Analysis of Lempel-Ziv'78 for Markov Sources

P. Jacquet,W. Szpankowski

Published 2020 in International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms

ABSTRACT

9 Lempel-Ziv’78 is one of the most popular data compression algorithms. Over the last few decades 10 fascinating properties of LZ’78 were uncovered. Among others, in 1995 we settled the Ziv conjecture 11 by proving that for a memoryless source the number of LZ’78 phrases satisfies the Central Limit 12 Theorem (CLT). Since then the quest commenced to extend it to Markov sources. However, despite 13 several attempts this problem is still open. The 1995 proof of the Ziv conjecture was based on two 14 models: In the DST-model, the associated digital search tree (DST) is built over m independent 15 strings. In the LZ-model a single string of length n is partitioned into variable length phrases such 16 that the next phrase is not seen in the past as a phrase. The Ziv conjecture for memoryless source 17 was settled by proving that both DST-model and the LZ-model are asymptotically equivalent. The 18 main result of this paper shows that this is not the case for the LZ78 algorithm over Markov sources. 19 In addition, we develop here a large deviation for the number of phrases in the LZ78 and give a 20 precise asymptotic expression for the redundancy which is the excess of LZ78 code over the entropy 21 of the source. We establish these findings using a combination of combinatorial and analytic tools. 22 In particular, to handle the strong dependency between Markov phrases, we introduce and precisely 23 analyze the so called tail symbol which is the first symbol of the next phrase in the LZ’78 parsing. 24

PUBLICATION RECORD

  • Publication year

    2020

  • Venue

    International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms

  • Publication date

    Unknown publication date

  • Fields of study

    Mathematics, Computer Science

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    Open on Semantic Scholar

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    Semantic Scholar

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