Dictionary-Symbolwise Flexible Parsing

Maxime Crochemore (1, 2) , Laura Giambruno (3) , Alessio Langiu (3) , Filippo Mignosi (3) , Antonio Restivo (3)

1 Informatics
2 LIGM - Laboratoire d'Informatique Gaspard-Monge
3 Dipartimento di Matematica e Applicazioni [Palermo]

Linear time optimal parsing algorithms are very rare in the dictionary based branch of the data compression theory. The most recent is the Flexible Parsing algorithm of Mathias and Shainalp that works when the dictionary is prefix closed and the encoding of dictionary pointers has a constant cost. We present the Dictionary-Symbolwise Flexible Parsing algorithm that is optimal for prefix-closed dictionaries and any symbolwise compressor under some natural hypothesis. In the case of LZ78-alike algorithms with variable costs and any, linear as usual, symbolwise compressor it can be implemented in linear time. In the case of LZ77-alike dictionaries and any symbolwise compressor it can be implemented in O(n log(n)) time. We further present some experimental results that show the effectiveness of the dictionary-symbolwise approach.

Domaines: Algorithme et structure de données [cs.DS]

Maxime Crochemore, Laura Giambruno, Alessio Langiu, Filippo Mignosi, Antonio Restivo. Dictionary-Symbolwise Flexible Parsing. Journal of Discrete Algorithms, 2011, 14 (-), pp.74-90. ⟨hal-00742078⟩