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

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

The EventHorizon

Provides the interface between Wormhole and external environment.Two types of interactions

Conversion of particles passing through EventHorizonAccomplished 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())

Galaxy Star Wormhole (a runnable

withUniverse (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

TerminalsCRN

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

ATM ATM

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 56000 and

96000 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

Source Link

Current Research

Ptolemy II 2.0.1 made available in August 2002

Ptolemy II 2.0.1 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: http://ptolemy.eecs.berkeley.edu