arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2102.11360cs.DScs.DMmath.CO
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部分最优边容错生成器

Partially Optimal Edge Fault-Tolerant Spanners

Greg Bodwin, Michael Dinitz, Caleb Robelle

摘要:

最近的工作已经确定,对于每个正整数$k$,每个$n$ -节点图在$O(f^{1-1/k} n^{1+1/k})$边上都有一个$(2k-1)$ -节点,它对$f$边或顶点故障是有弹性的.对于顶点故障,这个界是紧的。然而,边缘故障的情况并没有得到很好的理解:一般$k$的最佳已知下限是$Ω(f^{\frac12 - \frac{1}{2k}} n^{1+1/k} +fn)$。我们的主要结果是接近这个差距与改进的上限,从而分离的情况下,边缘和顶点故障。对于奇数$k$,我们的新上界是$O_k(f^{\frac12 - \frac{1}{2k}} n^{1+1/k} + fn)$,它紧到隐藏的$poly(k)$因子。对于偶数$k$,我们的新上界是$O_k(f^{1/2} n^{1+1/k} +fn)$,这留下了$poly(k) f^{1/(2k)}$的间隙。我们的证明是一个分析的容错贪婪算法,这需要指数时间,但我们也表明,有一个多项式时间算法,创建边缘容错spectrum,只有$k$的因素更大。

英文摘要:

Recent work has established that, for every positive integer $k$, every $n$-node graph has a $(2k-1)$-spanner on $O(f^{1-1/k} n^{1+1/k})$ edges that is resilient to $f$ edge or vertex faults. For vertex faults, this bound is tight. However, the case of edge faults is not as well understood: the best known lower bound for general $k$ is $Ω(f^{\frac12 - \frac{1}{2k}} n^{1+1/k} +fn)$. Our main result is to nearly close this gap with an improved upper bound, thus separating the cases of edge and vertex faults. For odd $k$, our new upper bound is $O_k(f^{\frac12 - \frac{1}{2k}} n^{1+1/k} + fn)$, which is tight up to hidden $poly(k)$ factors. For even $k$, our new upper bound is $O_k(f^{1/2} n^{1+1/k} +fn)$, which leaves a gap of $poly(k) f^{1/(2k)}$. Our proof is an analysis of the fault-tolerant greedy algorithm, which requires exponential time, but we also show that there is a polynomial-time algorithm which creates edge fault tolerant spanners that are larger only by factors of $k$.

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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