Team Veridis

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Section: Software

The veriT solver

Participants : Diego Caminha Barbosa de Oliveira, David Déharbe, Pascal Fontaine [correspondant] , Bruno Woltzenlogel Paleo.

The veriT solver is an SMT (Satisfiability Modulo Theories) solver developed in cooperation with David Déharbe from the Federal University of Rio Grande do Norte in Natal, Brazil. The solver can handle large quantifier-free formulas containing uninterpreted predicates and functions, and arithmetic on integers and reals. It features a very efficient decision procedure for difference logic, as well as a simplex-based reasoner for full linear arithmetic. It also has some support for user-defined theories, quantifiers, and lambda-expressions. This allows users to easily express properties about concepts involving sets, relations, etc. The prover can produce an explicit proof trace when it is used as a decision procedure for quantifier-free formulas with uninterpreted symbols and arithmetic. To support the development of the tool, a regression platform using INRIA's grid infrastructure is used; it allows us to extensively test the solver on thousands of benchmarks in a few minutes.

The veriT solver is available as open source under the BSD license, and distributed through the web site http://www.veriT-solver.org . It entered for the third time the international competition of SMT solvers SMT-COMP 2011 , a joint event with the SMT workshop 2011 and the CAV conference. As in the previous competitions, it performed decently against the other participating SMT solvers. It embeds an original symmetry reduction technique that greatly improved its efficiency on some categories of formulas. This technique was immediately incorporated also in other competing solvers, in particular Z3 (Microsoft) and CVC3 (University of New-York and University of Iowa).

Efforts in 2011 have been focused on the extension of the expressiveness of the tool (with improvements in the handling of quantifiers), and on its efficiency (which was significantly improved at different levels, including a purpose-built SAT solver underlying veriT). A lot of work was also devoted to improve the proof production of the tool, with the definition of a precise proof language. This proof language has been presented to the community as a standard for describing SMT proofs [17] . We are collaborating on this with Laurent Théry and Benjamin Grégoire (Marelle, INRIA Sophia-Antipolis), Laurent Voisin (Systerel), and Frédéric Besson (Celtique, INRIA Rennes).

Future research and implementation efforts will be directed to furthermore extend the accepted language, and increase the efficiency. We target applications where validation of formulas is crucial, such as the validation of TLA+ and B specifications, and work together with the developers of the respective verification platforms to make veriT even more useful in practice.

The software will be supported by an INRIA ADT, which will start at the beginning of 2012.