117 research outputs found

    Truthful Mechanisms For Real-Time System Scheduling In Competitive Environments

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    In a non-competitive environment, sporadic real-time task scheduling on a single processor is well understood. In this thesis, we consider a competitive environment comprising several real-time tasks vying for execution upon a shared single processor. Each task obtains a value if the processor successfully schedules all its jobs. Our objective is to select a feasible subset of these tasks to maximize the sum of values of selected tasks. We consider both dynamic-priority and static-priority scheduling algorithms. There are algorithms for solving these problems in non-competitive settings. However, we consider these problems in an economic setting in which each task is owned by a selfish agent. Each agent reports the characteristics of her own task to the processor owner. The processor owner uses a mechanism to allocate the processor to a subset of agents and to determine the payment of each agent. Since agents are selfish, they may try to manipulate the mechanism to obtain the processor. We are interested in truthful mechanisms in which it is always in agents\u27 best interest to report the true characteristics of their tasks. We design exact and approximate truthful mechanisms for this competitive environment and study their performance

    08071 Abstracts Collection -- Scheduling

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    From 10.02. to 15.02., the Dagstuhl Seminar 08071 ``Scheduling\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

    Decentralising resource management in operating systems

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    This dissertation explores operating system mechanisms to allow resource-aware applications to be involved in the process of managing resources under the premise that these applications (1) potentially have some (implicit) notion of their future resource demands and (2) can adapt their resource demands. The general idea is to provide feedback to resource-aware applications so that they can proactively participate in the management of resources. This approach has the benefit that resource management policies can be removed from central entities and the operating system has only to provide mechanism. Furthermore, in contrast to centralised approaches, application specific features can be more easily exploited. To achieve this aim, I propose to deploy a microeconomic theory, namely congestion or shadow pricing, which has recently received attention for managing congestion in communication networks. Applications are charged based on the potential "damage" they cause to other consumers by using resources. Consumers interpret these congestion charges as feedback signals which they use to adjust their resource consumption. It can be shown theoretically that such a system with consumers merely acting in their own self-interest will converge to a social optimum. This dissertation focuses on the operating system mechanisms required to decentralise resource management this way. In particular it identifies four mechanisms: pricing & charging, credit accounting, resource usage accounting, and multiplexing. While the latter two are mechanisms generally required for the accurate management of resources, pricing & charging and credit accounting present novel mechanisms. It is argued that congestion prices are the correct economic model in this context and provide appropriate feedback to applications. The credit accounting mechanism is necessary to ensure the overall stability of the system by assigning value to credits

    DRIVE: A Distributed Economic Meta-Scheduler for the Federation of Grid and Cloud Systems

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    The computational landscape is littered with islands of disjoint resource providers including commercial Clouds, private Clouds, national Grids, institutional Grids, clusters, and data centers. These providers are independent and isolated due to a lack of communication and coordination, they are also often proprietary without standardised interfaces, protocols, or execution environments. The lack of standardisation and global transparency has the effect of binding consumers to individual providers. With the increasing ubiquity of computation providers there is an opportunity to create federated architectures that span both Grid and Cloud computing providers effectively creating a global computing infrastructure. In order to realise this vision, secure and scalable mechanisms to coordinate resource access are required. This thesis proposes a generic meta-scheduling architecture to facilitate federated resource allocation in which users can provision resources from a range of heterogeneous (service) providers. Efficient resource allocation is difficult in large scale distributed environments due to the inherent lack of centralised control. In a Grid model, local resource managers govern access to a pool of resources within a single administrative domain but have only a local view of the Grid and are unable to collaborate when allocating jobs. Meta-schedulers act at a higher level able to submit jobs to multiple resource managers, however they are most often deployed on a per-client basis and are therefore concerned with only their allocations, essentially competing against one another. In a federated environment the widespread adoption of utility computing models seen in commercial Cloud providers has re-motivated the need for economically aware meta-schedulers. Economies provide a way to represent the different goals and strategies that exist in a competitive distributed environment. The use of economic allocation principles effectively creates an open service market that provides efficient allocation and incentives for participation. The major contributions of this thesis are the architecture and prototype implementation of the DRIVE meta-scheduler. DRIVE is a Virtual Organisation (VO) based distributed economic metascheduler in which members of the VO collaboratively allocate services or resources. Providers joining the VO contribute obligation services to the VO. These contributed services are in effect membership “dues” and are used in the running of the VOs operations – for example allocation, advertising, and general management. DRIVE is independent from a particular class of provider (Service, Grid, or Cloud) or specific economic protocol. This independence enables allocation in federated environments composed of heterogeneous providers in vastly different scenarios. Protocol independence facilitates the use of arbitrary protocols based on specific requirements and infrastructural availability. For instance, within a single organisation where internal trust exists, users can achieve maximum allocation performance by choosing a simple economic protocol. In a global utility Grid no such trust exists. The same meta-scheduler architecture can be used with a secure protocol which ensures the allocation is carried out fairly in the absence of trust. DRIVE establishes contracts between participants as the result of allocation. A contract describes individual requirements and obligations of each party. A unique two stage contract negotiation protocol is used to minimise the effect of allocation latency. In addition due to the co-op nature of the architecture and the use of secure privacy preserving protocols, DRIVE can be deployed in a distributed environment without requiring large scale dedicated resources. This thesis presents several other contributions related to meta-scheduling and open service markets. To overcome the perceived performance limitations of economic systems four high utilisation strategies have been developed and evaluated. Each strategy is shown to improve occupancy, utilisation and profit using synthetic workloads based on a production Grid trace. The gRAVI service wrapping toolkit is presented to address the difficulty web enabling existing applications. The gRAVI toolkit has been extended for this thesis such that it creates economically aware (DRIVE-enabled) services that can be transparently traded in a DRIVE market without requiring developer input. The final contribution of this thesis is the definition and architecture of a Social Cloud – a dynamic Cloud computing infrastructure composed of virtualised resources contributed by members of a Social network. The Social Cloud prototype is based on DRIVE and highlights the ease in which dynamic DRIVE markets can be created and used in different domains

