Osman Y. Ozaltin

Anesthesiologist Scheduling with Handoffs: A Combined Approach of Optimization and Human Factors

  • Ankit Bansal
  • Osman Y. Ozaltin
    • Categories Integer Programming, Scheduling, Stochastic Programming

    We present a two-stage stochastic programming model for optimizing anesthesiologist schedules, explicitly accounting for uncertainty in surgery durations and anesthesiologist handoffs. To inform model design, we conducted an online survey at our partner institution to identify key factors affecting the quality of intraoperative anesthesiologist handoffs. Insights from the survey results are incorporated into the model, … Read more

    A Two-stage Stochastic Programming Approach for CRNA Scheduling with Handovers

  • Ankit Bansal
  • Osman Y. Ozaltin
    • Categories (Mixed) Integer Linear Programming, Scheduling, Stochastic Programming Tags , , ,

    We present a two-stage stochastic integer program for assigning Certified Registered Nurse Anesthetists (CRNAs) to Operating Rooms (ORs) under surgery duration uncertainty. The proposed model captures the trade-offs between CRNA staffing levels, CRNA handovers and under-staffing in the ORs. Since the stochastic program includes binary variables in both stages, we present valid inequalities to tighten … Read more

    A Branch-and-Cut Algorithm for Discrete Bilevel Linear Programs

  • Osman Y. Ozaltin
  • Junlong Zhang
    • Categories (Mixed) Integer Linear Programming, Branch and Cut Algorithms

    We present a branch-and-cut algorithm for solving discrete bilevel linear programs where the upper-level variables are binary and the lower-level variables are either pure integer or pure binary. This algorithm performs local search to find improved bilevel feasible solutions. We strengthen the relaxed node subproblems in the branch-and-cut search tree by generating cuts to eliminate … Read more

    A scalable bounding method for multi-stage stochastic integer programs

  • Osman Y. Ozaltin
  • Burhaneddin Sandikçi
    • Categories Integer Programming, Parallel Algorithms, Stochastic Programming Tags , , , ,

    Many dynamic decision problems involving uncertainty can be appropriately modeled as multi-stage stochastic programs. However, most practical instances are so large and/or complex that it is impossible to solve them on a single computer, especially due to memory limitations. Extending the work of Sandikci et al. (2013) on two-stage stochastic mixed-integer-programs (SMIPs), this paper develops … Read more

    Two-Stage Quadratic Integer Programs with Stochastic Right-Hand Sides

  • Osman Y. Ozaltin
  • Oleg A. Prokopyev
  • Andrew J. Schaefer
    • Categories (Mixed) Integer Nonlinear Programming, Quadratic Programming, Stochastic Programming Tags , , ,

    We consider two-stage quadratic integer programs with stochastic right-hand sides, and present an equivalent reformulation using value functions. We fi rst derive some basic properties of value functions of quadratic integer programs. We then propose a two-phase solution approach. The first phase constructs the value functions of quadratic integer programs in both stages. The second phase … Read more

    Visualizing Branch-and-Bound Algorithms

  • Brady Hunsaker
  • Osman Y. Ozaltin
  • Ted K. Ralphs
    • Categories Integer Programming

    We present a suite of tools for visualizing the status and progress of branch-and-bound algorithms for mixed integer programming. By integrating these tools with the open-source codes CBC, SYMPHONY, and GLPK, we demonstrate the potential usefulness of visual representations in helping a user predict future progress of the algorithm or analyzing the algorithm’s performance. We … Read more