arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2107.01673cs.DS
收藏

求最大r-SAT的次线性空间近似算法

Sublinear-Space Approximation Algorithms for Max r-SAT

Arindam Biswas, Venkatesh Raman

摘要:

在Max $r$ -SAT问题中,输入是一个带有$n$变量的CNF公式,其中每个子句是至多$r$文字的析取。我们的目标是计算一个分配,满足尽可能多的条款。虽然对于这个问题有大量的多项式时间近似算法,但我们采用空间复杂度的观点[Biswas et al.,2021],并设计子线性空间近似算法的问题。我们表明,经典的算法[Lieberherr和Specker,JACM 1981]可以实现运行在$n^{O(1)}$时间,而使用$(\log{n})$位的空间。更高级的算法使用线性或半定规划,并且似乎更难在次线性空间中执行。我们表明,一个更近的算法与近似比$\sqrt{2}/2$ [周等人,FOCS 2020]是为流模型设计的,可以使用$O(r \log{n})$空间位来实现$n^{O(r)}$的实时运行。虽然已知的流算法的问题近似最优值和使用随机化,我们的算法是确定性的,可以输出近似最优的分配在次线性空间。对于最大$r$与平面关联图的实例,我们设计了一个因子- $(1 - ε)$近似方案,该方案计算时间$n^{O(r / ε)}$中的分配,并使用空间的$\max\{\sqrt{n} \log{n}, (r / ε) \log^2{n}\}$位。

英文摘要:

In the Max $r$-SAT problem, the input is a CNF formula with $n$ variables where each clause is a disjunction of at most $r$ literals. The objective is to compute an assignment which satisfies as many of the clauses as possible. While there are a large number of polynomial-time approximation algorithms for this problem, we take the viewpoint of space complexity following [Biswas et al., Algorithmica 2021] and design sublinear-space approximation algorithms for the problem. We show that the classical algorithm of [Lieberherr and Specker, JACM 1981] can be implemented to run in $n^{O(1)}$ time while using $(\log{n})$ bits of space. The more advanced algorithms use linear or semi-definite programming, and seem harder to carry out in sublinear space. We show that a more recent algorithm with approximation ratio $\sqrt{2}/2$ [Chou et al., FOCS 2020], designed for the streaming model, can be implemented to run in time $n^{O(r)}$ using $O(r \log{n})$ bits of space. While known streaming algorithms for the problem approximate optimum values and use randomization, our algorithms are deterministic and can output the approximately optimal assignments in sublinear space. For instances of Max $r$-SAT with planar incidence graphs, we devise a factor-$(1 - ε)$ approximation scheme which computes assignments in time $n^{O(r / ε)}$ and uses $\max\{\sqrt{n} \log{n}, (r / ε) \log^2{n}\}$ bits of space.

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。

↑