oblivious 重采样预言机与 Lopsided Lovász Local Lemma 的并行算法
Oblivious resampling oracles and parallel algorithms for the Lopsided Lovasz Local Lemma
AI总结:
本文提出重采样预言机的 oblivious 性质,据此实现统一的并行 LLLL 算法,首次给出彩虹完美匹配和彩虹哈密顿圈的 RNC 算法,并构建了相应的顺序与交换重采样预言机。
摘要:
Lovász Local Lemma (LLL) 是一个概率工具,它表明:如果概率空间中的一组“坏”事件 $\mathcal B$ 不太可能发生且相互依赖程度不高,那么存在正概率使得 $\mathcal B$ 中没有坏事件发生。Moser & Tardos (2010) 给出了顺序和并行算法,将变量赋值 LLL 的大多数应用转化为高效算法。Harvey & Vondrák (2015) 基于“重采样预言机”的框架将其推广到满足 Lopsided Lovász Local Lemma (LLLL) 的其他概率空间的一般顺序算法。\n我们描述了一个新的结构性质,该性质对所有已知的重采样预言机都成立,我们称之为“obliviousness”(无意识性)。本质上,它意味着两个坏事件 $B, B'$ 之间的相互作用仅取决于用于重采样 $B$ 的随机性,而不取决于 $B$ 内部的具体状态。\n这一性质有两个主要后果。首先,结合 Kolmogorov (2016) 的框架,它是实现统一的并行 LLLL 算法的关键,该算法比之前针对变量赋值 LLLL 算法的 Harris (2016) 和针对排列的 Harris & Srinivasan (2014) 的问题特定算法更快。这给出了 $K_n$ 的彩虹完美匹配和彩虹哈密顿圈的首次 RNC 算法。\n其次,这一性质允许我们从相对简单的“原子”事件构建 LLLL 概率空间。这提供了完整 $s$-均匀超图 $K_n^{(s)}$ 上彩虹完美匹配的第一个顺序重采样预言机,以及 $K_n$ 的哈密顿圈的第一个交换重采样预言机。
英文摘要:
The Lovász Local Lemma (LLL) is a probabilistic tool which shows that, if a collection of "bad" events $\mathcal B$ in a probability space are not too likely and not too interdependent, then there is a positive probability that no bad-events in $\mathcal B$ occur. Moser & Tardos (2010) gave sequential and parallel algorithms which transformed most applications of the variable-assignment LLL into efficient algorithms. A framework of Harvey & Vondrák (2015) based on "resampling oracles" extended this to general sequential algorithms for other probability spaces satisfying the Lopsided Lovász Local Lemma (LLLL). We describe a new structural property which holds for all known resampling oracles, which we call "obliviousness." Essentially, it means that the interaction between two bad-events $B, B'$ depends only on the randomness used to resample $B$, and not the precise state within $B$ itself. This property has two major consequences. First, combined with a framework of Kolmogorov (2016), it is the key to achieving a unified parallel LLLL algorithm, which is faster than previous, problem-specific algorithms of Harris (2016) for the variable-assignment LLLL algorithm and of Harris \& Srinivasan (2014) for permutations. This gives the first RNC algorithms for rainbow perfect matchings and rainbow hamiltonian cycles of $K_n$. Second, this property allows us to build LLLL probability spaces out of relatively simple "atomic" events. This provides the first sequential resampling oracle for rainbow perfect matchings on the complete $s$-uniform hypergraph $K_n^{(s)}$, and the first commutative resampling oracle for hamiltonian cycles of $K_n$.
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