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Publications : Stéphane Lescuyer

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lescuyer
[11] Stéphane Lescuyer. Formalisation et développement d'une tactique réflexive pour la démonstration automatique en Coq. Thèse de doctorat, Université Paris-Sud, January 2011. [ bib | .pdf ]
[10] Stéphane Lescuyer and Sylvain Conchon. Improving Coq propositional reasoning using a lazy CNF conversion scheme. In Silvio Ghilardi and Roberto Sebastiani, editors, Frontiers of Combining Systems, 7th International Symposium, Proceedings, volume 5749 of Lecture Notes in Computer Science, pages 287-303, Trento, Italy, September 2009. Springer. [ bib | DOI ]
[9] Romain Bardou, Jean-Christophe Filliâtre, Johannes Kanig, and Stéphane Lescuyer. Faire bonne figure avec Mlpost. In Vingtièmes Journées Francophones des Langages Applicatifs, Saint-Quentin sur Isère, January 2009. INRIA. [ bib | .pdf ]
Cet article présente Mlpost, une bibliothèque Ocaml de dessin scientifique. Elle s'appuie sur Metapost, qui permet notamment d'inclure des fragments LATEX dans les figures. Ocaml offre une alternative séduisante aux langages de macros LATEX, aux langages spécialisés ou même aux outils graphiques. En particulier, l'utilisateur de Mlpost bénéficie de toute l'expressivité d'Ocaml et de son typage statique. Enfin Mlpost propose un style déclaratif qui diffère de celui, souvent impératif, des outils existants.

[8] François Bobot, Sylvain Conchon, Évelyne Contejean, and Stéphane Lescuyer. Implementing Polymorphism in SMT solvers. In Clark Barrett and Leonardo de Moura, editors, SMT 2008: 6th International Workshop on Satisfiability Modulo, volume 367 of ACM International Conference Proceedings Series, pages 1-5, 2008. [ bib | DOI | PDF | .pdf | Abstract ]
[7] Sylvain Conchon, Évelyne Contejean, Johannes Kanig, and Stéphane Lescuyer. CC(X): Semantical combination of congruence closure with solvable theories. In Post-proceedings of the 5th International Workshop on Satisfiability Modulo Theories (SMT 2007), volume 198(2) of Electronic Notes in Computer Science, pages 51-69. Elsevier Science Publishers, 2008. [ bib | DOI ]
We present a generic congruence closure algorithm for deciding ground formulas in the combination of the theory of equality with uninterpreted symbols and an arbitrary built-in solvable theory X. Our algorithm CC(X) is reminiscent of Shostak combination: it maintains a union-find data-structure modulo X from which maximal information about implied equalities can be directly used for congruence closure. CC(X) diverges from Shostak's approach by the use of semantical values for class representatives instead of canonized terms. Using semantical values truly reflects the actual implementation of the decision procedure for X. It also enforces to entirely rebuild the algorithm since global canonization, which is at the heart of Shostak combination, is no longer feasible with semantical values. CC(X) has been implemented in Ocaml and is at the core of Ergo, a new automated theorem prover dedicated to program verification.

[6] Sylvain Conchon, Johannes Kanig, and Stéphane Lescuyer. SAT-MICRO : petit mais costaud ! In Dix-neuvièmes Journées Francophones des Langages Applicatifs, Étretat, France, January 2008. INRIA. [ bib | .ps ]
Le problème SAT, qui consiste `a déterminer si une formule booléenne est satisfaisable, est un des problèmes NP-complets les plus célèbres et aussi un des plus étudiés. Basés initialement sur la procédure DPLL, les SAT-solvers modernes ont connu des progrès spectaculaires ces dix dernières années dans leurs performances, essentiellement grâce à deux optimisations: le retour en arrière non-chronologique et l'apprentissage par analyse des clauses conflits. Nous proposons dans cet article une étude formelle du fonctionnement de ces techniques ainsi qu'une réalisation en Ocaml d'un SAT-solver, baptisé SAT-MICRO, intégrant ces optimisations. Le fonctionnement de SAT-MICRO est décrit par un ensemble de règles d'inférence et la taille de son code, 70 lignes au total, permet d'envisager sa certification complète.

[5] François Bobot, Sylvain Conchon, Évelyne Contejean, Mohamed Iguernelala, Stéphane Lescuyer, and Alain Mebsout. The Alt-Ergo automated theorem prover, 2008. http://alt-ergo.lri.fr/. [ bib ]
[4] Stéphane Lescuyer and Sylvain Conchon. A reflexive formalization of a SAT solver in Coq. In Emerging Trends of the 21st International Conference on Theorem Proving in Higher Order Logics, 2008. [ bib ]
[3] Jean-François Couchot and Stéphane Lescuyer. Handling polymorphism in automated deduction. In 21th International Conference on Automated Deduction (CADE-21), volume 4603 of LNCS (LNAI), pages 263-278, Bremen, Germany, July 2007. [ bib | PDF | .pdf ]
Polymorphism has become a common way of designing short and reusable programs by abstracting generic definitions from type-specific ones. Such a convenience is valuable in logic as well, because it unburdens the specifier from writing redundant declarations of logical symbols. However, top shelf automated theorem provers such as Simplify, Yices or other SMT-LIB ones do not handle polymorphism. To this end, we present efficient reductions of polymorphism in both unsorted and many-sorted first order logics. For each encoding, we show that the formulas and their encoded counterparts are logically equivalent in the context of automated theorem proving. The efficiency keynote is to disturb the prover as little as possible, especially the internal decision procedures used for special sorts, e.g. integer linear arithmetic, to which we apply a special treatment. The corresponding implementations are presented in the framework of the Why/Caduceus toolkit.

[2] Sylvain Conchon, Évelyne Contejean, Johannes Kanig, and Stéphane Lescuyer. Lightweight Integration of the Ergo Theorem Prover inside a Proof Assistant. In John Rushby and N. Shankar, editors, Proceedings of the second workshop on Automated formal methods, pages 55-59. ACM Press, 2007. [ bib | DOI | PDF | .pdf ]
Ergo is a little engine of proof dedicated to program verification. It fully supports quantifiers and directly handles polymorphic sorts. Its core component is CC(X), a new combination scheme for the theory of uninterpreted symbols parameterized by a built-in theory X. In order to make a sound integration in a proof assistant possible, Ergo is capable of generating proof traces for CC(X). Alternatively, Ergo can also be called interactively as a simple oracle without further verification. It is currently used to prove correctness of C and Java programs as part of the Why platform.

[1] Stéphane Lescuyer. Codage de la logique du premier ordre polymorphe multi-sortée dans la logique sans sortes. Master's thesis, Master Parisien de Recherche en Informatique, 2006. [ bib ]

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