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java.lang.Objectorg.apache.commons.math.ode.RungeKuttaIntegrator
public abstract class RungeKuttaIntegrator
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
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 StepHandler |
handler
Step handler. |
private RungeKuttaStepInterpolator |
prototype
Prototype of the step interpolator. |
private double |
step
Integration step. |
private double |
stepSize
Current stepsize. |
private double |
stepStart
Current step start time. |
protected SwitchingFunctionsHandler |
switchesHandler
Switching functions handler. |
Constructor Summary | |
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protected |
RungeKuttaIntegrator(double[] c,
double[][] a,
double[] b,
RungeKuttaStepInterpolator prototype,
double step)
Simple constructor. |
Method Summary | |
---|---|
void |
addSwitchingFunction(SwitchingFunction function,
double maxCheckInterval,
double convergence,
int maxIterationCount)
Add a switching function to the integrator. |
double |
getCurrentSignedStepsize()
Get the current signed value of the integration stepsize. |
double |
getCurrentStepStart()
Get the current value of the step start time ti. |
abstract java.lang.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. |
private void |
resetInternalState()
Reset internal state to dummy values. |
private void |
sanityChecks(FirstOrderDifferentialEquations equations,
double t0,
double[] y0,
double t,
double[] y)
Perform some sanity checks on the integration parameters. |
void |
setStepHandler(StepHandler handler)
Set the step handler for this integrator. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
private double[] c
private double[][] a
private double[] b
private RungeKuttaStepInterpolator prototype
private double step
private StepHandler handler
protected SwitchingFunctionsHandler switchesHandler
private double stepStart
private double stepSize
Constructor Detail |
---|
protected RungeKuttaIntegrator(double[] c, double[][] a, double[] b, RungeKuttaStepInterpolator prototype, double step)
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 arrayprototype
- prototype of the step interpolator to usestep
- integration stepMethod Detail |
---|
public abstract java.lang.String getName()
getName
in interface FirstOrderIntegrator
public void setStepHandler(StepHandler handler)
setStepHandler
in interface FirstOrderIntegrator
handler
- handler for the accepted stepspublic StepHandler getStepHandler()
getStepHandler
in interface FirstOrderIntegrator
public void addSwitchingFunction(SwitchingFunction function, double maxCheckInterval, double convergence, int maxIterationCount)
addSwitchingFunction
in interface FirstOrderIntegrator
function
- switching functionmaxCheckInterval
- 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 searchmaxIterationCount
- upper limit of the iteration count in
the event time searchprivate void sanityChecks(FirstOrderDifferentialEquations equations, double t0, double[] y0, double t, double[] y) throws IntegratorException
equations
- differential equations sett0
- start timey0
- state vector at t0t
- target time for the integrationy
- placeholder where to put the state vector
IntegratorException
- if some inconsistency is detectedpublic void integrate(FirstOrderDifferentialEquations equations, double t0, double[] y0, double t, double[] y) throws DerivativeException, IntegratorException
This method solves an Initial Value Problem (IVP).
Since this method stores some internal state variables made
available in its public interface during integration (getCurrentSignedStepsize()
), it is not thread-safe.
integrate
in interface FirstOrderIntegrator
equations
- differential equations to integratet0
- initial timey0
- initial value of the state vector at t0t
- 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
IntegratorException
- if the integrator cannot perform integration
DerivativeException
- this exception is propagated to the caller if
the underlying user function triggers onepublic double getCurrentStepStart()
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.apache.commons.math.ode.FirstOrderDifferentialEquations, double, double[], double, double[])
getCurrentStepStart
in interface FirstOrderIntegrator
public double getCurrentSignedStepsize()
This method can be called during integration (typically by
the object implementing the differential equations
problem) if the signed 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.apache.commons.math.ode.FirstOrderDifferentialEquations, double, double[], double, double[])
getCurrentSignedStepsize
in interface FirstOrderIntegrator
private void resetInternalState()
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