Albano Alves

Geographical partition for distributed web crawling

This paper evaluates scalable distributed crawling by means of the geographical partition of the Web. The approach is based on the existence of multiple distributed crawlers each one responsible for the pages belonging to one or more previously identified geographical zones. The work considers a distributed crawler where the assignment of pages to visit is based on page content geographical scope. For the initial assignment of a page to a partition we use a simple heuristic that marks a page within the same scope of the hosting web server geographical location. During download, if the analyze of a page contents recommends a different geographical scope, the page is forwarded to the well-located web server.A sample of the Portuguese Web pages, extracted during the year 2005, was used to evaluate: a) page download communication times and the b) overhead of pages exchange among servers. Evaluation results permit to compare our approach to conventional hash partitioning strategies.

cl OpenCL: supporting distributed heterogeneous computing in HPC clusters

Clusters that combine heterogeneous compute device architectures, coupled with novel programming models, have created a true alternative to traditional (homogeneous) cluster computing, allowing to leverage the performance of parallel applications. In this paper we introduce clOpenCL, a platform that supports the simple deployment and efficient running of OpenCL-based parallel applications that may span several cluster nodes, expanding the original single-node OpenCL model. clOpenCL is deployed through user level services, thus allowing OpenCL applications from different users to share the same cluster nodes and their compute devices. Data exchanges between distributed clOpenCL components rely on Open-MX, a high-performance communication library. We also present extensive experimental data and key conditions that must be addressed when exploiting clOpenCL with real applications.

PCor: A Prototype For Resource Oriented Computing

In this paper we present COR a resource oriented computing model that address the question of how to integrate user-level fine-grained multithreading, communication and coordination into a cluster of symmetrical multiprocessor computers. To support the design of complex distributed application using the proposed paradigm we built pCoR a run-time system which has new areas that represents extensions to the strict shared memory and message passing models supported by other platforms: remote operations, dynamic domains, communication ports, multithreading management, shared memory, replication and partition are some of its distinguished features. In addition, it provides a thread-safe transport communication layer to take advantage of modem high-performance commodity hardware/software like Myrinet network.

RoCL: A Resource Oriented Communication Library

RoCL is a communication library that aims to exploit the low-level communication facilities of today’s cluster networking hardware and to merge, via the resource oriented paradigm, those facilities and the high-level degree of parallelism achieved on SMP systems through multi-threading.

A cluster oriented model for dynamically balanced DHTs

Summary form only given. We refine previous work on a model for a distributed hash table (DHT) with support to dynamic balancement across a set of heterogeneous cluster nodes. We present new high-level entities, invariants and algorithms developed to increase the level of parallelism and globally reduce memory utilization. In opposition to a global distribution mechanism, that relies on complete knowledge about the current distribution of the hash table, we adopt a local approach, based on the division of the DHT into separated regions, that possess only partial knowledge of the global hash table. Simulation results confirm the hypothesis that the increasing of parallelism has as counterpart the degradation of the quality of the balancement achieved with the global approach. However, when compared with consistent hashing and our global approach, the same results clarify the relative merits of the extension, showing that, when properly parameterized, the model is still competitive, both in terms of the quality of the distribution and scalability.

Domus – an architecture for cluster-oriented distributed hash tables

This paper presents a high level description of Domus, an architecture for cluster-oriented Distributed Hash Tables. As a data management layer, Domus supports the concurrent execution of multiple and heterogeneous DHTs, that may be simultaneously accessed by different distributed/parallel client applications. At system level, a load balancement mechanism allows for the (re)distribution of each DHT over cluster nodes, based on the monitoring of their resources, including CPUs, memory, storage and network. Two basic units of balancement are supported: vnodes, a coarse-grain unit, and partitions, a fine-grain unit. The design also takes advantage of the strict separation of object lookup and storage, at each cluster node, and for each DHT. Lookup follows a distributed strategy that benefits from the joint analysis of multiple partition-specific routing information, to shorten routing paths. Storage is accomplished through different kinds of data repositories, according to the specificity and requirements of each DHT.

