P t o l e m y A Framework For Simulating and Prototyping Heterogeneous Systems by Joseph Buck, Soonhoi Ha, Edward A. Lee & David G. Messerschmitt P r e s e n t e r s A r u n T M & S u l e n T h o m a s

T o p i c s Concept of Ptolemy Internal Structure of Ptolemy Wormhole EventHorizon Code Generation Practical Details Applications Current Research

C o n c e p t provides an environment for simulation and rapid prototyping of heterogeneous systems use of modern OO technology to model subsystems core :: uses OO class definitions to make assumptions provides generic interfaces examples of applications :: network and transport, call processing and signaling software etc.

C o n c e p t alternative to heterogeneity is generality disadvantages :: - analysis is difficult to perform - compilers are difficult to implement - increase in complexity of design key :: non dogmatic kernel which combines descriptions to ensure heterogeneity coordination framework

C o n c e p t uses OO concepts to achieve the following goals  agility :: support distinctiveness in model design  heterogeneity :: allows co existence of different systems  extensibility :: allows integration of old and new models  friendliness :: friendly GUI

Internal Structure Blocks & Particles  block :: module of code invoked at runtime  porthole :: standard interfaces  particle :: base message type  geodesic :: connection framework  plasma :: reclamation of used particles

Internal Structure Stars, Galaxies and Universe provides hierarchy for the system star :: - derived from block - performs computation galaxy :: - contains other blocks - contains other galaxies & stars universe :: - complete Ptolemy application advantages of hierarchy

Internal Structure Targets & Schedulers  target :: - controls the execution - features vary based on application  scheduler :: - defines the operational semantics of the domain - manages the order of execution of star methods

Internal Structure Domain  definition :: - set of blocks, targets and associated schedulers - computational model Sub Domain  implements a more specialized computational model  stars and targets can be used with an outer one  scheduler cannot be used with outside domain

Internal Structure

Examples of Domain  dynamic data flow (DDF) :: - data driven model of computation  synchronous data flow (SDF) :: - sub domain of DDF - advantages :: - ease of programming - syntax checking - runtime efficiency - automatic parallel scheduling

Internal Structure Examples of Domain  boolean data flow ( BDF) :: - intermediate between SDF and DDF  discrete event ( DE ) :: - models only changes in a system state - differences :: - incorporates global time - orders block invocations properly  message queue ( MQ ) :: - dynamically creates and destroys blocks - eg software control applications

W o r m h o l e critical design element block which externally looks like a star contains of a private universe ( separate scheduler and stars ) can be introduced into any domain objects contain target pointers used to run simulations in different environments

The EventHorizon

Provides the interface between Wormhole and external environment. Two types of interactions Conversion of particles passing through EventHorizon Accomplished by ToEventHorizon and FromEventHorizon derived from EventHorizon Particles are read from XXXtoUniversal to YYYFromUniversal and sent to YYY domain Responsibilities of EventHorizon  DEWormhole is executed when input has data.

The EventHorizon Scheduler Coordination Scheduler has a set of polymorphic methods (setup(), run(), setStopTime() and resetStopTime()) for coordination of Schedulers on both sides of EventHorizon setup() method takes place before execution of blocks. run() method executes the blocks StopTime specifies the time upto which run() executes setStopTime() allows StopTime to be set externally These methods make multiple Schedulers behave logically as a single Scheduler. Schedulers divided into timed and untimed

The EventHorizon  Inheritance Structure of Blocks Block (initialize() Runnable ( run() and start() and stop()) setStopTime()) GalaxyStar Wormhole (a runnable with Universe (includes target and XXXStar internal target & is a runnable)galaxy) XXXUniverse XXXWormhole

Code Generation go() method of Star adds ASCII text to data structure in Target Scheduler controls sequence of code Target collects code and supervised compilation and execution

Practical Details The Graphical User Interface Ptolemy Interactive Graphical Interface (pigi) is the design editor InterpGalaxy is used to dynamically construct simulations Runs as Vem graphic editor and pigiRpc, the Ptolemy kernel States Used to monitor and control the simulation Star Preprocessor Language Generates documentation for Star and Galaxy class.

A p p l i c a t i o n s Broadband Networking Cell relay network connects a set of terminals DE domain used to model non-empty cells Signaling ATM Switches DE Modeling Domain Terminals CRN

A p p l i c a t i o n s Broadband Networks Network consists of signaling entity & a set of switches Call processing entity present within the switch Signaling Signaling (MQ) ATM

A p p l i c a t i o n s Signal Processing Algorithms are defined within data flow model Ptolemy capable of partitioning, scheduling and generating DSP assembly language. Ptolemy can generate C code, Motorola and assembly code Hardware-Software Co-Design Thor domain can be combined with code generation domain to design boards with programmable DSP Hardware and Software are modeled within the same software framework. Ptolemy has the ability to mix behavioral, hardware and software entities in a natural way.

A p p l i c a t i o n s Source and Link modeling Source generates data packets or speech samples, link consists of single-bit error model. Particle has methods convertToBits() and convertFromBits Link model accepts Particles, applies the first method, applies link model to the bit string and uses second method to convert bit string back to particles. Particles Particles SourceLink

Current Research Ptolemy II made available in August 2002 Ptolemy II is the first release that includes a limited prototype of our code generation facility that will generate class files for non-hierarchical SDF models  Other Ptolemy information may be found at: