构造型的D^2FA生成算法

Research of Constructing Algorithm to Create D^2FA

Delayed input DFA(D2FA)中引入默认边来对确定状态机(DFA)进行状态转移精简.为了提高D2FA生成算法的效率,分析了对正则表达式X得到的DFA(∧X)与DFA(X)间的相关性,提出一种从DFA(∧X)到D2FA(X)的构造型算法.该算法将DFA(X)中的状态用DFA(∧X)中的状态序列进行表示,从而基于状态序列进行默认边的选择,而不需要生成实际的DFA(X).理论分析和实验结果表明,该算法降低了构造D2FA的算法复杂度,同时仍能保证进行模式匹配时的解析时间下限,以及对DFA的状态转移精简能力.

Delayed input deterministic finite automata （D^2FA） reduces the transition edges of de- terministic finite automata （DFA） by introducing default edges. The relevance between DFA（^X） and DFA（X） is analyzed to improve the efficiency of constructing algorithm to create D^2FA. A constructing algorithm is presented to create D^2FA from DFA. The algorithm expresses the state of DFA（X） with the state sequence of DFA （^X）, hence the choice of default edges is relayed on the state sequence, rather than creating actual DFA（X）. Experiments show that the algorithm greatly reduces the complexity of constructing D^2FA, meanwhile it ensures a lower time bounds of pattern match and capacity of reducing state transition.