org.apache.commons.math4.ode.nonstiff

Class RungeKuttaFieldIntegrator<T extends RealFieldElement<T>>

• Constructor Summary

Constructors
Modifier Constructor and Description
protected  RungeKuttaFieldIntegrator(Field<T> field, String name, T step)
Simple constructor.
• Method Summary

All Methods
Modifier and Type Method and Description
protected abstract org.apache.commons.math4.ode.nonstiff.RungeKuttaFieldStepInterpolator<T> createInterpolator(boolean forward, T[][] yDotK, FieldODEStateAndDerivative<T> globalPreviousState, FieldODEStateAndDerivative<T> globalCurrentState, FieldEquationsMapper<T> mapper)
Create an interpolator.
protected T fraction(int p, int q)
Create a fraction.
FieldODEStateAndDerivative<T> integrate(FieldExpandableODE<T> equations, FieldODEState<T> initialState, T finalTime)
Integrate the differential equations up to the given time.
T[] singleStep(FirstOrderFieldDifferentialEquations<T> equations, T t0, T[] y0, T t)
Fast computation of a single step of ODE integration.
• Methods inherited from class org.apache.commons.math4.ode.AbstractFieldIntegrator

acceptStep, addEventHandler, addEventHandler, addStepHandler, clearEventHandlers, clearStepHandlers, computeDerivatives, getCurrentSignedStepsize, getCurrentStepStart, getEquations, getEvaluations, getEvaluationsCounter, getEventHandlers, getField, 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.apache.commons.math4.ode.nonstiff.FieldButcherArrayProvider

getA, getB, getC
• Constructor Detail

• RungeKuttaFieldIntegrator

protected RungeKuttaFieldIntegrator(Field<T> field,
String name,
T step)
Simple constructor. Build a Runge-Kutta integrator with the given step. The default step handler does nothing.
Parameters:
field - field to which the time and state vector elements belong
name - name of the method
step - integration step
• Method Detail

• fraction

protected T fraction(int p,
int q)
Create a fraction.
Parameters:
p - numerator
q - denominator
Returns:
p/q computed in the instance field
• createInterpolator

protected abstract org.apache.commons.math4.ode.nonstiff.RungeKuttaFieldStepInterpolator<T> createInterpolator(boolean forward,
T[][] yDotK,
FieldODEStateAndDerivative<T> globalPreviousState,
FieldODEStateAndDerivative<T> globalCurrentState,
FieldEquationsMapper<T> 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 FieldODEStateAndDerivative<T> integrate(FieldExpandableODE<T> equations,
FieldODEState<T> initialState,
T finalTime)
throws NumberIsTooSmallException,
DimensionMismatchException,
MaxCountExceededException,
NoBracketingException
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 (FirstOrderFieldIntegrator.getCurrentSignedStepsize()), it is not thread-safe.

Specified by:
integrate in interface FirstOrderFieldIntegrator<T extends RealFieldElement<T>>
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 FieldEventHandler stops it at some point.
Throws:
NumberIsTooSmallException - if integration step is too small
MaxCountExceededException - if the number of functions evaluations is exceeded
NoBracketingException - if the location of an event cannot be bracketed
DimensionMismatchException
• singleStep

public T[] singleStep(FirstOrderFieldDifferentialEquations<T> equations,
T t0,
T[] y0,
T 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(FieldExpandableODE, FieldODEState, RealFieldElement) 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