Welcome
The idea of predictable architectures has gained momentum with the concept of a Precision Timed Machine (or the PRET machine). The central idea of a PRET machine is to guarantee precise timing without sacrificing throughput. Another crucial objective of a PRET machine is to simplify the worst case timing analysis of code executing on PRET machines. PRET Architectures have been designed since 2002 at Auckland University under the banner of reactive processors .
PRETzel research group aims at the development of PRET architectures by simple customizations to embedded softcore processors. The key design objectives of our research may be summarized as:
- Time
- Time is logical and the mapping of logical time to physical time is achieved by the compiler and the WCRT analyzer.
- Concurrency
- Concurrency is logical but execution is sequential. This is used to ensure both synchronous execution and thread-safe shared memory communication. This has been the founding principle of the synchronous programming languages.
- Design approach
- We have designed a processor called ARPRET (Auckland Reactive PRET) that achieves PRET by simple customizations of GPPs. Programmers write applications using a language called PRET-C with a minimal set of extensions to support synchronous concurrency that implements thread-safe shared memory communication, features for capturing both physical time (though a library of time) and logical time through an instruction called EOT. In addition, there is support for preemption without the use of interrupts. These extensions to the C are minimal are implemented through C-macros.
Pretzel: pret·zel· [pret-suhl]
A pretzel is a bread pastry of Medieval European origin, that has the shape of a three looped knot or twisted braid [Wikipedia].
PRETzel in our context signifies the Precision Timed (PRET) Architecture research that brings together three different research groups, namely the University of Auckland in New Zealand, INRIA Research Lab in Grenoble France and the real-time systems research group in Kiel University, Germany .