Un environnement pour le calcul intensif pair à pair

Le concept de pair à pair (P2P) a connu récemment de grands développements dans les domaines du partage de fichiers, du streaming vidéo et des bases de données distribuées. Le développement du concept de parallélisme dans les architectures de microprocesseurs et les avancées en matière de réseaux à haut débit permettent d'envisager de nouvelles applications telles que le calcul intensif distribué. Cependant, la mise en oeuvre de ce nouveau type d'application sur des réseaux P2P pose de nombreux défis comme l'hétérogénéité des machines, le passage à l'échelle et la robustesse. Par ailleurs, les protocoles de transport existants comme TCP et UDP ne sont pas bien adaptés à ce nouveau type d'application. Ce mémoire de thèse a pour objectif de présenter un environnement décentralisé pour la mise en oeuvre de calculs intensifs sur des réseaux pair à pair. Nous nous intéressons à des applications dans les domaines de la simulation numérique et de l'optimisation qui font appel à des modèles de type parallélisme de tâches et qui sont résolues au moyen d'algorithmes itératifs distribués or parallèles. Contrairement aux solutions existantes, notre environnement permet des communications directes et fréquentes entre les pairs. L'environnement est conçu à partir d'un protocole de communication auto-adaptatif qui peut se reconfigurer en adoptant le mode de communication le plus approprié entre les pairs en fonction de choix algorithmiques relevant de la couche application ou d'éléments de contexte comme la topologie au niveau de la couche réseau. Nous présentons et analysons des résultats expérimentaux obtenus sur diverses plateformes comme GRID'5000 et PlanetLab pour le problème de l'obstacle et des problèmes non linéaires de flots dans les réseaux. ABSTRACT : The concept of peer-to-peer (P2P) has known great developments these years in the domains of file sharing, video streaming or distributed databases. Recent advances in microprocessors architecture and networks permit one to consider new applications like distributed high performance computing. However, the implementation of this new type of application on P2P networks gives raise to numerous challenges like heterogeneity, scalability and robustness. In addition, existing transport protocols like TCP and UDP are not well suited to this new type of application. This thesis aims at designing a decentralized and robust environment for the implementation of high performance computing applications on peer-to-peer networks. We are interested in applications in the domains of numerical simulation and optimization that rely on tasks parallel models and that are solved via parallel or distributed iterative algorithms. Unlike existing solutions, our environment allows frequent direct communications between peers. The environment is based on a self adaptive communication protocol that can reconfigure itself dynamically by choosing the most appropriate communication mode between any peers according to decisions concerning algorithmic choice made at the application level or elements of context at transport level, like topology. We present and analyze computational results obtained on several testeds like GRID’5000 and PlanetLab for the obstacle problem and nonlinear network flow problems

An agent-based visualisation system.

This thesis explores the concepts of visual supercomputing, where complex distributed systems are used toward interactive visualisation of large datasets. Such complex systems inherently trigger management and optimisation problems; in recent years the concepts of autonomic computing have arisen to address those issues. Distributed visualisation systems are a very challenging area to apply autonomic computing ideas as such systems are both latency and compute sensitive, while most autonomic computing implementations usually concentrate on one or the other but not both concurrently. A major contribution of this thesis is to provide a case study demonstrating the application of autonomic computing concepts to a computation intensive, real-time distributed visualisation system. The first part of the thesis proposes the realisation of a layered multi-agent system to enable autonomic visualisation. The implementation of a generic multi-agent system providing reflective features is described. This architecture is then used to create a flexible distributed graphic pipeline, oriented toward real-time visualisation of volume datasets. Performance evaluation of the pipeline is presented. The second part of the thesis explores the reflective nature of the system and presents high level architectures based on software agents, or visualisation strategies, that take advantage of the flexibility of the system to provide generic features. Autonomic capabilities are presented, with fault recovery and automatic resource configuration. Performance evaluation, simulation and prediction of the system are presented, exploring different use cases and optimisation scenarios. A performance exploration tool, Delphe, is described, which uses real-time data of the system to let users explore its performance

