Aplicações paralelas geralmente são executadas com o máximo número de threads de hardware disponíveis no sistema para maximizar o seu desempenho. Contudo, esta abordagem pode não ser a melhor escolha quando se busca eficiência energética e, em alguns casos, pode até mesmo degradar o desempenho. Desta maneira, o presente trabalho aplica a adaptação dinâmica do número de threads para otimizar o Energy-Delay Product (EDP) de aplicações paralelas OpenMP executadas em sistemas embarcados. Ao contrário de soluções anteriores, que focam em processadores de propósito geral (GPP, do inglês General Purpose Processors), o presente trabalho considera as características intrínsecas de sistemas embarcados, os quais geralmente possuem menos núcleos disponíveis, assim como apresentam diferenças significativas em relação à micro-arquitetura e à hierarquia de memória. Por meio de experimentos realizados em um sistema embarcado real com processador octa-core, este trabalho mostrou que a adaptação dinâmica do número de threads permite, em média, economizar 15,35% no consumo de energia com apenas 3,41% de perda de desempenho, gerando assim 12,47% de otimização de EDP em relação à configuração padrão (uso do máximo número de threads disponíveis no sistema). No melhor caso, a adaptação dinâmica foi capaz de economizar 26,97% em energia enquanto promoveu 25,74% de aumento no desempenho, resultando em 45,77% de melhora no EDP. / Parallel applications usually execute using the maximum number of threads allowed by the available hardware at hand to maximize performance. However, this approach may not be the best when it comes to energy efficiency and may even lead to performance decrease in some particular cases. In this way, the present work proposes a new apporach for the dynamic adaptation of the number of threads to optimize Energy-Delay Product (EDP) of OpenMP applications when running on Embedded Systems. Differently from previous solutions, which focus on General Purpose Processors (GPP), the current one takes into account the intrinsic characteristics of embedded systems, which usually have a lower number of cores and significantly different characteristics concerning the microarchitecture and memory hierarchy when compared to GPPs. Through experiments on a real embedded system with an octa-core processor, this work demonstrates that adapting the number of threads at runtime saves energy, on average, by 15,35% with only 3,41% loss performance, improving the EDP by 12,47% over the default configuration (maximum number of threads available in the system). In the best case, the dynamic adaptation saves 26,97 % in energy while promoting a 25,74 % increase in performance, resulting in a 45,77 % improvement in EDP.

Aplicações paralelas geralmente são executadas com o máximo número de threads de hardware disponíveis no sistema para maximizar o seu desempenho. Contudo, esta abordagem pode não ser a melhor escolha quando se busca eficiência energética e, em alguns casos, pode até mesmo degradar o desempenho. Desta maneira, o presente trabalho aplica a adaptação dinâmica do número de threads para otimizar o Energy-Delay Product (EDP) de aplicações paralelas OpenMP executadas em sistemas embarcados. Ao contrário de soluções anteriores, que focam em processadores de propósito geral (GPP, do inglês General Purpose Processors), o presente trabalho considera as características intrínsecas de sistemas embarcados, os quais geralmente possuem menos núcleos disponíveis, assim como apresentam diferenças significativas em relação à micro-arquitetura e à hierarquia de memória. Por meio de experimentos realizados em um sistema embarcado real com processador octa-core, este trabalho mostrou que a adaptação dinâmica do número de threads permite, em média, economizar 15,35% no consumo de energia com apenas 3,41% de perda de desempenho, gerando assim 12,47% de otimização de EDP em relação à configuração padrão (uso do máximo número de threads disponíveis no sistema). No melhor caso, a adaptação dinâmica foi capaz de economizar 26,97% em energia enquanto promoveu 25,74% de aumento no desempenho, resultando em 45,77% de melhora no EDP. / Parallel applications usually execute using the maximum number of threads allowed by the available hardware at hand to maximize performance. However, this approach may not be the best when it comes to energy efficiency and may even lead to performance decrease in some particular cases. In this way, the present work proposes a new apporach for the dynamic adaptation of the number of threads to optimize Energy-Delay Product (EDP) of OpenMP applications when running on Embedded Systems. Differently from previous solutions, which focus on General Purpose Processors (GPP), the current one takes into account the intrinsic characteristics of embedded systems, which usually have a lower number of cores and significantly different characteristics concerning the microarchitecture and memory hierarchy when compared to GPPs. Through experiments on a real embedded system with an octa-core processor, this work demonstrates that adapting the number of threads at runtime saves energy, on average, by 15,35% with only 3,41% loss performance, improving the EDP by 12,47% over the default configuration (maximum number of threads available in the system). In the best case, the dynamic adaptation saves 26,97 % in energy while promoting a 25,74 % increase in performance, resulting in a 45,77 % improvement in EDP.

