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Search Results: 1 - 10 of 8188 matches for " Michel Rueher "
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Handling software upgradeability problems with MILP solvers
Claude Michel,Michel Rueher
Electronic Proceedings in Theoretical Computer Science , 2010, DOI: 10.4204/eptcs.29.1
Abstract: Upgradeability problems are a critical issue in modern operating systems. The problem consists in finding the "best" solution according to some criteria, to install, remove or upgrade packages in a given installation. This is a difficult problem: the complexity of the upgradeability problem is NP complete and modern OS contain a huge number of packages (often more than 20 000 packages in a Linux distribution). Moreover, several optimisation criteria have to be considered, e.g., stability, memory efficiency, network efficiency. In this paper we investigate the capabilities of MILP solvers to handle this problem. We show that MILP solvers are very efficient when the resolution is based on a linear combination of the criteria. Experiments done on real benchmarks show that the best MILP solvers outperform CP solvers and that they are significantly better than Pseudo Boolean solvers.
An Efficient Algorithm for a Sharp Approximation of Universally Quantified Inequalities
Alexandre Goldsztejn,Claude Michel,Michel Rueher
Computer Science , 2008,
Abstract: This paper introduces a new algorithm for solving a sub-class of quantified constraint satisfaction problems (QCSP) where existential quantifiers precede universally quantified inequalities on continuous domains. This class of QCSPs has numerous applications in engineering and design. We propose here a new generic branch and prune algorithm for solving such continuous QCSPs. Standard pruning operators and solution identification operators are specialized for universally quantified inequalities. Special rules are also proposed for handling the parameters of the constraints. First experimentation show that our algorithm outperforms the state of the art methods.
Revisiting the upper bounding process in a safe Branch and Bound algorithm
Alexandre Goldsztejn,Yahia Lebbah,Claude Michel,Michel Rueher
Mathematics , 2008,
Abstract: Finding feasible points for which the proof succeeds is a critical issue in safe Branch and Bound algorithms which handle continuous problems. In this paper, we introduce a new strategy to compute very accurate approximations of feasible points. This strategy takes advantage of the Newton method for under-constrained systems of equations and inequalities. More precisely, it exploits the optimal solution of a linear relaxation of the problem to compute efficiently a promising upper bound. First experiments on the Coconuts benchmarks demonstrate that this approach is very effective.
Searching input values hitting suspicious Intervals in programs with floating-point operations
Hélène Collavizza,Claude Michel,Michel Rueher
Computer Science , 2015,
Abstract: Programs with floating-point computations are often derived from mathematical models or designed with the semantics of the real numbers in mind. However, for a given input, the computed path with floating-point numbers may differ from the path corresponding to the same computation with real numbers. A common practice when validating such programs consists in estimating the accuracy of floating-point computations with respect to the same sequence of operations in an ide-alized semantics of real numbers. However, state-of-the-art tools compute an over-approximation of the error introduced by floating-point operations. As a consequence, totally inappropriate behaviors of a program may be dreaded but the developer does not know whether these behaviors will actually occur, or not. In this paper, we introduce a new constraint-based approach that searches for test cases in the part of the over-approximation where errors due to floating-point arithmetic would lead to inappropriate behaviors.
Comparison between CPBPV, ESC/Java, CBMC, Blast, EUREKA and Why for Bounded Program Verification
Hélène Collavizza,Michel Rueher,Pascal Van Hentenryck
Computer Science , 2008,
Abstract: This report describes experimental results for a set of benchmarks on program verification. It compares the capabilities of CPBVP "Constraint Programming framework for Bounded Program Verification" [4] with the following frameworks: ESC/Java, CBMC, Blast, EUREKA and Why.
CPBVP: A Constraint-Programming Framework for Bounded Program Verification
Hélène Collavizza,Michel Rueher,Pascal Van Hentenryck
Computer Science , 2008,
Abstract: This paper studies how to verify the conformity of a program with its specification and proposes a novel constraint-programming framework for bounded program verification (CPBPV). The CPBPV framework uses constraint stores to represent the specification and the program and explores execution paths nondeterministically. The input program is partially correct if each constraint store so produced implies the post-condition. CPBPV does not explore spurious execution paths as it incrementally prunes execution paths early by detecting that the constraint store is not consistent. CPBPV uses the rich language of constraint programming to express the constraint store. Finally, CPBPV is parametrized with a list of solvers which are tried in sequence, starting with the least expensive and less general. Experimental results often produce orders of magnitude improvements over earlier approaches, running times being often independent of the variable domains. Moreover, CPBPV was able to detect subtle errors in some programs while other frameworks based on model checking have failed.
Un algorithme incrémental dirigé par les flots et basé sur les contraintes pour l'aide à la localisation d'erreurs
Mohammed Bekkouche,Hélène Collavizza,Michel Rueher
Computer Science , 2015,
Abstract: In this article, we present our improved algorithm for error localization from counterexamples, LocFaults, flow-driven and constraint-based. This algorithm analyzes the paths of CFG (Control Flow Graph) of the erroneous program to calculate the subsets of suspicious instructions to correct the program. Indeed, we generate a system of constraints for paths of control flow graph for which at most k conditional statements can be wrong. Then we compute the MCSs (Minimal Correction Set) of bounded size on each of these paths. Removal of one of these sets of constraints gives maximal satisfiable subset, in other words, a maximal satisfiable subset satisfying the postcondition. To calculate the MCSs, we extend the generic algorithm proposed by Liffiton and Sakallah in order to deal programs with numerical instructions more effectively. We are interested to present the incremental aspect of this new algorithm that is not yet presented.
Une approche CSP pour l'aide à la localisation d'erreurs
Mohammed Bekkouche,Hélène Collavizza,Michel Rueher
Computer Science , 2014,
Abstract: We introduce in this paper a new CP-based approach to support errors location in a program for which a counter-example is available, i.e. an instantiation of the input variables that violates the post-condition. To provide helpful information for error location, we generate a constraint system for the paths of the CFG (Control Flow Graph) for which at most k conditional statements may be erroneous. Then, we calculate Minimal Correction Sets (MCS) of bounded size for each of these paths. The removal of one of these sets of constraints yields a maximal satisfiable subset, in other words, a maximal subset of constraints satisfying the post condition. We extend the algorithm proposed by Liffiton and Sakallah \cite{LiS08} to handle programs with numerical statements more efficiently. We present preliminary experimental results that are quite encouraging.
City Development, Natural Resources and Human Impact: The Case of Medellin, Colombia  [PDF]
Michel Hermelin
Natural Resources (NR) , 2013, DOI: 10.4236/nr.2013.48058

