The Prague Stringology Club Workshop '98

Bruce W. Watson and Richard E. Watson

An Early-Retirement Plan for the States

New applications of finite automata, such as NLP and asynchronous circuit simulation, can require automata of millions or even billions of states. All known construction methods (in particular, the interesting reachability-based ones that save memory, such as the subset construction, and simultaneously minimizing constructions, such as Brzozowski's) have intermediate memory usage much larger than the final automaton, thereby restricting the maximum size of the automata which can be built. In this paper, we present a reachability-based optimization which can be used in any one of the construction algorithms to reduce the intermediate memory requirements. The optimization is presented in conjunction with an easily understood (and implemented) canonical automaton construction algorithm.

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