比较SMT与MILP求解护士排班问题,发现SMT在复杂场景下表现更优。
A Comparative Study of SMT and MILP for the Nurse Rostering Problem
- 用通用约束建模真实排班需求,分别转化为SMT和MILP问题
- 在复杂排班问题上,SMT求解器(Z3)优于MILP求解器(Gurobi)
- 适合处理多类型班次、人员多样性的实际排班场景
人员排班对医疗质量与医护人员工作条件影响深远。由于需求持续且约束复杂多变,医疗排班极具挑战性。尽管该问题已研究数十年,但针对可满足性模理论(SMT)的应用研究仍有限。近年来,SMT求解器在形式验证领域取得显著进展,性能已超越传统数学规划方法。本文提出通用约束建模方法,可覆盖多种现实排班约束。将这些约束分别构建为SMT与MILP问题,并使用主流求解器Z3(SMT)和Gurobi(MILP)在学术及真实场景启发的问题上进行对比实验。结果表明:当问题高度约束或不可行时,MILP求解器整体表现更优;而在包含多样化班次与人员的现实问题中,SMT求解器更具优势。此外,实验发现SMT求解器对约束建模方式更为敏感,需精细调整才能发挥最佳性能。结论:基于SMT的方法为人员调度研究提供了有前景的新方向。
原文摘要 · Abstract (English)
The effects of personnel scheduling on the quality of care and working conditions for healthcare personnel have been thoroughly documented. However, the ever-present demand and large variation of constraints make healthcare scheduling particularly challenging. This problem has been studied for decades, with limited research aimed at applying Satisfiability Modulo Theories (SMT). SMT has gained momentum within the formal verification community in the last decades, leading to the advancement of SMT solvers that have been shown to outperform standard mathematical programming techniques. In this work, we propose generic constraint formulations that can model a wide range of real-world scheduling constraints. Then, the generic constraints are formulated as SMT and MILP problems and used to compare the respective state-of-the-art solvers, Z3 and Gurobi, on academic and real-world inspired rostering problems. Experimental results show how each solver excels for certain types of problems; the MILP solver generally performs better when the problem is highly constrained or infeasible, while the SMT solver performs better otherwise. On real-world inspired problems containing a more varied set of shifts and personnel, the SMT solver excels. Additionally, it was noted during experimentation that the SMT solver was more sensitive to the way the generic constraints were formulated, requiring careful consideration and experimentation to achieve better performance. We conclude that SMT-based methods present a promising avenue for future research within the domain of personnel scheduling.
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