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Short Regular Expressions from Finite Automata: Empirical Results

  • Hermann Gruber
  • Markus Holzer
  • Michael Tautschnig
Part of the Lecture Notes in Computer Science book series (LNCS, volume 5642)

Abstract

We continue our work [H. Gruber, M. Holzer: Provably shorter regular expressions from deterministic finite automata (extended abstract). In Proc. DLT, LNCS 5257, 2008] on the problem of finding good elimination orderings for the state elimination algorithm, one of the most popular algorithms for the conversion of finite automata into equivalent regular expressions. Here we tackle this problem both from the theoretical and from the practical side. First we show that the problem of finding optimal elimination orderings can be used to estimate the cycle rank of the underlying automata. This gives good evidence that the problem under consideration is difficult, to a certain extent. Moreover, we conduct experiments on a large set of carefully chosen instances for five different strategies to choose elimination orderings, which are known from the literature. Perhaps the most surprising result is that a simple greedy heuristic by [M. Delgado, J. Morais: Approximation to the smallest regular expression for a given regular language. In Proc. CIAA, LNCS 3317, 2004] almost always outperforms all other strategies, including those with a provable performance guarantee.

Keywords

Regular Expression Regular Language Finite Automaton Elimination Ordering Input Alphabet 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • Hermann Gruber
    • 1
  • Markus Holzer
    • 1
  • Michael Tautschnig
    • 2
  1. 1.Institut für InformatikUniversität GiessenGiessenGermany
  2. 2.Fachbereich InformatikTechnische Universität DarmstadtDarmstadtGermany

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