A Multi-Rate Precision Timed Programming Language for Multi-Cores

Precision Timed (PRET) is a conceptual solution proposed in 2007 to address the ever increasing unpredictability of embedded processors, which results from features such as multi-level caches or deep pipelines. For many real-time systems, it is mandatory to compute a strict bound on the program's execution time. Yet, in general, computing a tight bound is extremely difficult. The rationale of PRET is to simplify both the programming language and the execution platform to allow precise execution times to be easily computed. ForeC is a PRET programming language. It is a multithreaded variant of C with a synchronous execution semantics. ForeC programs are designed to be executed on multi-core processors, built around either PRET cores or classical cores. A drawback of ForeC is that programs are single rate, i.e., all reactions must be implemented to run at the fastest rate imposed by the environment. This represents a high overhead, both at design time and at run-time. In this paper, we propose a multi-rate version of ForeC to improve its practicality and usability for industrial acceptance. We detail the syntax and semantics of the ForeC language in the context of multi-rate applications and present an implementation on a PRET multi-core architecture. Both the languages and its implementation are illustrated over a robotic application.