1,537 research outputs found
A Multilevel Introspective Dynamic Optimization System For Holistic Power-Aware Computing
Power consumption is rapidly becoming the dominant limiting factor for
further improvements in computer design. Curiously, this applies both
at the "high end" of workstations and servers and the "low end" of
handheld devices and embedded computers. At the high-end, the
challenge lies in dealing with exponentially growing power
densities. At the low-end, there is a demand to make mobile devices
more powerful and longer lasting, but battery technology is not
improving at the same
rate that power consumption is rising. Traditional power-management
research is fragmented; techniques are being developed at specific
levels, without fully exploring their synergy with other levels.
Most software techniques target either operating systems or
compilers but do not explore the interaction between the two
layers. These techniques also have not fully explored the potential
of virtual machines for power management.
In contrast, we are developing
a system that integrates information from multiple levels of software
and hardware, connecting these levels through a communication
channel. At the heart of this
system are a virtual machine that compiles and dynamically profiles
code, and an optimizer that reoptimizes
all code, including that of applications and the virtual machine itself.
We believe this introspective, holistic approach
enables more informed power-management decisions
Achieving High Performance and High Productivity in Next Generational Parallel Programming Languages
Processor design has turned toward parallelism and heterogeneity
cores to achieve performance and energy efficiency. Developers
find high-level languages attractive because they use abstraction
to offer productivity and portability over hardware complexities.
To achieve performance, some modern implementations of high-level
languages use work-stealing scheduling for load balancing of
dynamically created tasks. Work-stealing is a promising approach
for effectively exploiting software parallelism on parallel
hardware. A programmer who uses work-stealing explicitly
identifies potential parallelism and the runtime then schedules
work, keeping otherwise idle hardware busy while relieving
overloaded hardware of its burden.
However, work-stealing comes with substantial overheads. These
overheads arise as a necessary side effect of the implementation
and hamper parallel performance. In addition to runtime-imposed
overheads, there is a substantial cognitive load associated with
ensuring that parallel code is data-race free. This dissertation
explores the overheads associated with achieving high performance
parallelism in modern high-level languages.
My thesis is that, by exploiting existing underlying mechanisms
of managed runtimes; and by extending existing language design,
high-level languages will be able to deliver productivity and
parallel performance at the levels necessary for widespread
uptake.
The key contributions of my thesis are: 1) a detailed analysis of
the key sources of overhead associated with a work-stealing
runtime, namely sequential and dynamic overheads; 2) novel
techniques to reduce these overheads that use rich features of
managed runtimes such as the yieldpoint mechanism, on-stack
replacement, dynamic code-patching, exception handling support,
and return barriers; 3) comprehensive analysis of the resulting
benefits, which demonstrate that work-stealing overheads can be
significantly reduced, leading to substantial performance
improvements; and 4) a small set of language extensions that
achieve both high performance and high productivity with minimal
programmer effort.
A managed runtime forms the backbone of any modern implementation
of a high-level language. Managed runtimes enjoy the benefits of
a long history of research and their implementations are highly
optimized. My thesis demonstrates that converging these highly
optimized features together with the expressiveness of high-level
languages, gives further hope for achieving high performance and
high productivity on modern parallel hardwar
Sistema de recomendação Web usando agentes
O crescimento da Web trouxe vários problemas aos utilizadores. A grande quantidade de informação existente hoje em dia em alguns sĂtios Web torna a procura de informação Ăştil muito difĂcil. Os objetivos dos proprietários dos sĂtios Web e dos utilizadores nem sempre coincidem. O conhecimento dos padrões de visitas dos utilizadores Ă© crucial para que os proprietários possam transformar e adaptar o sĂtio Web. Este Ă© o princĂpio do sĂtio Web adaptativo: o sĂtio Web adapta-se de forma a melhorar a experiĂŞncia do utilizador. Alguns algoritmos foram propostos para adaptar um sĂtio da Web. Neste artigo, descrevemos uma proposta de um sistema de recomendação Web baseado em agentes que combina dois algoritmos: regras de associação e filtragem colaborativa. Ambos os algoritmos sĂŁo incrementais e funcionam com dados binários. Os resultados mostram que, em algumas situações, a abordagem multiagente melhora a capacidade preditiva quando comparada com os agentes individuais.The growth of the Web has brought several problems for users. Today the vast amount of information on some web sites makes useful information finding very difficult. The objectives of the owners of the web sites and users do not always coincide. The knowledge of patterns of user visits is crucial to the owners to transform and adapt their web site. This is the adaptive website principle: the website adapts to improve the user experience. Some algorithms have been proposed to tailor a website. In this paper, we describe a proposal for a web recommendation system based on agents that combines two algorithms: association rules and collaborative filtering. Both algorithms are incremental and work with binary data. The results show that, in some situations, the multi-agent approach overcomes the predictive capacity of individual agents
The distributed ASCI supercomputer project
The Distributed ASCI Supercomputer (DAS) is a homogeneous wide-area distributed system consisting of four cluster computers at different locations. DAS has been used for research on communication software, parallel languages and programming systems, schedulers, parallel applications, and distributed applications. The paper gives a preview of the most interesting research results obtained so far in the DAS project
LA TECHNOLOGIE AGENT ET LES RESEAUX SANS FIL
La technologie agent aura un rôle de plus en plus important à jouer dans les télécommunications grâce à leur propriétés, notamment, d'autonomie, d'intelligence et/ou de mobilité. Les réseaux sans fil joueront également un rôle de plus en plus important offrant un accès omniprésent au réseau, favorisant ainsi la mobilité de l'utilisateur. Dans ce contexte, nous avons identifié un certain nombre de domaines d'application des agents dans les réseaux sans fil. Nous avons décrit, ensuite, un exemple d'utilisation des agents en prenant comme scénario de référence un utilisateur de la 4ème génération de mobile ayant à sa disposition plusieurs technologies d'accès sans fil. Cet utilisateur voudra être connecté au mieux, n'importe où, n'importe quand et avec n'importe quel réseau d'accès. La technologie agent est, dans ce cas, utilisée pour adapter le handover horizontal (changement au sein d'une même technologie d'accès) et vertical (changement de technologie d'accès) aux besoins de qualité de service de l'utilisateur
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