Improved and self-tuned occurrence heuristics

In this note we present three efficient variations of the occurrence heuristic, adopted by many exact string matching algorithms and first introduced in the well-known Boyer–Moore algorithm. Our first heuristic, called improved-occurrence heuristic, is a simple improvement of the rule introduced by...

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Bibliographic Details
Published in:Journal of discrete algorithms (Amsterdam, Netherlands) Vol. 28; pp. 73 - 84
Main Authors: Cantone, Domenico, Faro, Simone
Format: Journal Article
Language:English
Published: Elsevier B.V 01.09.2014
Subjects:
Experimental algorithms
Frequency of characters
Occurrence heuristics
String matching
Text-processing
Tuned-search approach
Tuned-search approach
Text-processing
String matching
Experimental algorithms
Occurrence heuristics
Frequency of characters
ISSN:1570-8667, 1570-8675
Online Access:Get full text
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Summary:In this note we present three efficient variations of the occurrence heuristic, adopted by many exact string matching algorithms and first introduced in the well-known Boyer–Moore algorithm. Our first heuristic, called improved-occurrence heuristic, is a simple improvement of the rule introduced by Sunday in his Quick-Search algorithm. Our second heuristic, called worst-occurrence heuristic, achieves its speed-up by selecting the relative position which yields the largest average advancement. Finally, our third heuristic, called jumping-occurrence heuristic, uses two characters for computing the next shift. Setting the distance between these two characters optimally allows one to maximize the average advancement. The worst-occurrence and jumping-occurrence heuristics tune their parameters according to the distribution of the characters in the text. Experimental results show that the newly proposed heuristics achieve very good results on average, especially in the case of small alphabets.
ISSN:1570-8667
1570-8675
DOI:10.1016/j.jda.2014.07.006