Small NFAs from Regular Expressions: Some Experimental Results

TL;DR

This paper explores the relationship between regular expression measures and the size of equivalent epsilon-free NFAs, presenting experimental results from various algorithms within the FAdo system.

Contribution

It introduces and compares algorithms for constructing small epsilon-free NFAs from regular expressions, based on experimental analysis.

Findings

Smaller NFAs are achievable with certain algorithms.

Regular expression measures correlate with NFA size.

Experimental results guide optimal NFA construction methods.

Abstract

Regular expressions (res), because of their succinctness and clear syntax, are the common choice to represent regular languages. However, efficient pattern matching or word recognition depend on the size of the equivalent nondeterministic finite automata (NFA). We present the implementation of several algorithms for constructing small epsilon-free NFAss from res within the FAdo system, and a comparison of regular expression measures and NFA sizes based on experimental results obtained from uniform random generated res. For this analysis, nonredundant res and reduced res in star normal form were considered.