57 research outputs found
Formal Verification of Real-time Systems with Preemptive Scheduling
International audienceIn this paper, we propose a method for the verification of timed properties for real-time systems featuring a preemptive scheduling policy: the system, modeled as a scheduling time Petri net, is first translated into a linear hybrid automaton to which it is time-bisimilar. Timed properties can then be verified using HyTech. The efficiency of this approach leans on two major points: first, the translation features a minimization of the number of variables (clocks) of the resulting automaton, which is a critical parameter for the efficiency of the ensuing verification. Second, the translation is performed by an over-approximating algorithm, which is based on Difference Bound Matrix and therefore efficient, that nonetheless produces a time-bisimilar automaton despite the over-approximation. The proposed modeling and verification method are generic enough to account for many scheduling policies. In this paper, we specifically show how to deal with Fixed Priority and Earliest Deadline First policies, with the possibility of using Round-Robin for tasks with the same priority. We have implemented the method and give some experimental results illustrating its efficiency
Time Analysis of the State Space of Real-time Preemptive Systems
We present in this paper an algorithm making it possible an efficient time analysis of the state space of preemptive real time systems modeled using Time Petri Nets with inhibitor arcs. For this effect, we discuss how to determine from the reachability graph linear and quantitative properties of the remote model. Then, we propose an algorithm to compute an approximation of the minimal and the maximal time distances of any firing sequence. Contrarily to other techniques, our algorithm enjoys a linear complexity time cost and can be performed on the fly when building the reachability graph without requiring to extend the original model with observers
Improving the construction of the DBM over approximation of the state spce of real-time preemptive systems
We present in this paper an algorithm allowing an efficient computation of the tightest DBM over-approximation of the state space of preemptive systems modeled by using Time Petri Nets with inhibitor arcs. First of all, we propose an algorithm that reduces the effort of computing the tightest DBM over-approximated graph. For this effect, each class of this graph is expressed as a pair (M, D), where M is a marking and D is the system of all DBM inequalities even the redundant ones. We thereby make it possible to compute the system D straightforwardly in its normal form, without requiring to compute the intermediary polyhedra. Hence, we succeed to remove the errors reported in the implementation of other DBM approximations. Then we show that by relaxing a bit in the precision of the DBM approximation, we can achieve to construct more compact graphs while reducing still more the cost of their computation. We provide for this abstraction a suitable equivalence relation that contract yet more the graphs. The experimental results comparing the defined constructions with other approaches are reported
A Benchmarks Library for Extended Parametric Timed Automata
Parametric timed automata are a powerful formalism for reasoning on
concurrent real-time systems with unknown or uncertain timing constants. In
order to test the efficiency of new algorithms, a fair set of benchmarks is
required. We present an extension of the IMITATOR benchmarks library, that
accumulated over the years a number of case studies from academic and
industrial contexts. We extend here the library with several dozens of new
benchmarks; these benchmarks highlight several new features: liveness
properties, extensions of (parametric) timed automata (including stopwatches or
multi-rate clocks), and unsolvable toy benchmarks. These latter additions help
to emphasize the limits of state-of-the-art parameter synthesis techniques,
with the hope to develop new dedicated algorithms in the future.Comment: This is the author (and extended) version of the manuscript of the
same name published in the proceedings of the 15th International Conference
on Tests and Proofs (TAP 2021
Verification and Parameter Synthesis for Real-Time Programs using Refinement of Trace Abstraction
We address the safety verification and synthesis problems for real-time
systems. We introduce real-time programs that are made of instructions that can
perform assignments to discrete and real-valued variables. They are general
enough to capture interesting classes of timed systems such as timed automata,
stopwatch automata, time(d) Petri nets and hybrid automata.
We propose a semi-algorithm using refinement of trace abstractions to solve
both the reachability verification problem and the parameter synthesis problem
for real-time programs.
All of the algorithms proposed have been implemented and we have conducted a
series of experiments, comparing the performance of our new approach to
state-of-the-art tools in classical reachability, robustness analysis and
parameter synthesis for timed systems. We show that our new method provides
solutions to problems which are unsolvable by the current state-of-the-art
tools
Integrated Model-checking for the Design of Safe and Efficient Distributed Software Commissioning
International audienc
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