pDomus: a prototype for Cluster-oriented Distributed Hash Tables

The Domus architecture for distributed hash tables (DHTs) is specially designed to support the concurrent deployment of multiple and heterogeneous DHTs, in a dynamic shared-all cluster environment. The execution model is compatible with the simultaneous access of several distributed/parallel client applications to the same or different running DHTs. Support to distributed routing and storage is dynamically configurable per node, as a function of applications requirements, node base resources and the overall cluster communication, memory and storage usage. pDomus is a prototype of Domus that creates an environment where to evaluate the model embedded concepts and planned features. In this paper, we present a series of experiments conduced to obtain figures of merit i) for the performance of basic dictionary operations, and ii) for the storage overhead resulting from several storage technologies. We also formulate a ranking formula that takes into account access patterns of clients to DHTs, to objectively select the most adequate storage technology, as a valuable metric for a wide range of application scenarios. Finally, we also evaluate client applications and services scalability, for a select dictionary operation. Results of the overall evaluation are promising and a motivation for further work

me/spl mu/: unifying application modeling and cluster exploitation

The increasing complexity of high-demand long-running applications has faced programmers with the need to take into account both development hardness and execution time, me/spl mu/ provides the flexibility to control the amount of computational and communication power being used in order to maximize resources utilization and to deliver high performance. In this paper we focus on the aspects of the paradigm that go beyond traditional message passing approaches, promoting the idea that by raising the abstraction level of programming models, programmers will make better use of the available resources with clear impact on both productivity and performance. We introduce the resource as the abstraction used to represent and manage both physical resources - nodes, memory, processors and communication technologies - and logical resources - modules, processes, tasks, threads, groups, etc. We also concentrate on the task of specifying, locating and aggregating resources in order to support the mapping of applications into the target cluster hardware and the explicit management of memory hierarchy.

Management design as a strategic lever to add value to corporate reputation competitiveness in higher education institutions

The purpose of this paper is to aid the convergence of design and management as a strategic lever and innovative tool to improve corporate reputation in higher education institutions (HEIs), particularly in the Polytechnic Institute of Braganca, Portugal (IPB).,SWOT analysis is used to identify strengths and weaknesses in the context of an organization’s internal competencies (identity) and opportunities and threats in an analysis of the organization’s external competitive context (image). Quantitative analysis was used based on questionnaires conducted with IPB community to analyse if differences exist between identity (staff) and image (students) and where there are design structures (website, visual identity, advertising and environment. Corporate character scale developed by Davies et al. (2003, 2004) was used.,With the SWOT analysis, it is possible to outline IPB performance strategies that meet a positive reputation. A positive corporate reputation was found in IPB with the study of corporate character scale. It has been realized where there are differences from the point of view of identity and image, and thus, it is possible to indicate ideas of improvement to increase the competitiveness of HEIs.,The study is restricted to five schools of IPB. It would also be pertinent to broaden the scope of the stakeholders, encompassing the external community of the IPB that is extending the study to the external public, such as parents, companies, suppliers and secondary students.,HEI competitiveness implies student recruitment and public policies. A positive reputation implies a positive brand image. Design competencies of the public higher education sector can go much further acting at the strategic level, establishing its directives of action in the markets where it operates to reflect its corporate reputation in a positive way in the mind of the consumer. Intangible assets such as identity, image and corporate reputation, appear as very valuable elements, presenting an increasing importance in the management of universities that entered a market context where sustainability requires the adoption of more entrepreneurial management guidelines.,The paper is useful for the professionals and academics in perceiving the importance of use management and strategical tools to identify HEI communication and reputation difficulties for a thorough design thinking that delineates solutions that leverage the competitiveness of service organizations such as HEIs.

Deploying applications in multi-SAN SMP clusters

The effective exploitation of multi-SAN SMP clusters and the use of generic clusters to support complex information systems require new approaches; multi-SAN SMP clusters introduce new levels of parallelism and traditional environments are mainly used to run scientific computations. In this paper we present a novel approach to the exploitation of clusters that allows integrating in a unique metaphor: the representation of physical resources, the modelling of applications and the mapping of application into physical resources. The proposed abstractions favoured the development of an API that allows combining and benefiting from the shared memory, message passing and global memory paradigms.