ptolemy.domains.continuous.kernel

Class ContinuousIntegrator

java.lang.Object

ptolemy.kernel.util.NamedObj

ptolemy.kernel.InstantiableNamedObj

ptolemy.kernel.Entity<T>

ptolemy.kernel.ComponentEntity<T>

ptolemy.actor.AtomicActor<TypedIOPort>

ptolemy.actor.TypedAtomicActor

ptolemy.domains.continuous.kernel.ContinuousIntegrator

All Implemented Interfaces:

java.lang.Cloneable, Actor, ContinuousStatefulComponent, ContinuousStepSizeController, Executable, FiringsRecordable, Initializable, TypedActor, Changeable, Debuggable, DebugListener, Derivable, Instantiable, ModelErrorHandler, MoMLExportable, Moveable, Nameable

Direct Known Subclasses:

Integrator

public class ContinuousIntegrator
extends TypedAtomicActor
implements ContinuousStatefulComponent, ContinuousStepSizeController

The integrator in the continuous domain.

The derivative port receives the derivative of the state of the integrator with respect to time. The state output port shows the state of the integrator. So an ordinary differential equation (ODE), dx/dt = f(x, t), can be built as follows:

            +---------------+
     dx/dt  |               |   x
 +--------->|   Integrator  |---------+----->
 |          |               |         |
 |          +----^-----^----+         |
 |                                    |
 |             |---------|            |
 +-------------| f(x, t) |<-----------+
               |---------|
 

An integrator also has a port-parameter called initialState. The parameter provides the initial state for integration during the initialization stage of execution. If during execution an input token is provided on the port, then the state of the integrator will be reset at that time to the value of the token. The default value of the parameter is 0.0.

An integrator also has an input port named impulse. When present, a token at the impulse input port is interpreted as the weight of a Dirac delta function. It causes an increment or decrement to the state at the time of the arrival of the value. If both impulse and initialState have data on the same microstep, then initialState dominates.

Note that both impulse and reset expect to receive discrete inputs. To preserve continuity, this means that those inputs should be present only when the solver step size is zero. If this assumption is violated, then this actor will throw an exception.

An integrator can generate an output (its current state) before the derivative input is known, and hence can be used in feedback loops like that above without creating a causality loop. Since impulse and initialState inputs affect the output immediately, using them in feedback loops may require inclusion of a TimeDelay actor.

For different ODE solving methods, the functionality of an integrator may be different. The delegation and strategy design patterns are used in this class, the abstract ODESolver class, and the concrete ODE solver classes. Some solver-dependent methods of integrators delegate to the concrete ODE solvers.

An integrator can possibly have several auxiliary variables for the ODE solvers to use. The ODE solver class provides the number of variables needed for that particular solver. The auxiliary variables can be set and get by setAuxVariables() and getAuxVariables() methods.

This class is based on the CTBaseIntegrator by Jie Liu and Haiyang Zheng, but it has more ports and provides more functionality.

Since:

Ptolemy II 6.0

Version:

$Id$

Author:

Haiyang Zheng and Edward A. Lee

Pt.AcceptedRating:

Red (yuhong)

Pt.ProposedRating:

Yellow (hyzheng)

Nested Class Summary

Nested classes/interfaces inherited from class ptolemy.kernel.Entity

Entity.ContainedObjectsIterator

Field Summary

Fields

Modifier and Type	Field and Description
TypedIOPort	derivative The derivative port.
TypedIOPort	impulse The impulse input port.
PortParameter	initialState The initial state of type DoubleToken.
TypedIOPort	state The state port.

Fields inherited from class ptolemy.actor.TypedAtomicActor

_typesValid

Fields inherited from class ptolemy.actor.AtomicActor

_actorFiringListeners, _initializables, _notifyingActorFiring, _stopRequested

Fields inherited from class ptolemy.kernel.util.NamedObj

_changeListeners, _changeLock, _changeRequests, _debugging, _debugListeners, _deferChangeRequests, _elementName, _isPersistent, _verbose, _workspace, ATTRIBUTES, CLASSNAME, COMPLETE, CONTENTS, DEEP, FULLNAME, LINKS

Fields inherited from interface ptolemy.actor.Executable

COMPLETED, NOT_READY, STOP_ITERATING

Constructor Summary

Constructors

Constructor and Description
ContinuousIntegrator(CompositeEntity container, java.lang.String name) Construct an integrator with the specified name and a container.

