Cubicle is a new model checker for verifying safety properties of parameterized systems. It implements a parallel symbolic backward reachability procedure using Satisfiabilty Modulo Theories. Experiments done on classic and challenging mutual exclusion algorithms and cache coherence protocols show that Cubicle is effective and competitive with state-of-the-art model checkers. 2 System Description Language Cubicle's input language is a typed version of Murϕ [8] similar to the one of Uclid [6], rudimentary at the moment, but more user-friendly than mcmt and sufficiently expressive for typical parameterized systems. A system is described in Cubicle by: (1) a set of type, variable, and array declarations; (2) a formula for the initial states; and (3) a set of transitions. It is parametrized by a set of process identifiers, denoted by the built-in type proc. Standard types int, real, and bool are also built in. Additionally, the user

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This paper describes SMTCoq, a plug-in for the integration of external solvers into the Coq proof assistant. Based on a checker for generic first-order proof certificates fully implemented and proved correct in Coq, SMTCoq offers facilities to check answers from external SAT and SMT solvers and to increase Coq's automation using such solvers, all in a safe way. The current version supports proof certificates produced by the SAT solver ZChaff, for propositional logic, and the SMT solvers veriT and CVC4, for the quantifier-free fragment of the combined theory of fixed-size bit vectors, functional arrays with extensionality, linear integer arithmetic, and uninterpreted function symbols.

Abstract-Verification of safety properties of concurrent programs with an arbitrary numbers of processes is an old challenge. In particular, complex parameterized protocols like FLASH are still out of the scope of state-of-the-art model checkers. In this paper, we describe a new algorithm, called BRAB, that is able to automatically infer invariants strong enough to prove a protocol like FLASH. BRAB computes over-approximations of backward reachable states that are checked to be unreachable in a finite instance of the system. These approximations (candidate invariants) are then model checked together with the original safety properties. Completeness of the approach is ensured by a mechanism for backtracking on spurious traces introduced by too coarse approximations.