Package org.hipparchus.ode.nonstiff

Class FixedStepRungeKuttaIntegrator

java.lang.Object

org.hipparchus.ode.AbstractIntegrator

org.hipparchus.ode.nonstiff.FixedStepRungeKuttaIntegrator

All Implemented Interfaces:

ButcherArrayProvider, ExplicitRungeKuttaIntegrator, ODEIntegrator

Direct Known Subclasses:

ClassicalRungeKuttaIntegrator, EulerIntegrator, GillIntegrator, LutherIntegrator, MidpointIntegrator, ThreeEighthesIntegrator

public abstract class FixedStepRungeKuttaIntegrator
extends AbstractIntegrator
implements ExplicitRungeKuttaIntegrator

This class implements the common part of all fixed step Runge-Kutta integrators for Ordinary Differential Equations.

These methods are explicit Runge-Kutta methods, their Butcher arrays are as follows :

    0  |
   c2  | a21
   c3  | a31  a32
   ... |        ...
   cs  | as1  as2  ...  ass-1
       |--------------------------
       |  b1   b2  ...   bs-1  bs
 

See Also:

EulerIntegrator, ClassicalRungeKuttaIntegrator, GillIntegrator, MidpointIntegrator

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	FixedStepRungeKuttaIntegrator(String name, double step)	Simple constructor.

Method Summary

Modifier and Type	Method	Description
protected abstract RungeKuttaStateInterpolator	createInterpolator(boolean forward, double[][] yDotK, ODEStateAndDerivative globalPreviousState, ODEStateAndDerivative globalCurrentState, EquationsMapper mapper)	Create an interpolator.
double	getDefaultStep()	Getter for the default, positive step-size assigned at constructor level.
ODEStateAndDerivative	integrate(ExpandableODE equations, ODEState initialState, double finalTime)	Integrate the differential equations up to the given time.

Methods inherited from class org.hipparchus.ode.AbstractIntegrator

acceptStep, addEventDetector, addStepEndHandler, addStepHandler, clearEventDetectors, clearStepEndHandlers, clearStepHandlers, computeDerivatives, getCurrentSignedStepsize, getEquations, getEvaluations, getEvaluationsCounter, getEventDetectors, getMaxEvaluations, getName, getStepEndHandlers, getStepHandlers, getStepSize, getStepStart, incrementEvaluations, initIntegration, isLastStep, resetOccurred, sanityChecks, 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.nonstiff.ButcherArrayProvider

getA, getB, getC

Methods inherited from interface org.hipparchus.ode.nonstiff.ExplicitRungeKuttaIntegrator

getNumberOfStages, singleStep

Methods inherited from interface org.hipparchus.ode.ODEIntegrator

addEventDetector, addStepEndHandler, addStepHandler, clearEventDetectors, clearStepEndHandlers, clearStepHandlers, getCurrentSignedStepsize, getEvaluations, getEventDetectors, getMaxEvaluations, getName, getStepEndHandlers, getStepHandlers, getStepStart, integrate, setMaxEvaluations

Constructor Detail

FixedStepRungeKuttaIntegrator

protected FixedStepRungeKuttaIntegrator(String name,
                                        double step)

Simple constructor. Build a Runge-Kutta integrator with the given step. The default step handler does nothing.

Parameters:

name - name of the method

step - integration step

Method Detail

getDefaultStep

public double getDefaultStep()

Getter for the default, positive step-size assigned at constructor level.

Returns:

step

createInterpolator

protected abstract RungeKuttaStateInterpolator createInterpolator(boolean forward,
                                                                  double[][] yDotK,
                                                                  ODEStateAndDerivative globalPreviousState,
                                                                  ODEStateAndDerivative globalCurrentState,
                                                                  EquationsMapper mapper)

Create an interpolator.

Parameters:

forward - integration direction indicator

yDotK - slopes at the intermediate points

globalPreviousState - start of the global step

globalCurrentState - end of the global step

mapper - equations mapper for the all equations

Returns:

external weights for the high order method from Butcher array

integrate

public ODEStateAndDerivative integrate(ExpandableODE equations,
                                       ODEState initialState,
                                       double finalTime)
                                throws MathIllegalArgumentException,
                                       MathIllegalStateException

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 ODEIntegrator

Parameters:

equations - differential equations to integrate

initialState - initial state (time, primary and secondary state vectors)

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

Returns:

final state, its time will be the same as finalTime if integration reached its target, but may be different if some ODEEventHandler stops it at some point.

Throws:

MathIllegalArgumentException - if integration step is too small

MathIllegalStateException - if the number of functions evaluations is exceeded