ptolemy.domains.continuous.lib

Class PeriodicSampler

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.actor.lib.Transformer

ptolemy.domains.continuous.lib.PeriodicSampler

All Implemented Interfaces:

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

public class PeriodicSampler
extends Transformer

This actor generates discrete events by periodically sampling the input signal. The sampling rate is given by parameter samplePeriod, which has default value 0.1. Specifically, if the actor is initialized at time t and the sample period is T, then the output will have the value of the input at times t + nT, for all natural numbers n. By default, this sampler will send to the output the initial value of the input (the input value at microstep 0), but will send it one microstep later (at microstep 1). This ensures that the output at microstep 0 is always absent, thus ensuring continuity from the left. That is, the input is absent prior to the sample time, so continuity requires that it be absent at microstep 0 at the sample time.

To get this sampler to record values other than the initial value, set the microstep parameter to a value greater than 0. Setting it to 1, for example, will record the input value after a discontinuity rather than before the discontinuity. Note that Sampler normally records its inputs at microstep 1 (because it is triggered by a discrete signal, which has events at microstep 1), and therefore if you want this PeriodicSampler to behave the same as Sampler, you should set microstep to 1.

This actor has multiport inputs and outputs. Signals in each input channel are sampled and produced to corresponding output channel.

Note that this actor does not tolerate changing input or output connections during execution.

Since:

Ptolemy II 8.0

Version:

$Id$

Author:

Edward A. Lee

Pt.AcceptedRating:

Red (cxh)

Pt.ProposedRating:

Yellow (eal)

Nested Class Summary

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

Entity.ContainedObjectsIterator

Field Summary

Fields

Modifier and Type	Field and Description
Parameter	microstep The microstep at which to read the input.
Parameter	samplePeriod The parameter for the sampling period.

Fields inherited from class ptolemy.actor.lib.Transformer

input, output

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
PeriodicSampler(CompositeEntity container, java.lang.String name) Construct an actor in the specified container with the specified name.

Method Summary

Modifier and Type	Method and Description
void	attributeChanged(Attribute attribute) If the attribute is microstep, adjust the causality interface.
java.lang.Object	clone(Workspace workspace) Clone this actor into the specified workspace.
void	fire() Generate an output if the current time is one of the sampling times and the microstep matches.
void	initialize() Set the next sampling time for each input as the start time (i.e. the current time).
boolean	isStrict() Return false if the microstep value is zero.
boolean	postfire() If the current microstep is zero, sample the inputs and request a refiring at the current time.
void	preinitialize() Make sure the actor runs inside a domain that understands superdense time.

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, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, isFireFunctional, iterate, newReceiver, outputPortList, prefire, 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, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, newReceiver, outputPortList

Methods inherited from interface ptolemy.actor.Executable

isFireFunctional, iterate, prefire, stop, stopFire, terminate

Methods inherited from interface ptolemy.actor.Initializable

addInitializable, 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

microstep

public Parameter microstep

The microstep at which to read the input. This is an whose default value is 0.

samplePeriod

public Parameter samplePeriod

The parameter for the sampling period. This is a double whose default value is 0.1.

Constructor Detail

PeriodicSampler

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

Construct an actor in the specified container with the specified name. The name must be unique within the container or an exception is thrown. The container argument must not be null, or a NullPointerException will be thrown. The actor can be either dynamic, or not. It must be set at the construction time and can't be changed thereafter. A dynamic actor will produce a token at its initialization phase.

Parameters:

container - The container of this actor.

name - The actor's name

Throws:

IllegalActionException - If the entity cannot be contained by the proposed container.

NameDuplicationException - If name coincides with an entity already in the container.

Method Detail

attributeChanged

public void attributeChanged(Attribute attribute)
                      throws IllegalActionException

If the attribute is microstep, adjust the causality interface.

Overrides:

attributeChanged in class NamedObj

Parameters:

attribute - The attribute that changed.

Throws:

IllegalActionException - If the superclass throws it.

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

Generate an output if the current time is one of the sampling times and the microstep matches. In addition, if the microstep parameter has value 0, produce the output only if the current microstep is 1. The value of the event is the value of the input signal at the current time at the microstep specified by the microstep parameter.

Specified by:

fire in interface Executable

Overrides:

fire in class AtomicActor<TypedIOPort>

Throws:

IllegalActionException - If the transfer of tokens failed.

initialize

public void initialize()
                throws IllegalActionException

Set the next sampling time for each input as the start time (i.e. the current time). We do not register the start time as a breakpoint, since the director will fire at the start time any way.

Specified by:

initialize in interface Initializable

Overrides:

initialize in class AtomicActor<TypedIOPort>

Throws:

IllegalActionException - If thrown by the supper class.

isStrict

public boolean isStrict()

Return false if the microstep value is zero. In that case, this actor can produce some outputs even the inputs are unknown. This actor is usable for breaking feedback loops. It does not read inputs in the fire() method.

Specified by:

isStrict in interface Executable

Overrides:

isStrict in class AtomicActor<TypedIOPort>

Returns:

False.

postfire

public boolean postfire()
                 throws IllegalActionException

If the current microstep is zero, sample the inputs and request a refiring at the current time. If it is one, then request a refiring at the next sample time.

Specified by:

postfire in interface Executable

Overrides:

postfire in class AtomicActor<TypedIOPort>

Returns:

True.

Throws:

IllegalActionException - If the superclass throws it.

preinitialize

public void preinitialize()
                   throws IllegalActionException

Make sure the actor runs inside a domain that understands superdense time.

Specified by:

preinitialize in interface Initializable

Overrides:

preinitialize in class AtomicActor<TypedIOPort>

Throws:

IllegalActionException - If the director is not a SuperdenseTimeDirector or the parent class throws it.