17 research outputs found
Algebraic Principles for Rely-Guarantee Style Concurrency Verification Tools
We provide simple equational principles for deriving rely-guarantee-style
inference rules and refinement laws based on idempotent semirings. We link the
algebraic layer with concrete models of programs based on languages and
execution traces. We have implemented the approach in Isabelle/HOL as a
lightweight concurrency verification tool that supports reasoning about the
control and data flow of concurrent programs with shared variables at different
levels of abstraction. This is illustrated on two simple verification examples
An Event Structure Model for Probabilistic Concurrent Kleene Algebra
We give a new true-concurrent model for probabilistic concurrent Kleene
algebra. The model is based on probabilistic event structures, which combines
ideas from Katoen's work on probabilistic concurrency and Varacca's
probabilistic prime event structures. The event structures are compared with a
true-concurrent version of Segala's probabilistic simulation. Finally, the
algebraic properties of the model are summarised to the extent that they can be
used to derive techniques such as probabilistic rely/guarantee inference rules.Comment: Submitted and accepted for LPAR19 (2013
On partial order semantics for SAT/SMT-based symbolic encodings of weak memory concurrency
Concurrent systems are notoriously difficult to analyze, and technological
advances such as weak memory architectures greatly compound this problem. This
has renewed interest in partial order semantics as a theoretical foundation for
formal verification techniques. Among these, symbolic techniques have been
shown to be particularly effective at finding concurrency-related bugs because
they can leverage highly optimized decision procedures such as SAT/SMT solvers.
This paper gives new fundamental results on partial order semantics for
SAT/SMT-based symbolic encodings of weak memory concurrency. In particular, we
give the theoretical basis for a decision procedure that can handle a fragment
of concurrent programs endowed with least fixed point operators. In addition,
we show that a certain partial order semantics of relaxed sequential
consistency is equivalent to the conjunction of three extensively studied weak
memory axioms by Alglave et al. An important consequence of this equivalence is
an asymptotically smaller symbolic encoding for bounded model checking which
has only a quadratic number of partial order constraints compared to the
state-of-the-art cubic-size encoding.Comment: 15 pages, 3 figure
Event correlation with boxed pomsets
Abstract. This paper proposes a diagnosis framework for distributed systems based on pomset languages. Diagnosis is performed by projecting these models on a collection of observable labels and then synchronization with an observation. This paper first proposes a new model called boxed pomset languages, which extends classical pomset-based languages as so called High-level Message Sequence Charts. It can describe infinite scenarios, and has good properties with respect to projections. We then give a solution for the event correlation problem (knowing whether two observed alarms are causally related) for pomset languages.
Emptiness is Decidable for Asynchronous Cellular Machines
. We resume the investigation of asynchronous cellular automata. Originally, these devices were considered in the context of Mazurkiewicz traces, and later generalized to run on arbitrary pomsets without autoconcurrency by Droste and Gastin [DG96]. While the universality of the accepted language is known to be undecidable [Kus98], we show here that the emptiness is decidable. Our proof relies on a result due to Finkel and Schnoebelen [FS98b] on well-structured transition systems. 1 Introduction In a distributed system, some events may occur concurrently, meaning that they may occur in any order or simultaneously or even that their executions may overlap. This is the case in particular when two events use independent resources. On the other hand, some events may causally depend on each other. For instance, the receiving of a message must follow its sending. Therefore, a distributed behavior may be abstracted as a directed acyclic graph (dag), that is a set of events together wit..
A model theoretic proof of Büchi-type theorems and first-order logic for N-free pomsets
We give a uniform proof for the recognizability of sets of finite words, traces, or N-free pomsets that are axiomatized in monadic second order logic. This proof method uses Shelah's composition theorem for bounded monadic theories. Using this method, we can also show that elementary axiomatizable sets are aperiodic. In the second part of the paper, it is shown that width-bounded and aperiodic sets of N-free pomsets are elementary axiomatizable
A Kleene iteration for parallelism
This paper extends automata-theoretic techniques to unbounded parallel behaviour, as seen for instance in Petri nets. Languages are defined to be sets of (labelled) series-parallel posets --- or, equivalently, sets of terms in an algebra with two product operations: sequential and parallel. In an earlier paper, we restricted ourselves to languages of posets having bounded width and introduced a notion of branching automaton. In this paper, we drop the restriction to bounded width. We define rational expressions, a natural generalization of the usual ones over words, and prove a Kleene theorem connecting them to regular languages (accepted by finite branching automata). We also show that recognizable languages (inverse images by a morphism into a finite algebra) are strictly weaker