org.hipparchus.ode.nonstiff

• Type Parameters:
T - the type of the field elements
All Implemented Interfaces:
FieldODEIntegrator<T>
Direct Known Subclasses:
EmbeddedRungeKuttaFieldIntegrator, MultistepFieldIntegrator

public abstract class AdaptiveStepsizeFieldIntegrator<T extends CalculusFieldElement<T>>
extends AbstractFieldIntegrator<T>
This abstract class holds the common part of all adaptive stepsize integrators for Ordinary Differential Equations.

These algorithms perform integration with stepsize control, which means the user does not specify the integration step but rather a tolerance on error. The error threshold is computed as

 threshold_i = absTol_i + relTol_i * max (abs (ym), abs (ym+1))

where absTol_i is the absolute tolerance for component i of the state vector and relTol_i is the relative tolerance for the same component. The user can also use only two scalar values absTol and relTol which will be used for all components.

Note that only the main part of the state vector is used for stepsize control. The secondary parts of the state vector are explicitly ignored for stepsize control.

If the estimated error for ym+1 is such that

 sqrt((sum (errEst_i / threshold_i)^2 ) / n) < 1

(where n is the main set dimension) then the step is accepted, otherwise the step is rejected and a new attempt is made with a new stepsize.

• ### Constructor Summary

Constructors
Constructor and Description
AdaptiveStepsizeFieldIntegrator(Field<T> field, String name, double minStep, double maxStep, double[] vecAbsoluteTolerance, double[] vecRelativeTolerance)
Build an integrator with the given stepsize bounds.
AdaptiveStepsizeFieldIntegrator(Field<T> field, String name, double minStep, double maxStep, double scalAbsoluteTolerance, double scalRelativeTolerance)
Build an integrator with the given stepsize bounds.
• ### Method Summary

All Methods
Modifier and Type Method and Description
double getMaxStep()
Get the maximal step.
double getMinStep()
Get the minimal step.
protected StepsizeHelper getStepSizeHelper()
Get the stepsize helper.
double initializeStep(boolean forward, int order, T[] scale, FieldODEStateAndDerivative<T> state0, FieldEquationsMapper<T> mapper)
Initialize the integration step.
protected void resetInternalState()
Reset internal state to dummy values.
protected void sanityChecks(FieldODEState<T> initialState, T t)
Check the integration span.
void setInitialStepSize(double initialStepSize)
Set the initial step size.
void setStepSizeControl(double minimalStep, double maximalStep, double[] absoluteTolerance, double[] relativeTolerance)
Set the adaptive step size control parameters.
void setStepSizeControl(double minimalStep, double maximalStep, double absoluteTolerance, double relativeTolerance)
Set the adaptive step size control parameters.
• ### Methods inherited from class org.hipparchus.ode.AbstractFieldIntegrator

acceptStep, addEventHandler, addEventHandler, addStepHandler, clearEventHandlers, clearStepHandlers, computeDerivatives, getCurrentSignedStepsize, getEquations, getEvaluations, getEvaluationsCounter, getEventHandlers, getEventHandlersConfigurations, getField, getMaxEvaluations, getName, getStepHandlers, getStepSize, getStepStart, initIntegration, isLastStep, resetOccurred, setIsLastStep, setMaxEvaluations, setStateInitialized, setStepSize, setStepStart
• ### Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
• ### Methods inherited from interface org.hipparchus.ode.FieldODEIntegrator

integrate
• ### Constructor Detail

public AdaptiveStepsizeFieldIntegrator(Field<T> field,
String name,
double minStep,
double maxStep,
double scalAbsoluteTolerance,
double scalRelativeTolerance)
Build an integrator with the given stepsize bounds. The default step handler does nothing.
Parameters:
field - field to which the time and state vector elements belong
name - name of the method
minStep - minimal step (sign is irrelevant, regardless of integration direction, forward or backward), the last step can be smaller than this
maxStep - maximal step (sign is irrelevant, regardless of integration direction, forward or backward), the last step can be smaller than this
scalAbsoluteTolerance - allowed absolute error
scalRelativeTolerance - allowed relative error

