5 research outputs found
Parameterized Verification of Systems with Global Synchronization and Guards
Inspired by distributed applications that use consensus or other agreement
protocols for global coordination, we define a new computational model for
parameterized systems that is based on a general global synchronization
primitive and allows for global transition guards. Our model generalizes many
existing models in the literature, including broadcast protocols and guarded
protocols. We show that reachability properties are decidable for systems
without guards, and give sufficient conditions under which they remain
decidable in the presence of guards. Furthermore, we investigate cutoffs for
reachability properties and provide sufficient conditions for small cutoffs in
a number of cases that are inspired by our target applications.Comment: Accepted at CAV 202
Controlling a random population
Bertrand et al. introduced a model of parameterised systems, where each agent
is represented by a finite state system, and studied the following control
problem: for any number of agents, does there exist a controller able to bring
all agents to a target state? They showed that the problem is decidable and
EXPTIME-complete in the adversarial setting, and posed as an open problem the
stochastic setting, where the agent is represented by a Markov decision
process. In this paper, we show that the stochastic control problem is
decidable. Our solution makes significant uses of well quasi orders, of the
max-flow min-cut theorem, and of the theory of regular cost functions. We
introduce an intermediate problem of independence interest called the
sequential flow problem and study its complexity
Finding Cut-Offs in Leaderless Rendez-Vous Protocols is Easy
In rendez-vous protocols an arbitrarily large number of indistinguishable
finite-state agents interact in pairs. The cut-off problem asks if there exists
a number such that all initial configurations of the protocol with at least
agents in a given initial state can reach a final configuration with all
agents in a given final state. In a recent paper (Horn and Sangnier, CONCUR
2020), Horn and Sangnier proved that the cut-off problem is decidable (and at
least as hard as the Petri net reachability problem) for protocols with a
leader, and in EXPSPACE for leaderless protocols. Further, for the special
class of symmetric protocols they reduce these bounds to PSPACE and NP,
respectively. The problem of lowering these upper bounds or finding matching
lower bounds was left open. We show that the cut-off problem is P-complete for
leaderless protocols and in NC for leaderless symmetric protocols. Further, we
also consider a variant of the cut-off problem suggested in (Horn and Sangnier,
CONCUR 2020), which we call the bounded-loss cut-off problem and prove that
this problem is P-complete for leaderless protocols and NL-complete for
leaderless symmetric protocols. Finally, by reusing some of the techniques
applied for the analysis of leaderless protocols, we show that the cut-off
problem for symmetric protocols with a leader is NP-complete, thereby improving
upon all the elementary upper bounds of (Horn and Sangnier, CONCUR 2020)
Foundations of Software Science and Computation Structures
This open access book constitutes the proceedings of the 23rd International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2020, which took place in Dublin, Ireland, in April 2020, and was held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2020. The 31 regular papers presented in this volume were carefully reviewed and selected from 98 submissions. The papers cover topics such as categorical models and logics; language theory, automata, and games; modal, spatial, and temporal logics; type theory and proof theory; concurrency theory and process calculi; rewriting theory; semantics of programming languages; program analysis, correctness, transformation, and verification; logics of programming; software specification and refinement; models of concurrent, reactive, stochastic, distributed, hybrid, and mobile systems; emerging models of computation; logical aspects of computational complexity; models of software security; and logical foundations of data bases.
Foundations of Software Science and Computation Structures
This open access book constitutes the proceedings of the 24th International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2021, which was held during March 27 until April 1, 2021, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg and changed to an online format due to the COVID-19 pandemic. The 28 regular papers presented in this volume were carefully reviewed and selected from 88 submissions. They deal with research on theories and methods to support the analysis, integration, synthesis, transformation, and verification of programs and software systems