Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing最新文献

{"title":"The Energy Complexity of Broadcast","authors":"Yi-Jun Chang, Varsha Dani, Thomas P. Hayes, Qizheng He, Wenzheng Li, S. Pettie","doi":"10.1145/3212734.3212774","DOIUrl":"https://doi.org/10.1145/3212734.3212774","url":null,"abstract":"Energy is often the most constrained resource in networks of batterypowered devices, and as devices become smaller, they spend a larger fraction of their energy on communication (transceiver usage) not computation. As an imperfect proxy for true energy usage, we define energy complexity to be the number of time slots a device transmits/listens; idle time and computation are free. In this paper we investigate the energy complexity of fundamental communication primitives such as Broadcast in multi-hop radio networks. We consider models with collision detection (CD) and without (No-CD), as well as both randomized and deterministic algorithms. Some take-away messages from this work are as follows. Time lower bounds imply energy lower bounds. The energy complexity of Broadcast in a multi-hop network is connected to the time complexity of LeaderElection in a single-hop (clique) network. Many existing lower bounds on time complexity immediately transfer to energy complexity. For example, in the CD and No-CD models, Broadcast requires Ω(logn) and Ω(log2 n) energy, respectively, w.h.p. Energy- and time-efficient broadcasting. It requires Ω(D) time to solve Broadcast even allowing unlimited energy budget, where D is the diameter of the network. The complexity measures of energy and time are in conflict, and it is an open problem whether both can be minimized simultaneously. We show that it is possible to achieve near optimality in time complexity with only poly logn energy cost. For any constant ε > 0, Broadcast can be solved in O(D1+ε logO(1/ε) n) time with O(logO(1/ε) n) energy.","PeriodicalId":198284,"journal":{"name":"Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121276061","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}

{"title":"Deterministic Digital Clustering of Wireless Ad Hoc Networks","authors":"T. Jurdzinski, D. Kowalski, M. Różański, Grzegorz Stachowiak","doi":"10.1145/3212734.3212752","DOIUrl":"https://doi.org/10.1145/3212734.3212752","url":null,"abstract":"We consider deterministic distributed communication in wireless ad hoc networks of identical devices in the SINR model without predefined infrastructure. Most algorithmic results in this model rely on additional features or capabilities, e.g., randomization, access to geographic coordinates, power control, carrier sensing with various precision of measurements, and interference cancellation. We study a pure scenario, when no such features are available. Several distributed algorithms have been presented in recent years for the local and global broadcast problems considered in this paper. However, all these solutions were either randomized or relied on the assumption that nodes of a network know their own coordinates in a given metric space or devices has signal sensitivity limited to some area (typically smaller than transmission range). In contrast, the aim of this paper is to check how efficient could be solutions without randomization, availability of locations, limited sensitivity, power control, carrier sensing, interference cancellation or other features. Our research objective is motivated twofolds. Firstly, examination of necessity and impacf of randomization is a natural research topic in algorithm design. Moreover, as wireless ad hoc networks are usually built from computationally limited devices run on batteries, it is desirable to use simple and energy efficient algorithms which do not need access to several sensing capabilities or true randomness. As a general tool, we develop a deterministic distributed clustering algorithm, which splits nodes of a multi-hop ad hoc network into clusters of constant diameter. Our solution relies on a new type of combinatorial structures (called witnessed strong selectors), which might be of independent interest. Using the clustering, we develop a deterministic distributed local broadcast algorithm accomplishing this task in O(Δ log N log N) rounds, where Δ is the density of a network. This is the first solution in pure scenario which is only polylog(n) away from the universal lower bound Ω(Δ), valid also for scenarios with randomization and other features. Therefore, we conclude that none of these features substantially helps for the local broadcast task. Using clustering, we also build a deterministic global broadcast algorithm that terminates within O(D(Δ + log? N) log N) rounds, where D is the diameter of the network. This result is complemented by a lower bound Ω(DΔ1-1/∝ ), where ∝ > 2 is the path-loss parameter of the environment. This lower bound, in view of previous work, shows that randomization or knowledge of own location help substantially (by a factor polynomial in Δ) in the global broadcast. Similar clusterbased techniques can be used to build efficient (comparing to the lower bound) solutions to the wake-up problem and the global leader election problem. Summarizing, our results prove that additional model/environment features may help substantially in design of time-efficient solutions","PeriodicalId":198284,"journal":{"name":"Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129583071","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}

