• A comparison and hybridization of crossover operators for the nurse scheduling problem

      Maenhout, Broos; Vanhoucke, Mario (Annals of Operations Research, 2007)
    • A heuristic procedure to solve the project staffing problem with discrete time/resource trade-offs and personnel scheduling constraints

      Van Den Eeckhout, Mick; Maenhout, Broos; Vanhoucke, Mario (Computers & Operations Research, 2019)
      Highlights • Project staffing with discrete time/resource trade-offs and calendar constraints. • An iterated local search procedure is proposed. • Different problem decomposition techniques are applied. Abstract When scheduling projects under resource constraints, assumptions are typically made with respect to the resource availability and activities are planned each with its own duration and resource requirements. In resource scheduling, important assumptions are made with respect to the staffing requirements. Both problems are typically solved in a sequential manner leading to a suboptimal outcome. We integrate these two interrelated scheduling problems to determine the optimal personnel budget that minimises the overall cost. Integrating these problems increases the scheduling flexibility, which improves the overall performance. In addition, we consider some resource demand flexibility in this research as an activity can be performed in multiple modes. In this paper, we present an iterated local search procedure for the integrated multi-mode project scheduling and personnel staffing problem. Detailed computational experiments are presented to evaluate different decomposition heuristics and comparison is made with alternative optimisation techniques.
    • A hybrid scatter search heuristic for personalized crew rostering in the airline industry

      Maenhout, Broos; Vanhoucke, Mario (European Journal of Operational Research, 2010)
    • A perturbation matheuristic for the integrated personnel shift and task rescheduling problem

      Maenhout, Broos; Vanhoucke, Mario (European Journal of Operational Research, 2018)
      In this paper, we propose a heuristic optimisation procedure for the integrated personnel shift and task re-scheduling problem. We assume that schedule disruptions arise as the baseline personnel roster is subject to three sources of operational variability, i.e. uncertainty of capacity, uncertainty of demand and uncertainty of arrival. In order to restore the feasibility of the personnel roster and to minimise the number of deviations compared to the original roster, we propose a heuristic re-scheduling procedure that thrives on a perturbation mechanism to diversify the search and a variable neighbourhood search to intensify the search in the region of a solution point. In the computational experiments, we assess the contribution of the different algorithmic building blocks and benchmark our algorithm with other optimisation procedures.
    • A resource type analysis of the integrated project scheduling and personnel staffing problem

      Maenhout, Broos; Vanhoucke, Mario (Annals of Operations Research, 2017)
      In the integrated project scheduling and personnel staffing problem the project activities are scheduled and simultaneously a staffing plan is composed to carry out a single project. In this way, the project schedule that leads to the staffing plan with minimum cost is determined. In this paper, we evaluate different scheduling policies and practices for different personnel resource types. We examine the impact on the staffing cost when the personnel resources are scheduled in a cyclic versus a non-cyclic manner for different (days on, days off)-patterns. Furthermore, the impact of introducing more flexible resource types, such as overtime and temporary help, is explored in relationship with the activity resource demand variability. Computational results show that non-cyclic scheduling leads to a considerable lower staffing cost under all circumstances compared to cyclic scheduling. However, despite the tractability of the resource requirements, flexible temporary resources are essential on top of the regular personnel resources to respond to the variability in demand. The addition of overtime on a strategic staffing level only marginally decreases the personnel cost.
    • A scatter search for the extended resource renting problem

      Vandenheede, Len; Vanhoucke, Mario; Maenhout, Broos (International Journal of Production Research, 2016)
      In this paper, the extended Resource Renting Problem (RRP/extended) is presented. The RRP/extended is a time-constrained project scheduling problem, in which the total project cost is minimised. In the RRP/extended, this total project cost is determined by a number of extra costs, which are defined in this paper. These costs are based on the costs that are used in the traditional Resource Renting Problem and the Total Adjustment Cost Problem. Therefore, the RRP/extended represents a union of these two problems. To solve the RRP/extended, a scatter search is developed. The building blocks of this scatter search are specifically designed for the RRP/extended. We introduce two crossovers and an improvement method. The efficiency of these building blocks will be shown in the paper. Furthermore, a sensitivity analysis is presented in which the five costs have diverse values.
    • An electromagnetic Meta-heuristic for the Nurse Scheduling Problem

