EventHandler, double, double, int), ODEIntegrator.clearEventHandlers()

clearEventHandlers

public void clearEventHandlers()

Remove all the event handlers that have been added to the integrator.

Specified by:

clearEventHandlers in interface ODEIntegrator

See Also:

ODEIntegrator.addEventHandler(EventHandler, double, double, int), ODEIntegrator.getEventHandlers()

requiresDenseOutput

protected boolean requiresDenseOutput()

Check if dense output is needed.

Returns:

true if there is at least one event handler or if one of the step handlers requires dense output

getCurrentStepStart

public double getCurrentStepStart()

Get the current value of the step start time t_i.

This method can be called during integration (typically by the object implementing the differential equations problem) if the value of the current step that is attempted is needed.

The result is undefined if the method is called outside of calls to integrate.

Specified by:

getCurrentStepStart in interface ODEIntegrator

Returns:

current value of the step start time t_i

getCurrentSignedStepsize

public double getCurrentSignedStepsize()

Get the current signed value of the integration stepsize.

This method can be called during integration (typically by the object implementing the differential equations problem) if the signed value of the current stepsize that is tried is needed.

The result is undefined if the method is called outside of calls to integrate.

Specified by:

getCurrentSignedStepsize in interface ODEIntegrator

Returns:

current signed value of the stepsize

setMaxEvaluations

public void setMaxEvaluations(int maxEvaluations)

Set the maximal number of differential equations function evaluations.

The purpose of this method is to avoid infinite loops which can occur for example when stringent error constraints are set or when lots of discrete events are triggered, thus leading to many rejected steps.

Specified by:

setMaxEvaluations in interface ODEIntegrator

Parameters:

maxEvaluations - maximal number of function evaluations (negative values are silently converted to maximal integer value, thus representing almost unlimited evaluations)

getMaxEvaluations

public int getMaxEvaluations()

Get the maximal number of functions evaluations.

Specified by:

getMaxEvaluations in interface ODEIntegrator

Returns:

maximal number of functions evaluations

getEvaluations

public int getEvaluations()

Get the number of evaluations of the differential equations function.

The number of evaluations corresponds to the last call to the integrate method. It is 0 if the method has not been called yet.

Specified by:

getEvaluations in interface ODEIntegrator

Returns:

number of evaluations of the differential equations function

resetEvaluations

protected void resetEvaluations()

Reset the number of evaluations to zero.

setEquations

protected void setEquations(FirstOrderDifferentialEquations equations)

Set the differential equations.

Parameters:

equations - differential equations to integrate

See Also:

computeDerivatives(double, double[], double[])

computeDerivatives

public void computeDerivatives(double t,
                               double[] y,
                               double[] yDot)
                        throws DerivativeException

Compute the derivatives and check the number of evaluations.

Parameters:

t - current value of the independent time variable

y - array containing the current value of the state vector

yDot - placeholder array where to put the time derivative of the state vector

Throws:

DerivativeException - this user-defined exception should be used if an error is is triggered by user code

setStateInitialized

protected void setStateInitialized(boolean stateInitialized)

Set the stateInitialized flag.

This method must be called by integrators with the value false before they start integration, so a proper lazy initialization is done automatically on the first step.

Parameters:

stateInitialized - new value for the flag

Since:

2.2

acceptStep

protected double acceptStep(AbstractStepInterpolator interpolator,
                            double[] y,
                            double[] yDot,
                            double tEnd)
                     throws DerivativeException,
                            IntegratorException

Accept a step, triggering events and step handlers.

Parameters:

interpolator - step interpolator

y - state vector at step end time, must be reset if an event asks for resetting or if an events stops integration during the step

yDot - placeholder array where to put the time derivative of the state vector

tEnd - final integration time

Returns:

time at end of step

Throws:

DerivativeException - this exception is propagated to the caller if the underlying user function triggers one

IntegratorException - if the value of one event state cannot be evaluated

Since:

2.2

sanityChecks

protected void sanityChecks(FirstOrderDifferentialEquations ode,
                            double t0,
                            double[] y0,
                            double t,
                            double[] y)
                     throws IntegratorException

Perform some sanity checks on the integration parameters.

Parameters:

ode - differential equations set

t0 - start time

y0 - state vector at t0

t - target time for the integration

y - placeholder where to put the state vector

Throws:

IntegratorException - if some inconsistency is detected

addEndTimeChecker

@Deprecated
protected CombinedEventsManager addEndTimeChecker(double startTime,
                                                             double endTime,
                                                             CombinedEventsManager manager)

Deprecated. as of 2.2, this method is not used any more

Add an event handler for end time checking.

This method can be used to simplify handling of integration end time. It leverages the nominal stop condition with the exceptional stop conditions.

Parameters:

startTime - integration start time

endTime - desired end time

manager - manager containing the user-defined handlers

Returns:

a new manager containing all the user-defined handlers plus a dedicated manager triggering a stop event at entTime