org.apache.commons.math.ode.nonstiff
Class RungeKuttaIntegrator

java.lang.Object
  extended by org.apache.commons.math.ode.AbstractIntegrator
      extended by org.apache.commons.math.ode.nonstiff.RungeKuttaIntegrator
All Implemented Interfaces:
FirstOrderIntegrator, ODEIntegrator
Direct Known Subclasses:
ClassicalRungeKuttaIntegrator, EulerIntegrator, GillIntegrator, MidpointIntegrator, ThreeEighthesIntegrator

public abstract class RungeKuttaIntegrator
extends AbstractIntegrator

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
 

Since:
1.2
Version:
$Revision: 927202 $ $Date: 2010-03-24 18:11:51 -0400 (Wed, 24 Mar 2010) $
See Also:
EulerIntegrator, ClassicalRungeKuttaIntegrator, GillIntegrator, MidpointIntegrator

Field Summary
private  double[][] a
          Internal weights from Butcher array (without the first empty row).
private  double[] b
          External weights for the high order method from Butcher array.
private  double[] c
          Time steps from Butcher array (without the first zero).
private  RungeKuttaStepInterpolator prototype
          Prototype of the step interpolator.
private  double step
          Integration step.
 
Fields inherited from class org.apache.commons.math.ode.AbstractIntegrator
eventsHandlersManager, stepHandlers, stepSize, stepStart
 
Constructor Summary
protected RungeKuttaIntegrator(java.lang.String name, double[] c, double[][] a, double[] b, RungeKuttaStepInterpolator prototype, double step)
          Simple constructor.
 
Method Summary
 double integrate(FirstOrderDifferentialEquations equations, double t0, double[] y0, double t, double[] y)
          Integrate the differential equations up to the given time.
 
Methods inherited from class org.apache.commons.math.ode.AbstractIntegrator
addEndTimeChecker, addEventHandler, addStepHandler, clearEventHandlers, clearStepHandlers, computeDerivatives, getCurrentSignedStepsize, getCurrentStepStart, getEvaluations, getEventHandlers, getMaxEvaluations, getName, getStepHandlers, requiresDenseOutput, resetEvaluations, sanityChecks, setEquations, setMaxEvaluations
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

c

private final double[] c
Time steps from Butcher array (without the first zero).


a

private final double[][] a
Internal weights from Butcher array (without the first empty row).


b

private final double[] b
External weights for the high order method from Butcher array.


prototype

private final RungeKuttaStepInterpolator prototype
Prototype of the step interpolator.


step

private final double step
Integration step.

Constructor Detail

RungeKuttaIntegrator

protected RungeKuttaIntegrator(java.lang.String name,
                               double[] c,
                               double[][] a,
                               double[] b,
                               RungeKuttaStepInterpolator prototype,
                               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
c - time steps from Butcher array (without the first zero)
a - internal weights from Butcher array (without the first empty row)
b - propagation weights for the high order method from Butcher array
prototype - prototype of the step interpolator to use
step - integration step
Method Detail

integrate

public double integrate(FirstOrderDifferentialEquations equations,
                        double t0,
                        double[] y0,
                        double t,
                        double[] y)
                 throws DerivativeException,
                        IntegratorException
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.

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)
y - placeholder where to put the state vector at each successful step (and hence at the end of integration), can be the same object as y0
Returns:
stop time, will be the same as target time if integration reached its target, but may be different if some EventHandler stops it at some point.
Throws:
DerivativeException - this exception is propagated to the caller if the underlying user function triggers one
IntegratorException - if the integrator cannot perform integration


Copyright (c) 2003-2010 Apache Software Foundation