ptolemy.domains.dde.kernel
Class FeedBackDelay

java.lang.Object
  ptolemy.kernel.util.NamedObj
      ptolemy.kernel.InstantiableNamedObj
          ptolemy.kernel.Entity
              ptolemy.kernel.ComponentEntity
                  ptolemy.actor.AtomicActor
                      ptolemy.actor.TypedAtomicActor
                          ptolemy.domains.dde.kernel.DDEActor
                              ptolemy.domains.dde.kernel.FeedBackDelay

All Implemented Interfaces:

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

public class FeedBackDelay
extends DDEActor

FeedBackDelay actors are used to add delay to feedback topologies. If a FeedBackDelay actor consumes a token (real or Null), it has the option of producing an equivalent token on the output with an incremented time stamp value. Alternatively, the FeedBackDelay actor will simply produce the token without altering the time stamp.

Two parameters - nullDelay and realDelay - are available for determining whether an FeedBackDelay actor increments the time stamp of produced output tokens. The default value of nullDelay (realDelay) is true (false). If the nullDelay (realDelay) parameter is set to true, then the time stamps of NullTokens (real tokens) will be incremented as they pass through this actor.

The delay value that is applied (given that one of the above parameters is true) is determined by the setDelay() and getDelay() methods. More elaborate delay values can be made available by overriding the getDelay() method in derived classes.

FeedBackDelay actors are effective for preventing Zeno conditions involving cycles of null tokens. If a DDE model has a feedback topology, a FeedBackDelay actor should be added into the feedback loop.

The delay value of a FeedBackDelay actor must be wisely chosen. The delay value should be smaller than any other successive time stamp increment found in a given DDE model. This means that if a particular model might have any two time stamps with time difference delta, then the delay value should be smaller than delta.

Since:

Ptolemy II 0.4

Version:

$Id: FeedBackDelay.java 57040 2010-01-27 20:52:32Z cxh $

Author:

John S. Davis II

See Also:

NullToken, Serialized Form

Accepted Rating:

Red (yuhong)

Proposed Rating:

Red (davisj)

Nested Class Summary

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

Entity.ContainedObjectsIterator

Field Summary

Parameter	delay The delay for this actor.
TypedIOPort	input The input port.
Parameter	nullDelay The boolean parameter that indicates whether a delay value will be added to the time stamp of null tokens that are produced by this actor.
TypedIOPort	output The output port.
Parameter	realDelay The boolean parameter that indicates whether a delay value will be added to the time stamp of real tokens that are produced by this actor.

Fields inherited from class ptolemy.actor.AtomicActor

_actorFiringListeners, _initializables, _notifyingActorFiring, _stopRequested

Fields inherited from class ptolemy.kernel.util.NamedObj

_changeListeners, _changeLock, _changeRequests, _debugging, _debugListeners, _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

FeedBackDelay()
Construct a FeedBackDelay with no container and a name that is an empty string.

FeedBackDelay(CompositeEntity container, java.lang.String name)
Construct a FeedBackDelay with the specified container and name.

FeedBackDelay(Workspace workspace)
Construct a FeedBackDelay with the specified workspace and a name that is an empty string.

Method Summary

private void	_sendOutToken(Token token, Time time) Syntactic sugar for sending out tokens without depending on IOPort.send().
private void	_setVariables() Syntactic sugar for initializing parameters.
void	fire() Consume a single input token and produce an identical output token.
double	getDelay() Return the delay value of this actor.
void	initialize() Initialize this actor by setting all receivers so that they do not hide NullTokens.