    Organization of agricultural production:a contract theoretical approach

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    Technical Workshop: Advanced Helicopter Cockpit Design

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    Information processing demands on both civilian and military aircrews have increased enormously as rotorcraft have come to be used for adverse weather, day/night, and remote area missions. Applied psychology, engineering, or operational research for future helicopter cockpit design criteria were identified. Three areas were addressed: (1) operational requirements, (2) advanced avionics, and (3) man-system integration

    From commitment to control: a labour process study of workers' experiences of the transition from clerical to call centre work at British Gas

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    Despite their continuing importance to the UK economy and their employment of significant numbers of workers from a range of professions, the utilities have received scant attention from critical scholars of work. This neglect represents a missed opportunity to examine the impact of nearly twenty years of privatisation and marketisation on workers, their jobs and their unions. This thesis aims to make a contribution to knowledge here by investigating, contextualising and explaining changes in the labour processes of a privatised utility in the United Kingdom. The research is informed by oral history methods and techniques, rarely adopted in industrial sociology, and here used alongside labour process theory to reconstruct past experiences of work. Drawing on qualitative data sets, from in-depth interviews with a cohort of employees who worked continuously over three decades at the research site, British Gas’s Granton House, and on extensive company and trade union documentary evidence the research demonstrates how British Gas responded to restrictive regulation and the need to deliver shareholder value by transforming pre-existing forms of work organisation through introducing call centres. The call centre provided the opportunity for management to regain control over the labour process, intensify work and reduce costs. In doing so, the study identifies the principal drivers of organisational change, documents the process of change evaluates the impact on workers’ experience. Thus, as a corrective to much recent labour process theory the research offers both an ‘objective’ and ‘subjective’ account of change over an extended time. The contrast between workers’ experience of working in the clerical departments and in the call centre could not be starker. Almost every element of work from which workers derived satisfaction and purpose was abruptly dismantled. In their place workers had to endure the restrictive and controlling nature of call centre work. The relative absence of resistance to such a transformation is shown to be a consequence of failures in collective organisation, rather than the totalisation of managerial control, as the postmodernists and Foucauldians would have it

    Evolutionary Mechanism Design

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    The advent of large-scale distributed systems poses unique engineering challenges. In open systems such as the internet it is not possible to prescribe the behaviour of all of the components of the system in advance. Rather, we attempt to design infrastructure, such as network protocols, in such a way that the overall system is robust despite the fact that numerous arbitrary, non-certified, third-party components can connect to our system. Economists have long understood this issue, since it is analogous to the design of the rules governing auctions and other marketplaces, in which we attempt to achieve sociallydesirable outcomes despite the impossibility of prescribing the exact behaviour of the market participants, who may attempt to subvert the market for their own personal gain. This field is known as 'mechanism design': the science of designing rules of a game to achieve a specific outcome, even though each participant may be self-interested. Although it originated in economics, mechanism design has become an important foundation of multi-agent systems (MAS) research. In many scenarios mechanism design and auction theory yield clear-cut results; however, there are many situations in which the underlying assumptions of the theory are violated due to the messiness of the real-world. In this thesis I introduce an evolutionary methodology for mechanism design, which is able to incorporate arbitrary design objectives and domain assumptions, and I validate the methodology using empirical techniques

    Contributions to Wireless multi-hop networks : Quality of Services and Security concerns