Aplicações paralelas geralmente são executadas com o máximo número de threads de hardware disponíveis no sistema para maximizar o seu desempenho. Contudo, esta abordagem pode não ser a melhor escolha quando se busca eficiência energética e, em alguns casos, pode até mesmo degradar o desempenho. Desta maneira, o presente trabalho aplica a adaptação dinâmica do número de threads para otimizar o Energy-Delay Product (EDP) de aplicações paralelas OpenMP executadas em sistemas embarcados. Ao contrário de soluções anteriores, que focam em processadores de propósito geral (GPP, do inglês General Purpose Processors), o presente trabalho considera as características intrínsecas de sistemas embarcados, os quais geralmente possuem menos núcleos disponíveis, assim como apresentam diferenças significativas em relação à micro-arquitetura e à hierarquia de memória. Por meio de experimentos realizados em um sistema embarcado real com processador octa-core, este trabalho mostrou que a adaptação dinâmica do número de threads permite, em média, economizar 15,35% no consumo de energia com apenas 3,41% de perda de desempenho, gerando assim 12,47% de otimização de EDP em relação à configuração padrão (uso do máximo número de threads disponíveis no sistema). No melhor caso, a adaptação dinâmica foi capaz de economizar 26,97% em energia enquanto promoveu 25,74% de aumento no desempenho, resultando em 45,77% de melhora no EDP. / Parallel applications usually execute using the maximum number of threads allowed by the available hardware at hand to maximize performance. However, this approach may not be the best when it comes to energy efficiency and may even lead to performance decrease in some particular cases. In this way, the present work proposes a new apporach for the dynamic adaptation of the number of threads to optimize Energy-Delay Product (EDP) of OpenMP applications when running on Embedded Systems. Differently from previous solutions, which focus on General Purpose Processors (GPP), the current one takes into account the intrinsic characteristics of embedded systems, which usually have a lower number of cores and significantly different characteristics concerning the microarchitecture and memory hierarchy when compared to GPPs. Through experiments on a real embedded system with an octa-core processor, this work demonstrates that adapting the number of threads at runtime saves energy, on average, by 15,35% with only 3,41% loss performance, improving the EDP by 12,47% over the default configuration (maximum number of threads available in the system). In the best case, the dynamic adaptation saves 26,97 % in energy while promoting a 25,74 % increase in performance, resulting in a 45,77 % improvement in EDP.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A crescente utilizaÃÃo de dispositivos mÃveis, redes sem fio e aplicaÃÃes mÃveis evidencia a importÃncia da garantia de seguranÃa da informaÃÃo. Esta preocupaÃÃo surge devido aos riscos envolvidos no trÃfego de informaÃÃes sensÃveis por meio sem fio, uma vez que o meio nÃo limita os riscos de ataques, tal como nas redes convencionais. Adicionalmente, a tendÃncia no uso de prÃticas sustentÃveis defendidas pela ComputaÃÃo Verde impÃe a necessidade de concepÃÃo de aplicaÃÃes flexÃveis que busquem a reduÃÃo do consumo