Zeus: A distributed timed model-checker based on Kronos

In this work we present Zeus, a Distributed Model-Checker that evolves from the tool Kronos [8] and that currently can handle backwards computation of TCTL-reachability properties [1] over timed-automata [2]. Zeus was developed following a software architecture centric approach. It introduces some interesting features such as a priori graph partitioning, a sophisticated machinery to reach optimum performance (communication piggybacking and delayed messaging) and dead-time utilization, where every processor uses time intervals of inactivity to perform auxiliary, time-consuming tasks that will later speed up the rest of the computation. Although some good results have been obtained, early experiments pinpointed the difficulties of getting speedups using a parallel asynchronous version. We also propose some paths to overcome those obstacles. We would like to thank Sergio Yovine for making Kronos libraries available to us. © 2002 Published by Elsevier Science B.V.Fil:Braberman, V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Schapachnik, F. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Dealing with practical limitations of distributed timed model checking

Abstract. Two base algorithms are known for reachability verification over timed automata. They are called forward and backwards, and traverse the automata edges using either successors or predecessors. Both usually work with a data structure called Difference Bound Matrices (DBMs). Although forward is better suited for on-the-fly construction of the model, the one known as backwards provides the basis for the verification of arbitrary formulae of the TCTL logic, and more importantly, for controller synthesis. Zeus is a distributed model checker for timed automata that uses the backwards algorithm. It works assigning each automata location to only one processor. This design choice seems the only reasonable way to deal with some complex operations involving many DBMs in order to avoid huge overheads due to distribution. This article explores the limitations of Zeus-like approaches for the distribution of timed model checkers. Our findings justify why close-to-linear speedups are so difficult –and sometimes impossible – to achieve in the general case. Nevertheless, we present mechanisms based on the way model checking is usually applied. Among others, these include model-topology-aware partitioning and on-the-fly workload redistribution. Combined, they have a positive impact on the speedups obtained

Abstract PDMC 2004 Published Version On-the-fly Workload Prediction and Redistribution in the Distributed Timed Model Checker Zeus 1

In this work we present the on-the-fly workload prediction and redistribution techniques used in Zeus [12,13], a Distributed Model Checker that evolves from the tool Kronos [14]. After reviewing why it is so hard to have good speedups in distributed timed model checking, we present the methods used to get promising results when verifying reachability properties over timed automata [3]

Zeus: A Distributed Timed Model-Checker Based on Kronos Abstract

In this work we present Zeus, a Distributed Model-Checker that evolves from the tool Kronos [8] and that currently can handle backwards computation of TCTLreachability properties [1] over timed-automata [2]. Zeus was developed following a software architecture centric approach. It introduces some interesting features such as a priori graph partitioning, a sophisticated machinery to reach optimum performance (communication piggybacking and delayed messaging) and dead-time utilization, where every processor uses time intervals of inactivity to perform auxiliary, time-consuming tasks that will later speed up the rest of the computation. Although some good results have been obtained, early experiments pinpointed the difficulties of getting speedups using a parallel asynchronous version. We also propose some paths to overcome those obstacles.

Vintime: Combining high-level finesse with low-level muscle to verify real-time systems

Abstract. In this work we present the VInTiMe (Verifier of INtegrated TImed ModEls) suite of tools that combines high-level expressive power, unassisted property-preserving model-reduction and low-level distributed model checking power to describe and verify complex Real-Time Systems designs and their properties