Space-Efficient Representations for Glushkov Automata

Abstract

Glushkov automaton is an efficient structure for matching regular expressions. We present an [Formula: see text] bits space representation of Glushkov automata of regular expressions, where [Formula: see text] is the number of strings in the regular expression. The state transition runs in time [Formula: see text], where [Formula: see text] is the size of machine words, and [Formula: see text] is the number of states in the Glushkov automaton. For [Formula: see text], the time is [Formula: see text]. Our approach is based on two operations on words that retrieve and set bits on a specific set of positions of a word. We present implementations of these operations using bit-parallelism and a permutation network, which are simple and efficient.