The Energetic Reasoning Checker Revisited

Energetic Reasoning (ER) is a powerful filtering algorithm for the Cumulative constraint. Unfortunately, ER is generally too costly to be used in practice. One reason of its bad behavior is that many intervals are considered as relevant by the checker of ER, although most of them should be ignored. In this paper, we provide a sharp characterization that allows to reduce the number of intervals by a factor seven. Our experiments show that associating this checker with a Time-Table filtering algorithm leads to promising results.Comment: CP Doctoral Program 2013, Uppsala : Sweden (2013

Intermediary Local Consistencies

International audienceWe propose a new definition for characterizing levels of consistency. A perspective is to provide new tools for classifying filtering algorithms, including incomplete algorithms based on the semantics of constraints

A New Characterization of Relevant Intervals for Energetic Reasoning

International audienceEnergetic Reasoning (ER) is a powerful filtering algorithm for the Cumulative constraint. Unfortunately, ER is generally too costly to be used in practice. One reason of its bad behavior is that many intervals are considered as relevant, although most of them should be ignored. In the literature, heuristic approaches have been developed in order to reduce the number of intervals to consider, leading to a loss of filtering. In this paper, we provide a sharp characterization that allows to reduce the number of intervals by a factor seven without loss of filtering

Enriching Solutions to Combinatorial Problems via Solution Engineering

International audienceExisting approaches to identify multiple solutions to combinatorial problems in practice are at best limited in their ability to simultaneously incorporate both diversity among generated solutions, as well as problem-specific desires that may only be discovered or articulated by the user after further analysis of solver output. We propose a general framework for problems of a combinatorial nature that can generate a set of of multiple (near-)optimal, diverse solutions, that are further infused with desirable features. We call our approach solution engineering. A key novelty is that desirable solution properties need not be explicitly modeled in advance. We customize the framework to both the mathematical programming and constraint programming technologies, and subsequently demonstrate its prac-ticality by implementing and then conducting computational experiments on existing test instances from the literature. Our computational results confirm the very real possibility of generating sets of solutions infused with features that might otherwise remain undiscovered

Local Ensemble Transform Kalman Filter: a non-stationary control law for complex adaptive optics systems on ELTs

We propose a new algorithm for an adaptive optics system control law which allows to reduce the computational burden in the case of an Extremely Large Telescope (ELT) and to deal with non-stationary behaviors of the turbulence. This approach, using Ensemble Transform Kalman Filter and localizations by domain decomposition is called the local ETKF: the pupil of the telescope is split up into various local domains and calculations for the update estimate of the turbulent phase on each domain are performed independently. This data assimilation scheme enables parallel computation of markedly less data during this update step. This adapts the Kalman Filter to large scale systems with a non-stationary turbulence model when the explicit storage and manipulation of extremely large covariance matrices are impossible. First simulation results are given in order to assess the theoretical analysis and to demonstrate the potentiality of this new control law for complex adaptive optics systems on ELTs.Comment: Proceedings of the AO4ELT3 conference; 8 pages, 3 figure

Proceedings of the 6th international coral reef symposium

Two acoustic surveys have been done in the lagoon all around New Caledonia, with a digital integrator. The cruises lasting two weeks were done at six month interval. Much information has been obtained on stock biomass and spatial distribution of fish and schools. Fish are dispersed at night and stay near the surface. During the day they form schools, usually of very small size. Some species are found mostly along the coasts, on the reef flats and far inside in the bays. Some others stay in the middle of the bays or in the central part of the lagoon and occur usually in deeper water at some distance of the bottom. Aerial and diving observations have shown that the fish of coastal schools were feeding on the reef. Species schooling during the day in the middle of the bays usualy occur deep in the water, not far from the bottom where suspended organic matter is abundant. In a shallow water environment like a coral reef lagoon, the concept of pelagic fish is questionable and most species seem to have strong relations with the bottom. The small pelagic fish, preyed by larger pelagic species (jacks, scads, spanish mackerels ...), play a role of energy transfer from the benthic to the pelagic compartment. (Résumé d'auteur

Making Bound Consistency as Effective as Arc Consistency

International audienceWe study under what conditions bound consistency (BC) and arc consistency (AC), two forms of propagation used in constraint solvers, are equivalent to each other. We show that they prune exactly the same values when the propagated constraint is connected row convex / closed under median and its complement is row convex. This characterization is exact for binary constraints. Since row convexity depends on the order of the values in the domains, we give polynomial algorithms for computing orders under which BC and AC are equivalent, if any