João Lourenço

Os dispositivos móveis em proximidade geográfica representam um conjunto de recursos inexplorados, tanto em termos de capacidade de processamento como de rmazenamento, o que abre caminho para novas aplicações com oportunidades e desafios únicos. Os sistemas atuais de partilha de dados (e. g., fotos, música, vídeos) para dispositivos móveis exigem que exista conectividade com a Internet para funcionarem. No entanto, em ambientes onde a conectividade com a Internet não é constante ou de boa qualidade (e. g., eventos desportivos e concertos), ou em locais remotos onde as infraestruturas de rede não existem, é difícil (ou mesmo impossível) partilhar dados entre vários dispositivos móveis. Para resolver este problema, os dispositivos móveis podem formar uma rede ad hoc para compartilhar os seus dados e recursos. Neste artigo propomos um sistema de armazenamento distribuído para partilha de dados entre dispositivos móveis de uso diário, e. g., smartphones e tablets, usando um mecanismo de melhor esforço para garantir persistência e disponibilidade de dados suportando churn (entrada e saída inesperada de dispositivos).

Multi-threaded programs allow one to achieve better performance by doing a lot of work in parallel using multiple threads. Such parallel programs often contain code blocks that a thread must execute atomically, i.e., with no interference from the other threads of the program. Failing to execute these code blocks atomically leads to errors known as atomicity violations. However, frequently it not obvious to tell when a piece of code should be executed atomically, especially when that piece of code contains calls to some third-party library functions, about which the programmer has little or no knowledge at all. One solution to this problem is to associate a contract with such a library, telling the programmer how the library functions should be used, and then check whether the contract is indeed respected. For contract validation, static approaches have been proposed, with known limitations on precision and scalability. In this paper, we propose a dynamic method for contract validation, which is more precise and scalable than static approaches.

Transactional memory (TM) is an increasingly popular technique for synchronising threads in multi-threaded programs. To address both correctness and performance-related issues of TM programs, one needs to monitor and analyse their execution. However, monitoring concurrent programs (including TM programs) may have a non-negligible impact on their behaviour, which may hamper the objectives of the intended analysis. In this paper, we propose several approaches for monitoring TM programs and study their impact on the behaviour of the monitored programs. The considered approaches range from specialised lightweight monitoring to generic heavyweight monitoring. The implemented monitoring tools are publicly available to the scientific community, and the implementation techniques used for lightweight monitoring of TM programs may be used as an inspiration for developing other specialised lightweight monitors.

Os serviços Web são frequentemente suportados por sistemas com uma arquitetura em camadas, sendo utilizadas bases de dados relacionais para armazenamento dos dados. A replicação dos diversos componentes tem sido uma das formas utilizadas para obter melhorarias de escalabilidade destes serviços. Adicionalmente, a utilização de bases de dados em memória permite alcançar um desempenho mais elevado. No entanto é conhecida a fraca escalabilidade das bases de dados com o número de núcleos em máquinas multi-núcleo. Neste artigo propomos uma nova abordagem para lidar com este problema, intitulada MacroDDB. Utilizando uma solução de replicação hierárquica, a nossa proposta, replica a base da dados em vários nós, sendo que cada nó, por sua vez, executa um conjunto de réplicas da base de dados. Esta abordagem permite assim lidar com a falta de escalabilidade das bases de dados relacionais em máquinas multi-núcleo, o que por sua vez melhora a escalabilidade geral dos serviços.

n/a

In software, hardware, and embedded system domains, debugging is the process of locating and correcting faults in a system. Depending on the context, the various characteristics of debugging induce different challenges and solutions. Post-silicon hardware debugging, for example, needs to address issues such as limited visibility and controllability, while debugging software entails other issues, such as the handling of distributed or non-deterministic computation. The challenges that accompany such issues are the focus of many current research efforts. Solutions for debugging range from interactive tools to highly analytic techniques. We have seen great advances in debugging technologies in recent years, but bugs continue to occur, and debugging still encompasses significant portions of the life-cycles of many systems. The session covered state-of-the-art approaches as well as promising new research directions in both the hardware and software domains.

