org.spaceroots.mantissa.ode
Interface FirstOrderIntegrator

All Known Implementing Classes:

AdaptiveStepsizeIntegrator, RungeKuttaIntegrator

public interface FirstOrderIntegrator

This interface represents a first order integrator for differential equations.

The classes which are devoted to solve first order differential equations should implement this interface. The problems which can be handled should implement the FirstOrderDifferentialEquations interface.

Version:

$Id: FirstOrderIntegrator.java 1719 2007-09-26 19:46:57Z luc $

Author:

L. Maisonobe

See Also:

FirstOrderDifferentialEquations, StepHandler, SwitchingFunction

Method Summary

void	addSwitchingFunction(SwitchingFunction function, double maxCheckInterval, double convergence) Add a switching function to the integrator.
double	getCurrentStepsize() Get the current value of the integration stepsize.
double	getCurrentStepStart() Get the current value of the step start time ti.
String	getName() Get the name of the method.
StepHandler	getStepHandler() Get the step handler for this integrator.
void	integrate(FirstOrderDifferentialEquations equations, double t0, double[] y0, double t, double[] y) Integrate the differential equations up to the given time.
void	setStepHandler(StepHandler handler) Set the step handler for this integrator.

Method Detail

getName

public String getName()

Get the name of the method.

Returns:

name of the method

setStepHandler

public void setStepHandler(StepHandler handler)

Set the step handler for this integrator. The handler will be called by the integrator for each accepted step.

Parameters:

handler - handler for the accepted steps

getStepHandler

public StepHandler getStepHandler()

Get the step handler for this integrator.

Returns:

the step handler for this integrator

addSwitchingFunction

public void addSwitchingFunction(SwitchingFunction function,
                                 double maxCheckInterval,
                                 double convergence)

Add a switching function to the integrator.

Parameters:

function - switching function

maxCheckInterval - maximal time interval between switching function checks (this interval prevents missing sign changes in case the integration steps becomes very large)

convergence - convergence threshold in the event time search

integrate

public void 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 (getCurrentStepsize()), 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

Throws:

IntegratorException - if the integrator cannot perform integration

DerivativeException - this exception is propagated to the caller if the underlying user function triggers one

getCurrentStepStart

public double getCurrentStepStart()

Get the current value of the step start time t_i.

This method can be called during integration (typically by the object implementing the differential equations problem) if the value of the current step that is attempted is needed.

The result is undefined if the method is called outside of calls to integrate(org.spaceroots.mantissa.ode.FirstOrderDifferentialEquations, double, double[], double, double[])

Returns:

current value of the step start time t_i

getCurrentStepsize

public double getCurrentStepsize()

Get the current value of the integration stepsize.

This method can be called during integration (typically by the object implementing the differential equations problem) if the value of the current stepsize that is tried is needed.

The result is undefined if the method is called outside of calls to integrate(org.spaceroots.mantissa.ode.FirstOrderDifferentialEquations, double, double[], double, double[])

Returns:

current value of the stepsize