public AdaptiveStepsizeFieldIntegrator(Field<T> field,
String name,
double minStep,
double maxStep,
double[] vecAbsoluteTolerance,
double[] vecRelativeTolerance)
Build an integrator with the given stepsize bounds. The default step handler does nothing.
Parameters:
field - field to which the time and state vector elements belong
name - name of the method
minStep - minimal step (sign is irrelevant, regardless of integration direction, forward or backward), the last step can be smaller than this
maxStep - maximal step (sign is irrelevant, regardless of integration direction, forward or backward), the last step can be smaller than this
vecAbsoluteTolerance - allowed absolute error
vecRelativeTolerance - allowed relative error
• ### Method Detail

• #### setStepSizeControl

public void setStepSizeControl(double minimalStep,
double maximalStep,
double absoluteTolerance,
double relativeTolerance)
Set the adaptive step size control parameters.

A side effect of this method is to also reset the initial step so it will be automatically computed by the integrator if setInitialStepSize is not called by the user.

Parameters:
minimalStep - minimal step (must be positive even for backward integration), the last step can be smaller than this
maximalStep - maximal step (must be positive even for backward integration)
absoluteTolerance - allowed absolute error
relativeTolerance - allowed relative error
• #### setStepSizeControl

public void setStepSizeControl(double minimalStep,
double maximalStep,
double[] absoluteTolerance,
double[] relativeTolerance)
Set the adaptive step size control parameters.

A side effect of this method is to also reset the initial step so it will be automatically computed by the integrator if setInitialStepSize is not called by the user.

Parameters:
minimalStep - minimal step (must be positive even for backward integration), the last step can be smaller than this
maximalStep - maximal step (must be positive even for backward integration)
absoluteTolerance - allowed absolute error
relativeTolerance - allowed relative error
• #### getStepSizeHelper

protected StepsizeHelper getStepSizeHelper()
Get the stepsize helper.
Returns:
stepsize helper
Since:
2.0
• #### setInitialStepSize

public void setInitialStepSize(double initialStepSize)
Set the initial step size.

This method allows the user to specify an initial positive step size instead of letting the integrator guess it by itself. If this method is not called before integration is started, the initial step size will be estimated by the integrator.

Parameters:
initialStepSize - initial step size to use (must be positive even for backward integration ; providing a negative value or a value outside of the min/max step interval will lead the integrator to ignore the value and compute the initial step size by itself)
• #### sanityChecks

protected void sanityChecks(FieldODEState<T> initialState,
T t)
throws MathIllegalArgumentException
Check the integration span.
Overrides:
sanityChecks in class AbstractFieldIntegrator<T extends CalculusFieldElement<T>>
Parameters:
initialState - initial state
t - target time for the integration
Throws:
MathIllegalArgumentException - if integration span is too small
• #### initializeStep

public double initializeStep(boolean forward,
int order,
T[] scale,
FieldODEStateAndDerivative<T> state0,
FieldEquationsMapper<T> mapper)
throws MathIllegalArgumentException,
MathIllegalStateException
Initialize the integration step.
Parameters:
forward - forward integration indicator
order - order of the method
scale - scaling vector for the state vector (can be shorter than state vector)
state0 - state at integration start time
mapper - mapper for all the equations
Returns:
first integration step
Throws:
MathIllegalStateException - if the number of functions evaluations is exceeded
MathIllegalArgumentException - if arrays dimensions do not match equations settings
• #### resetInternalState

protected void resetInternalState()
Reset internal state to dummy values.
• #### getMinStep

public double getMinStep()
Get the minimal step.
Returns:
minimal step
• #### getMaxStep

public double getMaxStep()
Get the maximal step.
Returns:
maximal step