ptolemy.actor.lib
Class Clock

java.lang.Object
  ptolemy.kernel.util.NamedObj
      ptolemy.kernel.InstantiableNamedObj
          ptolemy.kernel.Entity
              ptolemy.kernel.ComponentEntity
                  ptolemy.actor.AtomicActor
                      ptolemy.actor.TypedAtomicActor
                          ptolemy.actor.lib.Source
                              ptolemy.actor.lib.TimedSource
                                  ptolemy.actor.lib.Clock

All Implemented Interfaces:

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

Direct Known Subclasses:

TriggeredClock, VariableClock

public class Clock
extends TimedSource

This actor produces a periodic signal, a sequence of events at regularly spaced intervals. At the beginning of each time interval of length given by period, starting from the time at which initialize() is invoked, this actor initiates a sequence of output events with values given by values and offset into the period given by offsets. These parameters contain arrays, which are required to have the same length. The offsets array contains doubles, which must be nondecreasing and nonnegative, or an exception will be thrown when it is set. If any entry is greater than or equal to the period then the corresponding output will never be produced.

The values parameter by default contains an array of IntTokens with values 1 and 0. The default offsets array is {0.0, 1.0}. Thus, the default output will be alternating 1 and 0 with 50% duty cycle. The default period is 2.0.

The type of the output can be any token type. This type is inferred from the element type of the values parameter.

If the period is changed at any time, either by providing an input or by changing the parameter, then the new period will take effect as soon as possible. That is, if there is already a period in progress, it may be cut short if the new period is shorter so that its time matches the new period. But it will only be cut short if current time has not passed the cycle start time plus the new period. Otherwise, the period in progress will run to completion.

This actor can generate finite sequences by specifying a finite numberOfCycles. The numberOfCycles has a default value UNBOUNDED, indicating infinite length of executions. If numberOfCycles is a positive number, once the specified number of cycles has been completed, then this actor returns false from the postfire() method, which indicates to the director that the actor should not be fired again. (A cycle is "completed" each time the last event in the values array is produced).

The actor can also generate a finite sequence by giving a finite value to the stopTime parameter. This gives a time rather than a number of cycles, and thus can be used to stop the clock in the middle of a cycle, unlike numberOfCycles. Just like numberOfCycles, when the stop time is reached, the actor's postfire() method returns false.

If the trigger input is connected, then an output will only be produced if a input has been received since the last output. The trigger input has no effect on the first output. After the first output event, no further output event will be produced until a time greater than or equal to the time at which a trigger input is received. At that time, the output produced will have whatever value would have been produced if the trigger input was not connected. Note that this trigger is typically useful in a feedback situation, where the output of the clock eventually results in a trigger input. If the time-stamp of that trigger input is less than the time between clock events, then the clock will behave as if there were no trigger input. Otherwise, it will "skip beats."

This actor can be a bit tricky to use inside a ModalModel. In particular, if the actor is in a state refinement, then it may "skip a beat" because of the state not being the current state at the time of the beat. If this occurs, the clock will simply stop firing, and will produce no further outputs. To prevent this, the clock may be reinitialized (by setting the reset flag of a modal model transition). Alternatively, you can assign a value to the the period of the Clock in the setActions of the transition. This will also have the effect of waking up the clock, but with a subtle difference. If you use a reset transition, the clock starts over upon entering the destination state. If you set the period parameter instead, then the clock behaves as if it had been running all along (except that its period may get changed). Thus, in the first case, the output events are aligned with the time of the transition, while in the second case, they are aligned with the start time of the model execution.

This actor is a timed source; the untimed version is Pulse.

Since:

Ptolemy II 0.3

Version:

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

Author:

Edward A. Lee, Haiyang Zheng

See Also:

Serialized Form

Accepted Rating:

Yellow (yuhong)

Proposed Rating:

Yellow (eal)

