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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Approche générative conjointe logicielle-matérielle au développement du support protocolaire d’applications réseaux / A generative codesign software-hardware based approach for building efficient network protocol parsers for embedded systems

Solanki, Jigar 27 November 2014 (has links)
Les communications entre les applications réseaux sont régies par un ensemble de règles regroupées sous forme de protocoles. Les messages protocolaires sont gérés par une couche de l’application réseau connue comme étant la couche de support protocolaire. Cette couche peut être de nature logicielle, matérielle ou conjointe. Cette couche se trouve à la frontière entre le coeur de l’application et le monde extérieur. A ce titre, elle représente un composant névralgique de l’application. Les performances globales de l’application sont ainsi directement liées aux performances de la couche de support protocolaire associée.Le processus de développement de ces couches consiste à traduire une spécification du protocole, écrite dans un langage de haut niveau tel que ABNF dans un langage bas niveau, logiciel ou matériel. Avec l’avènement des systèmes embarqués, de plus en plus de systèmes sur puce proposent l’utilisation de ressources matérielles afin d’accroître les performances des applicatifs. Néanmoins, peu de processus de développement de couches de support protocolaire tirent parti de ces ressources, en raison notamment de l’expertise nécessaire dans ce domaine.Cette thèse propose une approche générative conjointe logicielle-matérielle au développement du support protocolaire d’applications réseaux, pour améliorer leur performance tout en restant ergonomique pour le développeur de l’application. Notre approche est basée sur l’exploitation d’un langage dédié, appellé Zebra pour générer les différents composants logiciels et matériels formant la couche de support. L’expertise nécessaire est déportée dans l’utilisation du langage Zebra et les composants matériels générés permettent d’accroître les performances de l’application.Les contributions de cette thèse sont les suivantes : Nous avons effectué une analyse des protocoles et applications réseaux. Cette analyse nous a permis d’identifier les composants pour lesquels il est possible d’obtenir des gains de performances.Nous avons conçu et exploité un langage dédié, Zebra, permettant de décrire les différentes entités de la couche de support protocolaire et générant les éléments logiciels et matériels la composant. Nous avons construit un système sur puce exécutant un système d’exploitation Linux afin d’étayer notre approche. Nous avons conçu des accélérateurs matériels déployables pour différents protocoles réseaux sur ce système et pilotables par les applicatifs. Afin de rendre l’accès aux accélérateurs matériels transparent pour les applications réseaux, nous avons développé un intergiciel gérant l’ensemble de ces accès. Cet intergiciel permet à plusieurs applications et/ou à plusieurs clients d’une même application d’utiliser les accélérateurs pour le traitement des messages protocolaires. Nous avons évalué les performances de notre approche dans des conditions réelles. Nous avons comparé ces performances à celles de couches de supports faisant référence dans le domaine. Nous avons constaté un gain de performance conséquent pour l’approche que nous proposons. / Communications between network applications is achieved by using rulesets known as protocols. Protocol messages are managed by the application layer known as the protocol parsing layer or protocol handling layer. Protocol parsers are coded in software, in hardware or based on a co-design approach. They represent the interface between the application logic and the outside world. Thus, they are critical components of network applications. Global performances of network applications are directly linked to the performances of their protocol parser layers.Developping protocol parsers consists of translating protocol specifications, written in a high level language such as ABNF towards low level software or hardware code. As the use of embedded systems is growing, hardware ressources become more and more available to applications on systems on chip (SoC). Nonetheless, developping a network application that uses hardware ressources is challenging, requiring not only expertise in hardware design, but also a knowledge of the protocols involved and an understanding of low-level network programming.This thesis proposes a generative hardware-software co-design based approach to the developpement of network protocol message parsers, to improve their performances without increasing the expertise the developper may need. Our approach is based on a dedicated language, called Zebra, that generates both hardware and software elements that compose protocol parsers. The necessary expertise is deported in the use of the Zebra language and the generated hardware components permit to improve global performances.The contributions of this thesis are as follows : We provide an analysis of network protocols and applications. This analysis allows us to detect the elements which performances can be improved using hardware ressources. We present the domain specific language Zebra to describe protocol handling layers. Software and hardware components are then generated according to Zebra specifications. We have built a SoC running a Linux operating system to assess our approach.We have designed hardware accelerators for different network protocols that are deployed and driven by applications. To increase sharing of parsing units between several tasks, we have developped a middleware that seamlessly manages all the accesses to the hardware components. The Zebra middleware allows several clients to access the ressources of a hardware accelerator. We have conducted several set of experiments in real conditions. We have compared the performances of our approach with the performances of well-knownprotocol handling layers. We observe that protocol handling layers baded on our approach are more efficient that existing approaches.
2

Comparing Model-based and Design-based Structural Equation Modeling Approaches in Analyzing Complex Survey Data

Wu, Jiun-Yu 2010 August 1900 (has links)
Conventional statistical methods assuming data sampled under simple random sampling are inadequate for use on complex survey data with a multilevel structure and non-independent observations. In structural equation modeling (SEM) framework, a researcher can either use the ad-hoc robust sandwich standard error estimators to correct the standard error estimates (Design-based approach) or perform multilevel analysis to model the multilevel data structure (Model-based approach) to analyze dependent data. In a cross-sectional setting, the first study aims to examine the differences between the design-based single-level confirmatory factor analysis (CFA) and the model-based multilevel CFA for model fit test statistics/fit indices, and estimates of the fixed and random effects with corresponding statistical inference when analyzing multilevel data. Several design factors were considered, including: cluster number, cluster size, intra-class correlation, and the structure equality of the between-/within-level models. The performance of a maximum modeling strategy with the saturated higher-level and true lower-level model was also examined. Simulation study showed that the design-based approach provided adequate results only under equal between/within structures. However, in the unequal between/within structure scenarios, the design-based approach produced biased fixed and random effect estimates. Maximum modeling generated consistent and unbiased within-level model parameter estimates across three different scenarios. Multilevel latent growth curve modeling (MLGCM) is a versatile tool to analyze the repeated measure sampled from a multi-stage sampling. However, researchers often adopt latent growth curve models (LGCM) without considering the multilevel structure. This second study examined the influences of different model specifications on the model fit test statistics/fit indices, between/within-level regression coefficient and random effect estimates and mean structures. Simulation suggested that design-based MLGCM incorporating the higher-level covariates produces consistent parameter estimates and statistical inferences comparable to those from the model-based MLGCM and maintain adequate statistical power even with small cluster number.

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