1,721,756 research outputs found
Testing in learning conjunctive invariants
Get PDFWe show a new approach in learning conjunctive invariants using dynamic testing of the program. Coming up with correct set of loop invariant is the most challenging part of any verification methods. Although new methods tend to generate a large number of possible invariants hoping this set contains all required invariants needed to verify the program, this large number will cause a significant delay in verification which often ends up to a time out. Our approach introduce a new method in which we can solve this problem by reducing the number of generated candidate invariants.
We apply our method in a verification engine that uses natural proofs for heap verification. We implement our method by running tests for linked list data structures and evaluate it by comparing the results to the original approach without testing. We also use an existing GPU verification tool, called GPUVerify, and apply our method to it. Finally, we show that our approach can significantly improve the verification time and in some cases prove programs that were initially timed out.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2019-08-01The student, Peyman Mahdian, accepted the attached license on 2017-07-14 at 16:52.The student, Peyman Mahdian, submitted this Thesis for approval on 2017-07-14 at 17:02.This Thesis was approved for publication on 2017-07-17 at 10:52.DSpace SAF Submission Ingestion Package generated from Vireo submission #11479 on 2017-09-29 at 11:19:28Made available in DSpace on 2017-09-29T17:52:24Z (GMT). No. of bitstreams: 2
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Previous issue date: 2017-07-17Embargo set by: Colleen Fallaw for item 103503
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The complexity of LSH feasibility
No full textIn this paper we study the complexity of the following feasibility problem: given an n × n similarity matrix S as input, is there a locality sensitive hash (LSH) for S? We show that the LSH feasibility problem is NP-hard even in the following strong promise version: either S admits an LSH or S is at l1-distance at least n2 - ε{lunate} from every similarity that admits an LSH. We complement this hardness result by providing an over(O, ̃) (3n) algorithm for the LSH feasibility problem, which improves upon the naïve nΘ (n) time algorithm; we prove that this running time is tight, modulo constants, under the Exponential Time Hypothesis. © 2014 Elsevier B.V. All rights reserved
Influence and Correlation in Social Networks
No full textIn many online social systems, social ties between users play an important role in dictating their behavior. One of the ways this can happen is through social influence, the phenomenon that the actions of a user can induce his/her friends to behave in a similar way. In systems where social influence exists, ideas, modes of behavior, or new technologies can diffuse through the network like an epidemic. Therefore, identifying and understanding social influence is of tremendous interest from both analysis and design points of view. This is a difficult task in general, since there are factors such as homophily or unobserved confounding variables that can induce statistical correlation between the actions of friends in a social network. Distinguishing influence from these is essentially the problem of distinguishing correlation from causality, a notoriously hard statistical problem. In this paper we study this problem systematically. We define fairly general models that replicate the aforementioned sources of social correlation. We then propose two simple tests that can identify influence as a source of social correlation when the time series of user actions is available. We give a theoretical justification of one of the tests by proving that with high probability it succeeds in ruling out influence in a rather general model of social correlation. We also simulate our tests on a number of examples designed by randomly generating actions of nodes on a real social network (from Flickr) according to one of several models. Simulation results confirm that our test performs well on these data. Finally, we apply them to real tagging data on Flickr, exhibiting that while there is significant social correlation in tagging behavior on this system, this correlation cannot be attributed to social influence. Copyright 2008 ACM
Identification and measurement of social influence and correlation
No full textTechniques for detecting social influence between users in a set of users with regard to an activity are provided. Data for each user of the set of users is received that includes a time value at which the user became active with regard to the activity, and includes at least one indication of another user in the set of users associated with the user A first estimate of social correlation in the set of users is determined based on the data. The data is modified. For instance, the data may be modified according to a shuffle test and/or an edge reversal test. A decond estimate of social correlation in the set of users is determined based on the modified data. The first estimate is compared to the second estimate to determine a degree of social influence in the set of users
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
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