{"title":"Tight Bounds for Asymptotic and Approximate Consensus","authors":"Matthias Függer, Thomas Nowak, Manfred Schwarz","doi":"10.1145/3212734.3212762","DOIUrl":"https://doi.org/10.1145/3212734.3212762","url":null,"abstract":"We study the performance of asymptotic and approximate consensus algorithms under harsh environmental conditions. The asymptotic consensus problem requires a set of agents to repeatedly set their outputs such that the outputs converge to a common value within the convex hull of initial values. This problem, and the related approximate consensus problem, are fundamental building blocks in distributed systems where exact consensus among agents is not required or possible, e.g., man-made distributed control systems, and have applications in the analysis of natural distributed systems, such as flocking and opinion dynamics. We prove tight lower bounds on the contraction rates of asymptotic consensus algorithms in dynamic networks, from which we deduce bounds on the time complexity of approximate consensus algorithms. In particular, the obtained bounds show optimality of asymptotic and approximate consensus algorithms presented in [Charron-Bost et al., ICALP'16] for certain dynamic networks, including the weakest dynamic network model in which asymptotic and approximate consensus are solvable. As a corollary we also obtain asymptotically tight bounds for asymptotic consensus in the classical asynchronous model with crashes. Central to our lower bound proofs is an extended notion of valency, the set of reachable limits of an asymptotic consensus algorithm starting from a given configuration. We further relate topological properties of valencies to the solvability of exact consensus, shedding some light on the relation of these three fundamental problems in dynamic networks.","PeriodicalId":198284,"journal":{"name":"Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127839330","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}

{"title":"Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing","authors":"George Giakkoupis","doi":"10.1145/3212734","DOIUrl":"https://doi.org/10.1145/3212734","url":null,"abstract":"It is our great pleasure to welcome you to the 35th ACM SIGACT-SIGOPS Symposium on Principles of Distributed Computing (PODC 2016). This year's symposium continues its tradition of being the premier forum for presentation of research on all aspects of distributed computing, including the theory, design, implementation and applications of distributed algorithms, systems and networks. During the years, PODC has been the stage where many landmark results have been presented that have increased our understanding of this exciting and fundamental research endeavor. In the best tradition of theoretical discovery, the insights that have been provided have not only elucidated fundamental conceptual issues but also found their way into the real world of systems and applications. \u0000 \u0000The call for papers attracted 137 regular submissions and 12 brief announcement submissions. The Program Committee accepted 40 regular papers and 24 brief announcements (some of which come from the regular submissions that could not be accepted due to lack of space) that cover a wide variety of topics. Every submitted paper was read and evaluated by at least three reviewers. The final decisions regarding acceptance or rejection of each paper were made through electronic Program Committee discussions held during April 2016. Revised and expanded versions of a few selected papers will be considered for publication in a special issue of the journal Distributed Computing and in the Journal of the ACM. \u0000 \u0000The Program Committee selected the paper Analysing Snapshot Isolation, by Andrea Cerone and Alexey Gotsman, for this year's Best Paper Award. Moreover, the Program Committee decided to split the Best Student Paper Award between two papers: A Distributed (2+e)-Approximation for Vertex Cover in O(logΔ/eloglogΔ) Rounds, by Reuven Bar-Yehuda, Keren Censor-Hillel and Gregory Schwartzman, and The Greedy Spanner is Existentially Optimal, by Arnold Filtser and Shay Solomon. Three keynote talks will be given by Andrew A. Chien, Faith Ellen, and Phillip B. Gibbons. \u0000 \u0000The 2016 Edsger W. Dijkstra Prize in Distributed Computing was split between two papers: A Fast and Simple Randomized Parallel Algorithm for the Maximal Independent Set Problem, by Noga Alon, Laszlo Babai, and Alon Itai (published in the Journal of Algorithms 1986), and A Simple Parallel Algorithm for the Maximal Independent Set Problem by Michael Luby (published at STOC 1985 and in SIAM Journal on Computing 1986). The Prize will be presented at the conference. Finally, this year we will celebrate the 60th birthday of Faith Ellen.","PeriodicalId":198284,"journal":{"name":"Proceedings of the 2018 ACM Symposium on Principles of Distributed Computing","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134069005","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}