ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457601
Li Chen
{"title":"Iteration vs. Recursion","authors":"Li Chen","doi":"10.1145/3457588.3457601","DOIUrl":"https://doi.org/10.1145/3457588.3457601","url":null,"abstract":"Iteration and recursion are two essential approaches in Algorithm Design and Computer Programming. Both iteration and recursion are needed for repetitive processes in computing. An iterative structure is a loop in which a collection of instructions and statements will be repeated. A recursive structure is formed by a procedure that calls itself to make a complete performance, which is an alternate way to repeat the process.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117269181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457600
Shirly Cohen, I. Keidar, O. Naor
{"title":"Byzantine Agreement with Less Communication","authors":"Shirly Cohen, I. Keidar, O. Naor","doi":"10.1145/3457588.3457600","DOIUrl":"https://doi.org/10.1145/3457588.3457600","url":null,"abstract":"The development of reliable distributed systems often relies on Byzantine Agreement (BA) [26]. In this problem, a set of correct processes aim to reach a common decision, despite the presence of malicious ones. BA has been around for four decades, yet practical use-cases for it in large-scale systems have emerged only in the last decade. One major application for BA is cryptocurrencies. For example, Bitcoin [30], the rst cryptocurrency, requires a large set of users to agree on the state of the blockchain. Since Bitcoin is a real currency with real value, the need to protect it against Byzantine users is crucial. Following Bitcoin, many other blockchains and FinTech platforms have emerged, e.g., [6,21,30,36]. Consequently, an efficient implementation, in terms of communication, has become one of the main foci of BA solutions.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131567334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457594
D. Kelley
{"title":"Technical Report Column","authors":"D. Kelley","doi":"10.1145/3457588.3457594","DOIUrl":"https://doi.org/10.1145/3457588.3457594","url":null,"abstract":"Welcome to the Technical Reports Column. If your institution publishes technical reports that you'd like to have included here, please contact me at the email address above.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128013196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457592
S. Nagaraj
{"title":"Review of Network Flow Algorithms David P. Williamson","authors":"S. Nagaraj","doi":"10.1145/3457588.3457592","DOIUrl":"https://doi.org/10.1145/3457588.3457592","url":null,"abstract":"This book is on algorithms for network flows. Network flow problems are optimization problems where given a flow network, the aim is to construct a flow that respects the capacity constraints of the edges of the network, so that incoming flow equals the outgoing flow for all vertices of the network except designated vertices known as the source and the sink. Network flow algorithms solve many real-world problems. This book is intended to serve graduate students and as a reference. The book is also available in eBook (ISBN 9781316952894/US$ 32.00), and hardback (ISBN 9781107185890/US$99.99) formats. The book has a companion web site www.networkflowalgs.com where a pre-publication version of the book can be downloaded gratis.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126950486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457595
W. Gasarch, Erik Metz
{"title":"Open Problems Column","authors":"W. Gasarch, Erik Metz","doi":"10.1145/3457588.3457595","DOIUrl":"https://doi.org/10.1145/3457588.3457595","url":null,"abstract":"I invite any reader who has knowledge of some area to contact me and arrange to write a column about open problems in that area. That area can be (1) broad or narrow or anywhere inbetween, and (2) really important or really unimportant or anywhere inbetween.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131013901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457593
Stephen A. Fenner
{"title":"Review of The Theory of Quantum Information John Watrous","authors":"Stephen A. Fenner","doi":"10.1145/3457588.3457593","DOIUrl":"https://doi.org/10.1145/3457588.3457593","url":null,"abstract":"This is an extremely clear, carefully written book that covers the most important results in the sprawling field of quantum information. It is perfect for a reference, self-study, or a graduate course in quantum information. It makes no attempt to be broad or encyclopedic, but instead goes deep into the core topics. The definitions and theorems are all precisely worded, and (starting in Chapter 2) all results have complete proofs, making the book largely self-contained. The book focuses heavily on the mathematical results and nuts-and-bolts techniques underpinning current research, and as such gives the reader a thorough and flexible toolkit for proving new results. If you are just looking for a broad but cursory survey of the field, then this is probably not the book for you. If, however, you want a working knowledge of the core results and proof techniques of quantum information with an eye toward doing cutting-edge research in the field, then this book will