org.apache.commons.math.ode

Class ContinuousOutputModel

java.lang.Object

org.apache.commons.math.ode.ContinuousOutputModel

All Implemented Interfaces:

java.io.Serializable, StepHandler

public class ContinuousOutputModel
extends java.lang.Object
implements StepHandler, java.io.Serializable

This class stores all information provided by an ODE integrator during the integration process and build a continuous model of the solution from this.

This class act as a step handler from the integrator point of view. It is called iteratively during the integration process and stores a copy of all steps information in a sorted collection for later use. Once the integration process is over, the user can use the setInterpolatedTime and getInterpolatedState to retrieve this information at any time. It is important to wait for the integration to be over before attempting to call setInterpolatedTime because some internal variables are set only once the last step has been handled.

This is useful for example if the main loop of the user application should remain independent from the integration process or if one needs to mimic the behaviour of an analytical model despite a numerical model is used (i.e. one needs the ability to get the model value at any time or to navigate through the data).

If problem modeling is done with several separate integration phases for contiguous intervals, the same ContinuousOutputModel can be used as step handler for all integration phases as long as they are performed in order and in the same direction. As an example, one can extrapolate the trajectory of a satellite with one model (i.e. one set of differential equations) up to the beginning of a maneuver, use another more complex model including thrusters modeling and accurate attitude control during the maneuver, and revert to the first model after the end of the maneuver. If the same continuous output model handles the steps of all integration phases, the user do not need to bother when the maneuver begins or ends, he has all the data available in a transparent manner.

An important feature of this class is that it implements the Serializable interface. This means that the result of an integration can be serialized and reused later (if stored into a persistent medium like a filesystem or a database) or elsewhere (if sent to another application). Only the result of the integration is stored, there is no reference to the integrated problem by itself.

One should be aware that the amount of data stored in a ContinuousOutputModel instance can be important if the state vector is large, if the integration interval is long or if the steps are small (which can result from small tolerance settings in adaptive step size integrators).

Since:

1.2

See Also:

StepHandler, StepInterpolator, Serialized Form

Constructor Summary

Constructors

Constructor and Description
ContinuousOutputModel() Simple constructor.

Method Summary

Modifier and Type	Method and Description
void	append(ContinuousOutputModel model) Append another model at the end of the instance.
double	getFinalTime() Get the final integration time.
double	getInitialTime() Get the initial integration time.
double[]	getInterpolatedState() Get the state vector of the interpolated point.
double	getInterpolatedTime() Get the time of the interpolated point.
void	handleStep(StepInterpolator interpolator, boolean isLast) Handle the last accepted step.
boolean	requiresDenseOutput() Determines whether this handler needs dense output.
void	reset() Reset the step handler.
void	setInterpolatedTime(double time) Set the time of the interpolated point.

Methods inherited from class java.lang.Object

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

Constructor Detail

ContinuousOutputModel

public ContinuousOutputModel()

Simple constructor. Build an empty continuous output model.

Method Detail

append

public void append(ContinuousOutputModel model)
            throws DerivativeException

Append another model at the end of the instance.

Parameters:

model - model to add at the end of the instance

Throws:

DerivativeException - if user code called from step interpolator finalization triggers one

java.lang.IllegalArgumentException - if the model to append is not compatible with the instance (dimension of the state vector, propagation direction, hole between the dates)

requiresDenseOutput

public boolean requiresDenseOutput()

Determines whether this handler needs dense output.

The essence of this class is to provide dense output over all steps, hence it requires the internal steps to provide themselves dense output. The method therefore returns always true.

Specified by:

requiresDenseOutput in interface StepHandler

Returns:

always true

reset

public void reset()

Reset the step handler. Initialize the internal data as required before the first step is handled.

Specified by:

reset in interface StepHandler

handleStep

public void handleStep(StepInterpolator interpolator,
                       boolean isLast)
                throws DerivativeException

Handle the last accepted step. A copy of the information provided by the last step is stored in the instance for later use.

Specified by:

handleStep in interface StepHandler

Parameters:

interpolator - interpolator for the last accepted step.

isLast - true if the step is the last one

Throws:

DerivativeException - if user code called from step interpolator finalization triggers one

getInitialTime

public double getInitialTime()

Get the initial integration time.

Returns:

initial integration time

getFinalTime

public double getFinalTime()

Get the final integration time.

Returns:

final integration time

getInterpolatedTime

public double getInterpolatedTime()

Get the time of the interpolated point. If setInterpolatedTime(double) has not been called, it returns the final integration time.

Returns:

interpolation point time

setInterpolatedTime

public void setInterpolatedTime(double time)

Set the time of the interpolated point.

This method should not be called before the integration is over because some internal variables are set only once the last step has been handled.

Setting the time outside of the integration interval is now allowed (it was not allowed up to version 5.9 of Mantissa), but should be used with care since the accuracy of the interpolator will probably be very poor far from this interval. This allowance has been added to simplify implementation of search algorithms near the interval endpoints.

Parameters:

time - time of the interpolated point

getInterpolatedState

public double[] getInterpolatedState()
                              throws DerivativeException

Get the state vector of the interpolated point.

Returns:

state vector at time getInterpolatedTime()

Throws:

DerivativeException - if user code called from step interpolator finalization triggers one