org.apache.commons.math3.ode

Class AbstractIntegrator

java.lang.Object

org.apache.commons.math3.ode.AbstractIntegrator

All Implemented Interfaces:

FirstOrderIntegrator, ODEIntegrator

Direct Known Subclasses:

AdaptiveStepsizeIntegrator, RungeKuttaIntegrator

public abstract class AbstractIntegrator
extends java.lang.Object
implements FirstOrderIntegrator

Base class managing common boilerplate for all integrators.

Since:

2.0

Constructor Summary

Constructors

Constructor and Description
AbstractIntegrator(java.lang.String name) Build an instance.

Method Summary

Modifier and Type	Method and Description
void	addEventHandler(EventHandler handler, double maxCheckInterval, double convergence, int maxIterationCount) Add an event handler to the integrator.
void	addEventHandler(EventHandler handler, double maxCheckInterval, double convergence, int maxIterationCount, UnivariateSolver solver) 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.
java.util.Collection<EventHandler>	getEventHandlers() Get all the event handlers that have been added to the integrator.
int	getMaxEvaluations() Get the maximal number of functions evaluations.
java.lang.String	getName() Get the name of the method.
java.util.Collection<StepHandler>	getStepHandlers() Get all the step handlers that have been added to the integrator.
abstract void	integrate(ExpandableStatefulODE equations, double t) Integrate a set of differential equations up to the given time.
double	integrate(FirstOrderDifferentialEquations equations, double t0, double[] y0, double t, double[] y) Integrate the differential equations up to the given time.
void	setMaxEvaluations(int maxEvaluations) Set the maximal number of differential equations function evaluations.

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractIntegrator

public AbstractIntegrator(java.lang.String name)

Build an instance.

Parameters:

name - name of the method

Method Detail

getName

public java.lang.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 java.util.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. Uses a default UnivariateSolver with an absolute accuracy equal to the given convergence threshold, as root-finding algorithm to detect the state events.

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()

addEventHandler

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

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

solver - The root-finding algorithm to use to detect the state events.

See Also:

ODEIntegrator.getEventHandlers(), ODEIntegrator.clearEventHandlers()

getEventHandlers

public java.util.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()

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

integrate

public double integrate(FirstOrderDifferentialEquations equations,
                        double t0,
                        double[] y0,
                        double t,
                        double[] y)
                 throws DimensionMismatchException,
                        NumberIsTooSmallException,
                        MaxCountExceededException,
                        NoBracketingException

Integrate the differential equations up to the given time.

This method solves an Initial Value Problem (IVP).

Since this method stores some internal state variables made available in its public interface during integration (ODEIntegrator.getCurrentSignedStepsize()), it is not thread-safe.

Specified by:

integrate in interface FirstOrderIntegrator

Parameters:

equations - differential equations to integrate

t0 - initial time

y0 - initial value of the state vector at t0

t - target time for the integration (can be set to a value smaller than t0 for backward integration)

y - placeholder where to put the state vector at each successful step (and hence at the end of integration), can be the same object as y0

Returns:

stop time, will be the same as target time if integration reached its target, but may be different if some EventHandler stops it at some point.

Throws:

DimensionMismatchException - if arrays dimension do not match equations settings

NumberIsTooSmallException - if integration step is too small

MaxCountExceededException - if the number of functions evaluations is exceeded

NoBracketingException - if the location of an event cannot be bracketed

integrate

public abstract void integrate(ExpandableStatefulODE equations,
                               double t)
                        throws NumberIsTooSmallException,
                               DimensionMismatchException,
                               MaxCountExceededException,
                               NoBracketingException

Integrate a set of differential equations up to the given time.

This method solves an Initial Value Problem (IVP).

The set of differential equations is composed of a main set, which can be extended by some sets of secondary equations. The set of equations must be already set up with initial time and partial states. At integration completion, the final time and partial states will be available in the same object.

Since this method stores some internal state variables made available in its public interface during integration (getCurrentSignedStepsize()), it is not thread-safe.

Parameters:

equations - complete set of differential equations to integrate

t - target time for the integration (can be set to a value smaller than t0 for backward integration)

Throws:

NumberIsTooSmallException - if integration step is too small

DimensionMismatchException - if the dimension of the complete state does not match the complete equations sets dimension

MaxCountExceededException - if the number of functions evaluations is exceeded

NoBracketingException - if the location of an event cannot be bracketed

computeDerivatives

public void computeDerivatives(double t,
                               double[] y,
                               double[] yDot)
                        throws MaxCountExceededException,
                               DimensionMismatchException,
                               java.lang.NullPointerException

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:

MaxCountExceededException - if the number of functions evaluations is exceeded

DimensionMismatchException - if arrays dimensions do not match equations settings

java.lang.NullPointerException - if the ODE equations have not been set (i.e. if this method is called outside of a call to integrate(ExpandableStatefulODE, double) or integrate(FirstOrderDifferentialEquations, double, double[], double, double[]))