de recursos, como o de energia. Assim, mecanismos para o provimento de confidencialidade de informaÃÃes que trafegam por meio sem fio devem considerar a alocaÃÃo eficiente de recursos computacionais. Esta à uma questÃo chave a ser considerada no momento da concepÃÃo de aplicaÃÃes mÃveis seguras. Portanto, os mecanismos de proteÃÃo devem balancear o nÃvel de seguranÃa requerido de acordo com o consumo de recursos alocados para provÃ-lo. O emprego de informaÃÃes que caracterizam a situaÃÃo corrente (contexto) pode auxiliar nessa tarefa. Assim, a utilizaÃÃo de proteÃÃo adequada aos requisitos de seguranÃa das aplicaÃÃes e combinada com o contexto pode identificar situaÃÃes nas quais serà necessÃrio aumentar ou diminuir o nÃvel de seguranÃa, de forma a diminuir o consumo de recursos do dispositivo. Esse trabalho propÃe, portanto, um Mecanismo de SeguranÃa com AdaptaÃÃo DinÃmica (MeSAD), com foco na confidencialidade, capaz de adaptar o nÃvel de seguranÃa de acordo com o contexto e reduzir o consumo de recursos dos dispositivos mÃveis. O objetivo principal consiste em encontrar o ponto de equilÃbrio no tradeoff entre nÃvel de seguranÃa e consumo de recursos. A fim de atingir este objetivo, este trabalho apresenta tambÃm uma ferramenta de suporte à utilizaÃÃo do MeSAD durante o desenvolvimento de aplicaÃÃes mÃveis, alÃm de possibilitar a realizaÃÃo de avaliaÃÃes sobre o desempenho dos algoritmos criptogrÃficos que sÃo utilizados nos diferentes dispositivos. / The increasing use of mobile devices, wireless networks and mobile applications highlights the importance of ensuring information security. This concern arises because of the risks involved in traffic sensitive information via wireless, since it does not limit the risk of attacks, as in conventional networks. Additionally, the trend in the use of sustainable practices advocated by the Green Computing imposes the need for designing flexible applications that seek to reduce consumption of resources such as energy. Thus, mechanisms for providing confidentiality of information passing over the wireless medium should consider the efficient allocation of computing resources. This is a key issue to be considered when designing secure mobile applications. Therefore, the protection mechanisms should balance the security level required in accordance with the consumption of resources allocated to provide it. The use of information that characterizes the current situation (context) can assist in this task. Thus, the use of appropriate protective security requirements of applications and combined with the context can identify situations where you need to raise or lower the security level in order to reduce the resource consumption of the device. This work proposes a Security Mechanism Dynamic Adaptation (MeSAD), focusing on confidentiality, able to adapt the level of security according to the context and reduce the resource consumption of mobile devices. The main objective is to find the balance point in the tradeoff between the level of security and resource consumption. In order to achieve this goal, this paper presents a tool to support the use of MeSAD during the development of mobile applications, and enable the assessments on the performance of cryptographic algorithms that are used in different devices.