Nested Class Summary

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

Entity.ContainedObjectsIterator

Field Summary

protected int	_cycleCount The count of cycles executed so far, or 0 before the start.
protected Time	_cycleStartTime The most recent cycle start time.
protected boolean	_enabled Indicator of whether the specified number of cycles have been completed.
protected boolean	_firstOutputProduced Indicator of whether the first output has been produced.
protected Time	_nextOutputTime The time for the next output.
protected double[]	_offsets Cache of offsets array value.
protected boolean	_outputProduced Indicator of whether an output was produced in this iteration.
protected int	_phase The phase of the next output.
private double	_previousPeriod The previous value of the period.
private boolean	_tentative Flag indicating that an update to period is occurring in the fire() method.
private Time	_tentativeCycleStartTime The tentative start time of the most recent cycle.
private boolean	_tentativeEnabled The indicator of whether the specified number of cycles have been completed.
protected Time	_tentativeNextOutputTime The tentative time for the next output.
private int	_tentativePhase The tentative phase of the next output.
private boolean	_tentativeTriggered Tentative indicator of triggered state.
private boolean	_triggered Indicator of whether trigger inputs have arrived since the last output.
Parameter	numberOfCycles The number of cycles to produce, or UNBOUNDED to specify no limit.
Parameter	offsets The offsets at which the specified values will be produced.
PortParameter	period The period of the output waveform.
Parameter	values The values that will be produced at the specified offsets.

Fields inherited from class ptolemy.actor.lib.TimedSource

stopTime, stopTimeIsLocal

Fields inherited from class ptolemy.actor.lib.Source

output, trigger

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

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

Method Summary

protected void	_catchUp() Catch up the tentative view of what the next output time should be.
protected Token	_getValue(int index) Get the specified output value, checking the form of the values parameter.
protected boolean	_isTimeForOutput() Return true if the current time is the right time for an output.
protected void	_updateStates() Update the states and request refiring if necessary.
protected void	_updateTentativeValues() Copy values committed in initialize() or in the last postfire() into the corresponding tentative variables.
void	attributeChanged(Attribute attribute) If the argument is the offsets parameter, check that the array is nondecreasing and has the right dimension; if the argument is period, check that it is positive.
java.lang.Object	clone(Workspace workspace) Clone the actor into the specified workspace.
void	fire() Output the current value of the clock if the time is right and, if connected, a trigger has been received.
void	initialize() Schedule the first firing and initialize local variables.
boolean	postfire() Update the state of the actor and schedule the next firing, if appropriate.
boolean	prefire() Check that the length of the values and offsets parameters are the same.

Methods inherited from class ptolemy.actor.lib.TimedSource

getModelStopTime, getStopTime, wrapup

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, connectionsChanged, createReceivers, declareDelayDependency, getCausalityInterface, getDirector, getExecutiveDirector, getManager, inputPortList, isFireFunctional, isStrict, iterate, newReceiver, outputPortList, preinitialize, pruneDependencies, recordFiring, removeActorFiringListener, removeDependency, removeInitializable, setContainer, stop, stopFire, terminate

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, 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, stop, stopFire, terminate

Methods inherited from interface ptolemy.actor.Initializable

addInitializable, preinitialize, removeInitializable

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

numberOfCycles

public Parameter numberOfCycles

The number of cycles to produce, or UNBOUNDED to specify no limit. This is an integer with default UNBOUNDED.

offsets

public Parameter offsets

The offsets at which the specified values will be produced. This parameter must contain an array of doubles, and it defaults to {0.0, 1.0}.

period

public PortParameter period

The period of the output waveform. This is a double that defaults to 2.0.

values

public Parameter values

The values that will be produced at the specified offsets. This parameter must contain an ArrayToken, and it defaults to {1, 0}

_cycleCount

protected transient int _cycleCount

The count of cycles executed so far, or 0 before the start.

_cycleStartTime

protected transient Time _cycleStartTime

The most recent cycle start time.

_enabled

protected transient boolean _enabled

Indicator of whether the specified number of cycles have been completed. Also used in derived classes to turn on and off the clock.

_firstOutputProduced

protected transient boolean _firstOutputProduced

Indicator of whether the first output has been produced.

_nextOutputTime

protected transient Time _nextOutputTime

The time for the next output.

_offsets

protected transient double[] _offsets

Cache of offsets array value.

_outputProduced

protected transient boolean _outputProduced

Indicator of whether an output was produced in this iteration.

_phase

protected transient int _phase

The phase of the next output.

_tentativeNextOutputTime

protected transient Time _tentativeNextOutputTime

The tentative time for the next output.

_previousPeriod

private transient double _previousPeriod

The previous value of the period.

_tentativeCycleStartTime

private transient Time _tentativeCycleStartTime

The tentative start time of the most recent cycle.

_tentative

private transient boolean _tentative

Flag indicating that an update to period is occurring in the fire() method.

