1,720,972 research outputs found
A Calculus for Parallel Computations over Multidimensiona l Dense Arrays
No full textWe present a calculus to formalize and give costs to parallel computations over multidimensional dense arrays. The calculus
extends a simple distribution calculus (proposed in some previous work) with computation and data collection. We consider an
SPMD programming model in which process interaction can take place using point-to-point as well as collective operations, much
in the style of MPI. We want to give a rigorous description of all stages of data parallel applications working over dense arrays: initial
distribution (i.e., partition and replication) of arrays over a set of processors, parallel computation over distributed data, exchange of
intermediate results and final data gather. In the paper, beside defining the calculus, we give it a formal semantics, prove equations
between different combinations of operations, and show how to associate a cost to operation combinations. This last feature makes
possible to make quantitative cost-driven choices between semantically equivalent implementation strategies
Skeletal Parallel Programming with OcamlP3L 2.0
No full textParallel programming has proved to be an effective technique to increase the performance of computationally intensive applications. However, writing parallel programs is not easy, and activities such as debugging are usually hard and time consuming. To cope with these difficulties, skeletal parallel programming has been widely explored in recent years with very promising results. However, prototypal skeletal systems developed so far tend to be rather inflexible and difficult to adapt to many practical parallelization scenarios. For instance, many systems restrict all the substructures of an application being encapsulated together in term of possibly nested skeletons, which may be cumbersome when parallelizing some large and complex applications. Moreover, it is usually difficult to share resources among different skeleton instances and to reuse the same instance of a skeleton in different parts of the code. This paper reports on the current status of the OcamIP3I (2.0) system, which sensibly changes the skeletal model of the previous versions, making it more usable and flexible. In particular, we describe the new skeletons, the new skeletal execution model as well as related issues on design and implementation
On the compressibility of large-scale source code datasets
Get PDFStoring ultra-large amounts of unstructured data (often called objects or blobs) is a fundamental task for several object-based storage engines, data warehouses, data-lake systems, and key–value stores. These systems cannot currently leverage similarities between objects, which could be vital in improving their space and time performance. An important use case in which we can expect the objects to be highly similar is the storage of large-scale versioned source code datasets, such as the Software Heritage Archive (Di Cosmo and Zacchiroli, 2017). This use case is particularly interesting given the extraordinary size (1.5 PiB), the variegated nature, and the high repetitiveness of the at-issue corpus. In this paper we discuss and experiment with content- and context-based compression techniques for source-code collections that tailor known and novel tools to this setting in combination with state-of-the-art general-purpose compressors and the information coming from the Software Heritage Graph. We experiment with our compressors over a random sample of the entire corpus, and four large samples of source code files written in different popular languages: C/C++, Java, JavaScript, and Python. We also consider two scenarios of usage for our compressors, called Backup and File-Access scenario, where the latter adds to the former the support for single file retrieval. As a net result, our experiments show (i) how much “compressible” each language is, (ii) which content- or context-based techniques compress better and are faster to (de)compress by possibly supporting individual file access, and (iii) the ultimate compressed size that, according to our estimate, our best solution could achieve in storing all the source code written in these languages and available in the Software Heritage Archive: namely, in 3 TiB (down from their original 78 TiB total size, with an average compression ratio of 4%)
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
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
A Calculus for Dense Array Distributions
No full textInternational audienceWe introduce a very simple, yet powerful, distribution calculus aimed at describing different strategies that can be used to distribute (ie, partition and replicate) multidimensional dense arrays over a set of processors, like what is done in the implementation of the P3L Map skeleton. We give a formal semantics, that allows to prove equations between distributions, and we show how to associate a cost to such distributions, allowing to choose between semantically equivalent distribution strategies
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
Nitrogen Removal from Ink-Jet Textile Printing Wastewater by Autotrophic Biological Process: First Results at Lab and Pilot Scale
No full textDigital textile printing is a rapidly spreading technology in the textile finishing industry due to the great advantages in making printing much more flexible. On the other hand, wastewater originating from rinsing baths are rich in nitrogen (up to 600 mg/L of ammonium nitrogen) due to the massive use of urea in conditioning the textile before printing. Such high concentration prevents the direct discharge into water bodies or even in public sewers and specific dedicated on-site pre-treatment is necessary. PN/anammox processes can offer an economically feasible alternative to conventional nitrogen removal processes, as these require a COD/N ratio of at least 8. The first results of the EU-LIFE DeNTreat project, consisting in the start-up of PN/anammox lab and pilot scale reactors are promising in spite of the variability of the characteristics of the wastewater originating from rinsing digitally printed textiles
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