ANN : New release of Cheddar, a real time scheduling simulator

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The EA 2215 team is pleased to announce a new release of Cheddar,
a free real time scheduling simulator.

Cheddar is a free real time scheduling tool. Cheddar is designed for
checking task temporal constraints and buffer sizes of a real time
It can also help you for quick prototyping of real time schedulers. Finally,
it can be used for educational purposes.

Cheddar is composed of two independent parts : an editor used to
describe a real time application/system, and a framework.
The editor allows you to describe systems composed of several processors which
tasks, shared resources and buffers.
The framework includes feasibility tests and simulation tools. Feasibility tests
can be applied to check that task response times are met and that buffer size
are bounded.
When feasibility tests can not be applied, the studied application can be
with scheduling and buffer simulations.

The current release is now 1.3p1.

Cheddar is distributed under the GNU GPL license.
It's a free software, and you are welcome to  redistribute it under certain
See the GNU General Public License for  details.
Source code, binaries and documentations can be freely downloaded from

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

1) With Cheddar, you can :

        - Do scheduling simulations with classical real time schedulers
                (Rate Monotonic, Deadline Monotonic,
                Least Laxity First, Earliest Deadline
                First, POSIX.4 queueing policies : SCHED_OTHERS, SCHED_FIFO and
SCHED_RR) with
        different type of tasks (aperiodic, periodic, task
        activated with a poisson process law, ...)
    - Extract information from scheduling simulation  :
        (buffer utilization factor, task response times, task missed deadlines,
        number of preemption, ...)
        - Apply feasibility tests on tasks or buffers (without scheduling
simulation) :
                - Compute task response times.
                - Apply processor utilization test.
                - Schedule for a given base period.
        - Compute bound on buffer size (when buffer are shared by periodic tasks)
        - Shared resources support (scheduling and
                blocking time analysis).  Supported protocols : PIP, PCP.
        - Tools to express and do simulations/feasibility tests with task
precedencies :
        - Schedule tasks according to task precedencies
            - Compute Tindell end to end response time.
            - Apply Chetto and Blazewicz algorithms.
    - Do simulation when tasks are randomly activated.

2) The most important new features are :

    - Cheddar project files are now saved in a XML
        format. Project can then be shared
        between several plate-formes and tools
    - Add response time feasibility tests for RM/DM/POSIX.4 in the
        non preemptive case. Add EDF/LLF response time feasibility tests
        in the preemptive and the non preemptive case
    - Add response time from scheduling simulation    
    - When Cheddar crashes, the ongoing project is saved
        in a XML file called "cheddar_bug.xml"
        and then, project editing is not loosed any more
    - Add parametric schedulers
    - Produce simulation results in string or XML format
    - Add some classic Queueing results in the
        framework to help buffer analysis
    - Add a C inferface to the Ada framework
    - Add some tools to do random scheduling simulation
    - Fix some bugs (see BUGS file)

3) Work in progress  :

    During the next year, we plan to improve the tool with the following features :

        - Update the user's guide.
        - Improvement of the buffer analysis features.
        - Add feasibility tests and simulation features for multi-processors
        - Rebuild of shared resources support : adding new protocols and
            add parametric shared resource protocols.

Feel free to contact us for help or bugs report.

Best Regards,
The EA 2215 team

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