Cette thèse présente les résultats d'un projet de recherche multidisciplinaire (Agorantic) sur les systèmes de recommandation. Le but de ce travail était de proposer de nouvelles fonctionnalités qui peuvent rendre les systèmes de recommandations (RS) plus attrayants que ceux existants. Nous proposons également une nouvelle approche et une réflexion sur l'évaluation. Dans la conception du système, nous avons voulu répondre aux préoccupations suivantes: 1. Les gens s'habituent à recevoir des recommandations. Néanmoins, après quelques mauvaises recommandations, les utilisateurs ne seront plus convaincus par les RS. 2. En outre, si ces suggestions viennent sans explication, pourquoi les gens devraient les suivre ? 3. Le fait que la perception, les goûts et les humeurs des utilisateurs goûts varient au fil du temps est bien connue. Pourtant, la plupart des systèmes de recommandation ne parviennent pas à offrir le bon niveau de «réactivité» que les utilisateurs attendent, c'est à dire la capacité de détecter et d'intégrer des changements dans les besoins, les préférences, la popularité, etc. Recommander un film une semaine après sa sortie pourrait être trop tard. 4. L'utilisateur pourrait être intéressé par des articles moins populaires (dans la «longue traine»), c'est à dire des recommandations moins systématiques. Pour répondre à ces questions clés, nous avons conçu un nouveau système de recommandation sémantique et adaptatif (SRAS), comportant trois fonctionnalités innovantes, à savoir l'argumentation, l'adaptation dynamique et un algorithme d'appariement. • Adaptation dynamique: le système est mis à jour de façon continue, à chaque nouvelle note / évènement. (Chapitre 4) • Argumentation: chaque recommandation présente les raisons qui ont conduit à cette recommandation. Cela peut être considéré comme une première étape vers une argumentation plus sophistiqué. Notre volonté est de rendre les utilisateurs plus responsables de leur choix, en leur donnant le maximum d'informations. (Chapitre 5) • Algorithme d'appariement: permet aux articles les moins populaires d'être recommandés aux utilisateurs. (Chapitre 6) Nous avons conçu un nouveau système de recommandation capable de générer des recommandations textuellement bien argumentées dans lequel l'utilisateur final aura plusieurs éléments pour faire un choix éclairé. En outre, les paramètres du système sont dynamiquement et continuellement mis à jour, afin de fournir des recommandations et des arguments en la phase avec le passé très récent. Nous avons inclus un niveau sémantique, c'est à dire les mots, termes et expressions comme ils sont naturellement exprimés dans les commentaires utilisateurs. Nous n'utilisons pas d'étiquettes ou lexique pré-déterminé. Les performances de notre système sont comparables à l'état de l'art. En outre, le fait qu'il génère un argumentaire le rend encore plus attrayant et pourrait renforcer la fidélité des utilisateurs / This thesis presents the results of a multidisciplinary research project (Agorantic) on Recommender Systems. The goal of this work was to propose new features that may render recommender systems (RS) more attractive than the existing ones. We also propose a new approach to and a reflection about evaluation. In designing the system, we wanted to address the following concerns: 1. People are getting used to receive recommendations. Nevertheless, after a few bad recommendations, users will not be convinced anymore by the RS. 2. Moreover, if these suggestions come without explanations, why people should trust it? 3. The fact that item perception and user tastes and moods vary over time is well known. Still, most recommender systems fail to offer the right level of “reactivity” that users are expecting, i.e. the ability to detect and to integrate changes in needs, preferences, popularity, etc. Suggesting a movie a week after its release might be too late. In the same vein, it could take only a few ratings to make an item go from not advisable to advisable, or the other way around. 4. Users might be interested in less popular items (in the ” long tail”) and want less systematic recommendations. To answer these key issues, we have designed a new semantic and adaptive recommender system (SARS) including three innovative features, namely Argumentation, Dynamic Adaptation and a Matching Algorithm. • Dynamic Adaptation: the system is updated in a continuous way, as each new review/rating is posted. (Chapter 4) • Argumentation: each recommendation relies on and comes along with some keywords, providing the reasons that led to that recommendation. This can be seen as a first step towards a more sophisticated argumentation. We believe that, by making users more responsible for their choices, it will prevent them from losing confidence in the system. (Chapter 5) • Matching Algorithm: allows less popular items to be recommended by applying a match- ing game to users and items preferences. (Chapter 6) The system should be sensed as less intrusive thanks to relevant arguments (well-chosen words) and less responsible to unsatisfaction of the customers. We have designed a new recommender system intending to provide textually well-argued recommendations in which the end user will have more elements to make a well-informed choice. Moreover, the system parameters are dynamically and continuously updated, in order to pro- vide recommendations and arguments in phase with the very recent past. We have included a semantic level, i.e words, terms and phrases as they are naturally expressed in reviews about items. We do not use tags or pre-determined lexicon. The performances of our system are comparable to the state of the art. In addition, the fact that it provides argumentations makes it even more attractive and could enhance customers loyalty

