Automatic rate desynchronization of embedded reactive programs

• Authors: Alain Girault;Xavier Nicollin;Marc Pouzet
• Venue: ACM Transactions on Embedded Computing Systems (TECS)
• Year: 2006

Many embedded reactive programs perform computations at different rates, while still requiring the overall application to satisfy very tight temporal constraints. We propose a method to automatically distribute programs such that the obtained parts can be run at different rates, which we call rate desynchronization. We consider general programs whose control structure is a finite state automaton and with a DAG of actions in each state. The motivation is to take into account long-duration tasks inside the programs: these are tasks whose execution time is long compared to the other computations in the application, and whose maximal execution rate is known and bounded. Merely scheduling such a long duration task at a slow rate would not work since the whole program would be slowed down if compiled into sequential code. It would thus be impossible to meet the temporal constraints, unless such long duration tasks could be desynchronized from the remaining computations. This is precisely what our method achieves: it distributes the initial program into several parts, so that the parts performing the slow computations can be run at an appropriate rate, therefore not impairing the global reaction time of the program. We present in detail our method, all the involved algorithms, and a small running example. We also compare our method with the related work.