Journal Article

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  • (2001) Diessel, Oliver; Elgindy, Hossam
    Journal Article
    The development of FPGAs that can be programmed to implement custom circuits by modifying memory has inspired researchers to investigate how FPGAs can be used as a computational resource in systems designed for high performance applications. When such FPGA--based systems are composed of arrays of chips or chips that can be partially reconfigured, the programmable array space can be partitioned among several concurrently executing tasks. If partition sizes are adapted to the needs of tasks, then array resources become fragmented as tasks with varying requirements are processed. Tasks may end up waiting despite their being sufficient, albeit fragmented resources available. We examine the problem of repartitioning the system (rearranging a subset of the executing tasks) at run--time in order to allow waiting tasks to enter the system sooner. In this paper, we introduce the problems of identifying and scheduling feasible task rearrangements when tasks are moved by reloading. It is shown that both problems are NP--complete. We develop two very different heuristic approaches to finding and scheduling suitable rearrangements. The first method, known as Local Repacking, attempts to minimize the size of the subarray needing rearrangement. Candidate subarrays are repacked using known bin packing algorithms. Task movements are scheduled so as to minimize delays to their execution. The second approach, called Ordered Compaction, constrains the movements of tasks in order to efficiently identify and schedule feasible rearrangements. The heuristics are compared by time complexity and resulting system performance on simulated task sets. The results indicate that considerable scheduling advantages are to be gained for acceptable computational effort. However, the benefits may be jeopardized by delays to moving tasks when the average cost of reloading tasks becomes significant relative to task service periods. We indicate directions for future research to mitigate the cost of moving executing tasks.

  • (2004) Scheuermann, B; So, Kam-Ho; Guntsch, M; Middendorf, M; Diessel, Oliver; Elgindy, Hossam; Schmeck, H
    Journal Article
    We present a hardware implementation of population-based ant colony optimization (P-ACO) on field-programmable gate arrays (FPGAs). The ant colony optimization meta-heuristic is adopted from the natural foraging behavior of real ants and has been used to find good solutions to a wide spectrum of combinatorial optimization problems. We describe the P-ACO algorithm and present a circuit architecture that facilitates efficient FPGA implementations. The proposed design shows modest space requirements but leads to a significant reduction in runtime over software-based solutions. Several modifications and extensions of the basic algorithm are also presented, including the approximation of the heuristic function by a small, dynamically changing set of favorable decisions.

  • (2001) Diessel, Oliver; Milne, George
    Journal Article
    Reconfigurable computers based on field programmable gate array technology allow applications to be realised directly in digital logic. The inherent concurrency of hardware distinguishes such computers from microprocessor-based machines in which the concurrency of the underlying hardware is fixed and abstracted from the programmer by the software model. However, reconfigurable logic provides us with the potential to exploit `real` concurrency. It is therefore interesting to know how to exploit this concurrency, how to model concurrent computations, and which languages allow this dynamic hardware to be programmed most effectively. The purpose of this work is to describe an FPGA compiler for the Circal process algebra. In so doing, the authors demonstrate that behavioural descriptions expressed in a process algebraic language can be readily and intuitively compiled to reconfigurable logic and that this contributes to the goal of discovering appropriate high-level languages for run-time reconfiguration.

  • (1998) Armour, William Spencer
    Journal Article
    Traditionally, the LOTE teacher is positioned as the learners' language model. Ingram argues that since the L2 is both the target and the medium of instruction 'the teacher is often the principal (if not sole) model of the language for the student'. This implies that the language of instruction should define the particular teaching method. In practice, however, the teacher speaks and writes model dialogues or more precisely model texts that act as the major source of L2 input, especially in the initial stages of learning the language. Model dialogues are those 'simulated conversation dialogues found at the beginning of textbook language lessons' presented to learners at any time during a class. These models appear not only in textbooks, but also on cassette tapes, in computer 'interactive' multimedia software packages, on photocopied worksheets, the blackboard, and from teachers' mouths. Erickson describes model dialogues as 'stilted' and sometimes 'stereotypical'. The purpose of this paper is to examine the relationships between model dialogues, teachers, learners, and other stake holders by investigating what aspects of social reality model dialogues attempt to characterise; why model dialogues are used extensively as motifs representing actuality, motifs which learners (and teachers) are expected to memorise and use in the future; and whether it would be possible to teach and learn Japanese without using model dialogues.

  • (2004) Armour, William Spencer
    Journal Article
    This article discusses how Sarah Lamond, a Japanese language teacher in Sydney, Australia has juggled three of her identities: second language (L2) learner, L2 user, and L2 teacher. Data come from four interviews used to create an edited life history. These data are used to draw attention to the relationship between L2 learner and language user. The concept of “identity slippage” is briefly discussed and is introduced as a way of explaining this relationship. Although these three identities are foregrounded, it was found that Sarah's other identities of wife and mother also played a significant part in her becoming a Japanese language learner. Furthermore, Sarah's story also raises the native versus nonnative language teacher issue and in turn explores notions of authentic and impostor.