This dissertation proposes the Weaves runtime framework for the execution of large scale parallel programs over lightweight intra-process threads. The goal of the Weaves framework is to help process-based legacy parallel programs exploit the scalability of threads without any modifications. The framework separates global variables used by identical, but independent, threads of legacy parallel programs without resorting to thread-based re-programming. At the same time, it also facilitates low-overhead collaboration among threads of a legacy parallel program through multi-granular selective sharing of global variables. Applications that follow the tenets of the Weaves framework can load multiple identical, but independent, copies of arbitrary object files within a single process. They can compose the runtime images of these object files in graph-like ways and run intra-process threads through them to realize various degrees of multi-granular selective sharing or separation of global variables among the threads. Using direct runtime control over the resolution of individual references to functions and variables, they can also manipulate program composition at fine granularities. Most importantly, the Weaves framework does not entail any modifications to either the source codes or the native codes of the object files. The framework is completely transparent. Results from experiments with a real-world process-based parallel application show that the framework can correctly execute a thousand parallel threads containing non-threadsafe global variables on a single machine - nearly twice as many as the traditional process-based approach can - without any code modifications. On increasing the number of machines, the application experiences super-linear speedup, which illustrates scalability. Results from another similar application, chosen from a different software area to emphasize the breadth of this research, show that the framework's facilities for low-overhead collaboration among parallel threads allows for significantly greater scales of achievable parallelism than technologies for inter-process collaboration allow. Ultimately, larger scales of parallelism enable more accurate software modeling of real-world parallel systems, such as computer networks and multi-physics natural phenomena. / Ph. D.

As software applications are becoming increasingly distributed and mobile, their design and implementation are characterized by distributed software architectures, possibility of faults, and the need for energy awareness. Thus, software developers should be able to simultaneously reason about and handle the concerns of distribution, fault-tolerance, and energy-efficiency. Being closely intertwined, these concerns can introduce significant complexity into the design and implementation of modern software. In other words, to develop reliable and energy-efficient applications, software developers must understand how distribution, fault-tolerance, and energy-efficiency interplay with each other and how to implement these concerns while keeping the complexity in check. This dissertation addresses five technical issues that stand on the way of engineering reliable and energy-efficient software: (1) how can developers select and parameterize middleware to achieve the requisite levels of performance, reliability, and energy-efficiency? (2) how can one streamline the process of implementing and reusing fault tolerance functionality in distributed applications? (3) can automated techniques be developed to help transition centralized applications to using cloud-based services efficiently and reliably? (4) how can one leverage cloud-based resources to improve the energy-efficiency of mobile applications? (5) how can middleware be adapted to improve the energy-efficiency of distributed mobile applications operated over heterogeneous mobile networks? To address these issues, this research studies the concerns of distribution, fault-tolerance, and energy-efficiency as well as their interaction. It also develops novel approaches, techniques, and tools that effectively fuse and separate these concerns as required by particular software development scenarios. The specific innovations include (1) a systematic assessment of the performance, conciseness, complexity, reliability, and energy consumption of middleware mechanisms for accessing remote functionality, (2) a declarative approach to hardening distributed applications with resiliency against partial failure, (3) cloud refactoring, a set of automated program transformations for transitioning to using cloud-based services efficiently and reliably, (4) a cloud offloading approach that improves the energy-efficiency of mobile applications without compromising their reliability, (5) a middleware mechanism that optimizes energy consumption by adapting execution patterns dynamically in response to fluctuations in network conditions. / Ph. D.

