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Actor Libraries if SDF is the top-level domain, the current time will always be zero, which is likely to lead to some confusion with timed actors. 4.3 Actor Summaries In this section, we summarize the actors that are provided in the default Vergil actor library, shown at the left-hand side of the window in figure 4.2. Note that this library is organized for user convenience, and the organization does not exactly match the package structure. Here, we give brief descriptions of each actor to give a high-level view of what actors are available in the library. Refer to the class documentation for a complete description of these actors (in Vergil, you can right-click on an icon and select “Get Documentation” to get the detailed documentation for an actor). It is useful to know some general patterns of behavior: Unless otherwise stated, actors will read at most one input token from each input channel of each input port, and will produce at most one output token. No output token is produced unless there are input tokens. Unless otherwise stated, actors can operate in all domains except the FSM (finite state machine) domain, where components are instances of the State class. Additionally, actors that implement the SequenceActor or TimedActor interfaces may be rejected by some domains. 4.3.1 Sources A source actor is a source of tokens. Most source actors extend the Source base class, as shown in figure 4.1. Such actors have a trigger input port, which in some domains serves to stimulate an output. In the DE (discrete event) domain, for example, an input at the trigger port causes the current value of the source to be produced at the time stamp of the trigger input. The trigger port is a multiport, mean- FIGURE 4.2. The default Vergil actor library is shown at the left, expanded to the first level. 130 Ptolemy <strong>II</strong>
Actor Libraries ing that multiple channels can be connected to it. The trigger port can also be left unconnected in domains that will invoke the actor automatically (SDF, DT, PN, ...). There is no need for a trigger in these domains. Some source actors use the fireAt() method of the director to request that the actor be fired at particular times in the future. In domains that do not ignore fireAt(), such as DE, such actors will fire repeatedly even if there is no trigger input. In the DE domain, the fireAt() method schedules an event in the future to refire the actor. Source actors that extend TimedSource have a parameter called stopTime. When the current time of the model reaches this time, then the actor requests of the director that this actor not be invoked again. Thus, stopTime can be used to generate a finite source signal. By default, the stopTime parameter has value 0.0, which indicates unbounded execution. Source actors that extend SequenceSource have a parameter called firingCountLimit. When the number of iterations of the actor reaches this limit, then the actor requests of the director that this actor not be invoked again. Thus, firingCountLimit can be used to generate a finite source signal. By default, the firingCountLimit parameter has value 0, which indicates unbounded execution. In some domains, such as SDF and DT, it makes no sense to stop the execution of a single actor. The statically constructed schedule would be disrupted. In these domains, when the specified stopTime or firingCountLimit is reached, the execution of the entire model will stop. Some of the most useful actors are Clock, which is used extensively in DE models to trigger regularly timed events; Ramp, which produces a counting sequence; Const, which produces a constant; and Pulse, which produces an arbitrary sequence. In Vergil, the source library is divided into generic sources, timed sources, and sequence sources. The first group includes only one source, Const, which is agnostic about whether its output is interpreted as a timed output or a sequence output. The other two groups contain actors for which the output is either timed or is logically a sequence. Generic Sources Const (extends Source): Produce a constant output with value given by the value parameter. Timed Sources Clock (extends TimedSource): Produce samples of a piecewise constant signal with the specified values. The transitions between values occur with the specified period and offsets within the period. This actor uses fireAt() to schedule firings when time matches the transition times, and thus will at least produce outputs at these times. To generate a continuous-time clock, you will likely want to use ContinuousClock instead; that version produces two outputs at the transition times, one with the old value and one with the new. CurrentTime (extends TimedSource): Produce an output token with value equal to the current time (the model time when the actor is fired). PoissonClock (extends TimedSource): Produce samples of a piecewise constant signal with the specified values. The transitions between values occur according to a Poisson process (which has random interarrival times with an exponential distribution). This actor uses fireAt() to schedule firings when time matches the transition times, and thus will at least produce outputs at these times. Heterogeneous Concurrent Modeling and Design 131
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PTOLEMY II HETEROGENEOUS CONCURRENT
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VOLUME 1 INTRODUCTION TO PTOLEMY II
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Volume 1 Contents Introduction to P
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2.10.3. Constructing Modal Models 8
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7. MoML 191 7.1. Introduction 191 7
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1 Introduction Author: Edward A. Le
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Introduction heterochronous dataflo
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Introduction A major emphasis in Pt
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Introduction determine when actors
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Introduction provides levels of vis
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Introduction is a guard, and the se
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Introduction well. All of these are
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Introduction clients to update thei
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Introduction will be supplied with
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Introduction 1.3.12 Synchronous Dat
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Introduction FIGURE 1.10. Refinemen
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Introduction occlusions due to terr
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Introduction tion. The overall arch
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Introduction kernel.attributes This
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Introduction 1.5.2 Overview of Key
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Introduction Actor interfaces are k
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Heterogeneous Concurrent Modeling a
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Introduction actor actor.gui data.e
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Introduction cient, scalable, and u
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Introduction 1.5.8 Future Capabilit
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Introduction Appendix A: UML — Un
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Introduction grams, the only constr
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2 Using Vergil Authors: Edward A. L
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Using Vergil 2.2.2 Executing a Pre-