      Maenhout, Broos; Vanhoucke, Mario (Journal of Heuristics, 2007)
    • An evaluation of the adequacy of project network generators with systematically sampled networks

      Vanhoucke, Mario; Coelho, José; Debels, Dieter; Maenhout, Broos; Tavares, Luis (European Journal of Operational Research, 2008)
    • An evolutionary approach for the nurse rerostering problem

      Maenhout, Broos; Vanhoucke, Mario (Computers and Operations Research, 2011)
    • An exact algorithm for an integrated project staffing problem with a homogeneous workforce

      Maenhout, Broos; Vanhoucke, Mario (Journal of Scheduling, 2016)
      When scheduling projects under resource constraints, assumptions are typically made with respect to the resource availability. In resource scheduling problems important assumptions are made with respect to the resource requirements. As projects are typically labour intensive, the underlying (personnel) resource scheduling problems tend to be complex due to different rules and regulations. In this paper, we aim to integrate these two interrelated scheduling problems to minimise the overall cost. For that purpose, we propose an exact algorithm for the project staffing with resource scheduling constraints. Detailed computational experiments are presented to evaluate different branching rules and pruning strategies and to compare the proposed procedure with other optimisation techniques.
    • An integrated nurse staffing and scheduling analysis for longer-term nursing staff allocation problems

      Maenhout, Broos; Vanhoucke, Mario (Omega - International Journal of Management Science, 2013)
      The efficient and effective management of nursing personnel is of critical importance in a hospital's environment comprising a vast share of the operational costs. The adopted nurse workforce practices and policies highly affect the nurses' working conditions and the provided quality of care. Policy decisions on the staffing level have an impact on the outcome of the scheduling level and vice versa. Isolated reasoning typically leads to suboptimal decisions often resulting in ineffective outcomes of care. In order to overcome these inefficiencies, we propose in this paper a new integrative nurse staffing and shift scheduling approach. We test and assess the benefits of our approach in a reallife environment. Moreover, we examine the impact of several personnel policies on the staffing decision.
    • Analyzing the nursing organizational structure and process from a scheduling perspective

      Maenhout, Broos; Vanhoucke, Mario (Health Care Management Science, 2013)
      The efficient and effective management of nursing personnel is of critical importance in a hospital’s environment comprising approximately 25 % of the hospital’s operational costs. The nurse organizational structure and the organizational processes highly affect the nurses’ working conditions and the provided quality of care. In this paper, we investigate the impact of different nurse organization structures and different organizational processes for a real-life situation in a Belgian university hospital. In order to make accurate nurse staffing decisions, the employed solution methodology incorporates shift scheduling characteristics in order to overcome the deficiencies of the many phase-specific methodologies that are proposed in the academic literature.
    • Comparison and hybridization of crossover operators for the nurse scheduling problem

      Maenhout, Broos; Vanhoucke, Mario (Annals of Operations Research, 2008)
    • A decomposed branch-and-price procedure for integrating demand planning in personnel staffing problems

