The Cheddar project : a free real time scheduling analyzer



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What is Cheddar ?


Cheddar is a free real time scheduling tool. Cheddar is designed for checking task temporal constraints of a real time application/system. It can help you for quick prototyping of real time schedulers. It can also be used for educational purpose. Cheddar is developed and maintened by the LISYC Team, University of Brest.

Our real time scheduling simulator is composed of two independent parts : a graphical editor used to describe a real time application/system, and a framework which includes most of classical real time scheduling/feasibility algotithms/tests.

Cheddar is written in Ada. The graphical editor is made with GtkAda. Cheddar runs on Solaris, Linux and win32 boxes and should run on every GNAT/GtkAda supported platforms ( see AdaCore web site for details).

Cheddar provides two kind of features : a simulation engine and feasisibility tests. Feasibility tests allow a user to study a real time application/system without computing a scheduling. In the contrary, the simulation engine can be used firstly to computing a scheduling and secondly, to automatically looking for task constraint properties in the computed scheduling. Most of the time, feasibility tests are less complex tools but they are available only for few schedulers and tasks models. To solve this problem, the Cheddar simulation engine provides tools to design specific schedulers and task models : the system is then analyzed according to a given scheduling.

For each analysis result, Cheddar gives the name of the applied equation and the related publication. See the publications topic of this web page to get these publications.


The main features provided by Cheddar are then :



The picture below is a screenshot of Cheddar : on the top of the picture, scheduling is drawn according to the scheduler of each processor. On the bottom, some task information is provided (response times, missed deadlines, processor utilization level, ...).


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Download Cheddar



- Download Cheddar binaries (current version is Cheddar-1.3p5, release date : November the 1st, 2005) :

Cheddar is a free software under the GNU General Public License.
You can get the current stable Cheddar source code here .

Previous releases can be found here . See ChangesLog to have history of modifications.

You can also access to a dayly built cvs snapshot of Cheddar. Source code and binaries you get from there are not stable : use them with care. Finally, a remote cvs access is also available. If you plan to write code with Cheddar, contact us to get an account on this cvs repository.





Install Cheddar

1) Tested platforms :

Cheddar runs on :


2) What do you need ?

On windows boxes, just unzip the zip file. To install Cheddar on Unix boxes, you need :

  1. The GNU make command (gmake).
  2. Gtk and GtkAda librairies must be installed on your system (GtkAda is the Ada binding of Gtk). You need Gtk 1.2 or laters and GtkAda 1.2.20 or laters.

    All necessary software used to compile or install Cheddar can be found here.

3) Basic Installation :

For unix, the simpliest way to install this program is:

  1. Edit the Makefile to give the name of the directory where cheddar must be installed. To do this, update the CHEDDAR_ROOT variable. If you do not change CHEDDAR_ROOT, Cheddar will be installed in /usr/local
  2. Type `gmake' to install the package.
  3. Play and have fun.




Last patch

There is nos patch currently distributed...
See the BUGS file to have the detailed list of fixed bugs.


Work in progress


We will release the next version of Cheddar on September/november 2006 with the following features :
  1. Update user's guide according to features related to buffer analysis and task precedencies tools.
  2. Update the graphical editor in order to switch from GtkAda 1.2 towards GtkAda 2.x
  3. Hierarchical schedulers support.
  4. Provide a global memory analysis (task stack, text/data segments ...)
  5. End to end response time with message scheduling.
  6. User's defined message scheduler.
  7. Improvement of message scheduling with :
  8. Fixing a buggy service which should detect deadlock from simulation.

Mailing List

Cheddar users and developers can now share information with a mailing list hosted by The University of Brest.
To post to the list, send e-mail to cheddar@listes.univ-brest.fr. Warning : to post on this list, you have to be subscribed.


To subscribe to the list : send a request to sympa@listes.univ-brest.fr with the following text in the body :

SUBSCRIBE cheddar foo@bar.com

where foo@bar.com is the requester.


To unsubscribe to the list : send a request to sympa@listes.univ-brest.fr with the following text in the body :

SIGNOFF cheddar




Related documents and publications



Educational Material

This section is dedicated for teachers who plan to use Cheddar for their Real time scheduling courses. You can find here some examples of real time scheduling courses which are built with the help of Cheddar :

Authors and contributors


This program is developed and maintened by the LISYC Team, mainly by Frank Singhoff. The following people have also contributed to the project: M. Auer, N. Chauvin, V. Cuiec, S. Bothorel, S. Demurget, R. Frin, H. Ihamouten, D. Geffroy, M. Gning, W. Guillo, S. Herry, T. Huertas, A. Huopana, A. Le bot, J. Legrand, H. Martin, L. Moal, L. Morin, L. Nana, M. Nivala, P. Normand, G. Oliva, R. Prevot, D. Saulnier, E. Thomas, E. Vilain.

Thanks to people who sent us bug reports and/or advices : Bert Baron, Peter Mueller, Hugues Bonnin, Tim Ren, Kevin Bryan, Nick Hoogland, Jan Stemerdink, Thomas Vergnaud, Fabio Rodrigues de la Rocha ...


Bugs report and new tested platforms


Please, report bugs and new tested platforms to cheddar@listes.univ-brest.fr (Warning : to post, you have to subscribe to the list).





Feedback from users



You are using Cheddar ? If so, please, let us know why you are using it (study of real time applications, educational purposes, prototyping of schedulers, ...) and what kind of features you would like to see in this program.


Users can contact us with cheddar@listes.univ-brest.fr (Warning : to post, you have to subscribe to the list).





Thanks for all people who sent us comments, bugs and advices.




EA LISYC Team (cheddar@listes.univ-brest.fr)
Last updated : October the 31th 2005.