Medellin is a 3.5 M inhabitant city located in an Andean valley in northwestern Colombia. Its initial prosperity was due to agriculture and cattle-raising carried out in the valley itself and sold to the surrounding gold mining fields. The investment of these monies in coffee plantations and industry boosted the city development, accelerated urban growth, and since the middle of twentieth century, relegated food production to surrounding regions, which are also responsible for almost the totality of natural resource supply: water, electricity, food, building and industrial raw materials. Among the problems which will have to be solved in order to reach a sustainable development are relocation of population living in areas exposed to natural risks, improvement of road communications with surrounding regions and of internal public transportation and pollution control.

Main Features of a Complete Ultrasonic Measurement Model: Formal Aspects of Modeling of Both Transducers Radiation and Ultrasonic Flaws Responses  [PDF]
Michel Darmon, Sylvain Chatillon
Open Journal of Acoustics (OJA) , 2013, DOI: 10.4236/oja.2013.33A008

This paper aims at describing the theoretical fundamentals of a reciprocity-based ultrasonic measurement model. This complete inspection simulation can be decomposed in two modeling steps, one dedicated to transducer radiation and one to flaw scattering and echo synthesis. The physical meaning of the input/output signals used in these two modeling tools is defined and the theoretical principles of both field calculation and echo computation models are then detailed. The influence on the modeling results of some changes in the simulated configuration (as the incident angle) or some input signal parameters (like the frequency) are studied: it is thus theoretically established that the simulated results can be compared between each other in terms of amplitude for numerous applications when changing some inspection parameters in the simulation but that a calibration for echo calculation is generally required.

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