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Using Vergil The Lorenz attractor m
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Using Vergil The Continuous-Time (C
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Using Vergil box in figure 2.11. En
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Using Vergil Don’t panic! Excepti
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Using Vergil tions are a normal par
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Using Vergil 2.4 Hierarchy Ptolemy
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Using Vergil Then using these ports
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Using Vergil the default 0.1 to 0.0
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Using Vergil pan window, it is easy
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Using Vergil FIGURE 2.33. The pan w
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Using Vergil we have modified the c
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Using Vergil model, simply copy (or
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Using Vergil A key issue is to deci
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Using Vergil instances. This proble
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Using Vergil quick tour for more de
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Page 91 and 92: Using Vergil AddSubtract actor, and
Page 93 and 94: Using Vergil If you look inside the
Page 95 and 96: Using Vergil If you look inside the
Page 97 and 98: Using Vergil transition (or right c
Page 99 and 100: Using Vergil Once you have created
Page 101 and 102: Using Vergil The grid is turned off
Page 103 and 104: Authors: Edward A. Lee Xiaojun Liu
Page 105 and 106: Expressions classes to create a gen
Page 107 and 108: Expressions The % operation is a mo
Page 109 and 110: Expressions attribute, which includ
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Page 115 and 116: Expressions from it. For instance,
Page 117 and 118: Expressions defined. For example, >
Page 119 and 120: Expressions length is given by the
Page 121 and 122: Expressions Thus, for example, you
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Page 125 and 126: Expressions value. For example, fix
Page 127 and 128: Expressions In the example in figur
Page 129 and 130: Expressions A.2 Basic Mathematical
Page 131 and 132: Expressions A.3 Matrix, Array, and
Page 133 and 134: Expressions A.5 Signal Processing F
Page 135 and 136: Expressions TABLE 8: Functions perf
Page 137 and 138: 4 Actor Libraries Authors: Elaine C
Page 139: Actor Libraries properly in the CT
Page 143 and 144: Actor Libraries TypedAtomicActor «
Page 145 and 146: Actor Libraries SequenceScope (exte
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Page 149 and 150: Actor Libraries MobileFunction (ext
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Page 157 and 158: Actor Libraries Integrator: Integra
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Page 161 and 162: 5 Designing Actors Authors: Christo
Page 163 and 164: Designing Actors /** Javadoc commen
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Page 167 and 168: Designing Actors import ptolemy.act
Page 169 and 170: Designing Actors makes such actors
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Page 173 and 174: Designing Actors morphic actor comp
Page 175 and 176: Designing Actors To get data polymo
Page 177 and 178: Designing Actors public class Seque
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Page 181 and 182: Designing Actors alComm actor. Beca
Page 183 and 184: Designing Actors attribute has valu
Page 185 and 186: Designing Actors import ptolemy.act
Page 187 and 188: 6 Coding Style Authors: Christopher
Page 189 and 190: Coding Style /* One line descriptio
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Coding Style Copyright (c) 2004 The
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Coding Style @version $Id: NamedObj
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Coding Style } We use instead the i
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Coding Style * @exception MyExcepti
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Coding Style + "it does not impleme
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Authors: Edward A. Lee Steve Neuend
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MoML cutes it forever, until you hi
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MoML A second difference between ou
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MoML
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MoML 7.3.3 Names and Classes Most M
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MoML Here, the element named
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MoML implement. 7.3.7 Doc Element S
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MoML It is also sometimes necess
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MoML then there will be a link t
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MoML found. For example, if the cla
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MoML it cannot collide with the nam
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MoML The rendering of the icon is d
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MoML 7.4.5 Deleting Entities, Relat
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MoML This unlinks a port from the s
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MoML model. The EntityLibrary class
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MoML Suppose that using incremental
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MoML Generate a sine wave.
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MoML
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MoML Number of iterations in
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MoML -P- The f
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MoML -P- The phase,
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8 Custom Applets Authors: Edward A.
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Custom Applets html code, see the J
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Custom Applets public class Tutoria
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Custom Applets then the result of
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Custom Applets 8.3.5 Using Model Pa
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Custom Applets ptolemy/domains/doma
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References [1] G. Agha, Actors: A M
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[33] S. A. Edwards, “The Specific
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[67] E. Kohler, The Click Modular R
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[95] J. Liu, X. Liu, T. J. Koo, B.
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[132]W. R. Sutherland, "The on-Line
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Glossary abstract syntax ..........
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Ptolemy II ........................
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Index Symbols - in UML 41 # in UML
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coin flips 142 Color class 173 colo
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entity in XML 198 EntityLibrary cla
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Director class 159 inverse FFT 124
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CompositeEntity class 206 nextPower
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safety 34 SampleDelay actor 78, 138
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type constraint 155 type constraint
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