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Introduction SR models are excellent for applications with concurrent and complex control logic. Because of the tight synchronization, safety-critical real-time applications are a good match. However, also because of the tight synchronization, some applications are overspecified in the SR model, limiting the implementation alternatives. Moreover, in most realizations, modularity is compromised by the need to seek a global fixed point at each clock tick. The SR domain implementation in Ptolemy II is similar to the SR implementation in Ptolemy Classic by Stephen Edwards[33]. 1.3.14 Timed Multitasking - TM The timed multitasking (TM) domain, created by Jie Liu [92], supports the design of concurrent real-time software. It assumes an underlying priority-driven preemptive scheduler, such as that typically found in a real-time operating systems (RTOS). But the behavior of models is more deterministic than that obtained by more ad hoc uses of an RTOS. In TM, each actor executes (conceptually) as a concurrent task. It is a timed domain, meaning that there is a notion of “model time” that advances monotonically and uniformly. Each actor has a specified execution time T, and it delays the production of the outputs until it has had access to the CPU for that specified amount of time (in model time, which may or may not match real time). Actors execute when they receive new inputs, so the execution is event driven. Conceptually, the actor begins execution at some time t, and its output is produced at time t + T + P, where T is the declared execution time, and P is the amount of time where the actor is suspended due to being preempted by a higher priority actor. At any given model time t, the task with the highest priority that has received inputs but not yet produced its outputs has the CPU. All other tasks are suspended. TM offers a way to design real-time systems that is more deterministic than ad hoc uses of an RTOS. In particular, typically, a task produces outputs at a time that depends on the actual execution time of the task, rather than on some declared parameter. This means that consumers of that data may or may not see updates to the data, depending on when their execution occurs relative to the actual execution time. Thus, the computational results that are produced depend on the actual execution time. TM avoids this by declaring the time that elapses before production of the outputs. By maintaining model time correctly, TM ensures that the data computation is deterministic, irrespective of actual execution time. 1.3.15 Wireless The wireless domain, described in [10], is an extension of the discrete-event domain that supports modeling and simulation of wireless and sensor network systems. An example model is shown in figure 1.11. Notice that the syntax is very different from that in figure 1.2. This example models a SoundSource (whose icon is large, transparent concentric circles) moving through a field of sensors (SoundSensor actors, which have translucent blue circle icons) that detect the sound and communicate with a Triangulator actor (whose icon consists of overlapping ellipses). The Triangulator is a composite, shown at the bottom of the figure, that uses the DE domain to perform sensor fusion to triangulate the location of the sound source. It generates a plot with estimated locations. When this model is executed, the sensors’ icons turn red when they detect a sound. Upon detecting a sound, they transmit the time at which they detect the sound and their current location. If a location can be found, then the model plots that location. The wireless domain generally uses channel models to mediate communication. A library of channel models is provided, but it is expected that users will create their own channel models. The domain can model such effects as propagation delay, packet losses, directional gain (such as antenna gain), 22 Ptolemy II
Introduction occlusions due to terrain, etc. The wireless domain is also packaged separately as the VisualSense system, a Ptolemy II configuration [11]. channel models sensor node models triangulator node FIGURE 1.11. Example of a model in the wireless domain, where communication is mediated by channel models. Although the actors in the top diagram communicate through ports, the ports are hidden because they are not visually meaningful. Heterogeneous Concurrent Modeling and Design 23
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 9 and 10: 7. MoML 191 7.1. Introduction 191 7
Page 11 and 12: 1 Introduction Author: Edward A. Le
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Page 15 and 16: Introduction A major emphasis in Pt
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Page 45 and 46: Introduction actor actor.gui data.e
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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 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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