General algorithms for testing the ambiguity of finite automata

Cyril Allauzen, Mehryar Mohri, Ashish Rastogi

Research output: Chapter in Book/Report/Conference proceedingConference contribution


This paper presents efficient algorithms for testing the finite, polynomial, and exponential ambiguity of finite automata with ε-transitions. It gives an algorithm for testing the exponential ambiguity of an automaton A in time O(|A|E2, and finite or polynomial ambiguity in time O(|A|E3, where |A| E denotes the number of transitions of A. These complexities significantly improve over the previous best complexities given for the same problem. Furthermore, the algorithms presented are simple and based on a general algorithm for the composition or intersection of automata. We also give an algorithm to determine in time O(|A|E3 the degree of polynomial ambiguity of a polynomially ambiguous automaton A. Finally, we present an application of our algorithms to an approximate computation of the entropy of a probabilistic automaton.

Original languageEnglish (US)
Title of host publicationDevelopments in Language Theory - 12th International Conference, DLT 2008, Proceedings
Number of pages13
StatePublished - 2008
Event12th International Conference on Developments in Language Theory, DLT 2008 - Kyoto, Japan
Duration: Sep 16 2008Sep 19 2008

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume5257 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Other12th International Conference on Developments in Language Theory, DLT 2008

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


Dive into the research topics of 'General algorithms for testing the ambiguity of finite automata'. Together they form a unique fingerprint.

Cite this