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ACM SIGACT News Distributed Computing Column 28
ACM SIGACT News Distributed Computing Column 28 Idit Keidar Dept. of Electrical Engineering, Technion Haifa, 32000, Israel [email protected] Sergio Rajsbaum, who edited this column for seven years and established it as a relevant and popular venue, is stepping down. This issue is my first step in the big shoes he vacated. I would like to take this opportunity to thank Sergio for providing us with seven years’ worth of interesting columns. In producing these columns, Sergio has enjoyed the support of the community at-large and obtained material from many authors, who greatly contributed to the column’s success. I hope to enjoy a similar level of support; I warmly welcome your feedback and suggestions for material to include in this column! The main two conferences in the area of principles of distributed computing, PODC and DISC, took place this summer. This issue is centered around these conferences, and more broadly, distributed computing research as reflected therein, ranging from reviews of this year’s instantiations, through influential papers in past instantiations, to examining PODC’s place within the realm of computer science. I begin with a short review of PODC’07, and highlight some “hot” trends that have taken root in PODC, as reflected in this year’s program. Some of the forthcoming columns will be dedicated to these up-and- coming research topics. This is followed by a review of this year’s DISC, by Edward (Eddie) Bortnikov. For some perspective on long-running trends in the field, I next include the announcement of this year’s Edsger W. -
Temporal Verification of Reactive Systems Springer New York Berlin Heidelberg Barcelona Budapest Hong Kong London Milan Paris Tokyo Zohar Manna Amir Pnueli
Temporal Verification of Reactive Systems Springer New York Berlin Heidelberg Barcelona Budapest Hong Kong London Milan Paris Tokyo Zohar Manna Amir Pnueli Temporal Verification of Reactive Systems Safety With 181 Illustrations , Springer Zohar Manna Amir Pnueli Department of Computer Science Computer Science Department Stanford University Weizmann Institute of Science Stanford, CA 94305 USA Rehovot, 76100 Israel Library of Congress Cataloging-in-Publication Data Manna, Zohar. Temporal verification of reactive systems:safety / Zohar Manna and Amir Pnueli. p. cm. Includes bibliographical references and index. ISBN-13:978-1-4612-8701-8 e-ISBN -13:978-1-4612-4222-2 D0I.10.100/978-1-4612-4222-2 1. Computer software-Verification. 2. Parallel processing (Electronic computers) I. Pnueli, A. II. Title. 005.2-dc20 95-5442 Printed on acid-free paper. @ 1995 Springer-Verlag New York, Inc. Softcover reprint of the hardcover 1st edition 1995 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer-Verlag New York, Inc., 175 Fifth Avenue, New York, NY 10010, USA) except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. -
The Best Nurturers in Computer Science Research
The Best Nurturers in Computer Science Research Bharath Kumar M. Y. N. Srikant IISc-CSA-TR-2004-10 http://archive.csa.iisc.ernet.in/TR/2004/10/ Computer Science and Automation Indian Institute of Science, India October 2004 The Best Nurturers in Computer Science Research Bharath Kumar M.∗ Y. N. Srikant† Abstract The paper presents a heuristic for mining nurturers in temporally organized collaboration networks: people who facilitate the growth and success of the young ones. Specifically, this heuristic is applied to the computer science bibliographic data to find the best nurturers in computer science research. The measure of success is parameterized, and the paper demonstrates experiments and results with publication count and citations as success metrics. Rather than just the nurturer’s success, the heuristic captures the influence he has had in the indepen- dent success of the relatively young in the network. These results can hence be a useful resource to graduate students and post-doctoral can- didates. The heuristic is extended to accurately yield ranked nurturers inside a particular time period. Interestingly, there is a recognizable deviation between the rankings of the most successful researchers and the best nurturers, which although is obvious from a social perspective has not been statistically demonstrated. Keywords: Social Network Analysis, Bibliometrics, Temporal Data Mining. 1 Introduction Consider a student Arjun, who has finished his under-graduate degree in Computer Science, and is seeking a PhD degree followed by a successful career in Computer Science research. How does he choose his research advisor? He has the following options with him: 1. Look up the rankings of various universities [1], and apply to any “rea- sonably good” professor in any of the top universities. -
