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Bellatreche L.,University of Poitiers | Bouchakri R.,National School in Computer Science | Cuzzocrea A.,CNR Institute for High Performance Computing and Networking | Maabout S.,LaBRI Inc
Proceedings of the ACM Symposium on Applied Computing | Year: 2013

With the explosion of the size of data warehousing applications, the horizontal data partitioning is well adapted to reduce the cost of complex OLAP queries and the warehouse manageability. It is considered as a non redundant optimization technique. Selecting a fragmentation schema for a given data warehouse is NP-hard problem. Several studies exist and propose heuristics to select near optimal solutions. Most of these heuristics are static, since they assume the existence of a priori known set of queries. Note that in real life applications, queries may change dynamically and fragmentation heuristics need to integrate these changes. In this paper, we propose an incremental selection of fragmentation schemes using on genetic algorithms. Intensive experiments are conducted to validate our proposal. Copyright 2013 ACM.

Bourgeade L.,Bordeaux University | Chauve C.,Simon Fraser University | Allali J.,LaBRI Inc
Journal of Computational Biology | Year: 2015

We describe a new method to compare a query RNA with a static set of target RNAs. Our method is based on (i) a static indexing of the sequence/structure seeds of the target RNAs; (ii) searching the target RNAs by detecting seeds of the query present in the target, chaining these seeds in promising candidate homologs; and then (iii) completing the alignment using an anchor-based exact alignment algorithm. We apply our method on the benchmark Bralibase2.1 and compare its accuracy and efficiency with the exact method LocARNA and its recent seeds-based speed-up ExpLoc-P. Our pipeline RNA-unchained greatly improves computation time of LocARNA and is comparable to the one of ExpLoc-P, while improving the overall accuracy of the final alignments. © 2015 Mary Ann Liebert, Inc.

Bourhis P.,CNRS Lille Research Center in Informatics, Signal and Automatic control | Puppis G.,LaBRI Inc | Riveros C.,University of Computer Science of Chile
Theory of Computing Systems | Year: 2015

In this paper we consider the problem of repairing, that is, restoring validity of, documents with respect to XML schemas. We formalize this as the problem of determining, given an XML schema, whether or not a streaming procedure exists that transforms an input document so as to satisfy the XML schema, using a number of edits independent of the document. We show that this problem is decidable. In fact, we show the decidability of a more general problem, which allows the repair procedure to work on documents that are already known to satisfy another XML schema. The decision procedure relies on the analysis of the structure of an automaton model specifying the restriction and target XML schemas and reduces te problem to a novel notion of game played on pushdown systems associated with the schemas. © 2015 Springer Science+Business Media New York

Kelmendi E.,LaBRI Inc | Gimbert H.,French National Center for Scientific Research
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

Two-player, turn-based, stochastic games with reachability conditions are considered, where the maximizer has no information (he is blind) and is restricted to deterministic strategies whereas the minimizer is perfectly informed. We ask the question of whether the game has maxmin value of 1 in other words we ask whether for all ϵ > 0 there exists a deterministic strategy for the (blind) maximizer such that against all the strategies of the minimizer, it is possible to reach the set of final states with probability larger than 1−ϵ. This problem is undecidable in general, but we define a class of games, called leaktight half-blind games where the problem becomes decidable. We also show that mixed strategies in general are stronger for both players and that optimal strategies for the minimizer might require infinite-memory. © Springer-Verlag Berlin Heidelberg 2016.

Broquedis F.,University of Bordeaux 1 | Clet-Ortega J.,University of Bordeaux 1 | Moreaud S.,French Institute for Research in Computer Science and Automation | Furmento N.,French National Center for Scientific Research | And 4 more authors.
Proceedings of the 18th Euromicro Conference on Parallel, Distributed and Network-Based Processing, PDP 2010 | Year: 2010

The increasing numbers of cores, shared caches and memory nodes within machines introduces a complex hardware topology. High-performance computing applications now have to carefully adapt their placement and behavior according to the underlying hierarchy of hardware resources and their software affinities. We introduce the Hardware Locality (hwloc) software which gathers hardware information about processors, caches, memory nodes and more, and exposes it to applications and runtime systems in a abstracted and portable hierarchical manner. hwloc may significantly help performance by having runtime systems place their tasks or adapt their communication strategies depending on hardware affinities. We show that hwloc can already be used by popular highperformance OPENMP or MPI software. Indeed, scheduling OPENMP threads according to their affinities or placing MPI processes according to their communication patterns shows interesting performance improvement thanks to hwloc. An optimized MPI communication strategy may also be dynamically chosen according to the location of the communicating processes in the machine and its hardware characteristics. © 2010 IEEE.

Jeannot E.,LaBRI Inc | Jeannot E.,French Institute for Research in Computer Science and Automation | Mercier G.,LaBRI Inc | Mercier G.,French Institute for Research in Computer Science and Automation | Mercier G.,Bordeaux Polytechnic Institute
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

MPI process placement can play a deterministic role concerning the application performance. This is especially true with nowadays architecture (heterogenous, multicore with different level of caches, etc.). In this paper, we will describe a novel algorithm called TreeMatch that maps processes to resources in order to reduce the communication cost of the whole application. We have implemented this algorithm and will discuss its performance using simulation and on the NAS benchmarks. © 2010 Springer-Verlag.

Liu Y.,University of Sichuan | Liu Y.,French Institute for Research in Computer Science and Automation | Granier X.,French Institute for Research in Computer Science and Automation | Granier X.,LaBRI Inc
IEEE Transactions on Visualization and Computer Graphics | Year: 2012

In augmented reality, one of key tasks to achieve a convincing visual appearance consistency between virtual objects and video scenes is to have a coherent illumination along the whole sequence. As outdoor illumination is largely dependent on the weather, the lighting condition may change from frame to frame. In this paper, we propose a full imagebased approach for online tracking of outdoor illumination variations from videos captured with moving cameras. Our key idea is to estimate the relative intensities of sunlight and skylight via a sparse set of planar featurepoints extracted from each frame. To address the inevitable feature misalignments, a set of constraints are introduced to select the most reliable ones. Exploiting the spatial and temporal coherence of illumination, the relative intensities of sunlight and skylight are finally estimated by using an optimization process. We validate our technique on a set of reallife videos and show that the results with our estimations are visually coherent along the video sequences. © 2011 IEEE.

Bardin S.,CEA Saclay Nuclear Research Center | Herrmann P.,CEA Saclay Nuclear Research Center | Leroux J.,LaBRI Inc | Ly O.,LaBRI Inc | And 2 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

This paper presents the BINCOA framework, whose goal is to ease the development of binary code analysers by providing an open formal model for low-level programs (typically: executable files), an XML format for easy exchange of models and some basic tool support. The BINCOA framework already comes with three different analysers, including simulation, test generation and Control-Flow Graph reconstruction. © 2011 Springer-Verlag.

Bouzid Z.,LaBRI Inc | Travers C.,LaBRI Inc
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

The paper investigates the consensus problem in anonymous, failures prone and asynchronous shared memory systems. It introduces a new class of failure detectors, called anonymity-preserving failure detectors suited to anonymous systems. As its name indicates, a failure detector in this class cannot be relied upon to break anonymity. For example, the anonymous perfect detector AP, which gives at each process an estimation of the number of processes that have failed belongs to this class. The paper then determines the weakest failure detector among this class for consensus. This failure detector, called C, may be seen as a loose failures counter: (1) after a failure occurs, the counter is eventually incremented, and (2) if two or more processes are non-faulty, it eventually stabilizes. © Springer-Verlag Berlin Heidelberg 2016.

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