Method Summary

Modifier and Type	Method and Description
void	attributeChanged(Attribute attribute) If the specified attribute is initialState, then reset the state of the integrator to its value.
java.lang.Object	clone(Workspace workspace) Clone this actor into the specified workspace.
void	fire() If the value at the derivative port is known, and the current step size is bigger than 0, perform an integration.
double[]	getAuxVariables() Return the auxiliary variables in a double array.
CausalityInterface	getCausalityInterface() Return a causality interface for this actor.
double	getDerivative() Get the current value of the derivative input port.
double	getState() Return the state of the integrator.
double	getTentativeState() Return the tentative state.
void	initialize() Initialize the integrator.
boolean	isStepSizeAccurate() Return true if the state is resolved successfully.
boolean	isStrict() Return false.
boolean	postfire() Update the state.
boolean	prefire() If either the impulse or initialState input is unknown, then return false.
double	refinedStepSize() Return the estimation of the refined next step size.
void	rollBackToCommittedState() Roll back to committed state.
void	setAuxVariables(int index, double value) Set the value of an auxiliary variable.
void	setTentativeState(double value) Set the tentative state.
double	suggestedStepSize() Return the suggested next step size.

Methods inherited from class ptolemy.actor.TypedAtomicActor

_containedTypeConstraints, _customTypeConstraints, _defaultTypeConstraints, _fireAt, _fireAt, attributeTypeChanged, clone, isBackwardTypeInferenceEnabled, newPort, typeConstraintList, typeConstraints

Methods inherited from class ptolemy.actor.AtomicActor

_actorFiring, _actorFiring, _declareDelayDependency, addActorFiringListener, addInitializable, connectionsChanged, createReceivers, declareDelayDependency, getDirector, getExecutiveDirector, getManager, inputPortList, isFireFunctional, iterate, newReceiver, outputPortList, preinitialize, pruneDependencies, recordFiring, removeActorFiringListener, removeDependency, removeInitializable, setContainer, stop, stopFire, terminate, wrapup

Methods inherited from class ptolemy.kernel.ComponentEntity

_adjustDeferrals, _checkContainer, _getContainedObject, _propagateExistence, getContainer, instantiate, isAtomic, isOpaque, moveDown, moveToFirst, moveToIndex, moveToLast, moveUp, propagateExistence, setName

Methods inherited from class ptolemy.kernel.Entity

_addPort, _description, _exportMoMLContents, _removePort, _validateSettables, connectedPortList, connectedPorts, containedObjectsIterator, getAttribute, getPort, getPorts, linkedRelationList, linkedRelations, portList, removeAllPorts, setClassDefinition, uniqueName

Methods inherited from class ptolemy.kernel.InstantiableNamedObj

_setParent, exportMoML, getChildren, getElementName, getParent, getPrototypeList, isClassDefinition, isWithinClassDefinition

Methods inherited from class ptolemy.kernel.util.NamedObj

_addAttribute, _adjustOverride, _attachText, _cloneFixAttributeFields, _containedDecorators, _copyChangeRequestList, _debug, _debug, _debug, _debug, _debug, _executeChangeRequests, _getIndentPrefix, _isMoMLSuppressed, _markContentsDerived, _notifyHierarchyListenersAfterChange, _notifyHierarchyListenersBeforeChange, _propagateValue, _removeAttribute, _splitName, _stripNumericSuffix, addChangeListener, addDebugListener, addHierarchyListener, attributeDeleted, attributeList, attributeList, decorators, deepContains, depthInHierarchy, description, description, event, executeChangeRequests, exportMoML, exportMoML, exportMoML, exportMoML, exportMoMLPlain, getAttribute, getAttributes, getChangeListeners, getClassName, getDecoratorAttribute, getDecoratorAttributes, getDerivedLevel, getDerivedList, getDisplayName, getFullName, getModelErrorHandler, getName, getName, getSource, handleModelError, isDeferringChangeRequests, isOverridden, isPersistent, lazyContainedObjectsIterator, message, notifyOfNameChange, propagateValue, propagateValues, removeAttribute, removeChangeListener, removeDebugListener, removeHierarchyListener, requestChange, setClassName, setDeferringChangeRequests, setDerivedLevel, setDisplayName, setModelErrorHandler, setPersistent, setSource, sortContainedObjects, toplevel, toString, validateSettables, workspace