Les architectures orientées services (SOA) sont considérées comme le moyen le plus avancé pour réaliser et intégrer rapidement des applications modulaires et flexibles.Dans ce domaine, les plates-formes SOA à disposition des développeurs et des architectes de produits logiciels sont multiples; les deux plus évoluées d'entre elles étant SCA et OSGi.Une application s'appuyant sur l'une de ces plates-formes peut ainsi être assemblée avec le minimum de composants nécessaires à la réalisation de ses tâches, afin de réduire sa consommation de ressources et d'augmenter sa maintenabilité.De plus, ces plates-formes autorisent l'ajout de composants greffons qui n'étaient pas connus lors des phases initiales de la réalisation du produit.Elles permettent ainsi de mettre à jour, d'étendre et d'adapter continuellement les fonctionnalités du produit de base ou des services techniques nécessaires à sa mise en production, sans interruption de service.Ces capacités sont notamment utilisées dans le cadre du paradigme DevOps et, plus généralement, pour mettre en œuvre le déploiement continu d'artefacts.Cependant, l'extensibilité offerte par ces plates-formes peut diminuer la fiabilité globale du système: une tendance forte pour développer un produit est l'assemblage de composants provenant de tierces-parties. De tels composants peuvent être d'une qualité inconnue voire douteuse.En cas d'erreur, de détérioration des performances, etc., il est difficile de diagnostiquer les composants ou combinaisons de composants incriminés.Il devient indispensable pour le producteur d'un logiciel de déterminer la responsabilité des différents composants impliqués dans un dysfonctionnement.Cette thèse a pour objectif de fournir une plate-forme, Cohorte, permettant de concevoir et d'exécuter des produits logiciels extensibles et résilients aux dysfonctionnements d'extensions non qualifiées.Les composants de tels produits pourront être développés dans différents langages de programmation et être déployés (ajout, mise à jour et retrait) en continu et sans interruption de service.Notre proposition adopte pour principe d'isoler les composants considérés comme instables ou peu sûrs.Le choix des composants à isoler peut être décidé par l'équipe de développement et l'équipe opérationnelle, à partir de leur expertise, ou bien déterminé à partir d'une combinaison d'indicateurs.Ces derniers évoluent au cours du temps pour refléter la fiabilité des composants.Par exemple, des composants peuvent être considérés fiables après une période de quarantaine; une mise à jour peut entraîner la dégradation de leur stabilité, etc..Par conséquent, il est indispensable de remettre en cause les choix initiaux dans l'isolation des composants afin, dans le premier cas, de limiter le coup des communications entre composants et, dans le deuxième cas, de maintenir le niveau de fiabilité du noyau critique du produit. / Service-Oriented architectures (SOA) are considered the most advanced way to develop and integrate modular and flexible applications.There are many SOA platforms available for software developers and architects; the most evolved of them being SCA and OSGi.An application based on one of these platforms can be assembled with only the components required for the execution of its tasks, which helps decreasing its resource consumption and increasing its maintainability.Furthermore, those platforms allow adding plug-ins at runtime, even if they were not known during the early stages of the development of the application.Thus, they allow updating, extending and adapting the features of the base product or of the technical services required for its execution, continuously and without outage.Those capabilities are applied in the DevOps paradigm and, more generally, to implement the continuous deployment of artifacts.However, the extensibility provided by those platforms can decrease the overall reliability of the system: a strong tendency in software development is the assembly of third-parties components.Such components may be of unknown or even questionable quality.In case of error, deterioration of performance, ... it is difficult to identify the implicated components or combinations of components.It becomes essential for the software producer to determine the responsibility of the various components involved in a malfunction.This thesis aims to provide a platform, Cohorte, to design and implement scalable software products, resilient to malfunctions of unqualified extensions.The components of such products may be developed in various programming languages and be deployed continuously (adding, updating and withdrawal) and without interruption of service.Our proposal adopts the principle of isolating the components considered unstable or insecure.The choice of the components to be isolated may be decided by the development team and the operational team, from their expertise, or determined from a combination of indicators.The latters evolve over time to reflect the reliability of components.For example, components can be considered reliable after a quarantine period; an update may result in deterioration of stability, ...Therefore, it is essential to question the initial choices in isolating components to limit, in the first case, the scope of communications between components and, in the second case, to maintain the reliability of the critical core of the product.