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    Ce document rĂ©sume mes travaux de recherche conduits au cours de ces 6 derniĂšres annĂ©es. Le principal sujet de recherche de mes contributions est la conception et l’évaluation des solutions pour les rĂ©seaux sans fil multi-sauts en particulier les rĂ©seaux mobiles adhoc (MANETs), les rĂ©seaux vĂ©hiculaires ad hoc (VANETs), et les rĂ©seaux de capteurs sans fil (WSNs). La question clĂ© de mes travaux de recherche est la suivante : « comment assurer un transport des donnĂ©es e cace en termes de qualitĂ© de services (QoS), de ressources Ă©nergĂ©tiques, et de sĂ©curitĂ© dans les rĂ©seaux sans fil multi-sauts? » Pour rĂ©pondre Ă  cette question, j’ai travaillĂ© en particulier sur les couches MAC et rĂ©seau et utilisĂ© une approche inter-couches.Les rĂ©seaux sans fil multi-sauts prĂ©sentent plusieurs problĂšmes liĂ©s Ă  la gestion des ressources et au transport des donnĂ©es capable de supporter un grand nombre de nƓuds, et d’assurer un haut niveau de qualitĂ© de service et de sĂ©curitĂ©.Dans les rĂ©seaux MANETs, l’absence d’infrastructure ne permet pas d’utiliser l’approche centralisĂ©e pour gĂ©rer le partage des ressources, comme l’accĂšs au canal.Contrairement au WLAN (rĂ©seau sans fil avec infrastructure), dans les rĂ©seaux Ad hoc les nƓuds voisins deviennent concurrents et il est di cile d’assurer l’équitĂ© et l’optimisation du dĂ©bit. La norme IEEE802.11 ne prend pas en compte l’équitĂ© entre les nƓuds dans le contexte des MANETs. Bien que cette norme propose di Ă©rents niveaux de transmission, elle ne prĂ©cise pas comment allouer ces dĂ©bits de maniĂšre e cace. En outre, les MANETs sont basĂ©s sur le concept de la coopĂ©ration entre les nƓuds pour former et gĂ©rer un rĂ©seau. Le manque de coopĂ©ration entre les nƓuds signifie l’absence de tout le rĂ©seau. C’est pourquoi, il est primordial de trouver des solutions pour les nƓuds non-coopĂ©ratifs ou Ă©goĂŻstes. Enfin, la communication sans fil multi-sauts peut participer Ă  l’augmentation de la couverture radio. Les nƓuds de bordure doivent coopĂ©rer pour transmettre les paquets des nƓuds voisins qui se trouvent en dehors de la zone de couverture de la station de base.Dans les rĂ©seaux VANETs, la dissĂ©mination des donnĂ©es pour les applications de suretĂ© est un vrai dĂ©fi. Pour assurer une distribution rapide et globale des informations, la mĂ©thode de transmission utilisĂ©e est la di usion. Cette mĂ©thode prĂ©sente plusieurs inconvĂ©nients : perte massive des donnĂ©es due aux collisions, absence de confirmation de rĂ©ception des paquets, non maĂźtrise du dĂ©lai de transmission, et redondance de l’information. De plus, les applications de suretĂ© transmettent des informations critiques, dont la fiabilitĂ© et l’authenticitĂ© doivent ĂȘtre assurĂ©es.Dans les rĂ©seaux WSNs, la limitation des ressources (bande passante, mĂ©moire, Ă©nergie, et capacitĂ© de calcul), ainsi que le lien sans fil et la mobilitĂ© rendent la conception d’un protocole de communication e cace di cile. Certaines applications nĂ©cessitent un taux important de ressources (dĂ©bit, Ă©nergie, etc) ainsi que des services de sĂ©curitĂ©, comme la confidentialitĂ© et l’intĂ©gritĂ© des donnĂ©es et l’authentification mutuelle. Ces paramĂštres sont opposĂ©s et leur conciliation est un vĂ©ritable dĂ©fi. De plus, pour transmettre de l’information, certaines applications ont besoin de connaĂźtre la position des nƓuds dans le rĂ©seau. Les techniques de localisation sou rent d’un manque de prĂ©cision en particulier dans un environnement fermĂ© (indoor), et ne permettent pas de localiser les nƓuds dans un intervalle de temps limitĂ©. Enfin, la localisation des nƓuds est nĂ©cessaire pour assurer le suivi d’objet communicant ou non. Le suivi d’objet est un processus gourmand en Ă©nergie, et requiert de la prĂ©cision.Pour rĂ©pondre Ă  ces dĂ©fis, nous avons proposĂ© et Ă©valuĂ© des solutions, prĂ©sentĂ©es de la maniĂšre suivante : l’ensemble des contributions dĂ©diĂ©es aux rĂ©seaux MANETs est prĂ©sentĂ© dans le deuxiĂšme chapitre. Le troisiĂšme chapitre dĂ©crit les solutions apportĂ©es dans le cadre des rĂ©seaux VANETs. Enfin, les contributions liĂ©es aux rĂ©seaux WSNs sont prĂ©sentĂ©es dans le quatriĂšme chapitre
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