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The invasion of multi-core and multi-processor platforms on all aspects of computing makes shared memory parallel programming mainstream. Yet, the fundamental problems of exploiting parallelism efficiently and correctly have not been fully addressed. Moreover, the execution model of these platforms (notably the relaxed memory models they implement) introduces new challenges to static and dynamic program analysis. In this work we address 1) the optimization of pessimistic implementations of critical sections and 2) the dynamic information flow analysis for parallel executions of multi-threaded programs. Critical sections are excerpts of code that must appear as executed atomically. Their pessimistic implementation reposes on synchronization mechanisms, such as mutexes, and consists into obtaining and releasing them at the beginning and end of the critical section respectively. We present a general algorithm for the acquisition/release of synchronization mechanisms and define on top of it several policies aiming to reduce contention by minimizing the possession time of synchronization mechanisms. We demonstrate the correctness of these policies (i.e. they preserve atomicity and guarantee deadlock freedom) and evaluate them experimentally. The second issue tackled is dynamic information flow analysis of parallel executions. Precisely tracking information flow of a parallel execution is infeasible due to non-deterministic accesses to shared memory. Most existing solutions that address this problem enforce a serial execution of the target application. This allows to obtain an explicit serialization of memory accesses but incurs both an execution-time overhead and eliminates the effects of relaxed memory models. In contrast, the technique we propose allows to predict the plausible serializations of a parallel execution with respect to the memory model. We applied this approach in the context of taint analysis , a dynamic information flow analysis widely used in vulnerability detection. To improve precision of taint analysis we further take into account the semantics of synchronization mechanisms such as mutexes, which restricts the predicted serializations accordingly. The solutions proposed have been implemented in proof of concept tools which allowed their evaluation on some hand-crafted examples. ; L'utilisation massive des plateformes multi-cœurs et multi-processeurs a pour effet de favoriser la programmation parallèle à mémoire partagée. Néanmoins, exploiter efficacement et de manière correcte le parallélisme sur ces plateformes reste un problème de recherche ouvert. De plus, leur modèle d'exécution sous-jacent, et notamment les modèles de mémoire "relâchés", posent de nouveaux défis pour les outils d'analyse statiques et dynamiques. Dans cette thèse nous abordons deux aspects importants dans le cadre de la programmation sur plateformes multi-cœurs et multi-processeurs: l'optimisation de sections critiques implémentées selon l'approche pessimiste, et l'analyse dynamique de flots d'informations. Les sections critiques définissent un ensemble d'accès mémoire qui doivent être exécutées de façon atomique. Leur implémentation pessimiste repose sur l'acquisition et le relâchement de mécanismes de synchronisation, tels que les verrous, en début et en fin de sections critiques. Nous présentons un algorithme générique pour l'acquisition/relâchement des mécanismes de synchronisation, et nous définissons sur cet algorithme un ensemble de politiques particulier ayant pour objectif d'augmenter le parallélisme en réduisant le temps de possession des verrous par les différentes threads. Nous montrons alors la correction de ces politiques (respect de l'atomicité et absence de blocages), et nous validons expérimentalement leur intérêt. Le deuxième point abordé est l'analyse dynamique de flot d'information pour des exécutions parallèles. Dans ce type d'analyse, l'enjeu est de définir précisément l'ordre dans lequel les accès à des mémoires partagées peuvent avoir lieu à l'exécution. La plupart des travaux existant sur ce thème se basent sur une exécution sérialisée du programme cible. Ceci permet d'obtenir une sérialisation explicite des accès mémoire mais entraîne un surcoût en temps d'exécution et ignore l'effet des modèles mémoire relâchées. A contrario, la technique que nous proposons permet de prédire l'ensemble des sérialisations possibles vis-a-vis de ce modèle mémoire à partir d'une seule exécution parallèle ("runtime prediction"). Nous avons développé cette approche dans le cadre de l'analyse de teinte, qui est largement utilisée en détection de vulnérabilités. Pour améliorer la précision de cette analyse nous prenons également en compte la sémantique des primitives de synchronisation qui réduisent le nombre de sérialisations valides. Les travaux proposé ont été implémentés dans des outils prototype qui ont permit leur évaluation sur des exemples représentatifs.

