Exascale machines require new programming paradigms and runtimes

Extreme scale parallel computing systems will have tens of thousands of optionally accelerator-equiped nodes with hundreds of cores each, as well as deep memory hierarchies and complex interconnect topologies. Such Exascale systems will provide hardware parallelism at multiple levels and will be energy constrained. Their extreme scale and the rapidly deteriorating reliablity of their hardware components means that Exascale systems will exhibit low mean-time-between-failure values. Furthermore, existing programming models already require heroic programming and optimisation efforts to achieve high efficiency on current supercomputers. Invariably, these efforts are platform-specific and non-portable. In this paper we will explore the shortcomings of existing programming models and runtime systems for large scale computing systems. We then propose and discuss important features of programming paradigms and runtime system to deal with large scale computing systems with a special focus on data-intensive applications and resilience. Finally, we also discuss code sustainability issues and propose several software metrics that are of paramount importance for code development for large scale computing systems

Supporting Internet Access and Quality of Service in Distributed Wireless Ad Hoc Networks

In this era of wireless hysteria, with continuous technological advances in wireless communication and new wireless technologies becoming standardized at a fast rate, we can expect an increased interest for wireless networks, such as ad hoc and mesh networks. These networks operate in a distributed manner, independent of any centralized device. In order to realize the practical benefits of ad hoc networks, two challenges (among others) need to be considered: distributed QoS guarantees and multi-hop Internet access. In this thesis we present conceivable solutions to both of these problems. An autonomous, stand-alone ad hoc network is useful in many cases, such as search and rescue operations and meetings where participants wish to quickly share information. However, an ad hoc network connected to the Internet is even more desirable. This is because Internet plays an important role in the daily life of many people by offering a broad range of services. In this thesis we present AODV+, which is our solution to achieve this network interconnection between a wireless ad hoc network and the wired Internet. Providing QoS in distributed wireless networks is another challenging, but yet important, task mainly because there is no central device controlling the medium access. In this thesis we propose EDCA with Resource Reservation (EDCA/RR), which is a fully distributed MAC scheme that provides QoS guarantees by allowing applications with strict QoS requirements to reserve transmission time for contention-free medium access. Our scheme is compatible with existing standards and provides both parameterized and prioritized QoS. In addition, we present the Distributed Deterministic Channel Access (DDCA) scheme, which is a multi-hop extension of EDCA/RR and can be used in wireless mesh networks. Finally, we have complemented our simulation studies with real-world ad hoc and mesh network experiments. With the experience from these experiments, we obtained a clear insight into the limitations of wireless channels. We could conclude that a wise design of the network architecture that limits the number of consecutive wireless hops may result in a wireless mesh network that is able to satisfy users’ needs. Moreover, by using QoS mechanisms like EDCA/RR or DDCA we are able to provide different priorities to traffic flows and reserve resources for the most time-critical applications

Agent Organization in the Knowledge Plane

In designing and building a network like the Internet, we continue to face the problems of scale and distribution. With the dramatic expansion in scale and heterogeneity of the Internet, network management has become an increasingly difficult task. Furthermore, network applications often need to maintain efficient organization among the participants by collecting information from the underlying networks. Such individual information collection activities lead to duplicate efforts and contention for network resources.The Knowledge Plane (KP) is a new common construct that provides knowledge and expertise to meet the functional, policy and scaling requirements of network management, as well as to create synergy and exploit commonality among many network applications. To achieve these goals, we face many challenging problems, including widely distributed data collection, efficient processing of that data, wide availability of the expertise, etc.In this thesis, to provide better support for network management and large-scale network applications, I propose a knowledge plane architecture that consists of a network knowledge plane (NetKP) at the network layer, and on top of it, multiple specialized KPs (spec-KPs). The NetKP organizes agents to provide valuable knowledge and facilities about the Internet to the spec-KPs. Each spec-KP is specialized in its own area of interest. In both the NetKP and the spec-KPs, agents are organized into regions based on different sets of constraints. I focus on two key design issues in the NetKP: (1) a regionbased architecture for agent organization, in which I design an efficient and non-intrusive organization among regions that combines network topology and a distributed hash table; (2) request and knowledge dissemination, in which I design a robust and efficient broadcast and aggregation mechanism using a tree structure among regions. In the spec-KPs, I build two examples: experiment management on the PlanetLab testbed and distributed intrusion detection on the DETER testbed. The experiment results suggest a common approach driven by the design principles of the Internet and more specialized constraints can derive productive organization for network management and applications

Rethinking Change

UIDB/00417/2020 UIDP/00417/2020No seguimento da Conferência Internacional sobre Arte, Museus e Culturas Digitais (Abril 2021), este e-book pretende aprofundar a discussão sobre o conceito de mudança, geralmente associado à relação entre cultura e tecnologia. Através dos contributos de 32 autores, de 12 países, questiona-se não só a forma como o digital tem motivado novas práticas artísticas e curatoriais, mas também o inverso, observando como propostas críticas e criativas no campo da arte e dos museus têm aberto vias alternativas para o desenvolvimento tecnológico. Assumindo a diversidade de perspectivas sobre o tema, de leituras retrospectivas à análise de questões e projectos recentes, o livro estrutura-se em torno de sete capítulos e um ensaio visual, evidenciando os territórios de colaboração e cruzamento entre diferentes áreas de conhecimento científico. Disponível em acesso aberto, esta publicação resulta de um projecto colaborativo promovido pelo Instituto de História da Arte, Faculdade de Ciências Sociais e Humanas, Universidade NOVA de Lisboa e pelo maat – Museu de Arte, Arquitectura e Tecnologia. Instituição parceira: Instituto Superior Técnico. Mecenas: Fundação Millennium bcp. Media partner: revista Umbigo. Following the International Conference on Art, Museums and Digital Cultures (April 2021), this e-book seeks to extend the discussion on the concept of change that is usually associated with the relationship between culture and technology. Through the contributions of 32 authors from 12 countries, the book not only questions how digital media have inspired new artistic and curatorial practices, but also how, conversely, critical and creative proposals in the fields of art and museums have opened up alternative paths to technological development. Acknowledging the different approaches to the topic, ranging from retrospective readings to the analysis of recent issues and projects, the book is divided into seven sections and a visual essay, highlighting collaborative territories and the crossovers between different areas of scientific knowledge. Available in open access, this publication is the result of a collaborative project promoted by the Institute of Art History of the School of Social Sciences and Humanities, NOVA University of Lisbon and maat – Museum of Art, Architecture and Technology. Partner institution: Instituto Superior Técnico. Sponsor: Millennium bcp Foundation. Media partner: Umbigo magazine.publishersversionpublishe