Package org.apache.commons.math.ode.nonstiff

Class EmbeddedRungeKuttaIntegrator

java.lang.Object
org.apache.commons.math.ode.AbstractIntegrator
org.apache.commons.math.ode.nonstiff.AdaptiveStepsizeIntegrator
org.apache.commons.math.ode.nonstiff.EmbeddedRungeKuttaIntegrator
All Implemented Interfaces:
FirstOrderIntegrator, ODEIntegrator
Direct Known Subclasses:
DormandPrince54Integrator, DormandPrince853Integrator, HighamHall54Integrator
public abstract class EmbeddedRungeKuttaIntegrator extends AdaptiveStepsizeIntegrator
This class implements the common part of all embedded Runge-Kutta integrators for Ordinary Differential Equations.

These methods are embedded explicit Runge-Kutta methods with two sets of coefficients allowing to estimate the error, their Butcher arrays are as follows : 

    0  |
   c2  | a21
   c3  | a31  a32
   ... |        ...
   cs  | as1  as2  ...  ass-1
       |--------------------------
       |  b1   b2  ...   bs-1  bs
       |  b'1  b'2 ...   b's-1 b's

In fact, we rather use the array defined by ej = bj - b'j to compute directly the error rather than computing two estimates and then comparing them.

Some methods are qualified as fsal (first same as last) methods. This means the last evaluation of the derivatives in one step is the same as the first in the next step. Then, this evaluation can be reused from one step to the next one and the cost of such a method is really s-1 evaluations despite the method still has s stages. This behaviour is true only for successful steps, if the step is rejected after the error estimation phase, no evaluation is saved. For an fsal method, we have cs = 1 and asi = bi for all i.

Since:
1.2

  • Method Details

    • getOrder

      public abstract int getOrder()
      Get the order of the method.
      Returns:
      order of the method

    • getSafety

      public double getSafety()
      Get the safety factor for stepsize control.
      Returns:
      safety factor

    • setSafety

      public void setSafety(double safety)
      Set the safety factor for stepsize control.
      Parameters:
      safety - safety factor

    • 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.

      Specified by:
      integrate in interface FirstOrderIntegrator
      Specified by:
      integrate in class AdaptiveStepsizeIntegrator
      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

    • getMinReduction

      public double getMinReduction()
      Get the minimal reduction factor for stepsize control.
      Returns:
      minimal reduction factor

    • setMinReduction

      public void setMinReduction(double minReduction)
      Set the minimal reduction factor for stepsize control.
      Parameters:
      minReduction - minimal reduction factor

    • getMaxGrowth

      public double getMaxGrowth()
      Get the maximal growth factor for stepsize control.
      Returns:
      maximal growth factor

    • setMaxGrowth

      public void setMaxGrowth(double maxGrowth)
      Set the maximal growth factor for stepsize control.
      Parameters:
      maxGrowth - maximal growth factor