org.apache.commons.math3.ode.nonstiff

Class EulerStepInterpolator

java.lang.Object

org.apache.commons.math3.ode.sampling.AbstractStepInterpolator

org.apache.commons.math3.ode.nonstiff.RungeKuttaStepInterpolator

org.apache.commons.math3.ode.nonstiff.EulerStepInterpolator

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, StepInterpolator

 class EulerStepInterpolator
extends RungeKuttaStepInterpolator

This class implements a linear interpolator for step.

This interpolator computes dense output inside the last step computed. The interpolation equation is consistent with the integration scheme :

• Using reference point at step start:
  y(t_n + θ h) = y (t_n) + θ h y'
• Using reference point at step end:
  y(t_n + θ h) = y (t_n + h) - (1-θ) h y'

where θ belongs to [0 ; 1] and where y' is the evaluation of the derivatives already computed during the step.

Since:

1.2

See Also:

EulerIntegrator

Field Summary

Fields

Modifier and Type	Field and Description
private static long	serialVersionUID Serializable version identifier.

Fields inherited from class org.apache.commons.math3.ode.nonstiff.RungeKuttaStepInterpolator

integrator, previousState, yDotK

Fields inherited from class org.apache.commons.math3.ode.sampling.AbstractStepInterpolator

currentState, h, interpolatedDerivatives, interpolatedPrimaryDerivatives, interpolatedPrimaryState, interpolatedSecondaryDerivatives, interpolatedSecondaryState, interpolatedState, interpolatedTime

Constructor Summary

Constructors

Constructor and Description
EulerStepInterpolator() Simple constructor.
EulerStepInterpolator(EulerStepInterpolator interpolator) Copy constructor.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	computeInterpolatedStateAndDerivatives(double theta, double oneMinusThetaH) Compute the state and derivatives at the interpolated time.
protected StepInterpolator	doCopy() Really copy the finalized instance.

Methods inherited from class org.apache.commons.math3.ode.nonstiff.RungeKuttaStepInterpolator

readExternal, reinitialize, shift, writeExternal

Methods inherited from class org.apache.commons.math3.ode.sampling.AbstractStepInterpolator

copy, doFinalize, finalizeStep, getCurrentTime, getGlobalCurrentTime, getGlobalPreviousTime, getInterpolatedDerivatives, getInterpolatedSecondaryDerivatives, getInterpolatedSecondaryState, getInterpolatedState, getInterpolatedTime, getPreviousTime, isForward, readBaseExternal, reinitialize, setInterpolatedTime, setSoftCurrentTime, setSoftPreviousTime, storeTime, writeBaseExternal

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

Serializable version identifier.

See Also:

Constant Field Values

Constructor Detail

EulerStepInterpolator

public EulerStepInterpolator()

Simple constructor. This constructor builds an instance that is not usable yet, the AbstractStepInterpolator.reinitialize(double[], boolean, org.apache.commons.math3.ode.EquationsMapper, org.apache.commons.math3.ode.EquationsMapper[]) method should be called before using the instance in order to initialize the internal arrays. This constructor is used only in order to delay the initialization in some cases. The RungeKuttaIntegrator class uses the prototyping design pattern to create the step interpolators by cloning an uninitialized model and later initializing the copy.

EulerStepInterpolator

public EulerStepInterpolator(EulerStepInterpolator interpolator)

Copy constructor.

Parameters:

interpolator - interpolator to copy from. The copy is a deep copy: its arrays are separated from the original arrays of the instance

Method Detail

doCopy

protected StepInterpolator doCopy()

Really copy the finalized instance.

This method is called by AbstractStepInterpolator.copy() after the step has been finalized. It must perform a deep copy to have an new instance completely independent for the original instance.

Specified by:

doCopy in class AbstractStepInterpolator

Returns:

a copy of the finalized instance

computeInterpolatedStateAndDerivatives

protected void computeInterpolatedStateAndDerivatives(double theta,
                                          double oneMinusThetaH)

Compute the state and derivatives at the interpolated time. This is the main processing method that should be implemented by the derived classes to perform the interpolation.

Specified by:

computeInterpolatedStateAndDerivatives in class AbstractStepInterpolator

Parameters:

theta - normalized interpolation abscissa within the step (theta is zero at the previous time step and one at the current time step)

oneMinusThetaH - time gap between the interpolated time and the current time