A parallel ruin and recreate heuristic for personnel scheduling in a flexible working environment

Personnel scheduling aims to determine least-cost personnel schedules to meet the demand for employees in each period of a planning horizon. In this article, we propose a parallel ruin and recreate heuristic, denoted PRRH, for solving a personnel scheduling problem. PRRH is an integrated approach for this type of problem that generates and assigns shifts simultaneously. Starting from an initial solution, the method is based on an iterative scheme that ruins the current solution at each iteration by inducing a disruption in an employee schedule and recreates a new solution by finding a cost-effective ejection chain. Each disruption is targeted according to predetermined probabilistic improvement scores, and each solution is created using an algorithm inspired by the heuristic of Hassani et al. (Eur J Oper Res 293:93–108, 2021), which re-optimizes a schedule following a minor disruption. The approach is also based on a partition of the current solution, which is updated at each iteration to treat a maximum number of disruptions in parallel. The proposed algorithm has been tested on real-life instances involving up to 94 employees and 10 jobs. PRRH found solutions of very good quality (1.9% from optimality on average) in fast computational times (less than three minutes on average).