L’exécution de programmes paralléles demande à établir un compromis entre le temps de calcul (nombre de threads) et le temps de synchronisation. Ce compromis dépend principalement du nombre de threads actifs. Un haut degré de parallélisme (beaucoup de threads) permet généralement de diminuer le temps de calcul, mais peut aussi avoir pour conséquence d’augmenter les surcoûts de synchronisation entre threads. De plus, le placement des threads sur les cœurs peut impacter les performances du programme, car le temps pour accéder aux données en mémoire peut varier d’un cœur à l’autre en raison de la contention sur la la hiérarchie mémoire. Ainsi, la performance d’un programme peut être améliorée en adaptant le nombre de threads actifs et en plaçant correctement les threads sur les cœurs de calcul. Cependant, il n’existe pas de règle universelle permettant de décider a priori du niveau de parallélisme optimal et du placement de threads d’un programme, en particulier pour un programme avec les changemets de comportement dynamique. D’ailleurs, un paramétrage hors ligne est moins précis. Cette thèse présente un travail sur la gestion dynamique du parallélisme et du placement de threads. Cette thèse s’attaque au problème de gestion de threads utilisant de la mémoire transactionnelle logicielle (Software Transactional Memory, STM). La mémoire transactionnelle logicielle constitue une technique prometteuse pour traiter le problème de synchronisation en évitant les verrous.Le concept de calcul autonomique offre aux programmeurs un cadre de méthodeset techniques pour construire des systèmes auto-adaptatifs ayant un comportementmaîtrisé. L’idée clé est d’implémenter des boucles de rétroaction afin de concevoir des contrôleurs sûrs, efficaces et prédictibles, permettant d’observer et d’ajuster de manière dynamique les systèmes contrôlés, tout en minimisant le surcoût d’une telle méthode. La thèse propose de concevoir des boucles de rétroaction afin d’automatiser le gestion de threads à l’exécution avec comme objectif la réduction du temps d’exécution des programmes. / Parallel programs need to manage the trade-off between the time spent in synchronisation and computation. The trade-off is significantly affected by the number of active threads. High parallelism may decrease computing time while increase synchronisation cost. Furthermore, thread placement on different cores may impact on program performance, as the data access time can vary from one core to another due to intricacies of its underlying memory architecture. Therefore, the performance of a program can be improved by adjusting its parallelism degree and the mapping of its threads to physical cores. Alas, there is no universal rule to decide them for a program from an offline view, especially for a program with online behaviour variation. Moreover, offline tuning is less precise. This thesis presents work on dynamical management of parallelism and thread placement. It addresses multithread issues via Software Transactional Memory (STM). STM has emerged as a promising technique, which bypasses locks, to tackle synchronisation through transactions. Autonomic computing offers designers a framework of methods and techniques to build autonomic systems with well-mastered behaviours. Its key idea is to implement feedback control loops to design safe, efficient and predictable controllers, which enable monitoring and adjusting controlled systems dynamically while keeping overhead low. This dissertation proposes feedback control loops to automate management of threads at runtime and diminish program execution time.

Depurar sistemas distribuídos continua uma tarefa difícil, mesmo após 30 anos de pesquisa intensa. Embora essa situação possa ser parcialmente atribuída à complexidade das execuções concorrentes, o rápido passo de desenvolvimento das plataformas e tecnologias para computação distribuída também carrega a sua parcela de culpa, por encurtar a vida de muitas ferramentas potencialmente úteis. Neste trabalho, apresentamos uma análise dos principais problemas, técnicas e ferramentas ligados à depuração de sistemas concorrentes e discutidos na literatura. Baseados nessa análise, desenvolvemos e apresentamos uma nova técnica, simples e portátil, que pode ser aplicada a sistemas distribuídos que utilizam chamadas síncronas e bloqueantes. Essa técnica, concebida para sobreviver à heterogeneidade, é validada por meio da implementação de um arcabouço escrito para plataforma Eclipse e instanciado para sistemas de objetos distribuídos baseados em Java/CORBA. / After over thirty years of intense research, debugging distributed systems is still regarded as a difficult task. While this situation could be partially blamed on the fact that concurrent executions are complex, the fast pace of evolution witnessed with distributed computing technologies have also played its by shortening the lifespan of many potentially useful debugging tools. This work presents an analysis of the main issues, techniques and tools in the field of parallel, distributed, and concurrent debugging in general. Based on this analysis, we develop and present a simple and portable technique targeted at synchronous-call-based distributed systems. This technique, designed for portability, is validated through the implementation of an Eclipse-based framework that is instantiated for Java/CORBA distributed object systems.

<p>The Ericsson AXE-based systems are programmed using an internally developed language called Plex-C. Plex-C is normally compiled to execute on an Ericsson internal processor architecture. A transition to standard processors is currently in progress. This makes it interesting to examine if Plex-C can be compiled to execute on the JVM, which would make it processor independent. </p><p>The purpose of the thesis is to examine if parts of the run-time environment of Plex-C can be translated to Java and if this can be done so that sufficient performance is obtained. It includes how language constructions in Plex-C can be translated to Java. </p><p>The thesis describes how a limited part of the Plex-C run-time environment is implemented in Java. Optimizations are an important part of the implementation. </p><p>It is also described how the JVM system was tested with a benchmark test. </p><p>The test results indicate that the implemented system is a few times faster than the Ericsson internal processor architecture. But this performance is still not sufficient for the JVM system to be an interesting replacement for the currently used processor architecture. It might still be useful as a processor independent test platform.</p>

