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DOI: 10.4230/LIPIcs.FSTTCS.2011.423

Optimal Packed String Matching

Authors: Oren Ben-Kiki, Philip Bille, Dany Breslauer, Leszek Gasieniec, Roberto Grossi, and Oren Weimann

Published in: LIPIcs, Volume 13, IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2011)

Abstract

In the packed string matching problem, each machine word accomodates alpha characters, thus an n-character text occupies n/alpha memory words. We extend the Crochemore-Perrin constant-space O(n)-time string matching algorithm to run in optimal O(n/alpha) time and even in real-time, achieving a factor alpha speedup over traditional algorithms that examine each character individually. Our solution can be efficiently implemented, unlike prior theoretical packed string matching work. We adapt the standard RAM model and only use its AC0 instructions (i.e. no multiplication) plus two specialized AC0 packed string instructions. The main string-matching instruction is available in commodity processors (i.e. Intel's SSE4.2 and AVX Advanced String Operations); the other maximal-suffix instruction is only required during pattern preprocessing. In the absence of these two specialized instructions, we propose theoretically-efficient emulation using integer multiplication (not AC0) and table lookup.

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Oren Ben-Kiki, Philip Bille, Dany Breslauer, Leszek Gasieniec, Roberto Grossi, and Oren Weimann. Optimal Packed String Matching. In IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2011). Leibniz International Proceedings in Informatics (LIPIcs), Volume 13, pp. 423-432, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2011)

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@InProceedings{benkiki_et_al:LIPIcs.FSTTCS.2011.423,
  author =	{Ben-Kiki, Oren and Bille, Philip and Breslauer, Dany and Gasieniec, Leszek and Grossi, Roberto and Weimann, Oren},
  title =	{{Optimal Packed String Matching}},
  booktitle =	{IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2011)},
  pages =	{423--432},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-34-7},
  ISSN =	{1868-8969},
  year =	{2011},
  volume =	{13},
  editor =	{Chakraborty, Supratik and Kumar, Amit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2011.423},
  URN =		{urn:nbn:de:0030-drops-33558},
  doi =		{10.4230/LIPIcs.FSTTCS.2011.423},
  annote =	{Keywords: String matching, bit parallelism, real time, space efficiency}
}

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Optimal Packed String Matching

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