LZD factorization: Simple and practical online grammar compression with variable-to-fixed encoding

Keisuke Goto, Hideo Bannai, Shunsuke Inenaga, Masayuki Takeda

研究成果: Chapter in Book/Report/Conference proceedingConference contribution

9 被引用数 (Scopus)

抄録

We propose a new variant of the LZ78 factorization which we call the LZ Double-factor factorization (LZD factorization). Each factor of the LZD factorization of a string is the concatenation of the two longest previous factors, while each factor of the LZ78 factorization is that of the longest previous factor and the following character. Interestingly, this simple modification drastically improves the compression ratio in practice. We propose two online algorithms to compute the LZD factorization in O(m(M +min(m, M) log σ)) time and O(m) space, or in O(N log σ) time and O(N) space, where m is the number of factors to output, M is the length of the longest factor(s), N is the length of the input string, and σ is the alphabet size. We also show two versions of our LZD factorization with variable-to-fixed encoding, and present online algorithms to compute these versions in O(N + min(m, 2L)(M + min(m, M, 2L) log σ)) time and O(min(2L, m)) space, where L is the bit-length of each fixed-length code word. The LZD factorization and its versions with variable-to fixed encoding are actually grammar-based compression, and our experiments show that our algorithms outperform the state-of-the-art online grammar-based compression algorithms on several data sets.

本文言語英語
ホスト出版物のタイトルCombinatorial Pattern Matching - 26th Annual Symposium, CPM 2015, Proceedings
編集者Ugo Vaccaro, Ely Porat, Ferdinando Cicalese
出版社Springer Verlag
ページ219-230
ページ数12
ISBN(印刷版)9783319199283
DOI
出版ステータス出版済み - 2015
イベント26th Annual Symposium on Combinatorial Pattern Matching, CPM 2015 - Ischia Island, イタリア
継続期間: 6 29 20157 1 2015

出版物シリーズ

名前Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
9133
ISSN(印刷版)0302-9743
ISSN(電子版)1611-3349

その他

その他26th Annual Symposium on Combinatorial Pattern Matching, CPM 2015
国/地域イタリア
CityIschia Island
Period6/29/157/1/15

All Science Journal Classification (ASJC) codes

  • 理論的コンピュータサイエンス
  • コンピュータ サイエンス(全般)

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