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arXiv 2007.06098cs.DScs.DM
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图的连通性和基于线性和OR的单元素恢复

Graph Connectivity and Single Element Recovery via Linear and OR Queries

Sepehr Assadi, Deeparnab Chakrabarty, Sanjeev Khanna

摘要:

我们研究了在两种基本查询模型下,在无向$n$ -顶点多重图中寻找生成森林的问题。一种是线性查询模型,它是对由边引起的关联向量的线性测量;另一种是较弱的OR查询模型,它只揭示给定的似然边子集是否为空。在我们的研究的核心在于一个基本的问题,我们称之为{ \em单元素恢复}问题:给定一个非负的实向量$x$在$N$维,返回一个单一的元素$x_j > 0$的支持。搜索可以在回合中进行,我们的目标是了解查询复杂性和解决这些问题所需的适应性回合之间的权衡,对于确定性算法和随机算法。这些问题与多个领域有联系和分支,例如草图绘制,流,图形重建和压缩传感。我们的主要结果是:* 对于单个元素恢复问题,很容易获得确定性的$r$ -轮算法,该算法使$(N^{1/r}-1)$ -每轮查询。我们证明,这是紧:任何$r$轮确定性算法必须使$\geq (N^{1/r} - 1)$线性查询在一些回合。相反,已知存在成功率为99%的$1$ -回合$O(\log^2 N)$ -查询随机化算法. * 我们设计了一个确定性的$O(r)$ -轮,$\tilde{O}(n^{1+1/r})$ -或查询算法图的连通性.我们补充这一点与$\tildeΩ(n^{1 + 1/r})$下限的任何$r$轮确定性算法的OR模型。* 我们设计了一个随机的$2$轮算法的图连通性问题,使$\tilde{O}(n)$ -或查询。相反,我们证明了任何$1$轮算法(可能是随机的)需要$\tildeΩ(n^2)$ -OR查询。

英文摘要:

We study the problem of finding a spanning forest in an undirected, $n$-vertex multi-graph under two basic query models. One is the Linear query model which are linear measurements on the incidence vector induced by the edges; the other is the weaker OR query model which only reveals whether a given subset of plausible edges is empty or not. At the heart of our study lies a fundamental problem which we call the {\em single element recovery} problem: given a non-negative real vector $x$ in $N$ dimension, return a single element $x_j > 0$ from the support. Queries can be made in rounds, and our goals is to understand the trade-offs between the query complexity and the rounds of adaptivity needed to solve these problems, for both deterministic and randomized algorithms. These questions have connections and ramifications to multiple areas such as sketching, streaming, graph reconstruction, and compressed sensing. Our main results are: * For the single element recovery problem, it is easy to obtain a deterministic, $r$-round algorithm which makes $(N^{1/r}-1)$-queries per-round. We prove that this is tight: any $r$-round deterministic algorithm must make $\geq (N^{1/r} - 1)$ linear queries in some round. In contrast, a $1$-round $O(\log^2 N)$-query randomized algorithm which succeeds 99% of the time is known to exist. * We design a deterministic $O(r)$-round, $\tilde{O}(n^{1+1/r})$-OR query algorithm for graph connectivity. We complement this with an $\tildeΩ(n^{1 + 1/r})$-lower bound for any $r$-round deterministic algorithm in the OR-model. * We design a randomized, $2$-round algorithm for the graph connectivity problem which makes $\tilde{O}(n)$-OR queries. In contrast, we prove that any $1$-round algorithm (possibly randomized) requires $\tildeΩ(n^2)$-OR queries.

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