Exploration of the scalability of LocFaults approach for error localization with While-loops programs

A model checker can produce a trace of counterexample, for an erroneous program, which is often long and difficult to understand. In general, the part about the loops is the largest among the instructions in this trace. This makes the location of errors in loops critical, to analyze errors in the overall program. In this paper, we explore the scala-bility capabilities of LocFaults, our error localization approach exploiting paths of CFG(Control Flow Graph) from a counterexample to calculate the MCDs (Minimal Correction Deviations), and MCSs (Minimal Correction Subsets) from each found MCD. We present the times of our approach on programs with While-loops unfolded b times, and a number of deviated conditions ranging from 0 to n. Our preliminary results show that the times of our approach, constraint-based and flow-driven, are better compared to BugAssist which is based on SAT and transforms the entire program to a Boolean formula, and further the information provided by LocFaults is more expressive for the user

Combinaison des techniques de Bounded Model Checking et de programmation par contraintes pour l'aide à la localisation d'erreurs : exploration des capacités des CSP pour la localisation d'erreurs

A model checker can produce a trace of counter-example for erroneous program, which is often difficult to exploit to locate errors in source code. In my thesis, we proposed an error localization algorithm from counter-examples, named LocFaults, combining approaches of Bounded Model-Checking (BMC) with constraint satisfaction problem (CSP). 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 calculate the MCSs (Minimal Correction Sets) of limited size on each of these paths. Removal of one of these sets of constraints gives a maximal satisfiable subset, in other words, a maximal subset of constraints satisfying the postcondition. To calculate the MCSs, we extend the generic algorithm proposed by Liffiton and Sakallah in order to deal with programs with numerical instructions more efficiently. This approach has been experimentally evaluated on a set of academic and realistic programs.Un vérificateur de modèle peut produire une trace de contreexemple, pour un programme erroné, qui est souvent difficile à exploiter pour localiser les erreurs dans le code source. Dans ma thèse, nous avons proposé un algorithme de localisation d'erreurs à partir de contreexemples, nommé LocFaults, combinant les approches de Bounded Model Checking (BMC) avec un problème de satisfaction de contraintes (CSP). Cet algorithme analyse les chemins du CFG (Control Flow Graph) du programme erroné pour calculer les sous-ensembles d'instructions suspectes permettant de corriger le programme. En effet, nous générons un système de contraintes pour les chemins du graphe de flot de contrôle pour lesquels au plus k instructions conditionnelles peuvent être erronées. Ensuite, nous calculons les MCSs (Minimal Correction Sets) de taille limitée sur chacun de ces chemins. La suppression de l'un de ces ensembles de contraintes donne un sous-ensemble satisfiable maximal, en d'autres termes, un sous-ensemble maximal de contraintes satisfaisant la postcondition. Pour calculer les MCSs, nous étendons l'algorithme générique proposé par Liffiton et Sakallah dans le but de traiter des programmes avec des instructions numériques plus efficacement. Cette approche a été évaluée expérimentalement sur des programmes académiques et réalistes

LocFaults: A new flow-driven and constraint-based error localization approach

International audienceWe introduce in this paper LocFaults, a new flow-driven and constraint-based approach for error localization. The input is a faulty program for which a counter-example and a postcondition are provided. To identify helpful informa-tion for error location, we generate a constraint system for the paths of the control flow graph for which at most k con-ditional 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 max-imal subset of constraints satisfying the post condition. To compute the MCS, we extend the algorithm proposed by Liffiton and Sakallah [21] in order to handle programs with numerical statements more efficiently. The main advantage of this flow-driven approach is that the computed sets of suspicious instructions are small, each of them being asso-ciated with an identified path. Moreover, the constraint-programming based framework of LocFaults allows mix-ing Boolean and numerical constraints in an efficient and straightforward way. Preliminary experiments are quite en-couraging. * This work was partially supported by ANR VAC-SIM (ANR-11-INSE-0004), ANR AEOLUS (ANR-10-SEGI-0013), and OSEO ISI PAJERO projects