be an indispensable addition to your library. The mathematical theory of quantum information studies the ultimate abilities and limits of transmitting and processing information using the laws of quantum mechanics. It owes much of its motivation to classical information theory, which was largely developed by Claude Shannon in the mid 20th century, and to quantum mechanics itself (of course). It addresses basic questions like: how much information can be transmitted through quantum channels, noisy or otherwise, and how entanglement helps. The theory informs, and is informed by, its sister disciplines of quantum computation and quantum communication (which overlap with physics and computer science), although in some sense it is more fundamental. Though he occasionally mentions applications to these other areas, Watrous seats his book squarely in the realm of pure mathematics.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129416704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457598
Rafael Pass, Muthuramakrishnan Venkitasubramaniam
{"title":"Guest Column","authors":"Rafael Pass, Muthuramakrishnan Venkitasubramaniam","doi":"10.1145/3457588.3457598","DOIUrl":"https://doi.org/10.1145/3457588.3457598","url":null,"abstract":"We review a study of average-case complexity through the lens of interactive puzzles- interactive games between a computationally bounded Challenger and computationally-bounded Solver/Attacker. Most notably, we use this treatment to review a recent result showing that if NP is hard-on-the-average, then there exists a sampleable distribution over only true statements of an NP language, for which no probabilistic polynomial time algorithm can find witnesses. We also discuss connections to the problem of whether average-case hardness in NP implies averagecase hardness in TFNP, or the existence of cryptographic one-way functions.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123111715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457590
Frederic Green
{"title":"The Book Review Column","authors":"Frederic Green","doi":"10.1145/3457588.3457590","DOIUrl":"https://doi.org/10.1145/3457588.3457590","url":null,"abstract":"In this column, we review these three books: 1. Algorithmic Aspects of Machine Learning, by Ankur Moitra. A succinct book about theoretical aspects of ML. Review by Sarvagya Upadhyay. 2. Network Flow Algorithms, by David Williamson. An examination of many aspects of these important algorithms. Review by S.V. Nagaraj. 3. The Theory of Quantum Information, by John Watrous. A new, unified treatment of this vital area. Review by Steve Fenner.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127967371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457599
Dan Alistarh
{"title":"Distributed Computing Column 81","authors":"Dan Alistarh","doi":"10.1145/3457588.3457599","DOIUrl":"https://doi.org/10.1145/3457588.3457599","url":null,"abstract":"Overview. In this edition of the column, we have an exciting contribution from Shir Cohen, Idit Keidar, and Oded Naor (Technion), who provide an in-depth perspective on communication-efficient Byzantine Agreement. With the huge popularity of blockchains, the classic area of Byzantine Agreement has seen a surge of interest, and, given the large-scale and widely-distributed deployments of such mechanisms, communication efficiency is a chief concern. This column provides a gentle introduction to the area, by rst the early work in the 80s. This provides the necessary context for the recent exciting work on communication reduction, from the King & Saia algorithm to Algorand. One very useful feature in this column's contribution is the fact that it provides a uni ed view of these results, along with the mathematical background to understand and di erentiate the underlying results. Many thanks to Shir, Idit and Oded for their contribution!","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132489690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ACM SIGACT NewsPub Date : 2021-03-16DOI: 10.1145/3457588.3457597
L. Hemaspaandra
{"title":"SIGACT News Complexity Theory Column 108","authors":"L. Hemaspaandra","doi":"10.1145/3457588.3457597","DOIUrl":"https://doi.org/10.1145/3457588.3457597","url":null,"abstract":"Warmest thanks to Rafael Pass and Muthu Venkitasubramaniam for this issue's guest column, \"Average-Case Complexity Through the Lens of Interactive Puzzles.\" When I mentioned to them that my introduction would have a section on Alan Selman's passing, they immediately wrote back that they were very sorry to hear of Alan's passing, and mentioned (as you will see discussed in the second page of their article), \"The main problem that we are addressing actually goes back to a paper of Even, Selman, and Yacobi from 1984: \"The Complexity of Promise Problems with Applications to Public-Key Cryptography'.\" It is beautiful, and a tribute to the lasting influence of Alan's research, that in the 2020s his work from many decades earlier is helping shape the field's dialogue.","PeriodicalId":387985,"journal":{"name":"ACM SIGACT News","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127333927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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