agi.foundation.numericalmethods

(agi.foundation.core-2025r1.jar)

Class GaussJacksonIntegrator

java.lang.Object

agi.foundation.numericalmethods.NumericalIntegrator

agi.foundation.numericalmethods.advanced.MultipleStepIntegrator

agi.foundation.numericalmethods.GaussJacksonIntegrator

All Implemented Interfaces:

ICloneWithContext, IThreadAware

public class GaussJacksonIntegrator
extends MultipleStepIntegrator

A multi-step second order integrator based on the Gauss-Jackson integration algorithm, using a RungeKuttaFehlberg78Integrator to start the integration and a summed Adams first order integration algorithm.

For more detailed information, see: "Implementation of Gauss-Jackson Integration for Orbit Propagation." Berry, Matthew M. and Liam M. Healy. The Journal of the Astronautical Sciences, Vol. 52, No. 3, July-September 2004, pp. 331-357.

Constructor Summary

Constructors

Modifier	Constructor and Description
	GaussJacksonIntegrator() Initializes a new instance.
protected	GaussJacksonIntegrator(GaussJacksonIntegrator existingInstance, CopyContext context) Initializes a new instance as a copy of an existing instance.

Method Summary

Modifier and Type	Method and Description
Object	clone(CopyContext context) Create a copy of this integrator.
double	getCurrentStepSize() Gets the current (positive) size of the step which the integrator will use for the next integration step.
void	initialize(double x, double[] y) Initialize the integrator's initial independent and dependent variables and reset the integration parameters.
void	integrate() Perform an integration step moving the independent and dependent variables from their initial (the final values of the previous step) to their new final values, using the CurrentStepSize (get).
void	integrate(double stepSize) Perform an integration step moving the independent and dependent variables from their initial (the final values of the previous step) to their new final values.
void	reintegrate(double stepSize) Repeats the last integration of the differential equations.
protected void	startNextStep() This performs the task of setting the Initial values to the previous Final values prior to taking the next step.
void	updateSavedDerivatives(double[] derivativeCorrections) This method is used in order to update the last step's derivatives with any post integration corrections.

Methods inherited from class agi.foundation.numericalmethods.NumericalIntegrator

getDimension, getDirection, getFinalDependentVariableValues, getFinalIndependentVariableValue, getInitialDependentVariableValues, getInitialIndependentVariableValue, getInitialStepSize, getIsThreadSafe, getPreviousStepSize, getStepSizeInformation, getSystemOfEquations, setDirection, setFinalDependentVariableValues, setFinalIndependentVariableValue, setInitialDependentVariableValues, setInitialIndependentVariableValue, setInitialStepSize, setStepSizeInformation, setSystemOfEquations

Methods inherited from class java.lang.Object

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

Constructor Detail

GaussJacksonIntegrator

public GaussJacksonIntegrator()

Initializes a new instance.

GaussJacksonIntegrator

protected GaussJacksonIntegrator(@Nonnull
                                 GaussJacksonIntegrator existingInstance,
                                 @Nonnull
                                 CopyContext context)

Initializes a new instance as a copy of an existing instance.

See ICloneWithContext.clone(CopyContext) for more information about how to implement this constructor in a derived class.

Parameters:

existingInstance - The existing instance to copy.

context - A CopyContext that controls the depth of the copy.

Throws:

ArgumentNullException - Thrown when existingInstance or context is null.

Method Detail

clone

public Object clone(CopyContext context)

Create a copy of this integrator.

Specified by:

clone in interface ICloneWithContext

Specified by:

clone in class NumericalIntegrator

Parameters:

context - The context in which to create the copy.

Returns:

The copy of this integrator.

getCurrentStepSize

public double getCurrentStepSize()

Gets the current (positive) size of the step which the integrator will use for the next integration step.

Specified by:

getCurrentStepSize in class NumericalIntegrator

updateSavedDerivatives

public void updateSavedDerivatives(double[] derivativeCorrections)

This method is used in order to update the last step's derivatives with any post integration corrections.

Specified by:

updateSavedDerivatives in class MultipleStepIntegrator

Parameters:

derivativeCorrections - The corrections to the last step's derivatives.

initialize

public void initialize(double x,
                       double[] y)

Initialize the integrator's initial independent and dependent variables and reset the integration parameters. This should be called by the user prior to performing the first integration step.

Overrides:

initialize in class NumericalIntegrator

Parameters:

x - The value of the initial independent variable.

y - The values for the initial dependent variables.

Throws:

IllegalStateException - Thrown if the SystemOfEquations (get / set) does not represent a first or second order system (or mixed order of both first and second orders).

startNextStep

protected void startNextStep()

This performs the task of setting the Initial values to the previous Final values prior to taking the next step. This method is called prior to integrating the step but not called during reintegration.

Overrides:

startNextStep in class NumericalIntegrator

integrate

public void integrate()

Perform an integration step moving the independent and dependent variables from their initial (the final values of the previous step) to their new final values, using the CurrentStepSize (get).

When overriding this method, GaussJacksonIntegrator.startNextStep() should be called prior to integration.

Overrides:

integrate in class NumericalIntegrator

integrate

public void integrate(double stepSize)

Perform an integration step moving the independent and dependent variables from their initial (the final values of the previous step) to their new final values.

When overriding this method, GaussJacksonIntegrator.startNextStep() should be called prior to integration. Also note that the CurrentStepSize (get) property should be unaffected by the stepSize parameter.

Overrides:

integrate in class NumericalIntegrator

Parameters:

stepSize - The increment made to the InitialIndependentVariableValue (get / set) to transition to the new FinalIndependentVariableValue (get / set).

reintegrate

public void reintegrate(double stepSize)

Repeats the last integration of the differential equations.

When overriding this method, note that the CurrentStepSize (get) property should be unaffected by the stepSize parameter.

Specified by:

reintegrate in class NumericalIntegrator

Parameters:

stepSize - The increment made to the InitialIndependentVariableValue (get / set) to transition to the new FinalIndependentVariableValue (get / set).