Le traitement de flux de données est au cœur des problématiques actuelles liées au Big Data. Face à de grandes quantités de données (Volume) accessibles de manière éphémère (Vélocité), des solutions spécifiques tels que les systèmes de gestion de flux de données (SGFD) ont été développés. Ces SGFD reçoivent des flux et des requêtes continues pour générer de nouveaux résultats aussi longtemps que des données arrivent en entrée. Dans le contexte de cette thèse, qui s’est réalisée dans le cadre du projet ANR Socioplug (ANR-13-INFR-0003), nous considérons une plateforme collaborative de traitement de flux de données à débit variant en termes de volume et de distribution des valeurs. Chaque utilisateur peut soumettre des requêtes continues et contribue aux ressources de traitement de la plateforme. Cependant, chaque unité de traitement traitant les requêtes dispose de ressources limitées ce qui peut engendrer la congestion du système en fonction des variations des flux en entrée. Le problème est alors de savoir comment adapter dynamiquement les ressources utilisées par chaque requête continue par rapport aux besoins de traitement. Cela soulève plusieurs défis : i) comment détecter un besoin de reconfiguration ? ii) quand reconfigurer le système pour éviter sa congestion ? Durant ces travaux de thèse, nous nous sommes intéressés à la gestion automatique de la parallélisation des opérateurs composant une requête continue. Nous proposons une approche originale basée sur une estimation des besoins de traitement dans un futur proche. Ainsi, nous pouvons adapter le niveau de parallélisme des opérateurs de manière proactive afin d’ajuster les ressources utilisées aux besoins des traitements. Nous montrons qu’il est possible d’éviter la congestion du système mais également de réduire significativement la consommation de ressources à performance équivalente. Ces différents travaux ont été implémentés et validés dans un SGFD largement utilisé avec différents jeux de tests reproductibles. / In a Big Data context, stream processing has become a very active research domain. In order to manage ephemeral data (Velocity) arriving at important rates (Volume), some specific solutions, denoted data stream management systems (DSMSs),have been developed. DSMSs take as inputs some queries, called continuous queries,defined on a set of data streams. Acontinuous query generates new results as long as new data arrive in input. In many application domains, data streams haveinput rates and distribution of values which change over time. These variations may impact significantly processingrequirements for each continuous query.This thesis takes place in the ANR project Socioplug (ANR-13-INFR-0003). In this context, we consider a collaborative platformfor stream processing. Each user can submit multiple continuous queries and contributes to the execution support of theplatform. However, as each processing unit supporting treatments has limited resources in terms of CPU and memory, asignificant increase in input rate may cause the congestion of the system. The problem is then how to adjust dynamicallyresource usage to processing requirements for each continuous query ? It raises several challenges : i) how to detect a need ofreconfiguration ? ii) when reconfiguring the system to avoid its congestion at runtime ?In this work, we are interested by the different processing steps involved in the treatment of a continuous query over adistributed infrastructure. From this global analysis, we extract mechanisms enabling dynamic adaptation of resource usage foreach continuous query. We focus on automatic parallelization, or auto-parallelization, of operators composing the executionplan of a continuous query. We suggest an original approach based on the monitoring of operators and an estimation ofprocessing requirements in near future. Thus, we can increase (scale-out), or decrease (scale-in) the parallelism degree ofoperators in a proactive many such as resource usage fits to processing requirements dynamically. Compared to a staticconfiguration defined by an expert, we show that it is possible to avoid the congestion of the system in many cases or to delay itin most critical cases. Moreover, we show that resource usage can be reduced significantly while delivering equivalentthroughput and result quality. We suggest also to combine this approach with complementary mechanisms for dynamic adaptation of continuous queries at runtime. These differents approaches have been implemented within a widely used DSMS and have been tested over multiple and reproductible micro-benchmarks.

