arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1811.03337cs.DCcs.DS
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近线性时间中分布精确加权最短路

Distributed Exact Weighted All-Pairs Shortest Paths in Near-Linear Time

Aaron Bernstein, Danupon Nanongkai

摘要:

在{ \em distributed all-pairs shortest paths}问题(APSP)中,加权无向分布式网络(CONGEST模型)中的每个节点都需要使用最少的通信轮数(通常称为{ \em时间复杂度})来知道与其他节点的距离。该问题允许$(1+o(1))$ -近似$\tildeΘ(n)$ -时间算法和接近紧的$\tilde Ω(n)$下界[Nanongkai,STOC'14; Lenzen和Patt-Shamir PODC'15] \footnote{$\tilde Θ$, $\tilde O$ and $\tilde Ω$ hide polylogarithmic factors. Note that the lower bounds also hold even in the unweighted case and in the weighted case with polynomial approximation ratios~\cite{LenzenP_podc13,HolzerW12,PelegRT12,Nanongkai-STOC14}.}。对于确切的情况,Elkin [STOC'17]提出了一个$O(n^{5/3} \log^{2/3} n)$时间界限,后来改进为$\tilde O(n^{5/4})$ [Huang,Nanongkai,Saranurak FOCS'17]。研究表明,任何超线性下限(在$n$中)都需要一种新的技术[Censor-Hillel、Khoury、Paz、DISC'17],但除此之外,是否存在用于精确情况的$\tilde O(n)$时间算法(该算法将匹配最佳可能的近似算法)仍然是一个广泛的开放问题。本文解决了这个问题积极:我们提出了一个随机(拉斯维加斯)的$\tilde O(n)$时间算法,匹配的下限多对数因子。与前面的$\tilde O(n^{5/4})$界一样,我们的结果适用于边权重为零(甚至为负)的有向图。除了改进的运行时间之外,我们的算法在比先前的$\tilde O(n^{5/4})$界限所要求的更一般的设置中工作;在我们的设置中(i)通信仅沿着边缘方向(与双向相反),以及(ii)边缘权重是任意的(与{1,2,. poly(n)})。...

英文摘要:

In the {\em distributed all-pairs shortest paths} problem (APSP), every node in the weighted undirected distributed network (the CONGEST model) needs to know the distance from every other node using least number of communication rounds (typically called {\em time complexity}). The problem admits $(1+o(1))$-approximation $\tildeΘ(n)$-time algorithm and a nearly-tight $\tilde Ω(n)$ lower bound [Nanongkai, STOC'14; Lenzen and Patt-Shamir PODC'15]\footnote{$\tilde Θ$, $\tilde O$ and $\tilde Ω$ hide polylogarithmic factors. Note that the lower bounds also hold even in the unweighted case and in the weighted case with polynomial approximation ratios~\cite{LenzenP_podc13,HolzerW12,PelegRT12,Nanongkai-STOC14}.}. For the exact case, Elkin [STOC'17] presented an $O(n^{5/3} \log^{2/3} n)$ time bound, which was later improved to $\tilde O(n^{5/4})$ [Huang, Nanongkai, Saranurak FOCS'17]. It was shown that any super-linear lower bound (in $n$) requires a new technique [Censor-Hillel, Khoury, Paz, DISC'17], but otherwise it remained widely open whether there exists a $\tilde O(n)$-time algorithm for the exact case, which would match the best possible approximation algorithm. This paper resolves this question positively: we present a randomized (Las Vegas) $\tilde O(n)$-time algorithm, matching the lower bound up to polylogarithmic factors. Like the previous $\tilde O(n^{5/4})$ bound, our result works for directed graphs with zero (and even negative) edge weights. In addition to the improved running time, our algorithm works in a more general setting than that required by the previous $\tilde O(n^{5/4})$ bound; in our setting (i) the communication is only along edge directions (as opposed to bidirectional), and (ii) edge weights are arbitrary (as opposed to integers in {1, 2, ... poly(n)}). ...

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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