An Experimental Study of Adaptive Control for Evolutionary Algorithms

The balance of exploration versus exploitation (EvE) is a key issue on evolutionary computation. In this paper we will investigate how an adaptive controller aimed to perform Operator Selection can be used to dynamically manage the EvE balance required by the search, showing that the search strategies determined by this control paradigm lead to an improvement of solution quality found by the evolutionary algorithm

Collectifs cosmopolitiques de réfugiés urbains en Afrique centrale : entre droits de l'homme et droit de cité

International audienceFrom a theoretical vantage point at the interface between political and urban sociology, this study analyzes collective action by urban refugees in Central Africa, focusing on efforts to adjust and adapt collective action to the global humanitarian environment in which it seeks to be embedded. In a context marked by political withdrawal at State level from refugee assistance issues and by the emergence of an international human rights regime as the principal normative framework in Central African host countries, we seek to identify the preconditions for the growth of "cosmopolitical collectives" of refugees. Further, we point up their propensity to call into question the relationship between human rights and the rights of citizens in urban areas where the boundaries between the international and domestic order have never before been as porous and undefined.Autour d'une posture théorique qui se situe à l'interface de la sociologie politique et de la sociologie urbaine, l'étude consiste à analyser les actions collectives des réfugiés urbains en Afrique centrale en privilégiant l'attention sur le travail de cadrage et d'ajustement des mobilisations à l'environnement humanitaire global dans lequel elles cherchent à s'insérer. Dans un contexte marqué par un dessaisissement politique sur le plan étatique de la question del'assistance aux réfugiés et par l'émergence du régime international des droits de l'homme comme cadre de production normatif central dans les pays d'accueil d'Afrique centrale, il s'agit ensuite de dégager les conditions d'émergence des " collectifs cosmopolitiques " de réfugiés et leur aptitude à remettre en question le rapport entre droit de l'homme et droit du citoyen dans des espaces urbains où les frontières entre ordre international et ordre interne n'ont jamais été aussi poreuses et indéfinies

Auto-adaptative Migration Policies in Island-Based Genetic Algorithms

Date du colloque : 2010International audienc

Set Constraint Model and Automated Encoding into SAT: Application to the Social Golfer Problem

On the one hand, Constraint Satisfaction Problems allow one to declaratively model problems. On the other hand, propositional satisfiability problem (SAT) solvers can handle huge SAT instances. We thus present a technique to declaratively model set constraint problems and to encode them automatically into SAT instances. We apply our technique to the Social Golfer Problem and we also use it to break symmetries of the problem. Our technique is simpler, more declarative, and less error-prone than direct and improved hand modeling. The SAT instances that we automatically generate contain less clauses than improved hand-written instances such as in [20], and with unit propagation they also contain less variables. Moreover, they are well-suited for SAT solvers and they are solved faster as shown when solving difficult instances of the Social Golfer Problem.Comment: Submitted to Annals of Operations researc

Modélisation du Social Golfer en SAT via les contraintes ensemblistes

National audienc

Autonomous Local Search Algorithms with Island Representation

The aim of this work is to use this dynamic island model to autonomously select local search operators within a classical evolutionary algorithm. In order to assess the relevance of this approach, we will use the model considering a population-based local search algorithm, with no crossover and where each island is associated to a particular local search operator. Here, contrary to recent works [6], the goal is not to forecast the most promising crossovers between individuals like in classical island models, but to detect at each time of the search the most relevant LS operators. This application constitutes an original approach in defining autonomous algorithms

Réduction et Encodage des Contraintes Ensemblistes en SAT

On the one hand, Constraint Satisfaction Problems(CSP) are a declarative and expressive approach for mo-deling problems. On the other hand, propositional sa-tisfiability problem (SAT) solvers can handle huge SATinstances up to millions of variables and clauses. In thisarticle, we present an approach for taking advantageof both CSP modeling and SAT solving. Our techniqueconsists in expressively modeling set constraint problemsas CSPs that are automatically treated by some reduc-tion rules to remove values that do not participate inany solution. These reduced CSPs are then encoded into”good” SAT instances that can be solved by standardSAT solvers. We illustrate our technique on various well-known problems such as Sudoku, the Social Golfer pro-blem, and the Sports Tournament Scheduling problem.Our technique is simpler, more expressive, and less error-prone than direct SAT modeling. The SAT instances thatwe automatically generate are rather small (even w.r.t.direct-written SAT instances for the Social Golfer pro-blem [18]) and can efficiently be solved up to huge ins-tances. Moreover, the reduction phase enables to pushback the limits and treat even bigger problems.D’un cˆot ́e, les probl`emes de satisfaction decontraintes (CSP) procurent une m ́ethode d ́eclarative etexpressive pour mod ́eliser les probl`emes. D’un autre cˆot ́e,les solveurs pour les probl`emes de satisfiabilit ́e de for-mules logique propositionnelle (SAT) peuvent manipulerdes instances ́enormes jusqu’`a des millions de clauses etvariables. Dans cet article, nous pr ́esentons une approcheb ́en ́eficiant de la mod ́elisation CSP et de la r ́esolutionSAT. Notre technique consiste `a mod ́eliser, de fa ̧con ex-pressive, des probl`emes de contraintes ensemblistes enen CSP qui sont ensuite automatiquement r ́eduits afinde retirer les valeurs des variables qui ne participent `aaucune solution. Ces CSPs r ́eduits sont ensuite encod ́esen de “bonnes” instances SAT qui peuvent ˆetre r ́esoluespar des solveurs SAT standards. Nous illustrons notretechnique par divers probl`emes standards : le Sudoku, leSocial Golfer Problem et le Sports Tournament Schedu-ling Problem.Notre technique est plus simple, plus expressive etmoins sensible aux erreurs qu’une mod ́elisation directeen SAT. De plus, les instances SAT automatiquementg ́en ́er ́ees sont g ́en ́eralement plus petites que celles direc-tement ́ecrite pour un probl`eme particulier (comme parexemple pour le Social Golfer Problem [18]) et peuventˆetre ́evalu ́ees efficacement mˆeme pour des instances ́enormes. Enfin, la phase de r ́eduction nous permet derepousser les limites et de traiter des probl`emes encoreplus gros

Photoinduced dynamics in protonated aromatic amino acid

UV photoinduced fragmentation of protonated aromatics amino acids have emerged the last few years, coming from a situation where nothing was known to what we think a good understanding of the optical properties. We will mainly focus this review on the tryptophan case. Three groups have mostly done spectroscopic studies and one has mainly been involved in dynamics studies of the excited states in the femtosecond/picosecond range and also in the fragmentation kinetics from nanosecond to millisecond. All these data, along with high level ab initio calculations, have shed light on the role of the different electronic states of the protonated molecules upon the fragmentation mechanisms