Methods inherited from class java.lang.Object

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

Methods inherited from interface ptolemy.actor.Actor

createReceivers, getDirector, getExecutiveDirector, getManager, inputPortList, newReceiver, outputPortList

Methods inherited from interface ptolemy.actor.Executable

isFireFunctional, iterate, stop, stopFire, terminate

Methods inherited from interface ptolemy.actor.Initializable

addInitializable, preinitialize, removeInitializable, wrapup

Methods inherited from interface ptolemy.kernel.util.Nameable

description, getContainer, getDisplayName, getFullName, getName, getName, setName

Methods inherited from interface ptolemy.kernel.util.Derivable

getDerivedLevel, getDerivedList, propagateValue

Field Detail

impulse

public TypedIOPort impulse

The impulse input port. This is a single port of type double.

derivative

public TypedIOPort derivative

The derivative port. This is a single port of type double.

state

public TypedIOPort state

The state port. This is a single port of type double.

initialState

public PortParameter initialState

The initial state of type DoubleToken. The default value is 0.0.

Constructor Detail

ContinuousIntegrator

public ContinuousIntegrator(CompositeEntity container,
                            java.lang.String name)
                     throws NameDuplicationException,
                            IllegalActionException

Construct an integrator with the specified name and a container. The integrator is in the same workspace as the container.

Parameters:

container - The container.

name - The name.

Throws:

NameDuplicationException - If the name is used by another actor in the container.

IllegalActionException - If ports can not be created, or thrown by the super class.

Method Detail

attributeChanged

public void attributeChanged(Attribute attribute)
                      throws IllegalActionException

If the specified attribute is initialState, then reset the state of the integrator to its value.

Overrides:

attributeChanged in class NamedObj

Parameters:

attribute - The attribute that has changed.

Throws:

IllegalActionException - If the new parameter value is not valid.

clone

public java.lang.Object clone(Workspace workspace)
                       throws java.lang.CloneNotSupportedException

Clone this actor into the specified workspace. The new actor is not added to the directory of that workspace (you must do this yourself if you want it there). The result is a new actor with the same ports as the original, but no connections and no container. A container must be set before much can be done with this actor.

Overrides:

clone in class TypedAtomicActor

Parameters:

workspace - The workspace for the cloned object.

Returns:

A new ComponentEntity.

Throws:

java.lang.CloneNotSupportedException - If cloned ports cannot have as their container the cloned entity (this should not occur), or if one of the attributes cannot be cloned.

See Also:

NamedObj.exportMoML(Writer, int, String), NamedObj.setDeferringChangeRequests(boolean)

fire

public void fire()
          throws IllegalActionException

If the value at the derivative port is known, and the current step size is bigger than 0, perform an integration. If the impulse port is known and has data, then add the value provided to the state; if the initialState port is known and has data, then reset the state to the provided value. If both impulse and initialState have data, then initialState dominates. If either is unknown, then simply return, leaving the output unknown. Note that the signals provided at these two ports are required to be purely discrete. This is enforced by throwing an exception if the current microstep is zero when they have input data.

Specified by:

fire in interface Executable

Overrides:

fire in class AtomicActor<TypedIOPort>

Throws:

IllegalActionException - If the input is infinite or not a number, or if thrown by the solver, or if data is present at either impulse or initialState and the step size is greater than zero.

getAuxVariables

public double[] getAuxVariables()

Return the auxiliary variables in a double array. The auxiliary variables are created in the prefire() method and may be set during each firing of the actor. Return null if the auxiliary variables have never been created.

Returns:

The auxiliary variables in a double array.

