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arXiv 1909.02579cs.LOcs.CCcs.FL
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仿射向量加法系统状态的可达性复杂性

The Complexity of Reachability in Affine Vector Addition Systems with States

Michael Blondin, Mikhail Raskin

AI总结:

该研究刻画了仿射VASS中整数可达性的复杂性,给出三分法:重置类NP完全,转移/复制类PSPACE完全,其余不可判定;标准可达性仅置换类可判定,并探讨了固定实例的复杂性任意性。

摘要:

带状态的向量加法系统(VASS)广泛用于并发系统的形式化验证。鉴于其巨大的计算复杂性,实际方法依赖于诸如可达性松弛等技术,例如允许中间计数器值为负。自然要质疑这些方法对于通过通常导致不可判定性的原语增强的VASS的可行性。受此担忧的驱动,我们精确刻画了关于任意仿射操作类的整数松弛的复杂性。更具体地,我们提供了扩展了仿射操作的VASS(仿射VASS)中整数可达性复杂性的三分法。即,我们证明对于带重置的VASS是NP完全的,对于带(伪)转移的VASS和带(伪)复制的VASS是PSPACE完全的,而对于任何其他类是不可判定的。我们进一步提出了仿射VASS中标准可达性的二分法:对于带置换的VASS是可判定的,而对于任何其他类是不可判定的。这产生了仿射VASS中可达性的完整且统一的复杂性图景。我们还考虑了由固定仿射VASS参数化的可达性问题,而不是由类参数化,并表明在此设置中复杂性图景是任意的。

英文摘要:

Vector addition systems with states (VASS) are widely used for the formal verification of concurrent systems. Given their tremendous computational complexity, practical approaches have relied on techniques such as reachability relaxations, e.g., allowing for negative intermediate counter values. It is natural to question their feasibility for VASS enriched with primitives that typically translate into undecidability. Spurred by this concern, we pinpoint the complexity of integer relaxations with respect to arbitrary classes of affine operations. More specifically, we provide a trichotomy on the complexity of integer reachability in VASS extended with affine operations (affine VASS). Namely, we show that it is NP-complete for VASS with resets, PSPACE-complete for VASS with (pseudo-)transfers and VASS with (pseudo-)copies, and undecidable for any other class. We further present a dichotomy for standard reachability in affine VASS: it is decidable for VASS with permutations, and undecidable for any other class. This yields a complete and unified complexity landscape of reachability in affine VASS. We also consider the reachability problem parameterized by a fixed affine VASS, rather than a class, and we show that the complexity landscape is arbitrary in this setting.

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