Improving WCET Evaluation using Linear Relation Analysis

International audienceThe precision of a worst case execution time (WCET) evaluation tool on a given program is highly dependent on how the tool is able to detect and discard semantically infeasible executions of the program. In this paper, we propose to use the classical abstract interpretation-based method of linear relation analysis to discover and exploit relations between execution paths. For this purpose, we add auxiliary variables (counters) to the program to trace its execution paths. The results are easily incorporated in the classical workflow of a WCET evaluator, when the evaluator is based on the popular implicit path enumeration technique. We use existing tools-a WCET evaluator and a linear relation analyzer-to build and experiment a prototype implementation of this idea. * This work is supported by the French research fundation (ANR) as part of the W-SEPT project (ANR-12-INSE-0001

When the worst-case execution time estimation gains from the application semantics

International audienceCritical embedded systems are generally composed of repetitive tasks that must meet drastic timing constraints, such as termination deadlines. Providing an upper bound of the worst-case execution time (WCET) of such tasks at design time is thus necessary to prove the correctness of the system. Static timing analysis methods compute safe WCET upper bounds, but at the cost of a potentially large over-approximation. Over-approximation may come from the fact that WCET analysis may consider as potential worst-cases some executions that are actually infeasible, because of the semantics of the program and/or because they correspond to unrealistic inputs. In this paper, we introduce a complete semantic-aware WCET estimation workflow. We introduce some program analysis to find infeasible paths: they can be performed at design, C or binary level, and may take into account information provided by the user. We design an annotation-aware compilation process that enables to trace the infeasible path properties through the program transformations performed by the compilers. Finally, we adapt the WCET estimation tool to take into account the kind of annotations produced by the workflow

Sleep-Related Hippocampo-Cortical Interplay during Emotional Memory Recollection

Emotional events are usually better remembered than neutral ones. This effect is mediated in part by a modulation of the hippocampus by the amygdala. Sleep plays a role in the consolidation of declarative memory. We examined the impact of sleep and lack of sleep on the consolidation of emotional (negative and positive) memories at the macroscopic systems level. Using functional MRI (fMRI), we compared the neural correlates of successful recollection by humans of emotional and neutral stimuli, 72 h after encoding, with or without total sleep deprivation during the first post-encoding night. In contrast to recollection of neutral and positive stimuli, which was deteriorated by sleep deprivation, similar recollection levels were achieved for negative stimuli in both groups. Successful recollection of emotional stimuli elicited larger responses in the hippocampus and various cortical areas, including the medial prefrontal cortex, in the sleep group than in the sleep deprived group. This effect was consistent across subjects for negative items but depended linearly on individual memory performance for positive items. In addition, the hippocampus and medial prefrontal cortex were functionally more connected during recollection of either negative or positive than neutral items, and more so in sleeping than in sleep-deprived subjects. In the sleep-deprived group, recollection of negative items elicited larger responses in the amygdala and an occipital area than in the sleep group. In contrast, no such difference in brain responses between groups was associated with recollection of positive stimuli. The results suggest that the emotional significance of memories influences their sleep-dependent systems-level consolidation. The recruitment of hippocampo-neocortical networks during recollection is enhanced after sleep and is hindered by sleep deprivation. After sleep deprivation, recollection of negative, potentially dangerous, memories recruits an alternate amygdalo-cortical network, which would keep track of emotional information despite sleep deprivation

Mutagenesis of Amino Acids at Two Tomato Ringspot Nepovirus Cleavage Sites: Effect on Proteolytic Processingin cisandin transby the 3C-like Protease

AbstractTomato ringspot nepovirus (ToRSV) encodes two polyproteins that are processed by a 3C-like protease at specific cleavage sites. Analysis of ToRSV cleavage sites identified previously and in this study revealed that cleavage occurs at conserved Q/(G or S) dipeptides. In addition, a Cys or Val is found in the −2 position. Amino acid substitutions were introduced in the −6 to +1 positions of two ToRSV cleavage sites: the cleavage site between the protease and putative RNA-dependent RNA polymerase, which is processedin cis, and the cleavage site at the N-terminus of the movement protein, which is cleavedin trans. The effect of the mutations on proteolytic processing at these sites was tested usingin vitrotranslation systems. Substitution of conserved amino acids at the −2, −1, and +1 positions resulted in a significant reduction in proteolytic processing at both cleavage sites. The effects of individual substitutions were stronger on the cleavage site processedin transthan on the one processedin cis. The cleavage site specificity of the ToRSV protease is discussed in comparison to that of related proteases

Exercices de programmation fonctionnelle en OCaml - Une approche pédagogique par l'algorithmique, la preuve et la complexité

National audienceCe livre d’exercices corrigés est destiné aussi bien aux étudiants de premier cycle en informatique qu’aux enseignants intéressés par la programmation fonctionnelle. L’ouvrage aborde notamment les notions de correction, de complexité et d’efficacité d’un algorithme fonctionnel, à travers les solutions détaillées d’une quarantaine ’exercices. Pour chacun de ces exercices, plusieurs solutions sont systématiquement proposées. Pour chaque solution, une analyse des temps de calcul et une preuve de correction sont entièrement rédigées. Les exercices traités sont classés en plusieurs catégories en fonction de la nature des données qu’ils manipulent : entiers, listes, arborescences. Cette distinction permet de mettre en avant un mode de programmation et de raisonnement guidé par la structure des données, si naturel en programmation fonctionnelle. Si les exercices proposés peuvent sembler simples et classiques au premier abord, ils ont été choisis pour permettre, par l’étude de leurs solutions, une découverte en profondeur de la programmation fonctionnelle, ce qui constitue l’originalité du livre

L-Exclusion autostabilisante revisitée

International audienceLa M-exclusion a pour but de partager L ressources identiques. Elle est définie par trois propriétés : l'équité, la sûreté et une propriété d'efficacité appelée évitement de L-interblocage. Nous montrons que tout algorithme réalisant ces trois propriétés a un temps d'attente en Omega(n-L) rondes dans un anneau de n processus. Donc, quand n est grand comparé à L, le gain d'avoir L ressources identiques au lieu d'une seule devient négligeable. Pour contourner ce problème, nous reformulons la définition de L-exclusion en remplaçant la propriété d'évitement de L-interblocage par une contrainte sur le temps d'attente. Nous illustrons cette nouvelle version du problème avec des algorithmes autostabilisants dont le temps d'attente est en O(n/L) rondes, la borne asymptotique optimale

Rendez-vous d'agents amnésiques

National audienceDans cet article, nous présentons un algorithme déterministe de rendez-vous pour des agents évoluant dans un graphe non orienté anonyme quelconque. Les agents considérés sont autonomes, amnésiques et se déplacent de manière asynchrone. L'algorithme proposé est optimal en espace et asymptotiquement optimal en nombre de rondes

Asymptotically Optimal Deterministic Rendezvous

International audienceIn this paper, we address the deterministic rendezvous in graphs where k mobile agents, disseminated at different times and different nodes, have to meet in finite time at the same node. The mobile agents are autonomous, oblivious, labeled, and move asynchronously. Moreover, we consider an undirected anonymous connected graph. For this problem, we exhibit some asymptotical time and space lower bounds as well as some necessary conditions. We also propose an algorithm that is asymptotically optimal in both space and round complexities