The Synchronous Blog

A blog about reactive programming languages.

Posts Tagged ‘preemption-constructs

“Céu: Embedded, Safe, and Reactive Programming”

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We have published a technical report entitled “Céu: Embedded, Safe, and Reactive Programming”.

Enjoy the reading!


Céu is a programming language that unifies the features found in dataflow and imperative synchronous reactive languages, offering a high-level and safe alternative to event-driven and multithreaded systems for embedded systems.

Céu supports concurrent lines of execution that run in time steps and are allowed to share variables. However, the synchronous and static nature of Céu enables a compile time analysis that can enforce deterministic and memory-safe programs.

Céu also introduces first-class support for “wall-clock” time (i.e. time from the real world), and offers seamless integration with C and simulation of programs in the language itself.

The Céu compiler generates single-threaded code comparable to handcrafted C programs in terms of size and portability.

Table of Contents:

  1. Introduction
  2. The Language Céu
    1. Parallel compositions
    2. Internal events & Dataflow support
    3. Wall-clock time
    4. Integration with C
    5. Bounded execution
    6. Determinism
    7. Asynchronous execution
    8. Simulation in Céu
    9. GALS execution
  3. Demo applications
    1. WSN ring
    2. Arduino ship game
    3. SDL game simulation
  4. Implementation of Céu
    1. Temporal analysis
    2. Memory layout
    3. Gate allocation
    4. Code generation
    5. Reactive execution
    6. Evaluation
  5. Related work
    1. Synchronous model
    2. Asynchronous model
  6. Conclusion

Paper accepted.

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Good news received last week:

Dear Mr. Francisco Sant’Anna,

I am pleased to confirm that your paper “LuaGravity, a Reactive Language
Based on Implicit Invocation” has been accepted for presentation and
publication at SBLP 2009.

All papers went through a rigorous reviewing process by the program
committee. Out of 30 research papers and 3 tutorials submitted, 12
papers and 1 tutorial were accepted.

Please make sure that in the preparation of the final paper you
carefully address the reviewers’ comments. Additionally, at least one
author is required to register in the conference for your paper to
appear in the proceedings.

Congratulations again on having your paper accepted. We look forward to
seeing you in Gramado!

Reviewer’s comments already addressed and final version submitted! One reviewer in particular pointed several constructive observations, which we took very seriously in the final version.

Follows the abstract for the paper:

The reactive programming paradigm covers a wide range of applications, such as
games and multimedia systems.
Mainstream languages do not offer proper support for reactive programming,
lacking language-level primitives that focus on synchronism and interactions
within application parts.
We propose an imperative reactive language, called
LuaGravity, based on
unconventional implicit invocation mechanisms.
LuaGravity allows dataflow programming, sequential imperative execution, and
deterministic use of shared-memory.
With this work, we intend to unite the essential features of reactive languages
while keeping a convenient imperative style of programming.

SBLP [1] is the main Brazilian congress on programming languages. This year it will be held in Gramado on August 18-21.


Esterel: A Unique Language

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Esterel was developed in the early ’80s in France in parallel with other two languages, Lustre and Signal. These, together with Statecharts, are considered the first synchronous languages.
Esterel found its niche in control intensive real-time applications and evolves as a standard, with several implementations.

Unlike all synchronous languages, Esterel is the only one to provide an imperative style of programming. This is kind of surprising for me considering the high popularity of imperative languages.
Why there’s no attempts to create new languages based on the Esterel foundations?

I cannot argue about functional vs imperative style of programming, but I do feel more comfortable with the latter (most people do), and they will be around for the next years.
I like the Lua approach, which seems to favor imperative style but concisely support most functional features without bloat.

The example below, written in Esterel, implements the basic training for an athlete:

module Runner:
    input  Second, Morning, Step, Meter, Lap;
    output ...; % not used
    every Morning do
                abort RunSlowly when 15 Second;
                    every Step do
                        Jump || Breathe
                    end every
                when 100 Meter;
            each Lap
        when 2 Lap
    end every
end module

Esterel authors argue that, following this imperative style, programs are almost software specifications given as recipes in natural English.

The communication in Esterel is made through broadcast input and output signals.
The synchronous preemption constructs (every do, loop each, abort when, etc) are the heart of the language.
LuaGravity provides constructs based on them, which I consider even more useful than the functional facilities.

Written by francisco

September 29, 2008 at 11:01 pm