In episodic recognition memory, differentiation is the assumption that a study item's pre-existing memory trace is updated when additional study for that item is provided. The differentiation models commonly suppose that episodic memory encoding conforms to this process. Although these models have received considerable support within the literature, results inconsistent with their predictions have also been found. The present paper examined conflicting findings that resulted from study list strength manipulations with rhyming word stimuli and semantically related stimuli. As part of the investigation into this discrepancy, 79 university students participated in a computer-based recognition memory task. In this task, word categories of varying length (short vs. long) and word type (rhyming vs. taxonomic) were presented either five times or once within a mixed study list. Following study, an old-new response paradigm was used to examine recognition memory performance. Results from both the rhyming and taxonomic category stimuli were largely consistent with the previous findings in the literature, indicating that word type does appear to influence recognition memory, even within a mixed study list. These findings are interpreted primarily in terms of word type similarity predictions made by one of the differentiation models. Other possible explanations are also discussed.

Representing graphs in Rust is a problematic issue, as ownership forbids typical representations found in e.g. C++. A common approach is to use reference counting to represent graphs, but this can easily lead to memory leaks if cycles are present in the graph. As naïve reference counting is not sufficient, we must search for alternative representations. In this thesis, we explore different memory models that allow safe representations of graph-like data structures in Rust. These memory models are later evaluated in terms of performance and usability. We find that region-based allocation is, in most cases, the best model to use when performance is of importance. In cases where usability is more important, either reference-counting with cycle collection or tracing garbage collection is a solid choice. When it comes to multi-threading, we propose a new implementation of a lock-free transactional graph in Rust. To our knowledge, this is the first lock-free graph representation in Rust. The model demonstrates poor scalability, but for certain graph topologies and sizes, it offers performance that exceeds the other graph models.

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La sémantique des jeux permet l'étude et la modélisation abstraite des langages de programmation d'un point de vue mathématique, en gardant assez d'informations concrètes sur la structure des programmes, mais en laissant de côté les détails superflus. Durant mon doctorat, j'ai travaillé sur l'association de la sémantique des jeux avec les structures d'événements pour proposer des modèles dénotationnels vraiment concurrents de langages concurrents d'ordresupérieur. Dans un premier temps, je construis un modèle réalisant cette association, qui retient suffisamment d'informations sur le comportement des programmes pour interpréter adéquatement une grande variété de langages concurrents et non déterministes pour des notions fines de convergences. La construction de ce modèle se base surl'introduction de symétrie afin d'établir que le modèle forme une catégorie cartésienne fermée. Dans un second temps, je propose une généralisation dans ce cadre des notions d'innocence et de bon parenthésage, essentielles en sémantiquedes jeux pour comprendre les effets calculatoires, et résolvant ainsi des problèmes ouverts de la sémantique des jeux concernant l'innocence concurrente et non-déterministe. Dans un dernier temps je propose une interprétation dans ce modèle, de langages concurrents avec mémoire faible, un des premiers travaux de sémantique dénotationnelle pour ce type de langages. Bien que théoriques, ces modèles sont compositionnels et basés sur des ordres partiels, et donc pourraient permettre de faire passer la vérification de programmes concurrents à l'échelle (une problématique importante du domaine). / Game semantics is an effective tool to study and model abstractly programming languages from a mathematical point of view, by keeping enough concrete information on the structure of programs but yet leaving aside superfluous details. During my PhD thesis, I worked on merging game semantics with event structures to propose truly concurrent denotational models of higher-order concurrent languages. In the first part, I build a model based on this merge, retaining enough information about the behaviour of programs to interpret adequately a large variety of concurrent programming languages for various notions of convergence. The construction of this model is based on the introduction of symmetry to prove that the model is indeed in a cartesian-closed category. In the second part, I propose a generalization, in this setting, of innocence and well-bracketing, key notions in game semantics to understand the computational effects, and thusly closing openproblems of game semantics about concurrent and nondeterministic innocence.In the last part, I propose an interpretation in this model of concurrent languages with weak shared memory, one of the first works of denotational semantics for these kinds of languages. Althoughtheoretical, these models are compositional and based on partial orders, and thus could permit scaling verification of concurrent programs (an important problem of the domain).

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Vérifier formellement des programmes concurrents est une tâche difficile. S’il existe différentes techniques pour la réaliser, très peu sont effectivement mises en oeuvre pour des programmes écrits dans des langages de programmation réalistes. En revanche, les techniques de vérification formelles de programmes séquentiels sont utilisées avec succès depuis plusieurs années déjà, et permettent d’atteindre de hauts degrés de confiance dans nos systèmes. Cette thèse propose une alternative aux méthodes d’analyses dédiées à la vérification de programmes concurrents consistant à transformer le programme concurrent en un programme séquentiel pour le rendre analysable par des outils dédiés aux programmes séquentiels. Nous nous plaçons dans le contexte de FRAMA-C, une plate-forme d’analyse de code C spécifié avec le langage ACSL. Les différentes analyses de FRAMA-C sont des greffons à la plate-forme, ceux-ci sont à ce jour majoritairement dédiés aux programmes séquentiels. La méthode de vérification que nous proposons est appliquée manuellement à la vérification d’un code concurrent issu d’un hyperviseur. Nous automatisons la méthode à travers un nouveau greffon à FRAMA-C qui permet de produire automatiquement, depuis un programme concurrent spécifié, un programme séquentiel spécifié équivalent. Nous présentons les bases de sa formalisation, ayant pour but d’en prouver la validité. Cette validité n’est valable que pour la classe des programmes séquentiellement consistant. Nous proposons donc finalement un prototype de solveur de contraintes pour les modèles mémoire faibles, capable de déterminer si un programme appartient bien à cette classe en fonction du modèle mémoire cible. / Formal verification of concurrent programs is a hard task. There exists different methods to perform such a task, but very few are applied to the verification of programs written using real life programming languages. On the other side, formal verification of sequential programs is successfully applied for many years, and allows to get high confidence in our systems. As an alternative to dedicated concurrent program analyses, we propose a method to transform concurrent programs into sequential ones to make them analyzable by tools dedicated to sequential programs. This work takes place within the analysis framework FRAMA-C, dedicated to the analysis of C code specified with ACSL. The different analyses provided by FRAMA-C are plugins to the framework, which are currently mostly dedicated to sequential programs. We apply this method to the verification of a concurrent code taken from an hypervisor. We describe the automation of the method implemented by a new plugin to FRAMAC that allow to produce, from a specified concurrent program, an equivalent specified sequential program. We present the basis of a formalization of the method with the objective to prove its validity. This validity is admissible only for the class of sequentially consistent programs. So, we finally propose a prototype of constraint solver for weak memory models, which is able to determine whether a program is in this class or not, depending on the targeted hardware.

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