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arXiv 2101.01151cs.CC
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宽度为3的只读分支程序命中集的多项式时间构造

A polynomial-time construction of a hitting set for read-once branching programs of width 3

Jiří Šíma, Stanislav Žák

AI总结:

本文通过丰富性条件刻画宽度为3的只读分支程序的命中集,并利用几乎O(log n)-wise独立集给出显式多项式时间构造,接受概率大于5/6。

摘要:

近年来,针对受限分支程序构造伪随机或命中集生成器的兴趣日益增加,这源于去随机化空间有界计算这一基本问题。此类构造此前仅在宽度为2以及有界宽度的非常受限情形下已知。本文通过所谓的丰富性条件刻画了宽度为3的只读分支程序的命中集。具体而言,我们证明了此类集合能命中DNF和CNF的只读合取类(即弱丰富性)。此外,我们证明了任何丰富集扩展上所有汉明距离为3以内的字符串后,即为宽度为3的只读分支程序的命中集。然后,我们证明了任何几乎$O(\log n)$-wise独立集都满足丰富性条件。通过使用Alon等人(1992)提出的此类集合,我们的结果提供了宽度为3的只读分支程序命中集的显式多项式时间构造,其接受概率$\varepsilon>5/6$。我们在十多年前的会议上宣布了这一结果,当时仅包含证明草图,这推动了后续一系列关于受限只读分支程序伪随机生成器的研究。本文包含我们此前未发表的原始详细证明。

英文摘要:

Recently, an interest in constructing pseudorandom or hitting set generators for restricted branching programs has increased, which is motivated by the fundamental issue of derandomizing space-bounded computations. Such constructions have been known only in the case of width 2 and in very restricted cases of bounded width. In this paper, we characterize the hitting sets for read-once branching programs of width 3 by a so-called richness condition. Namely, we show that such sets hit the class of read-once conjunctions of DNF and CNF (i.e. the weak richness). Moreover, we prove that any rich set extended with all strings within Hamming distance of 3 is a hitting set for read-once branching programs of width 3. Then, we show that any almost $O(\log n)$-wise independent set satisfies the richness condition. By using such a set due to Alon et al. (1992) our result provides an explicit polynomial-time construction of a hitting set for read-once branching programs of width 3 with acceptance probability $\varepsilon>5/6$. We announced this result at conferences more than ten years ago, including only proof sketches, which motivated a number of subsequent results on pseudorandom generators for restricted read-once branching programs. This paper contains our original detailed proof that has not been published yet.

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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