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arXiv 2101.05032cs.DS
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不确定性问题的并行循环竞争算法

Round-Competitive Algorithms for Uncertainty Problems with Parallel Queries

Thomas Erlebach, Michael Hoffmann, Murilo S. de Lima

摘要:

不确定性计算领域考虑的是一些关于输入元素的信息是不确定的,但可以通过查询获得的问题。例如,代替元素的权重,我们可以给出一个保证包含权重的区间,并且可以执行查询以揭示权重。虽然以前的工作已经考虑了模型,查询被要求顺序(自适应模型)或一次(非自适应模型),目标是最小化的查询,需要解决给定的问题,我们提出并研究了一个新的模型,$k$查询可以并行在每一轮,目标是尽量减少查询轮数。我们使用竞争分析,并提出了上限和下限的查询轮数所需的任何算法的查询轮数的最佳数量相比。给定一组不确定元素和该集合的$m$子集族,我们提出了一种算法,用于确定每个子集的最小值,该算法对于每个$0<\varepsilon<1$最多需要$(2+\varepsilon) \cdot \mathrm{opt}_k+\mathrm{O}\left(\frac{1}{\varepsilon} \cdot \lg m\right)$轮,其中$\mathrm{opt}_k$是最佳轮数,以及几乎匹配的下限。对于确定不确定元素集合中的第$i$个最小值并识别所有具有该值的元素的问题,我们给出了一个$2$轮竞争算法.我们还表明,家庭的不确定元素的集合排序的问题承认一个$2$轮竞争算法,这是最好的可能。

英文摘要:

The area of computing with uncertainty considers problems where some information about the input elements is uncertain, but can be obtained using queries. For example, instead of the weight of an element, we may be given an interval that is guaranteed to contain the weight, and a query can be performed to reveal the weight. While previous work has considered models where queries are asked either sequentially (adaptive model) or all at once (non-adaptive model), and the goal is to minimize the number of queries that are needed to solve the given problem, we propose and study a new model where $k$ queries can be made in parallel in each round, and the goal is to minimize the number of query rounds. We use competitive analysis and present upper and lower bounds on the number of query rounds required by any algorithm in comparison with the optimal number of query rounds. Given a set of uncertain elements and a family of $m$ subsets of that set, we present an algorithm for determining the value of the minimum of each of the subsets that requires at most $(2+\varepsilon) \cdot \mathrm{opt}_k+\mathrm{O}\left(\frac{1}{\varepsilon} \cdot \lg m\right)$ rounds for every $0<\varepsilon<1$, where $\mathrm{opt}_k$ is the optimal number of rounds, as well as nearly matching lower bounds. For the problem of determining the $i$-th smallest value and identifying all elements with that value in a set of uncertain elements, we give a $2$-round-competitive algorithm. We also show that the problem of sorting a family of sets of uncertain elements admits a $2$-round-competitive algorithm and this is the best possible.

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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