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Erschienen in:
2014 | OriginalPaper | Buchkapitel
Strategic Pattern Search in Factor-Compressed Text
verfasst von : Simon Gog, Alistair Moffat, Matthias Petri
Erschienen in: String Processing and Information Retrieval
Verlag: Springer International Publishing
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We consider the problem of pattern-search in compressed text in a context in which: (a) the text is stored as a sequence of factors against a static phrase-book; (b) decoding of factors is from right-to-left; and (c) extraction of each symbol in each factor requires Θ(log
σ
) time, where
σ
is the size of the original alphabet. To determine possible alignments given information about decoded characters we introduce two Boyer-Moore-like searching mechanisms, including one that makes use of a suffix array constructed over the pattern. The new mechanisms decode fewer than half the symbols that are required by a sequential left-to-right search such as the Knuth-Morris-Pratt approach, a saving that translates directly into improved execution time. Experiments with a two-level suffix array index structure for 4 GB of English text demonstrate the usefulness of the new techniques.