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arXiv 2004.08432cs.DS
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基于自适应Advertisement的全动态图稀疏器

Fully-Dynamic Graph Sparsifiers Against an Adaptive Adversary

Aaron Bernstein, Jan van den Brand, Maximilian Probst Gutenberg, Danupon Nanongkai, Thatchaphol Saranurak, Aaron Sidford, He Sun

摘要:

设计动态图算法对抗自适应攻击是动态图算法领域的一个主要目标。虽然有一些这样的算法是已知的生成树,匹配,和单源最短路径,很少有人知道一个重要的原语,如图稀疏。挑战在于如何近似地保留关于图的如此多的信息(例如,所有对距离和所有切割),而不向自适应对手揭示算法的潜在随机性。在本文中,我们提出了第一个非平凡的有效的自适应算法,以保持sparisifers和削减sparisifers。这些算法反过来又意味着对其他问题的现有算法的改进。我们的第一个算法在polylog $(n)$分摊更新时间中维护一个大小为$\tilde O(n)$的polylog $(n)$ -表。第二种算法在$\tilde O(n^{1/k})$分摊更新时间内为任何$k\ge1$维护大小为$\tilde O(n)$的$O(k)$近似切割稀疏因子,当$k=\log(n)$时,$k\ge1$是polylog $(n)$时间。第三种算法在polylog $(n)$分摊更新时间中保持polylog $(n)$近似谱稀疏因子。两种算法的摊销更新时间可以通过支付一些次多项式因子使最坏情况下。在我们的结果之前,存在针对不经意对手的接近最优的算法(例如Baswana等人[TALG'12]和Abraham等人[FOCS'16]),但是唯一的非平凡自适应动态算法需要$O(n)$分摊更新时间来分别维持大小为$O(n^{1+1/2})$和$O(n^{1+1/3})$的$3$ -和$5$ -队列[Ausiello等人ESA'05]。我们的研究结果是基于两个新的技术。第一种技术,是一个通用的黑盒约简,它允许我们假设图只经历边删除,更重要的是,它仍然是一个几乎均匀度的扩展器。第二种技术我们称之为主动回应。[...]

英文摘要:

Designing dynamic graph algorithms against an adaptive adversary is a major goal in the field of dynamic graph algorithms. While a few such algorithms are known for spanning trees, matchings, and single-source shortest paths, very little was known for an important primitive like graph sparsifiers. The challenge is how to approximately preserve so much information about the graph (e.g., all-pairs distances and all cuts) without revealing the algorithms' underlying randomness to the adaptive adversary. In this paper we present the first non-trivial efficient adaptive algorithms for maintaining spanners and cut sparisifers. These algorithms in turn imply improvements over existing algorithms for other problems. Our first algorithm maintains a polylog$(n)$-spanner of size $\tilde O(n)$ in polylog$(n)$ amortized update time. The second algorithm maintains an $O(k)$-approximate cut sparsifier of size $\tilde O(n)$ in $\tilde O(n^{1/k})$ amortized update time, for any $k\ge1$, which is polylog$(n)$ time when $k=\log(n)$. The third algorithm maintains a polylog$(n)$-approximate spectral sparsifier in polylog$(n)$ amortized update time. The amortized update time of both algorithms can be made worst-case by paying some sub-polynomial factors. Prior to our result, there were near-optimal algorithms against oblivious adversaries (e.g. Baswana et al. [TALG'12] and Abraham et al. [FOCS'16]), but the only non-trivial adaptive dynamic algorithm requires $O(n)$ amortized update time to maintain $3$- and $5$-spanner of size $O(n^{1+1/2})$ and $O(n^{1+1/3})$, respectively [Ausiello et al. ESA'05]. Our results are based on two novel techniques. The first technique, is a generic black-box reduction that allows us to assume that the graph undergoes only edge deletions and, more importantly, remains an expander with almost-uniform degree. The second technique we call proactive resampling. [...]

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