Kein Folientitel
182.703: Problems in Distributed Computing (Part 3) WS 2019 Ulrich Schmid Institute of Computer Engineering, TU Vienna Embedded Computing Systems Group E191-02 [email protected] Content (Part 3) The Role of Synchrony Conditions Failure Detectors Real-Time Clocks Partially Synchronous Models Models supporting lock-step round simulations Weaker partially synchronous models Dynamic distributed systems U. Schmid 182.703 PRDC 2 The Role of Synchrony Conditions U. Schmid 182.703 PRDC 3 Recall Distributed Agreement (Consensus) Yes No Yes NoYes? None? meet All meet Yes No No U. Schmid 182.703 PRDC 4 Recall Consensus Impossibility (FLP) Fischer, Lynch und Paterson [FLP85]: “There is no deterministic algorithm for solving consensus in an asynchronous distributed system in the presence of a single crash failure.” Key problem: Distinguish slow from dead! U. Schmid 182.703 PRDC 5 Consensus Solvability in ParSync [DDS87] (I) Dolev, Dwork and Stockmeyer investigated consensus solvability in Partially Synchronous Systems (ParSync), varying 5 „synchrony handles“ : • Processors synchronous / asynchronous • Communication synchronous / asynchronous • Message order synchronous (system-wide consistent) / asynchronous (out-of-order) • Send steps broadcast / unicast • Computing steps atomic rec+send / separate rec, send U. Schmid 182.703 PRDC 6 Consensus Solvability in ParSync [DDS87] (II) Wait-free consensus possible Consensus impossible s/r Consensus possible s+r for f=1 ucast bcast async sync Global message order message Global async sync Communication U. Schmid 182.703 PRDC 7 The Role of Synchrony Conditions Enable failure detection Enforce event ordering • Distinguish „old“ from „new“ • Ruling out existence of stale (in-transit) information • Distinguish slow from dead • Creating non-overlapping „phases of operation“ (rounds) U. -
Complete Issue
Volume 5, Issue 7, July 2015 Algorithms and Scheduling Techniques to Manage Resilience and Power Consumption in Distributed Systems (Dagstuhl Seminar 15281) Henri Casanova, Ewa Deelman, Yves Robert, and Uwe Schwiegelshohn ........... 1 The Constraint Satisfaction Problem: Complexity and Approximability (Dagstuhl Seminar 15301) Andrei A. Bulatov, Venkatesan Guruswami, Andrei Krokhin, and Dániel Marx . 22 Digital Scholarship and Open Science in Psychology and the Behavioral Sciences (Dagstuhl Perspectives Workshop 15302) Alexander Garcia Castro, Janna Hastings, Robert Stevens, and Erich Weichselgartner ....................................................... 42 DagstuhlReports,Vol.5,Issue7 ISSN2192-5283 ISSN 2192-5283 Published online and open access by Aims and Scope Schloss Dagstuhl – Leibniz-Zentrum für Informatik The periodical Dagstuhl Reports documents the GmbH, Dagstuhl Publishing, Saarbrücken/Wadern, program and the results of Dagstuhl Seminars and Germany. Online available at Dagstuhl Perspectives Workshops. http://www.dagstuhl.de/dagpub/2192-5283 In principal, for each Dagstuhl Seminar or Dagstuhl Perspectives Workshop a report is published that Publication date contains the following: January, 2016 an executive summary of the seminar program and the fundamental results, Bibliographic information published by the Deutsche an overview of the talks given during the seminar Nationalbibliothek (summarized as talk abstracts), and The Deutsche Nationalbibliothek lists this publica- summaries from working groups (if applicable). tion in the Deutsche Nationalbibliografie; detailed bibliographic data are available in the Internet at This basic framework can be extended by suitable http://dnb.d-nb.de. contributions that are related to the program of the seminar, e. g. summaries from panel discussions or License open problem sessions. This work is licensed under a Creative Commons Attribution 3.0 DE license (CC BY 3.0 DE). -
