Context-Based Algorithms for the List-Update Problem under Alternative Cost Models

Abstract

The List-Update Problem is a well studied online problem with direct applications in data compression. Although the model proposed by Sleator & Tarjan has become the standard in the field for the problem, its applicability in some domains, and in particular for compression purposes, has been questioned. In this paper, we focus on two alternative models for the problem that arguably have more practical significance than the standard model. We provide new algorithms for these models, and show that these algorithms outperform all classical algorithms under the discussed models. This is done via an empirical study of the performance of these algorithms on the reference data set for the list-update problem. The presented algorithms make use of the context-based strategies for compression, which have not been considered before in the context of the list-update problem and lead to improved compression algorithms. In addition, we study the adaptability of these algorithms to different measures of locality of reference and compressibility.