_tentativeEnabled

private transient boolean _tentativeEnabled

The indicator of whether the specified number of cycles have been completed.

_tentativePhase

private transient int _tentativePhase

The tentative phase of the next output.

_tentativeTriggered

private transient boolean _tentativeTriggered

Tentative indicator of triggered state.

_triggered

private transient boolean _triggered

Indicator of whether trigger inputs have arrived since the last output.

Constructor Detail

Clock

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

Construct an actor with the specified container and name.

Parameters:

container - The container.

name - The name of this actor.

Throws:

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

NameDuplicationException - If the container already has an actor with this name.

Method Detail

attributeChanged

public void attributeChanged(Attribute attribute)
                      throws IllegalActionException

If the argument is the offsets parameter, check that the array is nondecreasing and has the right dimension; if the argument is period, check that it is positive. Other sanity checks with period and values are done in the fire() method.

Overrides:

attributeChanged in class TimedSource

Parameters:

attribute - The attribute that changed.

Throws:

IllegalActionException - If the offsets array is not nondecreasing and nonnegative, or if the director will not respect the fireAt() call.

clone

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

Clone the actor into the specified workspace. This calls the base class and then sets the parameter public members to refer to the parameters of the new actor.

Overrides:

clone in class AtomicActor

Parameters:

workspace - The workspace for the new object.

Returns:

A new actor.

Throws:

java.lang.CloneNotSupportedException - If a derived class contains an attribute that cannot be cloned.

See Also:

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

fire

public void fire()
          throws IllegalActionException

Output the current value of the clock if the time is right and, if connected, a trigger has been received.

Specified by:

fire in interface Executable

Overrides:

fire in class Source

Throws:

IllegalActionException - If the value in the offsets parameter is encountered that is greater than the period, or if there is no director.

initialize

public void initialize()
                throws IllegalActionException

Schedule the first firing and initialize local variables.

Specified by:

initialize in interface Initializable

Overrides:

initialize in class TimedSource

Throws:

IllegalActionException - If the parent class throws it, or if the values parameter is not a row vector, or if the fireAt() method of the director throws it, or if the director will not respect the fireAt() call.

postfire

public boolean postfire()
                 throws IllegalActionException

Update the state of the actor and schedule the next firing, if appropriate.

Specified by:

postfire in interface Executable

Overrides:

postfire in class TimedSource

Returns:

True if execution can continue into the next iteration.

Throws:

IllegalActionException - If the director throws it when scheduling the next firing.

prefire

public boolean prefire()
                throws IllegalActionException

Check that the length of the values and offsets parameters are the same.

Specified by:

prefire in interface Executable

Overrides:

prefire in class TimedSource

Returns:

True.

Throws:

IllegalActionException - If the values and offsets parameters do not have the same length.

_catchUp

protected void _catchUp()
                 throws IllegalActionException

Catch up the tentative view of what the next output time should be. This sets _tentativeNextOutputTime to a value that is equal to or greater than current time, and it updates _tentativePhase and _tentativeCycleStartTime to correspond with this _tentativeNextOutputTime. If _tentativeNextOutputTime is already equal to or greater than current time, then do nothing.

Throws:

IllegalActionException - If the period is invalid.

_getValue

protected Token _getValue(int index)
                   throws IllegalActionException

Get the specified output value, checking the form of the values parameter.

Parameters:

index - The index of the output values.

Returns:

A token that contains the output value.

Throws:

IllegalActionException - If the index is out of the range of the values parameter.

_isTimeForOutput

protected boolean _isTimeForOutput()
                            throws IllegalActionException

Return true if the current time is the right time for an output.

Returns:

True if the current time matches the _nextOutputTime.

Throws:

IllegalActionException - If the time is not right an a refiring cannot be requested.

_updateTentativeValues

protected void _updateTentativeValues()
                               throws IllegalActionException

Copy values committed in initialize() or in the last postfire() into the corresponding tentative variables. In effect, this loads the last known good value for these variables, which is particularly important if time has gone backwards. This is done in a protected method because derived classes may want to override it.

Throws:

IllegalActionException - Not thrown in this base class.

_updateStates

protected void _updateStates()
                      throws IllegalActionException

Update the states and request refiring if necessary.

Throws:

IllegalActionException - If the numberOfCycles parameter does not contain a valid parameter or can not request refiring, or if the director will not respect the fireAt() call..