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arXiv 1402.3609cs.DS
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稀疏生成图的局部算法

Local Algorithms for Sparse Spanning Graphs

Reut Levi, Dana Ron, Ronitt Rubinfeld

摘要:

构造图的生成树是图论中最基本的任务之一。我们认为这个问题的一个轻松的版本中设置的本地算法。松弛是指所构造的子图是一个稀疏生成子图,它最多包含$(1+ε)n$条边(其中$n$是顶点数,$ε$是给定的近似/稀疏参数).在局部设置中,目标是快速确定给定边$e$是否属于这样的子图,而不构造整个子图,而是通过检查(查询)$e$的局部邻域。挑战在于保持一致性。也就是说,根据相同的生成子图提供关于不同边的答案。我们首先表明,对于一般的有界度图,任何这样的算法的查询复杂度必须是$Ω(\sqrt{n})$。这个下限适用于具有高度扩展的常度图。接下来,我们设计了一个算法(有界度)图与高扩展,获得一个结果,大致匹配的下限。然后,我们转向研究排除固定子图(因此是非扩张的)的图。我们设计了一个算法,这样的图,这可能有一个无界的最大程度。该算法的查询复杂度为$poly(1/ε, h)$(独立于$n$和最大度),其中$h$为排除子图中的顶点数。虽然我们的两个算法是为非常不同类型的图设计的(并且具有非常不同的复杂性),但在高层次上有几个相似之处,我们强调了相似之处和差异。

英文摘要:

Constructing a spanning tree of a graph is one of the most basic tasks in graph theory. We consider a relaxed version of this problem in the setting of local algorithms. The relaxation is that the constructed subgraph is a sparse spanning subgraph containing at most $(1+ε)n$ edges (where $n$ is the number of vertices and $ε$ is a given approximation/sparsity parameter). In the local setting, the goal is to quickly determine whether a given edge $e$ belongs to such a subgraph, without constructing the whole subgraph, but rather by inspecting (querying) the local neighborhood of $e$. The challenge is to maintain consistency. That is, to provide answers concerning different edges according to the same spanning subgraph. We first show that for general bounded-degree graphs, the query complexity of any such algorithm must be $Ω(\sqrt{n})$. This lower bound holds for constant-degree graphs that have high expansion. Next we design an algorithm for (bounded-degree) graphs with high expansion, obtaining a result that roughly matches the lower bound. We then turn to study graphs that exclude a fixed minor (and are hence non-expanding). We design an algorithm for such graphs, which may have an unbounded maximum degree. The query complexity of this algorithm is $poly(1/ε, h)$ (independent of $n$ and the maximum degree), where $h$ is the number of vertices in the excluded minor. Though our two algorithms are designed for very different types of graphs (and have very different complexities), on a high-level there are several similarities, and we highlight both the similarities and the differences.

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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