Methods inherited from class ptolemy.domains.dde.kernel.DDEActor

_getNextInput, getNextToken

Methods inherited from class ptolemy.actor.TypedAtomicActor

_addPort, _fireAt, _fireAt, attributeTypeChanged, clone, newPort, typeConstraintList, typeConstraints

Methods inherited from class ptolemy.actor.AtomicActor

_actorFiring, _actorFiring, addActorFiringListener, addInitializable, clone, connectionsChanged, createReceivers, declareDelayDependency, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, isFireFunctional, isStrict, iterate, newReceiver, outputPortList, postfire, prefire, 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

_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, _debug, _debug, _debug, _debug, _debug, _getIndentPrefix, _isMoMLSuppressed, _markContentsDerived, _propagateValue, _recordDecoratedAttributes, _removeAttribute, _splitName, _stripNumericSuffix, addChangeListener, addDebugListener, attributeChanged, attributeList, attributeList, 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, propagateValue, propagateValues, removeChangeListener, removeDebugListener, 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, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, newReceiver, outputPortList

Methods inherited from interface ptolemy.actor.Executable

isFireFunctional, isStrict, iterate, postfire, prefire, 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

delay

public Parameter delay

The delay for this actor. The initial default value is a double with value 1.0.

input

public TypedIOPort input

The input port.

nullDelay

public Parameter nullDelay

The boolean parameter that indicates whether a delay value will be added to the time stamp of null tokens that are produced by this actor. This parameter defaults to true.

output

public TypedIOPort output

The output port.

realDelay

public Parameter realDelay

The boolean parameter that indicates whether a delay value will be added to the time stamp of real tokens that are produced by this actor. This parameter defaults to false.

Constructor Detail

FeedBackDelay

public FeedBackDelay()
              throws IllegalActionException,
                     NameDuplicationException

Construct a FeedBackDelay with no container and a name that is an empty string.

Throws:

IllegalActionException - If the constructor of the superclass throws an IllegalActionException.

NameDuplicationException - If the constructor of the superclass throws a NameDuplicationException .

FeedBackDelay

public FeedBackDelay(Workspace workspace)
              throws IllegalActionException,
                     NameDuplicationException

Construct a FeedBackDelay with the specified workspace and a name that is an empty string.

Parameters:

workspace - The workspace for this FeedBackDelay.

Throws:

IllegalActionException - If the constructor of the superclass throws an IllegalActionException.

NameDuplicationException - If the constructor of the superclass throws a NameDuplicationException .

FeedBackDelay

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

Construct a FeedBackDelay with the specified container and name.

Parameters:

container - The container of this FeedBackDelay.

name - The name of this FeedBackDelay.

Throws:

IllegalActionException - If the constructor of the superclass throws an IllegalActionException.

NameDuplicationException - If the constructor of the superclass throws a NameDuplicationException .

Method Detail

fire

public void fire()
          throws IllegalActionException

Consume a single input token and produce an identical output token. If the input token is a NullToken and the nullDelay parameter is set to true, then produce an output NullToken to have a time stamp with a delay specified by getDelay(). Otherwise produce a NullToken that does not have a delayed time stamp value. If the input token is a real token and the realDelay parameter is set to true, then produce an output real token to have a time stamp with a delay specified by getDelay(). Otherwise produce a real token that does not have a delayed time stamp value.

Specified by:

fire in interface Executable

Overrides:

fire in class AtomicActor

Throws:

IllegalActionException - If there is an error when sending the output token or setting the current time.

getDelay

public double getDelay()
                throws IllegalActionException

Return the delay value of this actor.

Returns:

The delay value of this actor.

Throws:

IllegalActionException - If there is a problem reading the delay token.

initialize

public void initialize()
                throws IllegalActionException

Initialize this actor by setting all receivers so that they do not hide NullTokens.

Specified by:

initialize in interface Initializable

Overrides:

initialize in class AtomicActor

Throws:

IllegalActionException - If there is an error when when attempting to access the receivers of this actor.

See Also:

NullToken, DDEReceiver

_sendOutToken

private void _sendOutToken(Token token,
                           Time time)
                    throws IllegalActionException

Syntactic sugar for sending out tokens without depending on IOPort.send().

Throws:

IllegalActionException

_setVariables

private void _setVariables()
                    throws IllegalActionException,
                           NameDuplicationException

Syntactic sugar for initializing parameters.

Throws:

IllegalActionException

NameDuplicationException