CIRQUEIRA, Alexandre Correia. Um Mecanismo de Segurança com Adaptação Dinâmica em Tempo de Execução para Dispositivos Móveis. 2011. 110 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências, Departamento de Computação, Fortaleza-CE, 2011. / Submitted by guaracy araujo (guaraa3355@gmail.com) on 2016-05-19T19:32:40Z No. of bitstreams: 1 2011_dis_accirqueira.pdf: 5491223 bytes, checksum: 7f1b8cc28f5bf56687e6d0e34acc337f (MD5) / Approved for entry into archive by guaracy araujo (guaraa3355@gmail.com) on 2016-05-19T19:33:29Z (GMT) No. of bitstreams: 1 2011_dis_accirqueira.pdf: 5491223 bytes, checksum: 7f1b8cc28f5bf56687e6d0e34acc337f (MD5) / Made available in DSpace on 2016-05-19T19:33:29Z (GMT). No. of bitstreams: 1 2011_dis_accirqueira.pdf: 5491223 bytes, checksum: 7f1b8cc28f5bf56687e6d0e34acc337f (MD5) Previous issue date: 2011 / The increasing use of mobile devices, wireless networks and mobile applications highlights the importance of ensuring information security. This concern arises because of the risks involved in traffic sensitive information via wireless, since it does not limit the risk of attacks, as in conventional networks. Additionally, the trend in the use of sustainable practices advocated by the Green Computing imposes the need for designing flexible applications that seek to reduce consumption of resources such as energy. Thus, mechanisms for providing confidentiality of information passing over the wireless medium should consider the efficient allocation of computing resources. This is a key issue to be considered when designing secure mobile applications. Therefore, the protection mechanisms should balance the security level required in accordance with the consumption of resources allocated to provide it. The use of information that characterizes the current situation (context) can assist in this task. Thus, the use of appropriate protective security requirements of applications and combined with the context can identify situations where you need to raise or lower the security level in order to reduce the resource consumption of the device. This work proposes a Security Mechanism Dynamic Adaptation (MeSAD), focusing on confidentiality, able to adapt the level of security according to the context and reduce the resource consumption of mobile devices. The main objective is to find the balance point in the tradeoff between the level of security and resource consumption. In order to achieve this goal, this paper presents a tool to support the use of MeSAD during the development of mobile applications, and enable the assessments on the performance of cryptographic algorithms that are used in different devices. / A crescente utilização de dispositivos móveis, redes sem fio e aplicações móveis evidencia a importância da garantia de segurança da informação. Esta preocupação surge devido aos riscos envolvidos no tráfego de informações sensíveis por meio sem fio, uma vez que o meio não limita os riscos de ataques, tal como nas redes convencionais. Adicionalmente, a tendência no uso de práticas sustentáveis defendidas pela Computação Verde impõe a necessidade de concepção de aplicações flexíveis que busquem a redução do consumo de recursos, como o de energia. Assim, mecanismos para o provimento de confidencialidade de informações que trafegam por meio sem fio devem considerar a alocação eficiente de recursos computacionais. Esta é uma questão chave a ser considerada no momento da concepção de aplicações móveis seguras. Portanto, os mecanismos de proteção devem balancear o nível de segurança requerido de acordo com o consumo de recursos alocados para provê-lo. O emprego de informações que caracterizam a situação corrente (contexto) pode auxiliar nessa tarefa. Assim, a utilização de proteção adequada aos requisitos de segurança das aplicações e combinada com o contexto pode identificar situações nas quais será necessário aumentar ou diminuir o nível de segurança, de forma a diminuir o consumo de recursos do dispositivo. Esse trabalho propõe, portanto, um Mecanismo de Segurança com Adaptação Dinâmica (MeSAD), com foco na confidencialidade, capaz de adaptar o nível de segurança de acordo com o contexto e reduzir o consumo de recursos dos dispositivos móveis. O objetivo principal consiste em encontrar o ponto de equilíbrio no tradeoff entre nível de segurança e consumo de recursos. A fim de atingir este objetivo, este trabalho apresenta também uma ferramenta de suporte à utilização do MeSAD durante o desenvolvimento de aplicações móveis, além de possibilitar a realização de avaliações sobre o desempenho dos algoritmos criptográficos que são utilizados nos diferentes dispositivos.