arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2209.02767cs.LOcs.FL
收藏

连续Petri网中的分离器

Separators in Continuous Petri Nets

Michael Blondin, Javier Esparza

AI总结:

本文针对连续Petri网提出局部闭分离器,使不可达性可由多项式时间计算的分离器见证,且分离器验证属于NC,并进一步通过改造Petri网高效证明凸多面体集合间的不可达性。

摘要:

Leroux证明了Petri网中的不可达性可以由Presburger分离器见证,即如果一个标记$\vec{m}_\text{src}$不能到达标记$\vec{m}_\text{tgt}$,那么存在一个Presburger算术公式$φ$使得:$φ(\vec{m}_\text{src})$成立;$φ$是前向不变的,即$φ(\vec{m})$和$\vec{m} \rightarrow \vec{m}'$蕴含$φ(\vec{m}'$);并且$\neg φ(\vec{m}_\text{tgt})$成立。虽然这些分离器可以用作不可达性的解释和形式化证书,但由于其最坏情况下的规模至少是Ackermann级的,并且检查一个公式是否为分离器的复杂度至少是指数级的(相对于公式规模),这一方法尚未得到实际应用。我们证明了在连续Petri网中,这两个问题可以被克服。我们引入了局部闭分离器,并证明:(a) 不可达性可以由一个可在多项式时间内计算的局部闭分离器见证;(b) 检查一个公式是否为局部闭分离器属于NC(因此比不可达性更简单,后者是P-完全的)。我们进一步考虑了更一般的(存在性)集合到集合可达性问题,其中两组标记以凸多面体形式给出。我们证明了虽然我们的方法不能直接扩展,但可以通过一个改造后的Petri网高效地证明不可达性。

英文摘要:

Leroux has proved that unreachability in Petri nets can be witnessed by a Presburger separator, i.e. if a marking $\vec{m}_\text{src}$ cannot reach a marking $\vec{m}_\text{tgt}$, then there is a formula $φ$ of Presburger arithmetic such that: $φ(\vec{m}_\text{src})$ holds; $φ$ is forward invariant, i.e., $φ(\vec{m})$ and $\vec{m} \rightarrow \vec{m}'$ imply $φ(\vec{m}'$); and $\neg φ(\vec{m}_\text{tgt})$ holds. While these separators could be used as explanations and as formal certificates of unreachability, this has not yet been the case due to their worst-case size, which is at least Ackermannian, and the complexity of checking that a formula is a separator, which is at least exponential (in the formula size). We show that, in continuous Petri nets, these two problems can be overcome. We introduce locally closed separators, and prove that: (a) unreachability can be witnessed by a locally closed separator computable in polynomial time; (b) checking whether a formula is a locally closed separator is in NC (so, simpler than unreachability, which is P-complete). We further consider the more general problem of (existential) set-to-set reachability, where two sets of markings are given as convex polytopes. We show that, while our approach does not extend directly, we can efficiently certify unreachability via an altered Petri net.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