Distributed Consensus: Performance Comparison of Paxos and Raft
DEGREE PROJECT IN INFORMATION AND COMMUNICATION TECHNOLOGY, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2020 Distributed Consensus: Performance Comparison of Paxos and Raft HARALD NG KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE Distributed Consensus: Performance Comparison of Paxos and Raft HARALD NG Master in Software Engineering of Distributed Systems Date: September 10, 2020 Supervisor: Lars Kroll (RISE), Max Meldrum (KTH) Examiner: Seif Haridi School of Electrical Engineering and Computer Science Host company: RISE Swedish title: Distribuerad Konsensus: Prestandajämförelse mellan Paxos och Raft iii Abstract With the growth of the internet, distributed systems have become increasingly important in order to provide more available and scalable applications. Con- sensus is a fundamental problem in distributed systems where multiple pro- cesses have to agree on the same proposed value in the presence of partial failures. Distributed consensus allows for building various applications such as lock services, configuration manager services or distributed databases. Two well-known consensus algorithms for building distributed logs are Multi-Paxos and Raft. Multi-Paxos was published almost three decades before Raft and gained a lot of popularity. However, critics of Multi-Paxos consider it difficult to understand. Raft was therefore published with the motivation of being an easily understood consensus algorithm. The Raft algorithm shares similar characteristics with a practical version of Multi-Paxos called Leader- based Sequence Paxos. However, the algorithms differ in important aspects such as leader election and reconfiguration. Existing work mainly compares Multi-Paxos and Raft in theory, but there is a lack of performance comparisons in practice. Hence, prototypes of Leader- based Sequence Paxos and Raft have been designed and implemented in this thesis. -
The EATCS Award 2020 Laudatio for Toniann (Toni)Pitassi
The EATCS Award 2020 Laudatio for Toniann (Toni)Pitassi The EATCS Award 2021 is awarded to Toniann (Toni) Pitassi University of Toronto, as the recipient of the 2021 EATCS Award for her fun- damental and wide-ranging contributions to computational complexity, which in- cludes proving long-standing open problems, introducing new fundamental mod- els, developing novel techniques and establishing new connections between dif- ferent areas. Her work is very broad and has relevance in computational learning and optimisation, verification and SAT-solving, circuit complexity and communi- cation complexity, and their applications. The first notable contribution by Toni Pitassi was to develop lifting theorems: a way to transfer lower bounds from the (much simpler) decision tree model for any function f, to a lower bound, the much harder communication complexity model, for a simply related (2-party) function f’. This has completely transformed our state of knowledge regarding two fundamental computational models, query algorithms (decision trees) and communication complexity, as well as their rela- tionship and applicability to other areas of theoretical computer science. These powerful and flexible techniques resolved numerous open problems (e.g., the su- per quadratic gap between probabilistic and quantum communication complex- ity), many of which were central challenges for decades. Toni Pitassi has also had a remarkable impact in proof complexity. She in- troduced the fundamental algebraic Nullstellensatz and Ideal proof systems, and the geometric Stabbing Planes system. She gave the first nontrivial lower bounds on such long-standing problems as weak pigeon-hole principle and models like constant-depth Frege proof systems. She has developed new proof techniques for virtually all proof systems, and new SAT algorithms. -
COMPLEXITY CLASSIFICATION of EXACT and APPROXIMATE COUNTING PROBLEMS by Heng Guo a Dissertation Submitted in Partial Fulfillment
