解决时间约束不一致时的最大可满足子集问题,揭示其计算难度边界。
Maximum Satisfiability of Simple Temporal Problems
- 基于约束图结构与系数范围设计参数化算法
- 当系数范围固定时,可在单指数时间内求解
- 适合研究时空推理与复杂约束系统的从业者
简单时间问题(STP)是定量时间约束的核心框架。由于STP数据可能存在不一致,本文研究最大可满足性问题(MAXSTP):计算最大一致性约束子集。该问题为NP-hard,我们分析其在刻画实际实例特性的参数下的参数化复杂度,包括变量数 $n$(实例规模)、最大系数绝对值 $k$(数值范围)以及约束图的结构性参数如树宽 $tw$(可分解性)和顶点覆盖大小 $vc$(密度)。结果表明,MAXSTP 在参数 $n$ 下为 W[1]-hard,意味着 $n$ 及依赖于 $n$ 的参数(包括 $tw$ 与 $vc$)不足以实现固定参数可解性。对于组合参数,我们给出 $O^*(k^n)$ 时间算法,当 $k$ 固定时可得单指数可解性。尽管 $k+tw$ 仍为 W[1]-hard,但通过 $O^*((nullet k)^{tw})$ 算法可得在 XP 内求解。结果表明,MAXSTP 通常比优化定性约束满足问题更难。我们验证了包括 RCC-8 与 Allen 代数在内的多种问题在参数 $n$ 或 $tw$ 下为 FPT。然而,我们也证明了针对 MAXSTP 的 FPT 算法确实存在,但需使用其他参数如 $k + vc$。
原文摘要 · Abstract (English)
The Simple Temporal Problem (STP) is a core framework for quantitative temporal constraints. As STP data can be inconsistent, we study MAXSTP: compute a maximum-cardinality consistent subset of constraints. This extension is NP-hard, and we analyze its parameterized complexity under measures that capture practically relevant instance features: the number of variables $n$ (instance scale), the maximum coefficient magnitude $k$ (numeric range), and structural parameters of the constraint graph such as treewidth $tw$ (decomposability) and vertex cover size $vc$ (density). We show that MAXSTP is W[1]-hard parameterized by $n$, implying that $n$ and parameters that depend on $n$ (including $tw$ and $vc$) are insufficient for fixed-parameter tractability. For combined parameters, we give an $O^*(k^n)$-time algorithm, yielding single-exponential solvability for fixed $k$. While $k+tw$ remains W[1]-hard, MAXSTP is in XP via an $O^*((n\cdot k)^{tw})$ algorithm. Our results suggest that MAXSTP is often computationally harder than optimizing qualitative CSPs. We verify that many such problems (including RCC-8 and Allen's algebra) are FPT when parameterized by $n$ or $tw$. However, we also demonstrate that FPT algorithms for MAXSTP are indeed possible but with other parameters such as $k + vc$.
Thank you to arXiv for use of its open access interoperability. PaperDance 不是 arXiv 官方产品;中文卡片由大模型生成,请以原文为准。