Dual Finite Automata to Scan Regular Languages

A regular language is generally accepted by a single finite automaton. But when to increase the efficiency, we use Dual Finite Automata, An input string is scanned by two deterministic finite automata (DFA's): reading from the string's head and tail respectively. One of them accepts the regular language itself; the other accepts the language's reversal. Whether a string is accepted depends on the states of both automata, when their reading heads meet. Dual finite automata can be applied in compiler generation and parallel computing.