Pervasive computing in mobile ad hoc networks requires that applications query their network environment for services and react to a plethora of events fired by other devices in that network responding to such queries...
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ISBN:
(纸本)9781605583648
Pervasive computing in mobile ad hoc networks requires that applications query their network environment for services and react to a plethora of events fired by other devices in that network responding to such queries. Current context-aware and event-driven architectures require the programmer to react to these events via a carefully crafted network of observers and event handlers, while inherently introducing complex concurrency issues. This paper proposes the integration of two techniques to solve these problems: ambient references and reactive programming. Ambient references are object-oriented communication abstractions that represent nearby remote objects in the mobile network and that make it possible to generate the events mentioned above. The reactive programming paradigm provides an abstraction over events such that the application can be written in a conventional programming style with explicit control flow. Copyright 2008 ACM.
Extensions to the actor model have been proposed to ease the development of mobile ad hoc applications. However, programming in the actor model is still difficult as it does not provide abstractions to synchronously c...
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ISBN:
(纸本)9781605583648
Extensions to the actor model have been proposed to ease the development of mobile ad hoc applications. However, programming in the actor model is still difficult as it does not provide abstractions to synchronously coordinate multiple actors. Thus, when programmers want to coordinate two or more actors they have to do it by hand. Additionally, programmers need to write failure recovery code for failures caused by the concurrent access to the actors they are using. Coding this manually is error prone and might even be not feasible. We propose a language abstraction based on software transactional memory to coordinate actors. We show that the integration of software transactional memory with the actor model makes writing failure recovery code superuous. Moreover, we show that our system even handles those cases where manually writing the failure recovery code is not feasible. Copyright 2008 ACM.
The paper presents the study of the human body, as a mechanical system, seated inside an autovehicle and exposed under the vertical harmonic vibration action during the auto vehicle motion time. The human body may be ...
A DSM protocol ensures that a thread can access data allocated on another machine using some consistency protocol. The consistency protocol can either replicate the data and unify replica changes periodically or the t...
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ISBN:
(纸本)9780889867741
A DSM protocol ensures that a thread can access data allocated on another machine using some consistency protocol. The consistency protocol can either replicate the data and unify replica changes periodically or the thread, upon remote access, can migrate to the machine that hosts the data and access the data there. There is a performance tradeoff between these extremes. Data replication suffers from a high memory overhead as every replicated object or page consumes memory on each machine. On the other hand, it is as bad to migrate threads upon each remote access since repeated accesses to the same distributed data set will cause repeated network communication whereas replication will incur this only once (at the cost of increased administration overhead to manage the replicas). We propose a hybrid protocol that uses selective replication with thread migration as its default. Even in the presence of extreme memory pressure and thread-migrations, our protocol reaches or exceeds the performance that can be achieved by means of manual replication and explicit changes of the application's code.
Longitudinal elasticity modulus, E, is a material specific feature, which,. in general, is establish on the pieces by longitudinal stress. This procedure is possible to apply to the compact material but not to the sin...
In this paper, we propose an On-Demand Content Delivery Grid system that supplements the traditional content delivery network to deal with problems such as the huge influx of network traffic in a short period of time ...
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ISBN:
(纸本)9780980326727
In this paper, we propose an On-Demand Content Delivery Grid system that supplements the traditional content delivery network to deal with problems such as the huge influx of network traffic in a short period of time and the high cost in renting a fixed number of servers. We present its system architecture and describe its implementation in details. An experimental high-definition movie streaming site was setup using our content delivery grid system to demonstrate its capabilities with performance analysis.
As memory transactions have been proposed as a language-level replacement for locks, there is growing need for well-defined semantics. In contrast to database transactions, transaction memory (TM) semantics are compli...
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ISBN:
(纸本)9781595939739
As memory transactions have been proposed as a language-level replacement for locks, there is growing need for well-defined semantics. In contrast to database transactions, transaction memory (TM) semantics are complicated by the fact that programs may access the same memory locations both inside and outside transactions. Strongly atomic semantics, where non-transactional accesses are treated as implicit single-operation transactions, remain difficult to provide without specialized hardware support or significant performance overhead. As an alternative, many in the community have informally proposed that a single global lock semantics [18, 10], where transaction semantics are mapped to those of regions protected by a single global lock, provide an intuitive and efficiently implementable model for programmers. In this paper, we explore the implementation and performance implications of single global lock semantics in a weakly atomic STM from the perspective of Java, and we discuss why even recent STM implementations fall short of these semantics. We describe a new weakly atomic Java STM implementation that provides single global lock semantics while permitting concurrent execution, but we show that this comes at a significant performance cost. We also propose and implement various alternative semantics that loosen single lock requirements while still providing strong guarantees. We compare our new implementations to previous ones, including a strongly atomic STM. [24] Copyright 2008 ACM.
The authors present their latest research results and developments of a code generator for Matlab / Simulink block diagrams and to download the generated code onto safety related systems such as a safety PLC (Programm...
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The paper presents the on-going EC-funded Tempus project "MSc and PhD studies in Aerospace Critical Computing" executed by the National Aerospace University, Kharkiv, Ukraine with the support of Newcastle Un...
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ISBN:
(纸本)9781605580760
The paper presents the on-going EC-funded Tempus project "MSc and PhD studies in Aerospace Critical Computing" executed by the National Aerospace University, Kharkiv, Ukraine with the support of Newcastle University and City University of London, UK and Åbo Akademi University, Turku, Finland. The state-of-the-art, completed work as well as the next steps of the development of master and doctoral courses for the specialty in critical software engineering, computer systems and networks are described. The inputs from each of the European consortium members are presented. Copyright 2008 ACM.
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