prelude

                                Prelude
                                -------

Introduction
============

Prelude is a high-level language for programming embedded control
systems. It is built upon Synchronous Languages (such as Lustre) and
inherits their formal properties. It adds real-time primitives to enable
the programming of multi-periodic systems. The objective of the language
is not to replace other synchronous languages but instead to provide a
higher layer of abstraction, on top of classic synchronous languages. It
can be considered as a real-time software architecture language that
enables to assemble locally mono-periodic synchronous systems into a
globally multi-periodic synchronous system. A complete definition of the
language is available in [forgetPHD] (see Section 4 mainly). A shorter
presentation is available in [forgetSAC'10].

The preludec compiler generates synchronized multi-task C code that is
independent of the target OS. Communication is achieved by a tailor-made
buffering communication protocol. The compilation was defined formally
and produces completely deterministic code, which respects the real-time
semantics of the original program (period, deadlines, release dates and
precedences) as well as its functional semantics (respect of variables
consumption). Prelude compiler produces code for either monocore or
multicore architectures.

Distribution Directory Overview
===============================

- INSTALL: Installation instructions.

- README: This file.

- lib: C library files required to compile C code generated by Prelude
- lib/prelude: generic Prelude library files

- examples: contains Prelude program examples

- examples/sampling_loop: a complete example with everything required to
  execute it. For new users, the README there is a good starting point.

Using preludec
==============
Use preludec -help for a complete list of options.

The compiler generates two C files, named by default
<program>_c/<main_node>.c and <program>_c/<main_node>.h

As of version 1.2, there are two possible code generation modes:
1) preludec -node <main_node> <program.plu>
In this mode, precedences are encoded in task attributes. The resulting
task set will execute without synchronization mechanisms
(e.g. semaphores). This mode is suited for monocore architectures.

The function "get_task_set" returns the number of tasks in the set and
the task set itself. The structure of a task is defined in
"lib/encoded_task_params.h". This structure consists in the real time
attributes of the task and in a function pointer, which corresponds to
the execution of one instance of the task.


2) preludec -no_encoding -node <main_node> <program.plu>
In this mode, precedences are not encoded and must be ensured by the
scheduler at run-time. This mode is suited for multicore architectures.

The function "get_task_set" returns the number of tasks in the set and
the task set itself. The structure of a task is defined in
"lib/nonencoded_task_params.h". In addition, the function
"get_precedence_set" returns the number of precedence constraints and
the set of constraints. The constraints structure is defined in
"lib/multirate_precedence.h".

In both cases, the code is completely independent from the target RTOS.

Compiling and executing code generated by preludec
==================================================

The code generated by preludec is not the complete final program. An
"integration code" is required, to build threads from the task set
defined in the generated code. This part is OS-dependent. From there,
you have two choices:

A- Using SchedMCore.

Prelude integration is directly supported by the SchedMCore framework:
1) Install SchedMCore from http://sites.onera.fr/schedmcore/
2) Start by following the instructions in Examples/sampling_loop/README
and by executing the example there.
3) Follow the instructions in Examples/sampling_loop/README to adapt
this example to your own program.

B- Using your favorite RTOS:

1) You need to implement the EDF policy modified to support deadline
words, ie the equivalent of the "sched/sched_pluedf.c" included in
SchedMCore source distribution.
2) You need to implement the "integration code" that builds threads from
the code generated by Prelude. This can be partly inspired from
"tools/runner/schedmcore_main.c"
3) Compile, link, execute.

References
==========
[forgetPHD]
J. Forget
A Synchronous Language for Critical Embedded Systems with Multiple Real-Time Constraints.
PhD thesis, ISAE, Toulouse, France, November 2009.
http://www.lifl.fr/~forget/docs/jforget-thesis.pdf

[forgetSAC'10]
J. Forget, F. Boniol, D. Lesens, C. Pagetti
A Real-Time Architecture Design Language for Multi-Rate Embedded Control Systems
In 25th ACM Symposium on Applied Computing (SAC'10), Sierre, Switzerland, March 22-26 2010.
http://www.lifl.fr/~forget/docs/jforget-SAC10.pdf

[PreludeSchedMCore-RTNS2011]
M. Cordovilla, F. Boniol, J. Forget, E. Noulard, C. Pagetti
Developing critical embedded systems on multicore architectures: the Prelude-SchedMCore toolset
In 19th International Conference on Real-Time and Network Systems, RTNS2011, Sep. 3 2013.
http://sites.onera.fr/schedmcore/sites/sites.onera.fr.schedmcore/files/2011-PreludeSchedMCore-RTNS_0.pdf

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  Contact Address:                          Home site:
  julien.forget@lifl.fr           http://www.lifl.fr/~forget/
                                  https://svn.onera.fr/Prelude
                                  https://forge.onera.fr/projects/prelude
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