org.hipparchus.ode.nonstiff

## Class RungeKuttaIntegrator

• ### Constructor Summary

Constructors
Modifier Constructor and Description
protected  RungeKuttaIntegrator(String name, double step)
Simple constructor.
• ### Method Summary

All Methods
Modifier and Type Method and Description
protected abstract org.hipparchus.ode.nonstiff.RungeKuttaStateInterpolator createInterpolator(boolean forward, double[][] yDotK, ODEStateAndDerivative globalPreviousState, ODEStateAndDerivative globalCurrentState, EquationsMapper mapper)
Create an interpolator.
ODEStateAndDerivative integrate(ExpandableODE equations, ODEState initialState, double finalTime)
Integrate the differential equations up to the given time.
double[] singleStep(OrdinaryDifferentialEquation equations, double t0, double[] y0, double t)
Fast computation of a single step of ODE integration.
• ### Methods inherited from class org.hipparchus.ode.AbstractIntegrator

acceptStep, addEventHandler, addEventHandler, addStepHandler, clearEventHandlers, clearStepHandlers, computeDerivatives, getCurrentSignedStepsize, getEquations, getEvaluations, getEvaluationsCounter, getEventHandlers, getEventHandlersConfigurations, getMaxEvaluations, getName, getStepHandlers, getStepSize, getStepStart, 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.ODEIntegrator

integrate
• ### Constructor Detail

• #### RungeKuttaIntegrator

protected RungeKuttaIntegrator(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

• #### createInterpolator

protected abstract org.hipparchus.ode.nonstiff.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
• #### singleStep

public double[] singleStep(OrdinaryDifferentialEquation equations,
double t0,
double[] y0,
double t)
Fast computation of a single step of ODE integration.

This method is intended for the limited use case of very fast computation of only one step without using any of the rich features of general integrators that may take some time to set up (i.e. no step handlers, no events handlers, no additional states, no interpolators, no error control, no evaluations count, no sanity checks ...). It handles the strict minimum of computation, so it can be embedded in outer loops.

This method is not used at all by the integrate(ExpandableODE, ODEState, double) method. It also completely ignores the step set at construction time, and uses only a single step to go from t0 to t.

As this method does not use any of the state-dependent features of the integrator, it should be reasonably thread-safe if and only if the provided differential equations are themselves thread-safe.

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)
Returns:
state vector at t