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

{"title":"Ignore or Comply?: On Breaking Symmetry in Consensus","authors":"P. Berenbrink, A. Clementi, Robert Elsässer, Peter Kling, Frederik Mallmann-Trenn, Emanuele Natale","doi":"10.1145/3087801.3087817","DOIUrl":"https://doi.org/10.1145/3087801.3087817","url":null,"abstract":"We study consensus processes on the complete graph of n nodes. Initially, each node supports one up to n different opinions. Nodes randomly and in parallel sample the opinions of constantly many nodes. Based on these samples, they use an update rule to change their own opinion. The goal is to reach consensus, a configuration where all nodes support the same opinion. We compare two well-known update rules: 2-Choices and 3-Majority. In the former, each node samples two nodes and adopts their opinion if they agree. In the latter, each node samples three nodes: If an opinion is supported by at least two samples the node adopts it, otherwise it randomly adopts one of the sampled opinions. Known results for these update rules focus on initial configurations with a limited number of colors (say n1/3), or typically assume a bias, where one opinion has a much larger support than any other. For such biased configurations, the time to reach consensus is roughly the same for 2-Choices and 3-Majority. Interestingly, we prove that this is no longer true for configurations with a large number of initial colors. In particular, we show that 3-Majority reaches consensus with high probability in O(n3/4 · log7/8 n) rounds, while 2-Choices can need Ω(n / log n) rounds. We thus get the first unconditional sublinear bound for 3-Majority and the first result separating the consensus time of these processes. Along the way, we develop a framework that allows a fine-grained comparison between consensus processes from a specific class. We believe that this framework might help to classify the performance of more consensus processes.","PeriodicalId":324970,"journal":{"name":"Proceedings of the ACM Symposium on Principles of Distributed Computing","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129543247","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":"Brief Announcement: Proust: A Design Space for Highly-Concurrent Transactional Data Structures","authors":"Thomas D. Dickerson, Paul Gazzillo, Eric Koskinen, M. Herlihy","doi":"10.1145/3087801.3087866","DOIUrl":"https://doi.org/10.1145/3087801.3087866","url":null,"abstract":"Most STM systems are poorly equipped to support libraries of concurrent data structures. One reason is that they typically detect conflicts by tracking transactions' read sets and write sets, an approach that often leads to false conflicts. A second is that existing data structures and libraries often need to be rewritten from scratch to support transactional conflict detection and rollback. This brief announcement introduces Proust, a framework for the design and implementation of transactional data structures. Proust is designed to maximize reuse of existing well-engineered libraries by providing transactional \"wrappers\" to make existing thread-safe concurrent data structures transactional. Proustian objects are also integrated with an underlying STM system, allowing them to take advantage of well-engineered STM conflict detection mechanisms. Proust generalizes and unifies prior approaches such as boosting and predication.","PeriodicalId":324970,"journal":{"name":"Proceedings of the ACM Symposium on Principles of Distributed Computing","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130854198","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":"Greedy Routing and the Algorithmic Small-World Phenomenon","authors":"K. Bringmann, Ralph Keusch, J. Lengler, Yannic Maus, A. R. Molla","doi":"10.1145/3087801.3087829","DOIUrl":"https://doi.org/10.1145/3087801.3087829","url":null,"abstract":"The algorithmic small-world phenomenon, empirically established by Milgram's letter forwarding experiments from the 60s, was theoretically explained by Kleinberg in 2000. However, from today's perspective his model has several severe shortcomings that limit the applicability to real-world networks. In order to give a more convincing explanation of the algorithmic small-world phenomenon, we study decentralized greedy routing in a more flexible random graph model (geometric inhomogeneous random graphs) which overcomes all previous shortcomings. Apart from exhibiting good properties in theory, it has also been extensively experimentally validated that this model reasonably captures real-world networks. In this model, the greedy routing protocol is purely distributed as each vertex only needs to know information about its direct neighbors. We prove that it succeeds with constant probability, and in case of success almost surely finds an almost shortest path of length Θ(log log n), where our bound is tight including the leading constant. Moreover, we study natural local patching methods which augment greedy routing by backtracking and which do not require any global knowledge. We show that such methods can ensure success probability 1 in an asymptotically tight number of steps. These results also address the question of Krioukov et al. whether there are efficient local routing protocols for the internet graph. There were promising experimental studies, but the question remained unsolved theoretically. Our results give for the first time a rigorous and analytical affirmative answer.","PeriodicalId":324970,"journal":{"name":"Proceedings of the ACM Symposium on Principles of Distributed Computing","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127257078","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":"Stateless Computation","authors":"D. Dolev, Michael Erdmann, Neil Lutz, Michael Schapira, A. Zair","doi":"10.1145/3087801.3087854","DOIUrl":"https://doi.org/10.1145/3087801.3087854","url":null,"abstract":"We present and explore a model of stateless and self-stabilizing distributed computation, inspired by real-world applications such as routing on today's Internet. Processors in our model do not have an internal state, but rather interact by repeatedly mapping incoming messages (\"labels\") to outgoing messages and output values. While seemingly too restrictive to be