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arXiv 2012.15800cs.DC
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一个使用对数时间和状态的稳定多数人口协议

A stable majority population protocol using logarithmic time and states

David Doty, Mahsa Eftekhari, Eric Severson

摘要:

我们研究人口协议,分布式计算模型适合建模良好混合的化学反应网络和其他物理系统中的代理人在成对的相互作用交换信息,但没有控制他们的时间表的互动伙伴。经过充分研究的“多数”问题是,在初始的$n$主体群体中,每个主体都有两个意见之一:$A$或$B$,确定是否有更多的$A$、更多的$B$或平局。*stable* 协议通过最终进入一个配置来解决这个问题,在该配置中,所有代理都同意$A$、$B$或$T$的正确共识决定,共识不能从该配置改变。我们描述了一个协议,解决了这个问题,使用$O(\log n)$状态($\log \log n + O(1)$位的内存)和最佳预期时间$O(\log n)$。已知状态数$O(\log n)$对于“输出主导”和“单调”的稳定协议类是最优的。这是我们的协议满足的两个自然约束,使其成为该类的状态最优。我们使用,并开发新的分析,一个关键的技术,称为“固定分辨率时钟”由于Gasieniec,Stachowiak和Uznanski,谁显示了多数协议使用$O(\log n)$时间和状态,有一个积极的错误概率。我们的协议是 * 非均匀 *:转移函数的值$\left \lceil {\log n} \right \rceil$编码在它。我们表明,该协议可以修改为均匀的,而增加的状态复杂度$Θ(\log n \log \log n)$。

英文摘要:

We study population protocols, a model of distributed computing appropriate for modeling well-mixed chemical reaction networks and other physical systems where agents exchange information in pairwise interactions, but have no control over their schedule of interaction partners. The well-studied *majority* problem is that of determining in an initial population of $n$ agents, each with one of two opinions $A$ or $B$, whether there are more $A$, more $B$, or a tie. A *stable* protocol solves this problem with probability 1 by eventually entering a configuration in which all agents agree on a correct consensus decision of $A$, $B$, or $T$, from which the consensus cannot change. We describe a protocol that solves this problem using $O(\log n)$ states ($\log \log n + O(1)$ bits of memory) and optimal expected time $O(\log n)$. The number of states $O(\log n)$ is known to be optimal for the class of stable protocols that are "output dominant" and "monotone". These are two natural constraints satisfied by our protocol, making it state-optimal for that class. We use, and develop novel analysis of, a key technique called a "fixed resolution clock" due to Gasieniec, Stachowiak, and Uznanski, who showed a majority protocol using $O(\log n)$ time and states that has a positive probability of error. Our protocol is *nonuniform*: the transition function has the value $\left \lceil {\log n} \right \rceil$ encoded in it. We show that the protocol can be modified to be uniform, while increasing the state complexity to $Θ(\log n \log \log n)$.

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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