See Also:

setAuxVariables(int, double)

getCausalityInterface

public CausalityInterface getCausalityInterface()

Return a causality interface for this actor. This causality interface expresses dependencies that are instances of BooleanDependency that declare that the state output port does not depend on any of the input ports at this microstep. Moreover, the initialState and impulse ports are equivalent (to process inputs at either, you need to know about inputs at the other). You do not need to know about inputs at derivative.

Specified by:

getCausalityInterface in interface Actor

Overrides:

getCausalityInterface in class AtomicActor<TypedIOPort>

Returns:

A representation of the dependencies between input ports and output ports.

getDerivative

public double getDerivative()
                     throws NoTokenException,
                            IllegalActionException

Get the current value of the derivative input port.

Returns:

The current value at the derivative input port.

Throws:

NoTokenException - If reading the input throws it.

IllegalActionException - If thrown while reading the input.

getState

public final double getState()

Return the state of the integrator. The returned state is the latest confirmed state.

Returns:

The state of the integrator.

getTentativeState

public double getTentativeState()

Return the tentative state.

Returns:

The tentative state.

See Also:

setTentativeState(double)

initialize

public void initialize()
                throws IllegalActionException

Initialize the integrator. Check for the existence of a director and an ODE solver. Set the state to the value given by initialState.

Specified by:

initialize in interface Initializable

Overrides:

initialize in class AtomicActor<TypedIOPort>

Throws:

IllegalActionException - If there is no director, or the director has no ODE solver, or the initialState parameter does not contain a valid token, or the superclass throws it.

isStepSizeAccurate

public boolean isStepSizeAccurate()

Return true if the state is resolved successfully. If the input is not available, or the input is a result of divide by zero, a NumericalNonconvergeException is thrown.

Specified by:

isStepSizeAccurate in interface ContinuousStepSizeController

Returns:

True if the state is resolved successfully.

isStrict

public boolean isStrict()

Return false. This actor can produce some outputs even the derivative input is unknown. This actor is crucial at breaking feedback loops during simulation. The impulse and initialState ports, have to be known for prefire to return true (if they are connected).

Specified by:

isStrict in interface Executable

Overrides:

isStrict in class AtomicActor<TypedIOPort>

Returns:

False.

postfire

public boolean postfire()
                 throws IllegalActionException

Update the state. This commits the tentative state.

Specified by:

postfire in interface Executable

Overrides:

postfire in class AtomicActor<TypedIOPort>

Returns:

True always.

Throws:

IllegalActionException - Not thrown in this base class.

prefire

public boolean prefire()
                throws IllegalActionException

If either the impulse or initialState input is unknown, then return false. Otherwise, return true.

Specified by:

prefire in interface Executable

Overrides:

prefire in class AtomicActor<TypedIOPort>

Returns:

True If the actor is ready to fire.

Throws:

IllegalActionException - If the superclass throws it.

suggestedStepSize

public double suggestedStepSize()

Return the suggested next step size. This method delegates to the integratorPredictedStepSize() method of the current ODESolver.

Specified by:

suggestedStepSize in interface ContinuousStepSizeController

Returns:

The suggested next step size.

refinedStepSize

public double refinedStepSize()

Return the estimation of the refined next step size. If this integrator considers the current step to be accurate, then return the current step size, otherwise return half of the current step size.

Specified by:

refinedStepSize in interface ContinuousStepSizeController

Returns:

The refined step size.

rollBackToCommittedState

public void rollBackToCommittedState()

Roll back to committed state. This resets the tentative state to the current state.

Specified by:

rollBackToCommittedState in interface ContinuousStatefulComponent

setAuxVariables

public void setAuxVariables(int index,
                            double value)
                     throws InvalidStateException

Set the value of an auxiliary variable. The index indicates which auxiliary variable in the auxVariables array. If the index is out of the bound of the auxiliary variable array, an InvalidStateException is thrown to indicate an inconsistency in the ODE solver.

Parameters:

index - The index in the auxVariables array.

value - The value to be set.

Throws:

InvalidStateException - If the index is out of the range of the auxiliary variable array.

See Also:

getAuxVariables()

setTentativeState

public final void setTentativeState(double value)

Set the tentative state. Tentative state is the state that the ODE solver resolved in one step. This may not be the final state due to error control or event detection.

Parameters:

value - The value to be set.

See Also:

getTentativeState()