15:00 (CET)
University of Montpellier
Iterated Local Search Algorithms for Adjustable Robust Optimization Problems with Discrete Budget Uncertainty
SAP
Robust Optimization meets Quantum Optimization
Abstract:
Two-stage robust optimization problems with integer recourse are a notoriously difficult class of problems, yet they model many important applications. In this talk, we discuss heuristic approaches for solving these problems by addressing the first-stage problem through local search algorithms. We focus on the case where all decision variables, as well as the uncertainty set, are discrete. We numerically compare the performance of our algorithms with that of a recently proposed exact algorithm from the literature.
Abstract:
Many problems in quantum computing have inherently uncertain data. For example, the energies that specify a system are only known approximately. Also, current hardware is noisy and its error rates might change between the time it is calibrated and the time an algorithm actually runs. After an introduction to quantum basics and notation, I will describe some problems where uncertainty arises naturally and where the tools of robust optimization seem to fit. The aim of this talk is less to present finished results than to point to problems and questions that might be interesting for future research.
Bio:
Igor Malheiros received his PhD in Computer Science from Université de Montpellier, France, in 2026, under the supervision of Michael Poss and Anand Subramanian, with a research focus on robust optimization for routing problems. During his PhD, conducted in collaboration with Atoptima in Bordeaux, France, he developed scalable optimization algorithms for supply chain planning. His research interests include integer programming, robust optimization, exact and heuristic methods, and optimization applications in routing, logistics, and supply chain.
Bio:
Christian Biefel focused on theoretical aspects of robust optimization during his PhD at FAU Erlangen-Nürnberg. His research centered on complexity and approximation bounds for robust variants of optimization problems, e.g. complementarity problems and network flows under arc failures. Since 2022 he works at SAP, where he develops quantum algorithms for supply chain optimization.
17:00 (CET)
University of British Columbia
The Value of Flexibility in Robust Supply Chain Network Design
Abstract:
A supply chain network design problem (SCNDP) involves making long-term, irreversible strategic decisions whose cost efficiency depends on effectively leveraging flexibility and demand information. After analyzing the interaction of these factors, we propose five distinct policies for addressing the SCNDP. Starting with a localized production model where demand is satisfied locally, the study extends to scenarios where production capacity at one location serves other nodes (Policy II). Further flexibility is introduced by enabling capacity sharing among facilities with prearranged links (Policy III). Unlike these policies, which optimize capacities as proxies for production decisions prior to demand realization, Policies IV and V defer production decisions until demand is realized. The robustness and resilience of these policies are evaluated under varying levels of demand uncertainty and risks of supply disruptions. To provide actionable insights, we develop robust two-stage optimization frameworks for the proposed policies and design efficient methods to address varying uncertainty budgets for both supply and demand risks. Our results reveal that under demand uncertainty alone: (i) Capacity-sharing links among facilities yield the highest cost savings across all uncertainty budgets due to the pooling effect and significantly reduce shortage probability (Policy III), and (ii) production postponement offers only marginal benefits, highlighting the greater importance of upstream capacity-sharing over postponing production, particularly for moderate uncertainty budgets. Under simultaneous demand and supply risks, we demonstrate that (iii) capacity-sharing retains its value, while flexibility from production postponement deteriorates performance, favoring partially flexible networks with only capacity-sharing links over fully flexible ones with both sources of flexibility. To contextualize these findings, we apply the most effective policies to a real-world case study, quantifying their impact and providing design recommendations. Finally, we extend our models to an event-wise ambiguity set and demonstrate that by (iv) leveraging the supermodular structure of the second-stage problems, one can solve instances up to eight times larger.
Bio:
Amir Ardestani-Jaafari is an associate professor at Faculty of Management, University of British Columbia. He is also Principal’s research chair in data-driven operations management. His primary research interests lie at the interface of healthcare operations, supply chain management, and optimization under uncertainty. His research has been published in top-tier journals, including Operations Research, Management Science, Transportation Science, INFORMS Journal on Computing, and Production and Operations Management, among others. Dr. Ardestani-Jaafari’s research is funded by Mitacs, NSERC, SSHRC and others
15:00 (CET)