一句话:首次给出下推自动机弱互模拟等价判定的 ACKERMANN 复杂度上界,并证明其最优。
本文研究两个带受限静默动作的下推自动机是否弱互模拟等价这一经典判定问题。Sénizergues 曾证明该问题可判定,但其复杂度上界长期未知。作者在一阶文法的等价框架下进行复杂度分析,首次给出 ACKERMANN 上界,并证明该上界与已知下界匹配,从而得到 ACKERMANN-完全性。作为补充,论文还证明当自动机状态数固定时,强互模拟等价性是原始递归的。该结果刻画了互模拟等价判定在自动机与形式语言层面的精确计算复杂度。
Checking whether two pushdown automata with restricted silent actions are weakly bisimilar was shown decidable by Sénizergues (1998, 2005). We provide the first known complexity upper bound for this famous problem, in the equivalent setting of first-order grammars. This ACKERMANN upper bound is optimal, and we also show that strong bisimilarity is primitive-recursive when the number of states of the automata is fixed.