Network resilience

Many systems on our planet are known to shift abruptly and irreversibly from one state to another when they are forced across a "tipping point," such as mass extinctions in ecological networks, cascading failures in infrastructure systems, and social convention changes in human and animal networks. Such a regime shift demonstrates a system's resilience that characterizes the ability of a system to adjust its activity to retain its basic functionality in the face of internal disturbances or external environmental changes. In the past 50 years, attention was almost exclusively given to low dimensional systems and calibration of their resilience functions and indicators of early warning signals without considerations for the interactions between the components. Only in recent years, taking advantages of the network theory and lavish real data sets, network scientists have directed their interest to the real-world complex networked multidimensional systems and their resilience function and early warning indicators. This report is devoted to a comprehensive review of resilience function and regime shift of complex systems in different domains, such as ecology, biology, social systems and infrastructure. We cover the related research about empirical observations, experimental studies, mathematical modeling, and theoretical analysis. We also discuss some ambiguous definitions, such as robustness, resilience, and stability.Comment: Review chapter

An Introduction to Database Systems

This textbook introduces the basic concepts of database systems. These concepts are presented through numerous examples in modeling and design. The material in this book is geared to an introductory course in database systems offered at the junior or senior level of Computer Science. It could also be used in a first year graduate course in database systems, focusing on a selection of the advanced topics in the latter chapters

YALJOD Full Issue 3.1

The Young African Leaders Journal of Development (YALJOD) is a biennial journal and an official publication of the Young African Leaders Forum (YALF). It was established in 2015 to host scholarly analysis and competing viewpoints about the development of Africa; and it’s multidisciplinary approach makes it more formidable. YALJOD accepts papers from varied disciplinary areas — including Social Sciences, Physical Sciences and Humanities — that show direct relevance to the development of Africa. It publishes researches understood as the social, economic, political, cultural and technological processes of change in Africa. The intended audience of the journal remains the entire African people. Howbeit, for effectiveness, special emphasis is given to African leadership operators, development academics, researchers and youths — who appear to be the next African leaders

Putin's Grand Strategy: Russia's Campaign of Controlled Instability in Ukraine and Beyond

This thesis addresses the great lengths to which Vladimir Putin and the Russian Federation have gone to foster “controlled instability” in the former Soviet Union. It is said that those who do not learn from history are doomed to repeat it, and with Western policy makers who appear unwilling to act on intelligence regarding Russian actions as well as incontrovertible evidence of Putin’s aggressive strategy, this Western failure to learn has contributed significantly to a repeat of various Russian behaviors during past conflicts. Russian actions pose a clear and present danger to the stability of the global community. Because many of the current events are not yet published in texts or are classified, the author has had to depend heavily upon open-source references from the internet to provide key events as they chronologically happened, particularly when analyzing the crisis in Ukraine. In writing the thesis, my observations have been validated by Russia’s recent incursion into Syria to fortify the Russian leadership’s interests as a result of the continued inaction of Western policy makers. As a result, we will see significant additional instances of controlled instability from Russia in the future

Three Risky Decades: A Time for Econophysics?

Our Special Issue we publish at a turning point, which we have not dealt with since World War II. The interconnected long-term global shocks such as the coronavirus pandemic, the war in Ukraine, and catastrophic climate change have imposed significant humanitary, socio-economic, political, and environmental restrictions on the globalization process and all aspects of economic and social life including the existence of individual people. The planet is trapped—the current situation seems to be the prelude to an apocalypse whose long-term effects we will have for decades. Therefore, it urgently requires a concept of the planet's survival to be built—only on this basis can the conditions for its development be created. The Special Issue gives evidence of the state of econophysics before the current situation. Therefore, it can provide excellent econophysics or an inter-and cross-disciplinary starting point of a rational approach to a new era

Macrocriminology and Freedom

How can power over others be transformed to 'power with'? It is possible to transform many institutions to build societies with less predation and more freedom. These stretch from families and institutions of gender to the United Nations. Some societies, times and places have crime rates a hundred times higher than others. Some police forces kill at a hundred times the rate of others. Some criminal corporations kill thousands more than others. Micro variables fail to explain these patterns. Prevention principles for that challenge are macrocriminological. Freedom is conceived in a republican way as non-domination. Tempering domination prevents crime; crime prevention reduces domination. Many believe a high crime rate is a price of freedom. Not Braithwaite. His principles of crime control are to build freedom, temper power, lift people from poverty and reduce all forms of domination. Freedom requires a more just normative order. It requires cascading of peace by social movements for non-violence and non-domination. Periods of war, domination and anomie cascade with long lags to elevated crime, violence, inter-generational self-violence and ecocide. Cybercrime today poses risks of anomic nuclear wars. Braithwaite’s proposals refine some of criminology’s central theories and sharpen their relevance to all varieties of freedom. They can be reduced to one sentence. Strengthen freedom to prevent crime, prevent crime to strengthen freedom

Innovations for Sustainability: Pathways to an efficient and post-pandemic future

3rd Report prepared by The World in 2050 initiativ