1. Code Generation for Ptolemy II
Ye Zhou, Man-Kit Leung, Christopher Brooks, Edward Lee, Gang Zhou
University of California, Berkeley
Project Overview
Generate code in other languages such as C and VHDL for a Ptolemy model.
Build a code generation infrastructure for component-based and heterogeneous modeling.
Based on code generation work in Ptolemy Classic.
Current work focuses on generating C code for synchronous dataflow (SDF) models.
The Butterfly Example
The Ptolemy Model
The Code Generator GUI
C Code Output
Generated C Code
Code Generator Architecture
Macros and Variable Declarations
Helper classes contain code blocks written in pseudo language with interspersed macros.
Macros, which always begin with a ‘$’, take the places of ports and parameters to hold values.
Referenced macros will be replaced with a unique variable in the generated code.
Associate
A Ptolemy Model
invokes
E.g., the helper class for the Scale actor contains:
$ref(output) = $val(factor) * $ref(input);
$ref(output) refers to the output port of this Scale actor. $val(factor) is the concrete value of the factor parameter of this actor.
$ref(output) will be replaced in the C code with a unique static variable ActorFullName_output.
The CodeGenerator is like a manager in the Ptolemy model. It governs the overall code generation.
A director’s CodeGeneratorHelper defines the order of code generation for actors, the way of data exchange, etc.. It also governs time advance, buffer management, etc..
An actor’s CodeGeneratorHelper contains the basic C code that implements the function of this actor.
Conclusion
We present an infrastructure for code generation in Ptolemy II.
We have implemented a C code generator for SDF models.
Buffer Management
Each actor helper provides an interface to maintain the buffer size and offset for each of its communication channels.
The director helper determines the buffer size for each channel.
The director helper updates the offset of each channel while generating the code.
Handling Delays in SDF
The offset of an input port is the buffer position from which tokens are read. The offset of an output port is the buffer position to which tokens are written.
Code Structure Example
This basically follows the action methods in Ptolemy.
/*including necessary files*/
#include “stidio.h”
/* variable declarations */
Static int actorFullName_input;
Static int actorFullName_initial = 0;
main() {
/* generate initialize code */
/* generate body code */
/* generate wrapup code */ }
Future Work
Helper classes for type system.
Code generation for other domains, such as Giotto and Finite State Machine.
Code generation for heterogeneous models.
Code generation infrastructure for multiple target languages.
The CodeGenerator invokes the director helper, which will then invokes the actor helpers to generate code.
Benefit: actor helper classes are domain-independent.