The Cheddar project : a GPL real-time scheduling analyzer

What is Cheddar ?

In few words

Cheddar is a free real-time scheduling tool. Cheddar allows you to model software architectures of real-time systems and to check its schedulability or others performance criteria.

As many schedulability analysis tool, schedulability can be accessed with with both scheduling simulation and with feasibility tests.

With Cheddar, the modeling of the system to verify can be achieved with either AADL or with the Cheddar architecture design language. Some experiments also exits with MARTE UML.

Cheddar can help you : to perform schedulability analysis, to be used for educational purpose, and also to quickly prototype new real-time scheduling policies or task models (with its own domain specific language that allows user to design task models or scheduling policies).


Cheddar is developed and maintened by a team composed of the Lab-STICC laboratory UMR CNRS 6285 and Université de Bretagne Occidentale and Ellidiss Technologies.

The Cheddar project was started in 2002 by Frank Singhoff, University of Brest. The full list of the contributors can be read there. Since 2008, Ellidiss Technologies also contributes to the development of Cheddar and provides industrial support of AADLInspector an AADL verification tool embedding the commercial version of Cheddar.

Main features

Cheddar is composed of two independent parts : an editor used to model the real-time system to analyze, and a framework to perform such analysis.

The editor allows you to describe systems composed of several cores, processors which own tasks, shared resources, buffers and which may exchange messages or communication with buffers. Cheddar includes its own ADL, namely Cheddar ADL. However, Cheddar is also able to handle AADL models with a simple AADL V1.0 parser built with Ocarina , but also with a full compliant AADL V2 parsers thanks to is commercial version : AADLInspector.

The framework includes many feasibility tests and simulation tools. The framework can be embbed in specific tool set such as STOOD (Ellidiss Tech), TASTE (ESA) or AADLInspector (Ellidiss Tech).

Feasibility tests can be applied to check that task deadlines can be met and that buffers have bounded size. When feasibility tests can not be applied, the studied application can be analyzed with scheduling and buffer simulations. Cheddar provides a way to quickly define "user-defined schedulers" to model scheduling of ad-hoc applications/systems (ex : ARINC 653).

The main analysis tools of Cheddar are the following :

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 factor, ...).


Download Cheddar

- Download Cheddar binaries (current version is Cheddar-3.0, release date : the 2nd of November 2015) :

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 the ChangesLog.pdf file to have history of modifications. The file REQUESTED_FEATURES.pdf contains the new features required by users and which will be implemented din the next releases.

You can also get access to the SVN repository of Cheddar.

Cheddar is written in Ada, with GNAT and GtkAda Adacore products. Cheddar is known to run on Linux and windows boxes, but should run on every Adacore supported platforms ( see AdaCore web site for details).

How to install and run Cheddar

For installation procedures, please read HOWTO_INSTALL.txt

Last patch

There is no binary patch currently distributed as all fixed bug are integrated in the current binary release.
See the FIXED_BUGS.pdf file to have the detailed list of fixed bugs. The list of the bugs to be fixed can be read there (file BUGS_TO_FIX.pdf).

Work in progress

Current developments on Cheddar are about the following topics:
  1. Cache analysis support.
  2. Global multiprocessor scheduling.
  3. NoC support.
  4. PAES implementation.

Mailing List

Cheddar users and developers can share information with a mailing list hosted by the University of Brest.
To post to the list, send e-mail to Warning : this is a private mailing-list (to post on this mailing-list, you have to be subscribed).

To subscribe to the list : send a request to with the following text in the body :


where is your email adress.

To unsubscribe to the list : send a request to with the following text in the body :

SIGNOFF cheddar

Related documents and publications

Examples of use : application analysis, educational material and contributions from Cheddar's users

We distribute Cheddar with a set of AADL and XML examples. But this section also contains a set of contributions from Cheddar's users :

Authors, contributors, and Sponsors

Cheddar is developed and maintened by a team composed of members from the Lab-STICC laboratory UMR CNRS 6285/Université de Bretagne Occidentale and Ellidiss Technologies. The current members of this project are Pierre Dissaux (Ellidiss Technologies), Jérôme Legrand (Ellidiss Technologies), Alain Plantec (Lab-STICC/Université de Bretagne Occidentale), Stéphane Rubini (Lab-STICC/Université de Bretagne Occidentale), Jalil Boukhobza(Lab-STICC/Université de Bretagne Occidentale), Laurent Lemarchand (Lab-STICC/Université de Bretagne Occidentale) and Frank Singhoff (Lab-STICC/Université de Bretagne Occidentale).

The project has been funded by Ellidiss Technologies, Conseil régional de Bretagne, UBO, BMO/Brest Métrople Océance, BPI France, Conseil général du Finistère and EGIDE/Campus France PESSOA number 27380SA.

Researches on Cheddar are also performed in collaboration with the following partners:

The following people have also contributed to the project: see

Thanks to people who sent us bug reports and/or advices : B. Baron, P. Mueller, H. Bonnin, T. Ren, K. Bryan, N. Hoogland, V. Hugel, J. Stemerdink, T. Vergnaud, F. Rodrigues de la Rocha, G. Laurens, V. Hugel, C. Valle, Su Young Lee, P. Wong, and M. Zanconi, ...

Cheddar software developer work space : to get compilation instructions, to report bugs, to get developer documentation ...

For doing bug reports, fetching compilation instructions and developer documentations, a work space is available for Cheddar software developers on this wiki.

You can also report bugs and new tested platforms to (Warning : this is a private mailing-list. To post, you have to subscribe to the mailing-list first).

Contact : Frank Singhoff
Last update : November 2015