Correcting Instruction Expression Logic Errors with GenExp: A Genetic Programming Solution

Correcting logical errors in a program is not simple even with the availability of an error locating tool. In this article, we introduce GenExp, a genetic programming approach to automate the task of repairing instruction expressions from logical errors. \correction{Starting} from an error location specified by the programmer, we search for a replacement instruction that passes all test cases. Specifically, we generate expressions that will substitute the selected instruction expression until \correction{we} obtain one that \correction{corrects} the input program. \correction{The search space is exponentially large, making exhaustive methods inefficient.} \correction{Therefore, we utilize a genetic programming meta-heuristic that organizes the search process into stages, with each stage producing a group of individuals.} The results showed that our approach can find at least one plausible patch for almost all cases considered in experiments and outperforms a notable state-of-the-art error repair approach \correction{like} ASTOR. Although our tool is slower than ASTOR, it \correction{provides} greater precision in detecting plausible repairs, making it a suitable option for users who prioritize accuracy over speed

Analysis of energy consumption for Algerian building in extreme North-African climates

The objective of this study is to diagnose and quantify energy consumptions of a real residential building with local materials. Three sites belong to different radiative regimes: Algiers on the southern Mediterranean shore, Tlemcen on the west and Ghardaïa in the Sahara of Algeria. The followed method is based on an approach for assessing heating and cooling energy needs, solar gains, internal lighting loads, occupants and equipment are not considered. Annual heating and cooling requirements are calculated, according to climate data from 2014. We are also interested in a technical and economic study to have a monthly and annual estimation of heating and cooling needs in kilowatt hours and Algerian money per m3 (DA / m3).   The results show that this residential building is not affordable to live in. Facade walls, roof and ground are the major sources of heat losses in buildings (more than 70% of the total losses). The evaluation is devoted to adapt the construction to the region's climate. To improve the building's energy performance, it is necessary to integrate passive and active architectural concepts.&nbsp

Optimizing polymer-stabilized raw earth composite with plant fibers reinforcement for historic building rehabilitation

This research focuses on the optimization of formulation, characterization, and damage analysis of plant fiber-reinforced polyester resin composites (jute and date palm). To better understand the characteristics and mechanical behavior of these materials, this study investigates the influence of resin content and plant fibers on the physico-mechanical behavior of the resin composites. Resinous composites consisting of polyester resin and raw earth were studied using a novel formulation based on an empirical method that follows the principle of earth saturation with polyester resin. Saturation was achieved with a 28% content of polyester resin, which appeared to be an optimal blend for the earth–resin composite. Plant fibers were randomly incorporated as reinforcement in the composites at various percentages (1%, 2%, and 3%) and lengths (0.5 cm, 1 cm, and 1.5 cm). Mechanical tests including bending, compression, and indentation were conducted to evaluate the mechanical properties of the composites. Analysis of fracture morphology revealed that the deformation and rupture mechanisms in bending, compression, and indentation of these composites differ from those of traditional concrete and cement mortar. The obtained results indicate that the composites exhibit acceptable performance and could be favorably employed in the rehabilitation of historic buildings

Minimization of indoor temperatures and total solar insolation by optimizing the building orientation in hot climate

In order to reduce the energy load, understanding the overall architectural design features and optimizing building orientation are important. They are guided by natural elements like sunlight and its intensity, direction of the wind, seasons of the year and temperature variations. The main aim of presented analysis is to give solutions for architects to design standard and low energy buildings in a proper way. The orientation effect of a non-air-conditioned building on its thermal performance has been analyzed in terms of direct solar gain and temperature index for hot-dry climates. This paper aims at introducing an improved methodology for the dynamic modeling of buildings by the thermal nodal method. The study is carried out using computer simulation. This study examines also the effect of geometric shapes on the total solar insolation received by a real building. As a result, the influence of orientation changing depends on the floors and exterior walls construction materials, the insulation levels and application of the inseparable rules of the bioclimatic design. Solar radiation is the most major contributor to heat gain in buildings