Piranha Scheduling: Strategies and Their Implementation

Piranha is a execution model for Linda 1 developed at Yale by Kaminsky and others[4] to reclaim idle cycles from networked workstations for use in executing parallel programs. Piranha has proven to be an effective system for harnessing large amounts of computing power. Most Piranha research to this point has concentrated on efficiently executing a single application at a time. In this paper we evaluate strategies for scheduling multiple Piranha applications. We examine methods for predicting idle periods and the effectiveness of scheduling strategies which make use of these predictions. We present a prototype scheduler for the Piranha system implemented using the process trellis software architecture for networks of workstations.[6] This work was supported by AASERT Grant F49620-92-J-0240 and NASA Training Grant NGT50719. 1 Introduction The proliferation of low cost workstations in academic and corporate environments has given many institutions aggregate computational power rivali..

Teachers' intentions and learner' perceptions about corrective feedback in the L2 classroom

The efficacy of corrective feedback provided during classroom interaction is the topic of much current debate in the second language (L2) literature, and innovative methodology is needed in order to explore this complex issue. Several studies have investigated learners' perceptions about corrective feedback (Egi, in press; Kim & Han, in press; Mackey et al., 2000; Roberts, 1995); however, the degree of overlap between teachers' intentions and learners' perceptions about corrective feedback and the factors influencing such overlap are little understood. The current research investigated perceptions about feedback in Arabic foreign language classrooms. Corrective feedback was provided during authentic lessons on a range of linguistic targets (e.g. phonology, morphology/lexis and syntax) in a number of different ways (e.g. explicit feedback and implicit feedback, including declarative/interrogative recasts and negotiation). Shortly after the language classes, the teachers and their students viewed video clips of feedback episodes and provided comments about the episodes. These comments were analysed for evidence as to whether or not the learners understood the intentions of the teachers who provided the corrective feedback. The results demonstrated that learners' perceptions and teachers' intentions about the linguistic target of corrective feedback overlapped the most when feedback concerned lexis and was provided explicitly. Also, the linguistic targets of the feedback were perceived more accurately when feedback was directed at the learners themselves rather than at their classmates

Metalinguistic Knowledge in L2 Task Performance: A Verbal Protocol Analysis

This paper reports a study employing stimulated recall protocols to investigate how L1 English-speaking learners of L2 German use their metalinguistic knowledge during the resolution of selected form-focused tasks. Verbal report data from 10 university level learners were analysed to gain insight into explicit knowledge in action during controlled processing. A fne-grained analysis allowed for the characterisation of qualitative differences in learners’ reported implementations of metalinguistic knowledge during task performance and the identifcation of variables associated with such implementations. First, reported use of metalinguistic knowledge at different levels of complexity was in evidence. Second, co-occurrences of learners’ reported use of metalinguistic knowledge with success and consistency in item resolution and with different kinds of decision-making were identifed. In sum, the observed behaviour patterns suggest that metalinguistic knowledge may be a double-edged sword: while the use of such knowledge seems to be benefcial in some circumstances, it is apparently not necessarily a safeguard against inconsistent and unsuccessful task performance