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Les architectures des machines multi-coeurs actuelles deviennent de plus en plus complexes à cause du modèle de conception hiérarchique adopté. Par conséquent, assurer une meilleure stabilité, reproductibilité et prédictibilité des performances sur ces machines nécessite une compréhension approfondie des interactions qui existent entre les applications multi-threads et le matériel sous-jacent. Dans cette thèse, nous étudions deux aspects importants pour les performances des applications multi-threads. Nous montrons que la stabilité des performances est un critère important à considérer dans le processus d'évaluation des performances, et que le placement des threads est une technique efficace en termes de stabilité et d'amélioration des performances des programmes. Nous commençons par étudier la variabilité des temps d'exécution des programmes, nous définissons un protocole rigoureux d'évaluation des performances, puis nous analysons les raisons de cette variabilité et ses implications pour la mesure des performances. Ensuite, nous étudions la relation entre le partage des données entre threads et les stratégies de placement des threads sur machines hiérarchiques. Nous considérons plusieurs stratégies où le même placement est appliqué pour toute la durée d'exécution du programme. Alors que certaines reposent sur les caractéristiques des applications, d'autres non. Nous présentons aussi d'autres stratégies de placement des threads autorisant la migration des threads afin d'exploiter le partage des données au cours des différentes phases d'un programme.

This thesis is a part of the k-Wave project, which is a toolbox for the simulation and reconstruction of acoustic wave felds and one of its main contributions is the planning of focused ultrasound surgeries (HIFU). One simulation can take tens of hours and about 60% of the simulation time is taken by the calculation of the 3D Fast Fourier transforms. Up until now the 3D FFT has been calculated purely by the FFTW library and its 1D decomposition, whose major limitation is the maximum number of employable cores. Therefore we introduce a new approach, called the 2D hybrid decomposition of the 3D FFT (HybridFFT), where we combine both MPI processes and OpenMP threads to reach as best performance as possible. On a low number of cores, on the order of a few hundreds, we are about as fast or slightly faster than FFTW and pure MPI 2D decomposition libraries (PFFT and P3DFFT). One of the best results was achieved on a 512^3FFT using 512 cores, where our hybrid version run 31ms, FFTW run 39ms and PFFT run 44ms. The most significant performance advantage should be seen when employing around 8-16 thousand cores, however we haven't had an access to a machine with such resources. Almost a linear scalability has been proven for up to 2048 employed cores.

Tato diplomová práce byla vypracována v průmyslovém kontextu, během stáže ve firmě Metso. Zlepšení obráběcího procesu zajišťovacích šroubů bylo cílem této práce, aby byla umožněna budoucí automatizace zakládání obrobku do stroje. Zlepšení bylo zhodnoceno na základě úrovně autonomie během obrábění, eliminace neprogramovaných zastavení stroje operátorem a dostačujícího odvodu třísek. Implementace automatických systému do číslicově řízeného obráběcího centra umožňuje zvýšení produktivity. Před automatizováním obráběcího procesu však musí být proces optimalizován. Zejména dostatečná fragmentace třísek a jejich evakuace jsou klíčové. Dlouhé nedělené třísky můžou poškodit systémy jako například automatický měnič nástrojů, dopravník třísek nebo průmyslového robota. Dostatečná lámavost třísek může být zaručena správným výběrem technologie a strategie obrábění, výběrem řezného nástroje a řezných podmínek pro daný materiál obrobku.

The subject of this master thesis are state machines and their testing. To this purpose, an application is described, which is able to test these state machines autonomously. Application have two parts, first generator and editor of data is built and second part is testing procedure, which is able to test state machines in question and to give corresponding test report.

Aluminum alloys have been used for decades in aircraft as they offer a wide range of properties explicitly developed to provide a set of characteristics adapted to structural and non-structural components. However, aircraft components inevitably undergo degradation during service due to their extensive use and exposure to harsh environments. Typical repair methods are either not efficient for large scale repairs due to their low material growth rate, not suitable for field repair or involve the use of high process temperatures. The present research aims at evaluating the cold gas dynamic spray (CGDS) as a potential repair technology to restore Al7075-T6 nose landing gear steering actuator threads found on the Boeing 757 aircraft. Moreover, it studies the suitability of using cold spray to deposit Al2024 material. The influence of process parameters and substrate surface preparation on the material deposition efficiency and resulting microstructural and mechanical repair properties is also evaluated.

Exploiting better performance from computer programs translates to finding more instructions to execute in parallel. Since most general purpose programs are written in an imperatively sequential manner, closely lying instructions are always data dependent, making the designer look far ahead into the program for parallelism. This necessitates wider superscalar processors with larger instruction windows. But superscalars suffer from three key limitations, their inability to scale, sequential fetch bottleneck and high branch misprediction penalty. Recent studies indicate that current superscalars have reached the end of the road and designers will have to look for newer ideas to build computer processors. Speculative Multithreading (SpMT) is one of the most recent techniques to exploit parallelism from applications. Most SpMT architectures partition a sequential program into multiple threads (or tasks) that can be concurrently executed on multiple processing units. It is desirable that these tasks are sufficiently distant from each other so as to facilitate parallelism. It is also desirable that these tasks are control independent of each other so that execution of a future task is guaranteed in case of local control flow misspeculations. Some task prediction mechanisms rely on the compiler requiring recompilation of programs. Current dynamic mechanisms either rely on program constructs like loop iterations and function and loop boundaries, resulting in unbalanced loads, or predict tasks which are too short to be of use in an SpMT architecture. This thesis is the first proposal of a predictor that dynamically predicts control independent tasks that are consistently wide apart, and executes them on a novel SpMT architecture.