1,721,132 research outputs found
On the Borowsky-Gafni Simulation Algorithm (Extended Abstract)
No full textNancy Lynch Laboratory for Computer Science Massachusetts Institute of Technology Cambridge, MA 02139 [email protected] Sergio Rajsbaum Instituto de Matem aticas, UNAM Ciudad Universitaria D.F. 04510, M exico [email protected] Abstract The first precise description of a version of the BorowskyGafni fault-tolerant simulation algorithm is given, along with a careful description of what it accomplishes and a proof of correctness. The algorithm implements a notion of fault-tolerant reducibility between decision problems. This notion of reducibility is defined, and examples of its use are provided
A Wait-Free Classification of Loop Agreement Tasks
No full text) ? Maurice Herlihy 1 and Sergio Rajsbaum 2 1 Computer Science Department, Brown University, Providence RI 02912, USA, [email protected] 2 Instituto de Matem'aticas, U.N.A.M., Ciudad Universitaria, D.F. 04510, M'exico, [email protected] Abstract. Loop agreement is a family of wait-free tasks that includes set agreement and approximate agreement tasks. This paper presents a complete classification of loop agreement tasks. Each loop agreement task can be assigned an algebraic signature consisting of a finitely-presented group G and a distinguished element g in G. This signature completely characterizes the task's computational power. If G and H are loop agreement tasks with respective signatures hG; gi and hH; hi, then G implements H if and only if there exists a group homomorphism OE : G ! H carrying g to h. 1 Introduction A task is a distributed coordination problem in which each process starts with a private input value taken from a finite set, communicates with the..
The Decidability of Distributed Decision Tasks
No full text) Maurice Herlihy Computer Science Department Brown University, Providence RI 02912 [email protected] Sergio Rajsbaum y Instituto de Matem'aticas U.N.A.M., D.F. 04510, M'exico [email protected] Abstract A task is a distributed coordination problem in which each process starts with a private input value taken from a finite set, communicates with the other processes by applying operations to shared objects, and eventually halts with a private output value, also taken from a finite set. A protocol is a distributed program that solves a task. A protocol is t-resilient if it tolerates failures by t or fewer processes. A task is solvable in a given model of computation if it has a t-resilient protocol in that model. A set of tasks is decidable in a given model of computation if there exists an effective procedure for deciding whether any task in that set has a t-resilient protocol. This paper gives the first necessary and sufficient conditions for task decidability in ..
Bit Complexity of Breaking and Achieving Symmetry in Chains and Rings (Extended Abstract)
No full textYe m Dinitz Shlomo Moran Sergio Rajsbaum Abstract We consider a failure-free, asynchronous message passing network, with n processors arranged on a ring or a chain. The processes are identically programmed but have distinct identities, taken from f1; : : : ; Mg. We investigate the communication costs of three well studied tasks: Consensus, Leader, and MaxF ( nding the maximum identity, a restricted version of Leader). We show that in both chain and ring topologies, somewhat surprisingly, the message complexities of all three tasks are the same. Hence, we suggest as a ner measure of complexity the number of bits transmitted, BitC(). We show that in chains, w.r.t. this measure, Consensus is easier than Leader, which is easier than MaxF. More speci cally, we prove several new lower bounds (and some simple upper bounds) that imply the following results: For the two processors case, BitC(Consensus) = 2 and BitC(Leader) = BitC(MaxF) = 2 log 2 M O(1). For a chain, BitC(Consensus) = (n), and BitC(MaxF) = (n log M ). When the length is even BitC(Leader) = (n), while if the length is odd BitC(Leader) = (n + log M )
Congreso 50 años de la computación en México, Reflexión y Perspectiva Clip 01 de 14
No full textSesión I. Estado y perspectivas de la computación en México
Conferencia magistral
Dr. Sergio Rajsbaum
Investigador Titular, Instituto de Matemáticas, UNAM, México
Clip 01 de 02, 10:00 am Miércoles , Noviembre 12 2008 Duración: 45:00 minuto
Congreso 50 años de la computación en México, Reflexión y Perspectiva Clip 02 de 14
No full textSesión I. Estado y perspectivas de la computación en México
Conferencia magistral
Dr. Sergio Rajsbaum
Investigador Titular, Instituto de Matemáticas, UNAM, México
Clip 02 de 02, 10:00 am Miércoles , Noviembre 12 2008 Duración: 45:00 minuto
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
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