Octobre 2016

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Mardi 4 Octobre
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Évaluation multi-précision rigoureuse de fonctions D-finies en Sage
Description: Marc Mezzarobba Je présenterai une implémentation en développement d'algorithmes d'évaluation numérique de fonctions D-finies (c.-à-d. solutions d'équations différentielles linéaires à coefficients polynomiaux), pour le logiciel de calcul formel libre SageMath. Ce nouveau package a vocation à remplacer NumGfun, un package un peu similaire pour Maple que j'ai présenté au séminaire CALIN il y a quelques années. Si le temps le permet, je dirai aussi quelques mots des algorithmes originaux utilisés.La fonctionnalité centrale de ce code est le « prolongement analytique numérique » d'une fonction D-finie, qui fournit une approximation de la matrice envoyant un jeu de conditions initiales en un point donné du plan complexe sur les conditions « initiales » qui définissent la même fonction au voisinage d'un autre point. Le prolongement analytique numérique permet de calculer des valeurs ou encore des approximations polynomiales de fonctions D-finies n'importe où sur leur surface de Riemann, des matrices de monodromie d'opérateurs différentiels, etc. Le code traite complètement le cas limite important de conditions initiales généralisées données en un point singulier régulier de l'opérateur. Il peut donc être utilisé pour calculer des matrices de connexion entre singularités régulières, ce qui est utile notamment en combinatoire analytique. Par ailleurs, il s'agit d'une implémentation rigoureuse, au sens où elle renvoie des intervalles qui (sauf bug !) contiennent à coup sûr le résultat mathématique exact.
Jeudi 6 Octobre
Heure: 10:30 - 11:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Solving the Asymmetric Travelling Salesman Problem
Description: Luis Gouveia There are many ways of modelling the Asymmetric Traveling Salesman Problem (ATSP) and the related Precedence Constrained ATSP (PCATSP).
In this talk we present new formulations for the two problems that can be viewed as resulting from combining precedence variable based formulations, with network flow based formulations. As suggested in [1], the former class of formulations permits to integrate linear ordering constraints.
The motivating formulation for this work is a complicated and "ugly" formulation that results from
the separation of generalized subtour elimination constraints presented in [2] (see also [1]).
This so called "ugly" formulation exhibits, however, one interesting feature, namely the "disjoint subpaths" property that is further explored to create more complicated formulations that combine two (or three) "disjoint path" network flow based formulations and have a stronger linear programming bound.
Some of these stronger formulations are related to the ones presented for the PCATSP in [3] and can be viewed as generalizations in the space of the precedence based variables.
Several sets of projected inequalities in the space of the arc and precedence variables and in the spirit of many presented in [1] are obtained by projection from these network flow based formulations.
Computational results will be given for the ATSP and PCATSP to evaluate the quality of the new
models and inequalities.
[1] L. Gouveia and P. Pesneau. On extended formulations for the precedence constrainted asymmetric
traveling salesman problem. Networks, 48(2):77{89, 2006.
[2] L. Gouveia and J. M. Pires. The asymmetric travelling salesman problem: On generalizations of
disaggregated Miller-Tucker-Zemlin constraints. Discrete Applied Mathematics, 112:129{145, 2001.

Joint work with Pierre Pesneau (University of Bordeaux), Mario Ruthmair (University of Vienna) and Daniel Santos (University of Lisbon)
Heure: 13:00 - 15:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Automatic Extraction of Malicious Behaviors
Description: Khanh-Huu-The Dam
The number of new malwares is increasing everyday.
Thus malware detection is nowadays a big challenge. The
existing techniques for malware detection require a huge
effort of engineering to manually extract the malicious behaviors.
To avoid this tedious task, we propose in this paper
an approach to automatically extract the malicious behaviors.
We model a program using an API call graph,
and we represent the malicious behaviors using a malicious
API graph. We then reduce the malicious behavior extraction
problem to the problem of retrieving from the benign
and malicious API call graphs the set of subgraphs that
are relevant for malicious behaviors. We solve this issue
by applying and adapting well-known efficient Information
Retrieval techniques based on the TFIDF scheme. We use
our automatically extracted malicious behavior specification
for malware detection using a kind of product between
graphs. We obtained interesting experimental results, as we
get 99.04% of detection rate. Moreover, we were able to
detect several malwares that well-known and widely used
antiviruses such as Panda, Avira, Kaspersky, Avast, Qihoo-
360, McAfee, AVG, BitDefender, ESET-NOD32, F-Secure,
and Symantec could not detect.

