A Comparative Study of SMT and MILP for the Nurse Rostering Problem

Fuente: arXiv
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Auteurs principaux: Combrink, Alvin, Do, Stephie, Bengtsson, Kristofer, Roselli, Sabino Francesco, Fabian, Martin
Format: Preprint
Publié: 2025
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author Combrink, Alvin
Do, Stephie
Bengtsson, Kristofer
Roselli, Sabino Francesco
Fabian, Martin
author_facet Combrink, Alvin
Do, Stephie
Bengtsson, Kristofer
Roselli, Sabino Francesco
Fabian, Martin
contents 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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id arxiv_https___arxiv_org_abs_2505_10328
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publishDate 2025
record_format arxiv
spellingShingle A Comparative Study of SMT and MILP for the Nurse Rostering Problem
Combrink, Alvin
Do, Stephie
Bengtsson, Kristofer
Roselli, Sabino Francesco
Fabian, Martin
Artificial Intelligence
Systems and Control
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.
title A Comparative Study of SMT and MILP for the Nurse Rostering Problem
topic Artificial Intelligence
Systems and Control
url https://arxiv.org/abs/2505.10328