COMPLEXITY CLASSIFICATION OF EXACT AND APPROXIMATE COUNTING PROBLEMS by Heng Guo A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Computer Sciences) at the UNIVERSITY OF WISCONSIN–MADISON 2015 Date of final oral examination: 07/22/2015 The dissertation is approved by the following members of the Final Oral Committee: Jin-Yi Cai (Advisor), Professor Eric Bach, Professor Dieter van Melkebeek, Professor Shuchi Chawla, Associate Professor Sebastian Roch, Associate Professor © Copyright by Heng Guo 2015 All Rights Reserved i To my parents ii Acknowledgments First and foremost, I cannot express enough gratitude to Jin-Yi Cai, who has guided, advised, and tolerated me in the last five years. When I first came to Madison, I was an ambitious yet clueless young student. It is Jin-Yi who illustrated to me how to do research and solve problems. He also helped me to secure every possible opportunity: attending conferences, giving talks, visiting other institutions, and so on. His insights and knowledge helped me to develop my skill set, and his dedication and attitude inspired me to devote into academics. Truly my role model. There are also other people from whom I received wisdom and to whom I am in debt. Thanks to the hospitality of Leslie Ann Goldberg, I spent six amazing months in Oxford. It was a productive period full of wonderful events and stimulating discussions, and I enjoyed a lot the relaxed atmosphere there. Another big thanks goes to Pinyan Lu, whom I have been working with before and after starting my Ph. -
EMBARGOED for RELEASE MARCH 9, 2011 at 9 A.M. ET, 6 A.M
acm Association for Computing Machinery Advancing Computing as a Science & Profession EMBARGOED FOR RELEASE MARCH 9, 2011 AT 9 a.m. ET, 6 a.m. PT Contact: Virginia Gold 212-626-0505 [email protected] ACM TURING AWARD GOES TO INNOVATOR IN MACHINE LEARNING Valiant Opened New Frontiers that Transformed Learning Theory, Computational Complexity, and Parallel and Distributed Computing NEW YORK, March 9, 2011 – ACM, the Association for Computing Machinery, today named Leslie G. Valiant of Harvard University the winner of the 2010 ACM A.M. Turing Award http://www.acm.org/news/featured/turing-award-2010 for his fundamental contributions to the development of computational learning theory and to the broader theory of computer science. Valiant brought together machine learning and computational complexity, leading to advances in artificial intelligence as well as computing practices such as natural language processing, handwriting recognition, and computer vision. He also launched several subfields of theoretical computer science, and developed models for parallel computing. The Turing Award, widely considered the “Nobel Prize in Computing", is named for the British mathematician Alan M. Turing. The award carries a $250,000 prize, with financial support provided by Intel Corporation and Google Inc. “Leslie Valiant’s accomplishments over the last 30 years have provided the theoretical basis for progress in artificial intelligence and led to extraordinary achievements in machine learning. His work has produced modeling that offers computationally inspired -
Equad News Fall 2019 Volume 31, Number 1 School of Engineering and Applied Science Princeton, NJ 08544-5263
EQuad News Fall 2019 Volume 31, Number 1 School of Engineering and Applied Science Princeton, NJ 08544-5263 www.princeton.edu/engineering [email protected] 4 EQuad News DEAN’S Fall 2019 NOTE Volume 31, Number 1 Interim Dean H. Vincent Poor *77 Vice Dean Shaping Cities for People and the Planet Antoine Kahn *78 Associate Dean, As Professor Elie Bou-Zeid eloquently explains on page 14 of this magazine, the Undergraduate Affairs way we build and reshape urban areas over the coming decades will determine a lot Peter Bogucki Associate Dean, about the long-term health of society and this planet. Development Jane Maggard No small task, but Princeton excels at this kind of grand challenge. The future of Associate Dean, Diversity and Inclusion cities is a complex mix of societal, technological, environmental, economic, and Julie Yun ethical questions, and Princeton is well equipped to knit creative, effective solutions. Director of Engineering Communications More generally, the Metropolis Project that Elie introduces is just one example of Steven Schultz the