The recent developments in virtualization change completely the panorama of the Hardware/OS deployment. New bottlenecks arise in the deployment of application stacks, where IT industry will spend most of the time to assure automation. VIRTU tool aims at managing, configuring and testing distributed ground applications of space systems on a virtualized environment, based on open tools and cross virtualization support. This tool is a spin-off of previous activities performed by the European Space Operations Center (ESOC) and thus it covers the original needs from the ground data systems infrastructure division of the European Space Agency. VIRTU is a testing oriented solution. Its ability to group several virtual machines in an assembly provides the means to easily deploy a full testing infrastructure, including the client/server relationships. The possibility of making on-demand request of the testing infrastructure will provide some infrastructure optimizations, specially having in mind that ESA maintains Ground Control software of various missions, and each mission cam potentially have a different set of System baselines and last up to 15 years. The matrix array of supported system combinations is therefore enormous and any improvement on the process provides substantial benefits to ESA, by reducing the effort and schedule of each maintenance activity. The ESOC's case study focuses on the development and validation activities of infrastructure or mission Ground Systems solutions. The Ground Systems solutions are typically composed of distributed systems that could take advantage of virtualized environments for testing purposes. Virtualization is used as way to optimize maintenance for tasks such as testing new releases and patches, test different system's configurations and replicate tests. The main benefits identified are related to deployment test environment and the possibility to have on-demand infrastructure.

SmART (Smart Application Reconfiguration Tool) is a framework for the automatic configuration of systems and applications. The tool implements an application configuration workflow that resorts to the similarities between configuration files (i.e., patterns such as parameters, comments and blocks) to allow a syntax independent manipulation and transformation of system and application configuration files.Without compromising its generality, SmART targets virtualized IT infrastructures, configuring virtual appliances and its applications. SmART reduces the time required to (re)configure a set of applications by automating time-consuming steps of the process, independently of the nature of the application to be configured. Industrial experimentation and utilization of SmART show that the framework is able to correctly transform a large amount of configuration files into a generic syntax and back to their original syntax. They also show that the elapsed time in that process is adequate to what would be expected of an interactive tool. SmART is currently being integrated into the VIRTU bundle, whose trial version is available for download from the projects web page.

n/a

We describe our experimentation with the design and implementation of specific environments, consisting of heterogeneous computational, visualization, and control components. We illustrate the approach with the design of a problem–solving environment supporting the execution of genetic algorithms. We describe a prototype supporting parallel execution, visualization, and steering. A life cycle for the development of applications based on genetic algorithms is proposed.

We discuss the problem of building domain oriented environments by a composition of heterogeneous application components and tools. We describe several individual tools that support such environments, namely a distributed monitoring and control tool (DAMS), a process-based distributed debugger (PDBG) and a heterogeneous interconnection model (PHIS). We discuss our experience with the development of a Problem Oriented Environment in the domain of genetic algorithms, obtained by a composition of heterogeneous tools and application components.

We discuss debugging prototypes that can easily support new functionalities, depending on the requirements of high-level computational models, and allowing a coherent integration with other tools in a software engineering environment. Concerning the first aspect, we propose a framework that identifies two distinct levels of functionalities that should be supported by a parallel and distributed debugger using: a process and thread-level, and a coordination level concerning sets of processes or threads. An incremental approach is used to effectively develop prototypes that support both functionalities. Concerning the second aspect, we discuss how the interfacing with other tools has influenced the design of a process-level debugging interface (PDBG) and a distributed monitoring and control layer called (DAMS).

This paper presents an approach to education in Parallel and Distributed Processing undertaken in the Technical University of Gdansk and Technical University of Wroclaw. The paper gives a detailed structure of the project entitled "Teaching Parallel Processing: Development of Curriculum and Software Tools" which was started in 1994 and will be finish in 1997. Two universities from Poland: Technical University of Gdansk and Technical University of Wroclaw and two universities from EC countries: University Autònoma of Barcelona from Spain and University Nova of Lisbon from Portugal participate in the presented project. The main aim of the project is to develop existing curricula of Computer Science specialisation and to establish specialisation concerned with parallel and distributed processing at Polish universities.