This PhD research proposes to study the relationship between informal risk-coping strategies and the nature of land allocation. Informal risk-coping mechanisms are studied here as one potential factor in the failure of land market reforms and the persistence of 'non-market' exchange -gifts or free loans. In particular, we show that the bipolar view of land tenure, which opposes 'customary' to 'market' transfers, does not adequately approach informal risk-coping motivations in land transfers. Two hypotheses are analysed: first, in the absence of insurance markets and publicsocial protection, land has a 'safety net' function and households do not sell land but prefer other types of transfers (which retain part of the land's 'safety net' function). Secondly, informal risk-coping leads households to participate to hybrid forms of transfers (neither market nor non-market) allowing to combine risk-coping motives with other types of economic necessities. Those two hypotheses are then looked at empirically in two case studies: in Vietnam, where households sell their land only if they are economically stable or have suffered income shocks (distress sales); and in Thailand, where a survey has been done among permanent rural-urban migrants. This survey confirms that informal risk-coping slows down land sale markets and sustains transfers such as free-loans. Finally, the Thai data identify traditional risk-sharing institutions in the allocation of land, especially through intra-family free-loans or 'disguised rentals'. As a main conclusion, insurance and public protection policies could have a key role in the evaluation of land allocation systems in Thailand and Vietnam. ; Cette recherche de doctorat étudie la relation entre la gestion informelle des risques de subsistance et l'allocation des terres agricoles. La gestion informelle des risques de subsistance est analysée ici comme explication potentielle de l'échec des politiques foncières de marché, et de la persistance de modes d'échanges `non-marchands'. En particulier, ...

This PhD research proposes to study the relationship between informal risk-coping strategies and the nature of land allocation. Informal risk-coping mechanisms are studied here as one potential factor in the failure of land market reforms and the persistence of 'non-market' exchange -gifts or free loans. In particular, we show that the bipolar view of land tenure, which opposes 'customary' to 'market' transfers, does not adequately approach informal risk-coping motivations in land transfers. Two hypotheses are analysed: first, in the absence of insurance markets and publicsocial protection, land has a 'safety net' function and households do not sell land but prefer other types of transfers (which retain part of the land's 'safety net' function). Secondly, informal risk-coping leads households to participate to hybrid forms of transfers (neither market nor non-market) allowing to combine risk-coping motives with other types of economic necessities. Those two hypotheses are then looked at empirically in two case studies: in Vietnam, where households sell their land only if they are economically stable or have suffered income shocks (distress sales); and in Thailand, where a survey has been done among permanent rural-urban migrants. This survey confirms that informal risk-coping slows down land sale markets and sustains transfers such as free-loans. Finally, the Thai data identify traditional risk-sharing institutions in the allocation of land, especially through intra-family free-loans or 'disguised rentals'. As a main conclusion, insurance and public protection policies could have a key role in the evaluation of land allocation systems in Thailand and Vietnam. ; Cette recherche de doctorat étudie la relation entre la gestion informelle des risques de subsistance et l'allocation des terres agricoles. La gestion informelle des risques de subsistance est analysée ici comme explication potentielle de l'échec des politiques foncières de marché, et de la persistance de modes d'échanges `non-marchands'. En particulier, ...

