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1.3.9 Graphics - GR Introduction The GR domain, created by Chamberlain Fong, generates two and three dimensional animated figures that can be tightly coupled to simulation models created using other domains. An example of the output of this domain is shown in figure 1.8 below, where GR is being used to create an animation of motion of two masses on springs. The semantics of GR is optimized towards construction and updating of scene graphs, and it can be viewed as an extremely specialized form of dataflow. In this model, the data is provided to the GR model by periodically sampling the output of a continuous-time model, as shown in figure 1.9. 1.3.10 Hybrid Systems Hybrid systems are systems that combine continuous dynamics with discrete mode transitions. Strictly speaking hybrid systems are not a domain in Ptolemy II, but rather a combination of domains. Hybrid systems are constructed in Ptolemy II by hierarchically nesting the continuous-time domain with the FSM domain, with occasional uses of DE and GR domains as well. An example of a hybrid system model is shown in figure 1.8. In this model, two masses are mounted on springs. The model begins with the springs compresses or stretched, so the masses oscillate. When the masses collide, a discrete transitions in the model occurs, and the physics changes. This change is represented by the transitions in the state machine at the bottom of figure 1.9. The states in that state machine refine further to continuous-time models of the physics, as shown in figure 1.10. Overall, this model combines four distinct Ptolemy II domains. The hybrid systems modeling capability of Ptolemy II is also packaged separately as HyVisual, a Ptolemy II configuration [25]. The ability to create such separately branded and packaged subsets of Ptolemy II is a major feature. 1.3.11 Process Networks - PN In the process networks (PN) domain, created by Mudit Goel [46], processes communicate by sending messages through channels that can buffer the messages. The sender of the message need not wait for the receiver to be ready to receive the message. This style of communication is often called asynchronous message passing. There are several variants of this technique, but the PN domain specifically implements one that ensures determinate computation, namely Kahn process networks [63]. In the PN model of computation, the arcs represent sequences of data values (tokens), and the entities represent functions that map input sequences into output sequences. Certain technical restrictions on these functions are necessary to ensure determinacy, meaning that the sequences are fully specified. In particular, the function implemented by an entity must be prefix monotonic. The PN domain realizes a subclass of such functions, first described by Kahn and MacQueen [64], where blocking reads ensure monotonicity. PN models are loosely coupled, and hence relatively easy to parallelize or distribute. They can be implemented efficiently in both software and hardware, and hence leave implementation options open. A key weakness of PN models is that they are awkward for specifying control logic, although much of this awkwardness may be ameliorated by combining them with FSM. The PN domain in Ptolemy II has a highly experimental timed extension. This adds to the blocking reads a method for stalling processes until time advances. We anticipate that this timed extension will make interoperation with timed domains much more practical. 18 Ptolemy II
Introduction 1.3.12 Synchronous Dataflow - SDF The synchronous dataflow (SDF) domain, created by Steve Neuendorffer, handles regular computations that operate on streams. Dataflow models, popular in signal processing, are a special case of process networks (for the complete explanation of this, see [81]). Dataflow models construct processes of a process network as sequences of atomic actor firings. Synchronous dataflow (SDF) is a particularly restricted special case with the extremely useful property that deadlock and boundedness are decidable. Moreover, the schedule of firings, parallel or sequential, is computable statically, making SDF an extremely useful specification formalism for embedded real-time software and for hardware. Certain generalizations sometimes yield to similar analysis. Boolean dataflow (BDF) models sometimes yield to deadlock and boundedness analysis, although fundamentally these questions are FIGURE 1.8. Example of a hybrid system model, top-level view. masses on springs 3-D animation is generated using the GR domain Heterogeneous Concurrent Modeling and Design 19
Page 1 and 2: PTOLEMY II HETEROGENEOUS CONCURRENT
Page 3 and 4: VOLUME 1 INTRODUCTION TO PTOLEMY II
Page 5 and 6: Volume 1 Contents Introduction to P
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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
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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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Using Vergil uses the index in the
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Using Vergil AddSubtract actor, and
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Using Vergil If you look inside the
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Using Vergil If you look inside the
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Using Vergil transition (or right c
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Using Vergil Once you have created
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Using Vergil The grid is turned off
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Authors: Edward A. Lee Xiaojun Liu
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Expressions classes to create a gen
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Expressions The % operation is a mo
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Expressions attribute, which includ
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Expressions 3.3.5 State Machines Ex
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Expressions whose value is an array
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Expressions from it. For instance,
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Expressions defined. For example, >
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Expressions length is given by the
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Expressions Thus, for example, you
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Expressions number. With one additi
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Expressions value. For example, fix
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Expressions In the example in figur
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Expressions A.2 Basic Mathematical
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Expressions A.3 Matrix, Array, and
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Expressions A.5 Signal Processing F
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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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