1,720,956 research outputs found
A Systematic Literature Review of Lexical Analyzer Implementation Techniques in Compiler Design
No full textThe term “lexical” in lexical analysis process of the compilation is derived from the word “lexeme”, which is the basic conceptual unit of the linguistic morphological study. In computer science, lexical analysis, also referred to as lexing, scanning or tokenization, is the process of transforming the string of characters in source program to a stream of tokens, where the token is a string with a designated and identified meaning. It is the first phase of a two-step compilation processing model known as the analysis stage of compilation process used by compiler to understand the input source program. The objective is to convert character streams into words and recognize its token type. The generated stream of tokens is then used by the parser to determine the syntax of the source program. A program in compilation phase that performs a lexical analysis process is termed as lexical analyzer, lexer, scanner or tokenizer. Lexical analyzer is used in various computer science applications, such as word processing,information retrieval systems, pattern recognition systems and language-processing systems. However, the scope of our review study is related to language processing. Various tools are used for automatic generation of tokens and are more suitable for sequential execution of the process. Recent advances in multi-core architecture systems have led to the need to re-engineer the compilation process to integrate the multi-core architecture. By parallelization in the recognition of tokens in multiple cores, multi cores can be used optimally, thus reducing compilation time. To attain parallelism in tokenizationon multi-core machines, the lexical analyzer phase of compilation needs to be restructured to accommodate the multi-core architecture and by exploiting the language constructs which can run parallel and the concept of processor affinity. This paper provides a systematic analysis of literature to discuss emerging approaches and issues related to lexical analyzer implementation and the adoption of improved methodologies. This has been achieved by reviewing 30 published articles on the implementation of lexical analyzers. The results of this review indicate various techniques, latest developments, and current approaches for implementing auto generated scanners and hand-crafted scanners. Based on the findings, we draw on the efficacy of lexical analyzer implementation techniques from the results discussed in the selected review studies and the paper provides future research challenges and needs to explore the previously under-researched areas for scanner implementation processes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Parallel Scanner for the Concurrent Execution of Lexical Analyzer Tasks on Multi-Core Machines using Dynamic Task Allocation Algorithm
No full textPurpose: Massive multi-core architecture is rapidly becoming the standard in digital technology due to its high and parallel computational capability and performance benefits. To fully utilize the technological capabilities of multi-core systems, system software such as compilers should be re-engineered for parallel processing. Several important contributions have been made in the past to enhance the efficiency of the lexical analysis process by leveraging the innate parallel processing capability of multi-core computers. This trend of implementation shows that a parallel lexical analyzer tends to perform lexing tasks better than a conventional sequential lexical analyzer. This article discusses the way of making the tasks in parallel during the scanning of source program in the phase of lexical analysis. The objective of this study is to explore how to perform lexical analysis in parallel. On multi-core processors, multiple processes of the lexical analyzer program can run concurrently to scan multiple lines in the input stream in parallel for token detection. This is done by allocating tasks line-by-line to the core which is not engaged yet.
Design/Methodology/Approach: Developing a theoretical and experimental approach for parallelizing the lexical scanning process on a multi-core system.
Findings/Result: According to the theoretical and experimental results, the proposed methodology significantly outperforms the sequential approach in terms of tokenization. It considerably reduces the time required for lexical analysis during the compilation process. The result establishes unequivocally that the parallel lexical analyzer's performance should scale linearly with the number of cores. It is clearly observed that the speedup is expected to increase further if the number of CPU cores increases. This enhancement would speed up the compilation process even more.
Originality/Value: A dynamic task allocation algorithm is developed for the concurrent execution of a lexical analyzer task on multi-core systems.
Paper Type: Experimental Research
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