This PhD research proposes to study the relationship between informal risk-coping strategies and the nature of land allocation. Informal risk-coping mechanisms are studied here as one potential factor in the failure of land market reforms and the persistence of 'non-market' exchange -gifts or free loans. In particular, we show that the bipolar view of land tenure, which opposes 'customary' to 'market' transfers, does not adequately approach informal risk-coping motivations in land transfers. Two hypotheses are analysed: first, in the absence of insurance markets and publicsocial protection, land has a 'safety net' function and households do not sell land but prefer other types of transfers (which retain part of the land's 'safety net' function). Secondly, informal risk-coping leads households to participate to hybrid forms of transfers (neither market nor non-market) allowing to combine risk-coping motives with other types of economic necessities. Those two hypotheses are then looked at empirically in two case studies: in Vietnam, where households sell their land only if they are economically stable or have suffered income shocks (distress sales); and in Thailand, where a survey has been done among permanent rural-urban migrants. This survey confirms that informal risk-coping slows down land sale markets and sustains transfers such as free-loans. Finally, the Thai data identify traditional risk-sharing institutions in the allocation of land, especially through intra-family free-loans or 'disguised rentals'. As a main conclusion, insurance and public protection policies could have a key role in the evaluation of land allocation systems in Thailand and Vietnam. ; Cette recherche de doctorat étudie la relation entre la gestion informelle des risques de subsistance et l'allocation des terres agricoles. La gestion informelle des risques de subsistance est analysée ici comme explication potentielle de l'échec des politiques foncières de marché, et de la persistance de modes d'échanges `non-marchands'. En particulier, nous montrons que la vision bipolaire de l'allocation des terres opposant marchand et non-marchand n'est pas toujours pertinente pour l'analyse de la gestion des risques dans les pratiques foncières. Deux hypothèses sont analysées: en l'absence de moyens d'assurance publique ou privée, la terre prend une valeur de sécurité sociale qui peut détourner les ménages de la vente et leur faire préférer des transferts non-marchands ou temporaires, protégeant mieux la valeur assurance de la terre. Ensuite, des pratiques foncières hybrides, ni purement marchandes ni non-marchandes, se développent pour combiner la gestion des risques de subsistance avec d'autres motivations économiques. Ces hypothèses sont étudiées dans deux contextes: au Vietnam d'abord où les ménages les plus stables ou ceux subissant des chocs sévères vendent leur terre. En Thailande ensuite où, grâce à des données collectées sur le terrain, nous confirmons le rôle des stratégies de gestion des risques de subsistance dans l'activité ralentie des marchés de vente, et identifions ces fameuses pratiques foncières hybrides (ici des locations déguisées) . En conclusion, le développement de la protection (privée ou publique) des moyens de subsistance pourrait jouer un rôle privilégié dans l'évolution des modes d'allocation foncière.

The occurrence of a disaster exposes the vulnerability and resilience of the affected community. For the same reason, disasters represent windows of opportunity to modify these conditions. But is it really so? Is a disaster followed by a modification of the conditions of vulnerability that caused it or of the factors of resilience that mitigated its effects? And if so, at which conditions and how? This article tackles those questions via the historical analysis of post-disaster transformations. It focuses on seismic disasters, which are the main area of expertise of the author, but hopes to offer reflections that speak also to other kind of disasters. The analysis is grounded on a comparison between the 1908 Messina earthquake and the 1968 Belice Valley (Italy) earthquake, but makes reference also to other disasters. Based on this empirical evidence, the article sheds light on how post-disaster politics can transform those factors that contributed to the disaster as well as factors that can contribute to overcome it. The article focuses notably on three themes: the nexus between disaster interpretations and prevention policies; the long term consequences of emergence choices; the structures of institutional memory. These three themes illustrate how the modifications or the persistence of conditions of vulnerability and resilience depended on tensions and conflicts among multiple actors and their conflicting intentions. These intentions often do not correspond to those of disaster prevention and can produce, over the long term, unexpected consequences. ; L'avènement d'une catastrophe expose la vulnérabilité et la résilience d'une communauté. Pour la même raison, la catastrophe représente une fenêtre d'opportunité pour modifier ces conditions. Mais est-ce vraiment le cas? Est-ce que les catastrophes sont suivies par un changement des conditions de vulnérabilité qui l'ont générée ou des facteurs de résilience qui en ont mitigé les effets? À quelles conditions et comment? Cet article cherche à répondre à ces ...