integrators
Class BackwardEulerIntegrator

java.lang.Object
  integrators.Integrator
      integrators.BackwardEulerIntegrator

public class BackwardEulerIntegrator

extends Integrator

BackwardEulerIntegrator is a custom-modified backward Euler method with simple-minded adaptive stepsizing that exploits the same partially explicit corrector formula as the SemiExplicitAPCIntegrator. Basically it makes an estimate of y(t+h) by first making such an estimate with the forward Euler step y(t+h) = y(t) + hf(y(t)), then using that estimate to calculate the backward Euler step y(t+h) = y(t) + hf(y(t+h)), then iterating the backward step to convergence. At high accuracy (<10E-4) this is usually much slower than a higher-order method; however, since it is "guaranteed" to be stable at low accuracy (10E-2 or even 10E-1) it can often take much bigger steps than other methods, especially if the parameters are such as to render the equations relatively stiff... of course they are still low-accuracy steps.

Nested Class Summary

Nested classes inherited from class integrators.Integrator

Integrator.NVmatrix, Integrator.NVvector

Constructor Summary

BackwardEulerIntegrator()

Method Summary

protected void	getFhatAndDfdyi(NodeValues[] fhat_vals, NodeValues[] dfdyi_vals)
void	init(Model model) Any object planning to use an Integrator of any kind MUST call its init(Model) method, which (among other things) is generally used to allocate storage arrays for the intermediates in an integration method.
float	IntegrateOneStep() Integrates across a single time step.
void	reset() Should be called after the Integrator has crossed an entire interval.

Methods inherited from class integrators.Integrator

copyNVarray, getCurrentValues, getDerivatives, getErrorEstimate, isType, setDefaultStepSize, setErrorTolerance, setFinalValues, setIntegrationValues, setStepSize

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BackwardEulerIntegrator

public BackwardEulerIntegrator()

Method Detail

init

public void init(Model model)

Description copied from class: Integrator

Any object planning to use an Integrator of any kind MUST call its init(Model) method, which (among other things) is generally used to allocate storage arrays for the intermediates in an integration method. This method does NOT do any numerics so does not depend on the state of the model, but it DOES need to be called after the model has been properly populated with Cells and Nodes, and needs to be called again if these change.

Overrides:

init in class Integrator

reset

public void reset()

Description copied from class: Integrator

Should be called after the Integrator has crossed an entire interval. The base class does nothing; typical subclasses will override Integrator.reset() to reset the time step size to the default value. This method is NOT used to reallocate storage; that requires a call to init().

Overrides:

reset in class Integrator

IntegrateOneStep

public float IntegrateOneStep()

Description copied from class: Integrator

Integrates across a single time step. Return value is the size of the timestep, which may differ from that specified by the calling method if the Integrator subclass adapts the step size to match error requirements.

Overrides:

IntegrateOneStep in class Integrator

getFhatAndDfdyi

protected void getFhatAndDfdyi(NodeValues[] fhat_vals,
                               NodeValues[] dfdyi_vals)