of interest, stateless computation encompasses both classical game-theoretic notions of strategic interaction and a broad range of practical applications (e.g., Internet protocols, circuits, diffusion of technologies in social networks). Our main technical contribution is a general impossibility result for stateless self-stabilization in our model, showing that even modest asynchrony (with wait times that are linear in the number of processors) can prevent a stateless protocol from reaching a stable global configuration. Furthermore, we present hardness results for verifying stateless self-stabilization. We also address several aspects of the computational power of stateless protocols. Most significantly, we show that short messages (of length that is logarithmic in the number of processors) yield substantial computational power, even on very poorly connected topologies.","PeriodicalId":324970,"journal":{"name":"Proceedings of the ACM Symposium on Principles of Distributed Computing","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128781632","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 Distributed (Delta + o(Delta))-Edge-Coloring, and Vertex-Coloring of Graphs with Bounded Diversity","authors":"Leonid Barenboim, Michael Elkin, Tzalik Maimon","doi":"10.1145/3087801.3087812","DOIUrl":"https://doi.org/10.1145/3087801.3087812","url":null,"abstract":"In the distributed message-passing setting a communication network is represented by a graph whose vertices represent processors that perform local computations and communicate over the edges of the graph. In the distributed edge-coloring problem the processors are required to assign colors to edges, such that all edges incident on the same vertex are assigned distinct colors. The previously-known deterministic algorithms for edge-coloring employed at least (2Δ - 1) colors, even though any graph admits an edge-coloring with Δ + 1 colors [36]. Moreover, the previously-known deterministic algorithms that employed at most O(Δ) colors required superlogarithmic time [3,6,7,17]. In the current paper we devise deterministic edge-coloring algorithms that employ only Δ + o(Δ) colors, for a very wide family of graphs. Specifically, as long as the arboricity a of the graph is a = O(Δ1 - ε), for a constant ε > 0, our algorithm computes such a coloring within polylogarithmic deterministic time. We also devise significantly improved deterministic edge-coloring algorithms for general graphs for a very wide range of parameters. Specifically, for any value κ in the range [4Δ, 2o(log Δ) ⋅ Δ], our κ-edge-coloring algorithm has smaller running time than the best previously-known κ-edge-coloring algorithms. Our algorithms are actually much more general, since edge-coloring is equivalent to vertex-coloring of line graphs. Our method is applicable to vertex-coloring of the family of graphs with bounded diversity that contains line graphs, line graphs of hypergraphs, and many other graphs. We significantly improve upon previous vertex-coloring of such graphs, and as an implication also obtain the improved edge-coloring algorithms for general graphs. Our results are obtained using a novel technique that connects vertices or edges in a certain way that reduces clique size. The resulting structures, which we call connectors, can be colored more efficiently than the original graph. Moreover, the color classes constitute simpler subgraphs that can be colored even more efficiently using appropriate connectors. We introduce several types of connectors that are useful for various scenarios. We believe that this technique is of independent interest.","PeriodicalId":324970,"journal":{"name":"Proceedings of the ACM Symposium on Principles of Distributed Computing","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115690391","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":"Optimal Distance Labeling Schemes for Trees","authors":"Ofer Freedman, Paweł Gawrychowski, Patrick K. Nicholson, O. Weimann","doi":"10.1145/3087801.3087804","DOIUrl":"https://doi.org/10.1145/3087801.3087804","url":null,"abstract":"Labeling schemes seek to assign a short label to each node in a network, so that a function on two nodes (such as distance or adjacency) can be computed by examining their labels alone. For the particular case of trees, following a long line of research, optimal bounds (up to low order terms) were recently obtained for adjacency labeling [FOCS '15], nearest common ancestor labeling [SODA '14], and ancestry labeling [SICOMP '06]. In this paper we obtain optimal bounds for distance labeling. We present labels of size 1/4log^2n+o(log^2n), matching (up to low order terms) the recent 1/4log^2n-Oh(log n) lower bound [ICALP '16]. Prior to our work, all distance labeling schemes for trees could be reinterpreted as universal trees. A tree T is said to be universal if any tree on $n$ nodes can be found as a subtree of T. A universal tree with |T| nodes implies a distance labeling scheme with label size log |T|. In 1981, Chung et al. proved that any distance labeling scheme based on universal trees requires labels of size 1/2log^2 n -log n cdot loglog n+Oh(log n). Our scheme is the first to break this lower bound, showing a separation between distance labeling and universal trees. The θ (log2 n) barrier for distance labeling in trees has led researchers to consider distances bounded by k. The size of such labels was shown to be log n+Oh(ksqrt{log n}) in [WADS '01], and then improved to log n+Oh(k^2(log(klog n)) in [SODA '03] and finally to log n+Oh(klog(klog(n/k))) in [PODC '07]. We show how to construct labels whose size is the minimum between log n+Oh(klog((log n)/k)) and Oh(log n cdot log(k/log n)). We complement this with almost tight lower bounds of log n+Omega(klog(log n / (klog k))) and Omega(log n cdot log(k/log n)). Finally, we consider (1+eps)-approximate distances. We show that the recent labeling scheme of [ICALP '16] can be easily modified to obtain an Oh(log(1/eps)cdot log n) upper bound and we prove a matching Omega(log(1/eps)cdot log n) lower bound.","PeriodicalId":324970,"journal":{"name":"Proceedings of the ACM Symposium on Principles of Distributed Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129246180","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}