This is a joint work with Tayssir Touili.
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Évaluation multi-précision rigoureuse de fonctions D-finies
Description: Marc Mezzarobba
Mardi 11 Octobre
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Non-commutative differential equations and (some) geometrical hints
Description: Gérard Duchamp On prendra appui sur les intégrales itérées des systèmesfuschsiens pour proposer une théorie des équations différentiellesnon-commutatives. Plusieurs surprises et cadeaux nous attendentdans cette exploration.
Lundi 17 Octobre
Heure: 14:00 - 15:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Framester: A Wide Coverage Linguistic Linked Data Hub
Description: Mehwish Alam Semantic web applications leveraging NLP can benefit from easy access to expressive lexical resources such as FrameNet. However, the usefulness of FrameNet is affected by its limited coverage and non-standard semantics. The access to existing linguistic resources is also limited because of poor connectivity among them. We present some strategies based on Linguistic Linked Data to broaden FrameNet coverage and formal linkage of lexical and factual resources. We created a novel resource, Framester, which acts as a hub between FrameNet, WordNet, VerbNet, BabelNet, DBpedia, Yago, DOLCE-Zero, as well as other resources. Framester is not only a strongly connected knowledge graph, but also applies a rigorous formal treatment for Fillmore's frame semantics, enabling full-fl edged OWL querying and reasoning on a large frame-based knowledge graph. We also describe Word Frame Disambiguation, an application that reuses Framester data as a base in order to perform frame detection from text, with results comparable in precision to the state of the art, but with a much higher coverage. Open issues and current research directions will be also presented.
Mardi 18 Octobre
Heure: 12:30 - 13:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Lower bounds in resource constrained shortest path algorithms
Description: Axel Parmentier Resource constrained shortest path problems arise naturally as pricing sub-problems of column generation approaches to a wide range of routing and scheduling problems. The algorithms for these problems rely on dominance relations between paths to discard partial solutions in an enumeration of all the paths. It is well known that the use of bounds on paths resources in addition to dominance relations strongly accelerates these algorithms. Nonetheless, there is still no standard procedure to build such bounds in non-linear or stochastic settings. We provide such a bounding procedure and sho w its efficiency on several deterministic and stochastic path problems. Besides, enumeration algorithms exhibit poor performances when the number of constraints increases. We show that using sets of bounds instead of single bounds enable to discard more paths and thus to tackle better with these difficult instances. Finally, we prove the relevance of these procedures in the context of column generation on industrial instances of the airline crew pairing problem.Â
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Combinatoire des mots
Description: Johan Nilsson
Jeudi 20 Octobre
Heure: 15:30 - 16:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Integer-Complete Synthesis for Bounded Parametric Timed Automata
Description: Étienne André Ensuring the correctness of critical real-time systems, involving concurrent
behaviors and timing requirements, is crucial. Parameter synthesis aims at
computing dense sets of valuations for the timing requirements, guaranteeing a
good behavior. However, in most cases, the emptiness problem for reachability
(i.e. whether there exists at least one parameter valuation for which some
state is reachable) is undecidable and, as a consequence, synthesis procedures
do not terminate in general, even for bounded parameters. In this paper, we
introduce a parametric extrapolation, that allows us to derive an
underapproximation in the form of linear constraints containing all the
integer points ensuring reachability or unavoidability, and all the
(non-necessarily integer) convex combinations of these integer points, for
general PTA with a bounded parameter domain. Our algorithms terminate and can
output constraints arbitrarily close to the complete result.

Joint work with Didier Lime and Olivier H. Roux.
Vendredi 21 Octobre
Heure: 11:00 - 12:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Some interplays between proof theory and computational complexity
Description: Anupam Das Proof complexity is the branch of proof theory concerned with the size of proofs. Due to old and well-known results of Cook and Reckhow, many important questions about computational complexity are equivalent to natural problems in proof complexity. For instance, coNP = NP just if there is an 'efficient' proof system for classical propositional logic. I will survey a now well-developed line of work on the proof complexity of 'deep inference' systems which has culminated in several novel phenomena in proof complexity, including improved bounds for monotone proof systems. I will also discuss remaining open problems in the area and some of their consequences.

A closely related area to proof complexity is bounded arithmetic, which studies weak fragments of arithmetic whose representable functions are typically feasible complexity classes, via bounds on quantifiers. They also act as uniform versions of corresponding propositional systems, forming a three-way correspondence. I will show how this methodology can be extended to certain deep inference and monotone systems via intuitionistic versions of bounded arithmetic, making use of a novel technique that combines the usual 'witness function method' of bounded arithmetic with realisability style extraction. I will further motivate the study of such theories in 'linear logic' in order to address the remaining correspondences, and present some recent work along this line.

Finally I will present an upcoming research project that aims to unify various strands of this research in order to develop a comprehensive approach to monotone complexity classes.
Mardi 25 Octobre
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: TBA
Description: Vincent Pilaud