A framework for deadlock detection in core ABS

We present a framework for statically detecting deadlocks in a concurrent object-oriented language with asynchronous method calls and cooperative scheduling of method activations. Since this language features recursion and dynamic resource creation, deadlock detection is extremely complex and state-of-the-art solutions either give imprecise answers or do not scale. In order to augment precision and scalability we propose a modular framework that allows several techniques to be combined. The basic component of the framework is a front-end inference algorithm that extracts abstract behavioural descriptions of methods, called contracts, which retain resource dependency information. This component is integrated with a number of possible different back-ends that analyse contracts and derive deadlock information. As a proof-of-concept, we discuss two such back-ends: (i) an evaluator that computes a fixpoint semantics and (ii) an evaluator using abstract model checking.Comment: Software and Systems Modeling, Springer Verlag, 201

Modèle d'optimisation de la maintenance : application au processus de conception d'un avion

Cette thèse traite de la modélisation, en phase de conception, des performances de supportabilité des systèmes avions. La supportabilité est la capacité d'un produit, ainsi que de son système de soutien, à répondre aux besoins opérationnels des compagnies aériennes. L'objectif de ce travail de recherche est d'apporter un moyen d'aide à la décision aux intégrateurs des systèmes avions par rapport aux performances de supportabilité. Le modèle développé permet de prédire des critères quantitatifs de supportabilité permettant d'optimiser la conception des systèmes. Le but est de trouver des architectures de systèmes offrant le meilleur compromis entre les coûts d'exploitation d'un avion et sa disponibilité. Nous abordons les thèmes suivants : Le choix de critères pertinents de supportabilité permettant d'influencer la conception, pour obtenir de meilleures performances opérationnelles à un coût minimum pour la compagnie aérienne ; La sélection des paramètres d'entrée du modèle pour estimer les critères retenus ; La définition de modèles mathématiques afin d'explorer les relations de cause à effet entre les choix de conception et leurs impacts sur l'utilisation et la maintenance de l'avion une fois en service ; L'actualisation de la valeur des coûts pour les modèles présentés; La gestion des incertitudes des données d'entrées au moyen d'analyses globales de sensibilité.This thesis deals with supportability performance modeling for aircraft systems during the design phase. Supportability is the ability of a product, along with its support system, to meet and sustain airlines' operational needs. The purpose of this research is to support decision-making by system integrators accommodating supportability performance objectives. The model we developed provides supportability performance criteria to optimize system design. The objective is to find system architectures offering the best compromise between operating costs and availability. We discuss the following subjects: Choosing supportability performance criteria to drive the design towards enhanced operational performance at minimal cost for the airline; Selecting the driving factors necessary to assess the selected criteria; Defining mathematical models to enable the exploration of the cause and effect relationships between design decisions and their impact on aircraft operation and maintenance; Introducing the notion of time-value of money and discounting in supportability models; Managing input uncertainty with global sensitivity analyses

Removal and Contraction for n-Dimensional Generalized Maps

International audienceRemoval and contraction are basic operations for several methods conceived in order to handle irregular image pyramids, for multi-level image analysis for instance. Such methods are often based upon graph-like representations which do not maintain all topological information, even for 2-dimensional images. We study the definitions of removal and contraction operations in the generalized maps framework. These combinatorial structures enable us to unambiguously represent the topology of a well-known class of subdivisions of n-dimensional (discrete) spaces. The results of this study make a basis for a further work about irregular pyramids of n-dimensional images

Refactoring Delta-Oriented Product Lines to achieve Monotonicity

Delta-oriented programming (DOP) is a flexible transformational approach to implement software product lines. In delta-oriented product lines, variants are generated by applying operations contained in delta modules to a (possibly empty) base program. These operations can add, remove or modify named elements in a program (e.g., classes, methods and fields in a Java program). This paper presents algorithms for refactoring a delta-oriented product line into monotonic form, i.e., either to contain add and modify operations only (monotonic increasing) or to contain remove and modify operations only (monotonic decreasing). Because of their simpler structure, monotonic delta-oriented product lines are easier to analyze. The algorithms are formalized by means of a core calculus for DOP of product lines of Java programs and their correctness and complexity are given

Computing Canonical Polygonal Schemata with Generalized Maps

International audienceThis paper shows that a well-known algorithm proposed to compute the canonical polygonal schema of a surface can be transferred onto a 2-dimensional generalized map. We show that transformation rules on polygonal schemata can be achieved in O(1) with generalized maps, which can help optimizing existing algorithms

A type system for components

In modern distributed systems, dynamic reconfiguration, i.e., changing at runtime the communication pattern of a program, is chal- lenging. Generally, it is difficult to guarantee that such modifications will not disrupt ongoing computations. In a previous paper, a solution to this problem was proposed by extending the object-oriented language ABS with a component model allowing the programmer to: i) perform up- dates on objects by means of communication ports and their rebinding; and ii) precisely specify when such updates can safely occur in an object by means of critical sections. However, improper rebind operations could still occur and lead to runtime errors. The present paper introduces a type system for this component model that extends the ABS type system with the notion of ports and a precise analysis that statically enforces that no object will attempt illegal rebinding

Combinatorial models for topology-based geometric modeling

Many combinatorial (topological) models have been proposed in geometric modeling, computational geometry, image processing or analysis, for representing subdivided geometric objects, i.e. partitionned into cells of different dimensions: vertices, edges, faces, volumes, etc. We can distinguish among models according to the type of cells (regular or not regular ones), the type of assembly ("manifold" or "non manifold"), the type of representation (incidence graphs or ordered models), etc

Conversion between chains of maps and chains of surfaces; application to the computation of incidence graphs homology

Many combinatorial cellular structures have been defined in order to represent the topology of subdivided geometric objects. Two main classes can be distinguished. According to the terminology of [8], one is related to incidence graphs and the other to ordered models. Both classes have their own specificities and their use is relevant in different contexts. It is thus important to create bridges between them. So we define here chains of surfaces (a subclass of incidence graphs) and chains of maps without multi-incidence (a subclass of ordered models), which are able to represent the topology of subdivided objects, whose cells have " manifold-like " properties. We show their equivalence by providing conversion operations. As a consequence, it is hence possible to directly apply on each model results obtained on the other. We extend here classical results related to homology computation obtained for incidence graphs corresponding to regular CW −complexes and recent results about combinatorial cell complexes where cells are not necessarily homeomorphic to balls

Removal operations in nD generalized maps for efficient homology computation

In this paper, we present an efficient way for computing homology generators of nD generalized maps. The algorithm proceeds in two steps: (1) cell removals reduces the number of cells while preserving homology; (2) homology generator computation is performed on the reduced object by reducing incidence matrices into their Smith-Agoston normal form. In this paper, we provide a definition of cells that can be removed while preserving homology. Some results on 2D and 3D homology generators computation are presented

Building clinical trials capacity for tuberculosis drugs in high-burden countries

The long duration of TB therapy, the high prevalence of HIV coinfection, and the growing prevalence of drug-resistant TB underscore the urgent need for more effective treatments