Felix Engelhardt

A Combinatorial Branch-and-Bound Algorithm for the Capacitated Facility Location Problem under Strict Customer Preferences

  • Christina Büsing
  • Felix Engelhardt
  • Sophia Wrede
    • Categories Bilevel Optimization, Branch and Cut Algorithms, Combinatorial Optimization Tags , , , ,

    This work proposes a combinatorial branch-and-bound (B&B) algorithm for the capacitated facility location problem under strict customer preferences (CFLP-SCP). We use combinatorial insights into the problem structure to do preprocessing, model branching implications, enforce feasibility or prove infeasibility in each node, select variables and derive primal and dual bounds in each node of the B&B … Read more

    Counterfactual Explanations for Integer Optimization Problems

  • Felix Engelhardt
  • Jannis Kurtz
  • Ş. İlker Birbil
  • Ted K. Ralphs
    • Categories Bilevel Optimization, Integer Programming Tags , , ,

    Counterfactual explanations (CEs) offer a human-understandable way to explain decisions by identifying specific changes to the input parameters of a base or present model that would lead to a desired change in its outcome. For optimization models, CEs have primarily been studied in limited contexts, such as linear optimization problems with continuous decision variables or … Read more

    Minimum-Peak-Cost Flows Over Time

  • Mariia Anapolska
  • Christina Büsing
  • Felix Engelhardt
  • Timo Gersing
  • Sabrina Schmitz
  • Sophia Wrede
    • Categories Combinatorial Optimization, Network Optimization Tags , , , ,

    Peak cost is a novel objective for flows over time that describes the amount of workforce necessary to run a system. We focus on minimising peak costs in the context of maximum temporally repeated flows and formulate the corresponding MPC-MTRF problem. First, we discuss the limitations that emerge when restricting the solution space to integral … Read more

    Structural Insights and an IP-based Solution Method for Patient-to-room Assignment Under Consideration of Single Room Entitlements

  • Tabea Brandt
  • Christina Büsing
  • Felix Engelhardt
    • Categories 0-1 Programming, Applications - OR and Management Sciences, Combinatorial Optimization Tags , , ,

    Patient-to-room assignment (PRA) is a scheduling problem in decision support for large hospitals. This work proposes Integer Programming (IP) formulations for dynamic PRA, where either full, limited or uncertain information on incoming patients is available. The applicability is verified through a computational study. Results indicate that large, real world instances can be solved to a … Read more