Vítor Oliveira

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.

Running User-Provided Virtual Machines in Batch-Oriented Computing Clusters

The use of virtualization in HPC clusters can provide rich software environments, application isolation and efficient workload management mechanisms, but system-level virtualization introduces a software layer on the computing nodes that reduces performance and inhibits the direct use of hardware devices. We present an unobtrusive user-level platform to execute virtual machines inside batch jobs that does not handicap the computing clusters ability to execute the most demanding applications. A per-user platform uses a static mode in which the VMs run entirely within the resources of a single batch job and a dynamic mode in which the VMs navigate at runtime between the continuously allocated jobs node time-slots. In the dynamic mode fault-tolerant system agents are integrated using group communication to control the system, to execute user commands and to implement user-defined scheduling policies. In our tests compute intensive applications suffered negligible performance overhead compared to the native configuration, but the user-mode network overlay introduced a significant penalty on the more taxing networked applications.

Research with children and young people on sensitive topics – The case of poverty and delinquency

Research into child poverty and juvenile delinquency shares two features: both involve children and sensitive topics. This article focuses on the critical problem of the quality of children’s participation in research. Some of the ethical and methodological challenges faced in two research projects, a self-report survey on juvenile delinquency and a multi-method study of low-income families, will be discussed. The construct of engagement is proposed as a rationale to address these challenges.

Parallel Genetic Algorithms In A NetworkedWorkstation Environment

Parallel Genetic Algorithms are suited to deal with problems with very large solution spaces and they can support efficient parallel distribution of work. In a PGA Island Model the migration strategy can take advantage of high latency communication channels in a distributed system. This approach suggests the use of networked workstation environments as a cost effective alternative to MPP systems. A Genetic Algorithm Programming System (GAPS) was developed to evaluate the proposed approach, which supports the design of parallel genetic programs and its execution in a distributed workstation environment. GAPS separates the specification of the problem and the user application interface, from the implementation and management details of the run-time environment; it also addresses fault tolerance, needed to recover from a fault that may occur in a dynamic network of heterogeneous workstations. GAPS uses PVM to implement a structural load balance strategy, which distributes complex evaluation functions with large chromosomes across a parallel machine. The proposed system showed to be effective when tested with the knapsack problem.