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Using Vergil ure 2.45 depend on instance. E.g., set it to “instance * 0.1” and then set nInstances to 1. You will see a clean sine wave when you run the model. 2.8.2 Mobile Code A pair of (still experimental) actors in Ptolemy II support mobile code in two forms. The Mobile- Function actor accepts a function in the expression language (see the Expression Language chapter) at one input port and applies that function to data that arrives at the other input port. The MobileModel actor accepts a MoML description of a Ptolemy II model at an input port and then executes that model, streaming data from the other input port through it. A use of the MobileFunction actor is shown in figure 2.47. In that model, two functions are provided to the MobileFunction in an alternating fashion, one that computes x and the other that com- 2 putes . These two functions are provided by two instances of the Const actor, found in Sources, 2 x GenericSources. The functions are interleaved by the Commutator actor, from FlowControl, Aggregators. 2.8.3 Lifecycle Management Actors A few actors in the HigherOrderActors library provide in a single firing the entire execution of another Ptolemy II model. The RunCompositeActor actor executes the contained model. The Model- Reference actor executes a model that is defined elsewhere in its own file or URL. The VisualModel- Reference actor opens a Vergil view of a referenced model when it executes a referenced model. These actors generally associate ports (that the user of the actor creates) with parameters of the referenced or contained model. They can be used, for example, to create models that repeatedly run other models with varying parameter values. See the documentation of the actors and the demonstrations in the FIGURE 2.47. The MobileFunction actor accepts a function definition at one port and applies it to data that arrives at the other port. 76 Ptolemy II
Using Vergil quick tour for more details. 2.9 Domains A key innovation in Ptolemy II is that, unlike other design and modeling environments, there are several available models of computation that define the meaning of a diagram. In the above examples, we directed you to drag in an SDF Director without justifying why. A director in Ptolemy II gives meaning (semantics) to a diagram. It specifies what a connection means, and how the diagram should be executed. In Ptolemy II terminology, the director realizes a domain. Thus, when you construct a model with an SDF director, you have constructed a model “in the SDF domain.” The SDF director is fairly easy to understand. “SDF” stands for “synchronous dataflow.” In dataflow models, actors are invoked (fired) when their input data is available. SDF is particularly simple case of dataflow where the order of invocation of the actors can be determined statically from the model. It does not depend on the data that is processed (the tokens that are passed between actors). But there are other models of computation available in Ptolemy II. And the system is extensible. You can invent your own. This richness has a downside, however. It can be difficult to determine which one to use without having experience with several. Moreover, you will find that although most actors in the library do something in any domain in which you use them, they do not always do something useful. It is important to understand the domain you are working with and the actors you are using. Here, we give a very brief introduction to some of the domains. We begin first by explaining some of the subtleties in SDF. 2.9.1 SDF and Multirate Systems So far we have been dealing with relatively simple systems. They are simple in the sense that each actor produces and consumes one token from each port at a time. In this case, the SDF director simply ensures that an actor fires after the actors whose output values it depends on. The total number of output values that are created by each actor is determined by the number of iterations, but in this simple case only one token would be produced per iteration. It turns out that the SDF scheduler is actually much more sophisticated. It is capable of scheduling the execution of actors with arbitrary prespecified data rates. Not all actors produce and consume just a single sample each time they are fired. Some require several input token before they can be fired, and produce several tokens when they are fired. One such actor is a spectral estimation actor. Figure 2.48 shows a system that computes the spectrum of the same noisy sine wave that we constructed in figure 2.25. The Spectrum actor has a single FIGURE 2.48. A multirate SDF model. The Spectrum actor requires 256 tokens to fire, so one iteration of this model results in 256 firings of Sinewave, Channel, and SequencePlotter, and one firing of Spectrum. Heterogeneous Concurrent Modeling and Design 77
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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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Page 41 and 42: Introduction Actor interfaces are k
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Page 45 and 46: Introduction actor actor.gui data.e
Page 47 and 48: Introduction cient, scalable, and u
Page 49 and 50: Introduction 1.5.8 Future Capabilit
Page 51 and 52: Introduction Appendix A: UML — Un
Page 53 and 54: Introduction grams, the only constr
Page 55 and 56: 2 Using Vergil Authors: Edward A. L
Page 57 and 58: Using Vergil 2.2.2 Executing a Pre-
Page 59 and 60: Using Vergil The Lorenz attractor m
Page 61 and 62: Using Vergil The Continuous-Time (C
Page 63 and 64: Using Vergil box in figure 2.11. En
Page 65 and 66: Using Vergil Don’t panic! Excepti
Page 67 and 68: Using Vergil tions are a normal par
Page 69 and 70: Using Vergil 2.4 Hierarchy Ptolemy
Page 71 and 72: Using Vergil Then using these ports
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Page 83 and 84: Using Vergil A key issue is to deci
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Page 89 and 90: Using Vergil uses the index in the
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 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
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4 Actor Libraries Authors: Elaine C
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Actor Libraries properly in the CT
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Actor Libraries ing that multiple c
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Actor Libraries TypedAtomicActor «
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Actor Libraries SequenceScope (exte
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Actor Libraries UnsignedByteArrayTo
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Actor Libraries MobileFunction (ext
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Actor Libraries LogicFunction (exte
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Actor Libraries Sleep (extends Tran
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Actor Libraries VariableFIR (extend
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Actor Libraries Integrator: Integra
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Actor Libraries Figure 4.4 shows th
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5 Designing Actors Authors: Christo
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Designing Actors /** Javadoc commen
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Designing Actors although with most
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Designing Actors import ptolemy.act
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Designing Actors makes such actors
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Designing Actors same parameter val
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Designing Actors morphic actor comp
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Designing Actors To get data polymo
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Designing Actors public class Seque
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Designing Actors be used in domains
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Designing Actors alComm actor. Beca
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Designing Actors attribute has valu
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Designing Actors import ptolemy.act
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6 Coding Style Authors: Christopher
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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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