论文标题

转移到前或中间(MFM)在线列表更新算法的竞争分析

Competitive Analysis of Move-to-Front-or-Middle (MFM) Online List Update Algorithm

论文作者

Baisakh, Mohanty, Rakesh

论文摘要

对当前和过去输入的了解,对有效算法的设计和分析是计算机科学中的一个非平凡且具有挑战性的研究领域。在许多实际应用中,在任何时间的情况下,算法都无法使用未来的输入。因此,算法必须基于一系列秩序和即时的输入序列做出决策。这种算法称为在线算法。为了衡量在线算法的性能,文献中已广泛使用了一种称为竞争分析的标准度量。列表更新问题是自过去几十年以来在线算法领域的一个经过深入研究的研究问题。广泛使用的确定性在线列表更新算法之一是转移到前(MTF)算法,该算法已被证明是2竞争力,在实践现实生活中的最佳性能。在本文中,我们通过解决Albers提出的一个空旷的问题之一,即是否可以使用动态离线算法来寻找在线算法的竞争力中,使用竞争分析分析了转移到前或中间的算法(MFM)算法?通过使用卡尔加里语料库和坎特伯雷语料库数据集对实验研究并观察到移动前或中间(MFM)的性能优于MTF算法。但是,在MFM算法的竞争比率上找到下限和上限是有趣的,而且具有挑战性。我们首次尝试寻找MFM算法的竞争力。我们的新结果表明,相对于静态最佳离线算法,MFM不是2个竞争力,而相对于动态最佳离线算法,它具有2竞争力。我们的新理论结果可能会通过表征竞争性和非竞争性确定性在线算法的结构来为在线列表更新问题中的研究开辟一个新的研究方向。

The design and analysis of efficient algorithms with the knowledge of current and past inputs is a non-trivial and challenging research area in computer science. In many practical applications the future inputs are not available to the algorithm at any instance of time. So the algorithm has to make decisions based on a sequence of inputs that are in order and on the fly. Such algorithms are known as online algorithms. For measuring the performance of online algorithms, a standard measure, known as competitive analysis, has been extensively used in the literature. List update problem is a well studied research problem in the area of online algorithms since last few decades. One of the widely used deterministic online list update algorithm is the Move-To-Front (MTF) algorithm, which has been shown to be 2-competitive with best performance in practical real life inputs. In this paper we analyse the Move-to-Front-or-Middle (MFM) algorithm using competitive analysis by addressing one of an open question raised by Albers that whether dynamic offline algorithm can be used in finding the competitiveness of an online algorithm? Move-To-Front-or-Middle (MFM) was experimentally studied and observed to be performing better than MTF algorithm by using the Calgary Corpus and Canterbury Corpus data set. However, it is interesting and challenging to find the lower bound and upper bound on the competitive ratio of MFM algorithm. We make a first attempt to find the competitiveness of MFM algorithm. Our new results show that MFM is not 2-competitive with respect to static optimum offline algorithm, whereas it is 2-competitive with respect to dynamic optimum offline algorithm. Our new theoretical results may open up a new direction of research in the online list update problem by characterising the structure of competitive and non competitive deterministic online algorithms.

扫码加入交流群

加入微信交流群

微信交流群二维码

扫码加入学术交流群,获取更多资源