high-impact work and focus on societal benefit at the School of Engineering and Senior Editor Applied Science. We have tremendous momentum and growth in data science, John Sullivan Digital Media Editor bioengineering, and robotics and cyber- Aaron Nathans physical systems, as well as in advancing Writer the overall diversity and inclusion of Molly Sharlach Communications Specialist the school. Scott Lyon Science Communication Associate All this work brings together two distinctive Amelia Herb strengths of Princeton engineers: a culture Contributors Liz Fuller-Wright of fluidly integrating diverse viewpoints Adam Hadhazy and disciplines, and the ability to distill Bennett McIntosh Melissa Moss problems to their core constraints, then Molly Seltzer develop solutions with widespread impacts. -
A Complexity Trichotomy for Approximately Counting List H-Colourings‡§ 3
A COMPLEXITY TRICHOTOMY FOR APPROXIMATELY COUNTING LIST H-COLOURINGS‡§ ANDREAS GALANIS∗, LESLIE ANN GOLDBERG∗, AND MARK JERRUM† Abstract. We examine the computational complexity of approximately counting the list H-colourings of a graph. We discover a natural graph-theoretic trichotomy based on the structure of the graph H. If H is an irreflexive bipartite graph or a reflexive complete graph then counting list H-colourings is trivially in polynomial time. Otherwise, if H is an irreflex- ive bipartite permutation graph or a reflexive proper interval graph then approximately counting list H-colourings is equivalent to #BIS, the problem of approximately counting independent sets in a bipartite graph. This is a well-studied problem which is believed to be of intermediate complexity – it is believed that it does not have an FPRAS, but that it is not as difficult as approximating the most difficult counting problems in #P. For every other graph H, approximately counting list H-colourings is complete for #P with respect to approximation-preserving reductions (so there is no FPRAS unless NP = RP). Two pleasing features of the trichotomy are (i) it has a natural formulation in terms of hereditary graph classes, and (ii) the proof is largely self-contained and does not require any universal algebra (unlike similar dichotomies in the weighted case). We are able to extend the hardness results to the bounded-degree setting, showing that all hardness results apply to input graphs with maximum degree at most 6. 1. Overview In this paper we study the complexity of approximately counting the list H-colourings of a graph. -
MAURICE NIVAT, UNE GRANDE FIGURE 89 ◦◦◦◦••◦◦ Une Brève Biographie Scientifique De Maurice Nivat 2
HOMMAGE Maurice Nivat, une grande gure Pierre-Louis Curien 1 Le texte qui suit a été rédigé en 2001, pour le volume intitulé « Merci, Maurice : a mosaic in honour of Maurice Nivat », paru comme numéro spécial de la revue Theoretical Com- puter Science, que Maurice Nivat avait fon- dée. En écrivant ce texte, je me réjouissais par avance des travaux scientifiques que Maurice continuerait de poursuivre, des combats qu’il continuerait à livrer pour la pleine reconnais- sance de notre discipline et pour son enseigne- ment « de première classe », et de la liberté qu’il aurait, sa retraite prise, pour assouvir à loisir d’autres passions : celles pour le patri- moine, pour l’ethnographie, pour le théâtre, pour les voyages... Et, en effet, Maurice a poursuivi pendant plusieurs années ses travaux en tomographie discrète. Accompagné par son épouse Paule, il a parcouru le monde en long et en large, à six reprises. Il a mené un combat acharné pour l’introduction de l’informatique dans les programmes de l’enseignement secon- daire. Maurice nous a quittés au terme d’une maladie qu’il a combattue avec un im- mense courage, continuant à lire, à s’informer, à s’enflammer pour les causes qu’il 1. Institut de recherche en informatique fondamentale (IRIF, UMR 8243), CNRS et université Paris- Diderot. 1024 – Bulletin de la société informatique de France, numéro 12, juin 2018, pp. 87–107 88 PIERRE-LOUIS CURIEN ◦◦◦◦••◦◦ défendait. Je me souviendrai de la gourmandise qu’il avait encore dans les yeux et dans le verbe pour me parler, sur son lit d’hôpital, de sa fascination pour les iguanes, alors que je revenais d’une conférence aux îles Galápagos.