      Van Den Eeckhout, Mick; Vanhoucke, Mario; Maenhout, Broos (European Journal of Operational Research, 2020)
      Project staffing with discrete time/resource trade-offs and calendar constraints. • A cut-branch-and-price procedure is proposed. Decomposition into subproblems with a specific staffing composition. Dedicated cuts include personnel information in the workload pricing problem. The personnel staffing problem calculates the required workforce size and is determined by constructing a baseline personnel roster that assigns personnel members to duties in order to cover certain staffing requirements. In this research, we incorporate the planning of the duty demand in the staff scheduling problem in order to lower the staffing costs. More specifically, the demand originates from a project scheduling problem with discrete time/resource trade-offs, which embodies additional flexibility as activities can be executed in different modes. In order to tackle this integrated problem, we propose a decomposed branch-and-price procedure. A tight lower and upper bound are calculated using a problem formulation that models the project scheduling constraints and the time-related resource scheduling constraints implicitly in the decision variables. Based upon these bounds, the strategic problem is decomposed into multiple tactical subproblems with a fixed workforce size and an optimal solution is searched for each subproblem via branch-and-price. Fixing the workforce size in a subproblem facilitates the definition of resource capacity cuts, which limit the set of eligible project schedules, decreasing the size of the branching tree. In addition, in order to find the optimal integer solution, we propose a specific search strategy based upon the lower bound and dedicated rules to branch upon the workload generated by a project schedule. The computational results show that applying the proposed search space decomposition and the inclusion of resource capacity cuts lead to a well-performing procedure outperforming different other heuristic and exact methodologies.
    • Mode generation rules to define activity flexibility for the integrated project staffing problem with discrete time/resource trade-offs

      Van Den Eeckhout, Mick; Maenhout, Broos; Vanhoucke, Mario (Annals of Operations Research, 2020)
      In this paper, we study the project staffing problem with discrete time/resource trade-offs to minimise the personnel staffing budget. This staffing problem embeds activity scheduling flexibility by incorporating the project scheduling problem into the personnel staffing problem to improve the quality of the staffing plan. In addition, we introduce extra demand scheduling flexibility resulting from the design of alternative execution modes for the activities, modelled via discrete time/resource trade-offs. In this way, the project manager is able to decide on the team size and duration for every activity. We propose a two-stage methodology to first design specific alternative activity modes using heuristic rules-of-thumb and subsequently we assess the resulting quality, i.e. the staffing cost, via the integrated composition of the project schedule and associated staffing plan. The heuristic mode generation rules determine the selection of a limited set of relevant activities and modes. The computational results show that the impact of these heuristic generation rules on the staffing budget is dependent on the defined relation between different activity alternatives for a particular activity and on the estimated characteristics of the activity base modes. We show that by focusing on a particular well-chosen subset of activity alternatives or on a particular subset of activities, high-quality solutions realising most of the potential cost improvements resulting from the discrete time/resource trade-offs can be derived with a reduced effort.
    • New computational results for the nurse scheduling problem: a scatter search algorithm

      Maenhout, Broos; Vanhoucke, Mario (Lecture notes in Computer Science, 2006)
    • On the characterization and generation of nurse scheduling problem instances

      Vanhoucke, Mario; Maenhout, Broos (European Journal of Operational Research, 2009)
    • On the resource renting problem with overtime

      Kerkhove, Louis-Philippe; Vanhoucke, Mario; Maenhout, Broos (Computers & Industrial Engineering, 2017)
      In this paper the Resource Renting Problem with Overtime (RRP/overtime) is presented. The RRP/overtime is a new problem in which the assumptions of the basic RRP are combined with the possibility to schedule (parts of) activities during overtime. The addition of this extension increases the applicability of the RRP to real world problems. This paper also presents a solution technique for this extension of the resource renting problem. The solution procedure uses a scatter search heuristic to optimize a priority list, which is then in turn used by a schedule generation scheme (PatSGS). A variation on this schedule generation scheme is also used in dedicated local search procedures. The third contribution of this research is a new lower bound for the RRP/overtime problem, which is used to evaluate the results of the proposed heuristic solution method.
    • Reconstructing nurse schedules: computational insights in the problem size parameters

      Maenhout, Broos; Vanhoucke, Mario (Omega - International Journal of Management Science, 2013)
      Managing nursing personnel properly is of critical importance as these resources comprise a vast share of the hospital's operational costs. The organisational support and the managerial policy decisions on the scheduling level are important determinants for the nurses' working conditions and the related quality of care. In this paper, we gain insights and understanding in the consequences and outcomes of various personnel re-rostering characteristics and strategies. We explore the boundaries of the time horizon and the nurse staffing size to consider for the nurse re-rostering problem based on computational experiments in a real-life problem environment.