Run-time Support for Distributed Object Sharing in Safe Programming Languages

We present a new run-time system that supports object sharing in a distributed system. The key insight in this system is that a handle-based implementation of such a system enables effcient and transparent sharing of data with both fine-grained and coarse-grained access patterns. In addition, it supports effcient execution of garbage-collected programs. In contrast, conventional distributed shared memory (DSM) systems are limited to providing only one granularity with good performance, and have experienced diffculty in effciently supporting garbage collection. A safe language, in which no pointer arithmetic is allowed, can transparently be compiled into a handle-based system and constitutes its preferred mode of use. A programmer can also directly use a handle-based programming model that avoids pointer arithmetic on the handles, and achieve the same performance but without the programming benefits of a safe programming language. This new run-time system, DOSA (Distributed Object Sharing Architecture), provides a shared object space abstraction rather than a shared address space abstraction. The key to its effciency is the observation that a handle-based distributed implementation permits VM-based access and modification detection without suffering false sharing for fine-grained access patterns. We compare DOSA to TreadMarks, a conventional DSM system that is effcient at handling coarse-grained sharing. The performance of fine-grained applications and garbage-collected applications is considerably better than in TreadMarks. The performance of coarse-grained applications is nearly as good as in TreadMarks. Since the performance of such applications is already good in TreadMarks, we consider this an acceptable performance penalty

Combinaciones Léxicas en el Inglés de la Tecnología.

A part of corpus-based research has centered on the exploration of lexical phrases (Sinclair 1991; Gledhill 2000a, 2000b; Stubbs 2002) and has presented language as a series of choices determined by the context in which it is employed. Native speakers use recurrent lexico-grammatical patterns when communicating in particular registers. This is especially relevant in scientific academic discourse, where the conventions of genres are interwoven with their linguistic realisations. Following Sinclair (1991: 170), a collocation is defined as “the occurrence of two or more words within a spot of space of each other in a text”. The restrictive character of collocations is basically determined by their repetitive use, which makes word combinations more arbitrary than predictable. This is particularly evident when we try to translate these combinations into other languages. Benson et al. (1986) suggest that collocations are halfway between fixed expressions and free combinations of words. They are co-occurrent groups of words that present a certain degree of stability, although they are not completely lexicalised. Collocations can be situated along a scale or continuum limited by free combinations of words at one end and fixed expressions at the other. The study of collocational patterns has direct pedagogical applications. Learners are not usually taught collocations explicitly. However, we believe that the acquisition of phraseological competence is necessary for effective and precise communication. In the area of English language teaching, the works of Howarth (1993, 1996), Oakey (2002) and Tribble (1990, 2002) point out the importance of collocations in academic writing. Other studies propose the teaching of grammar prioritising the behaviour of individual lexical units (or pattern grammar), i.e. taking account of the lexical patterns of a given register (cf. Hunston 1995, 2002). The aim of this paper is to explore the collocational patterns of three semitechnical and specialised words used in a corpus of 54 engineering research articles in the fields of computing, robotics and nanotechnology: robot, performance and lattice. The analysis shows that, although these words can be found in general English, their collocates contribute to restrict and precise their meaning in a specialised corpus. Making learners aware of these patterns should arouse their consciousness of the use of language in specialized contexts and help them to improve their academic writing as regards accuracy and fluency

Run-Time Support for Distributed Sharing in Safe Languages

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