1,720,962 research outputs found
Change actions: from incremental computation to discrete derivatives
Get PDFIt seems to be a piece of folkloric knowledge among the incremental computation community that incremental programs behave, in some way, like derivatives. Indeed, they track the effect of a function on finite differences in the input, much like derivatives in calculus track the effect of a function on infinitesimal differences. This idea has recently come to the forefront when Kelly, Pearlmutter and Siskind proposed reinterpreting Cai's incremental lambda-calculus as a basis to understand automatic differentiation.
On the other hand, the differential lambda-calculus, an extension of the lambda-calculus equipped with a differential operator that can differentiate arbitrary higher-order terms, has been shown to constitute a model for differentiation in the traditional sense -- that is, there is a model of the differential lambda-calculus where function spaces correspond to spaces of smooth functions, and the term-level derivative operator corresponds to the usual notion of derivative of a multivariate function.
The goal of this thesis is threefold: first, to provide a general semantic setting for reasoning about incremental computation. Second, to establish and clarify the connection between derivatives in the incremental sense and derivatives in the analytic sense, that is to say, to provide a common definition of derivative of which the previous two are particular instances. Third, to give a theoretically sound calculus for this general setting.
To this end we define and explore the notions of change actions and differential maps between change actions and show how these notions relate to incremental computation through the concrete example of the semi-naive evaluation of Datalog queries. We also introduce the notion of a change action model as a setting for higher-order differentiation, and exhibit some interesting examples. Finally, we show how Cartesian difference categories, a family of particularly well-behaved change action models, generalise Cartesian differential categories and give rise to a calculus in the
spirit of Ehrhard and Regnier's differential lambda-calculus
Soundness for automatic differentiation via string diagrams
No full textReverse-mode automatic differentiation, especially in the presence of complex language
features, is notoriously hard to implement correctly, and most implementations focus on
differentiating straight-line imperative first-order code. Generalisations exist, however,
that can tackle more advanced features; for example, the algorithm described by Pearlmutter
and Siskind in their 2008 paper can differentiate (pure) code containing closures.
We show that AD algorithms can benefit enormously from being translated into the language
of string diagrams in two steps: first, we rephrase Pearlmutter and Siskind's algorithm as
a set of rules for transforming hierarchical graphs; rules which can -and indeed have been-
be implemented correctly and efficiently in a non-trivial language. Then, we sketch a proof
of soundness for it by reducing its transformations to the axioms of Cartesian reverse
differential categories, expressed as string diagrams.Non UBCUnreviewedAuthor affiliation: Huawei ResearchOthe
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
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
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