论文标题

在高度动态的网络中查找子图

Finding Subgraphs in Highly Dynamic Networks

论文作者

Censor-Hillel, Keren, Kolobov, Victor I., Schwartzman, Gregory

论文摘要

在本文中,我们考虑了在高度动态的分布式网络中查找子图的基本问题 - 允许每轮插入 /删除任意数量的链接。我们表明,$ k $ -clique会员资格列表(对于任何$ k \ geq 3 $),4周期清单和5周期清单的问题也可以在$ O(1)$(1)$ - 摊销的圆形复杂性中确定性解决,即使是有限的对数大小的消息。 为了实现$ k $ -clique会员列表,我们引入了非常有用的组合结构,我们将其命名为可靠的$ 2 $ -HOP社区。这是节点的2跳社区的一个子集,我们证明它可以在$ O(1)$ - 摊销的回合中维持在高度动态的网络中。我们还表明,保持节点的实际2跳社区需要接近线性摊销时间,这表明我们的定义是必要的。对于$ 4 $循环和$ 5 $循环清单,我们需要在Hop距离3中的边缘,为此我们类似地定义了稳健的$ 3 $ -HOP社区,并证明它可以在$ O(1)$ amortized的回合中维持在高度动态的网络中。 我们以几个不可能的结果来补充上述内容。我们表明,除$ k $ clique以外,$ k \ geq 3 $节点上任何其他图的会员列表几乎需要线性数量的摊销通信回合。我们还表明,$ k \ geq 6 $的$ k $循环清单需要$ω(\ sqrt {n} / \ log n)$摊销的回合。与我们的上限结合在一起,在这个高度动态的环境中绘制了超快速图查找算法的复杂性景观的详细图片。

In this paper we consider the fundamental problem of finding subgraphs in highly dynamic distributed networks - networks which allow an arbitrary number of links to be inserted / deleted per round. We show that the problems of $k$-clique membership listing (for any $k\geq 3$), 4-cycle listing and 5-cycle listing can be deterministically solved in $O(1)$-amortized round complexity, even with limited logarithmic-sized messages. To achieve $k$-clique membership listing we introduce a very useful combinatorial structure which we name the robust $2$-hop neighborhood. This is a subset of the 2-hop neighborhood of a node, and we prove that it can be maintained in highly dynamic networks in $O(1)$-amortized rounds. We also show that maintaining the actual 2-hop neighborhood of a node requires near linear amortized time, showing the necessity of our definition. For $4$-cycle and $5$-cycle listing, we need edges within hop distance 3, for which we similarly define the robust $3$-hop neighborhood and prove it can be maintained in highly dynamic networks in $O(1)$-amortized rounds. We complement the above with several impossibility results. We show that membership listing of any other graph on $k\geq 3$ nodes except $k$-clique requires an almost linear number of amortized communication rounds. We also show that $k$-cycle listing for $k\geq 6$ requires $Ω(\sqrt{n} / \log n)$ amortized rounds. This, combined with our upper bounds, paints a detailed picture of the complexity landscape for ultra fast graph finding algorithms in this highly dynamic environment.

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