SIGOPT 2022

Ulf Lorenz (University of Siegen)

Ulf Lorenz is professor for Business Economics, especially for Technology Management at the University of Siegen and the speaker of the Siegener Mittelstandsinstitut. He studied Computer Science at the University of Paderborn, received his Diploma degree in 1995, his PhD in 2001 and his Habilitation in 2006. From 2007 to 2014 he was assistant professor in Darmstadt and has been professor at the University of Siegen since 2014. He is a member of the Gesellschaft für Operations Research (GOR) and in particular editor and member of the working group for Technical Operations Research (TOR). He is also one of the developers of the chess machine HYDRA, one of the leading chess machines between 2002 and 2006. His research interests are in technical operations research and optimization under uncertainty.

Ruth Misener (Imperial College London)

Ruth Misener is a Professor at the Department of Computing, Imperial College London, where she develops software and optimization methods for energy efficient engineering and biomedical systems. She received a BSc in Chemical Engineering at MIT in 2007. Then she moved to Princeton, where she received PhD in 2012. She is the author of several publicly available computer programs for nonlinear optimization. Her work was awarded with several academic prizes.

Betwixt & Between: Intermediate Formulations & Relaxations for Computational Optimisation

A variety of theoretical frameworks, e.g. the Lasserre hierarchy of relaxations, basic steps in generalised disjunctive programming, and the reformulation linearisation technique, offer discrete levels for optimisation formulations and relaxations. These discrete choices, for instance picking the first versus the second level of the Lasserre hierarchy, may be problematic for computational optimisation strategies. For example, the first order Lasserre relaxation may be too loose but solving the second order Lasserre relaxation may be too computationally expensive. This presentation considers work in both my and other research teams on developing intermediates between theoretical optimisation frameworks that classically come with discrete levels. We show why developing “betwixt & between” formulations and relaxations is so important for computational optimisation. We close with challenges for future research.

Ira Neitzel (University of Bonn)

Ira Neitzel is a professor at the University of Bonn working on numerical analysis and optimal control of partial differential equations. She studied technomathematics at the Technical University of Berlin where she received her Diploma degree in 2006 and completed her PhD in 2011 under supervision of Fredi Tröltzsch. Afterwards, she worked as a research associate at the Technical University of Munich in the group of Boris Vexler before heading towards Bonn for her professorship in 2015.

Optimal Control of Quasilinear Parabolic PDEs

Anita Schöbel (TU Kaiserslautern)

Anita Schöbel is a Professor for Applied Mathematics at the Technical University in Kaiserslautern and head of the Fraunhofer Institute for Industrial Mathematics (ITWM). She studied Mathematics in Kaiserslautern, received her Diploma degree in 1994, her PhD in 1998 and her Habilitation in 2003. From 2003 to 2018 she was Professor in Göttingen and 2008/09 guest professor in Auckland. She is a member of the scientific senate of the National Research Data Infrastructure (NFDI) Germany, and speaker of the DFG Research Group on Integrated Optimization in Public Transport. In 2022/23, she will be President Elect of the Association of European Operational Research Societies (EURO). Her research interests are in the area of multicriteria optimization, robust optimization, and transport and logistic applications.

Integrated versus sequential planning: The case of public transport optimization

Many real-world problems are treated sequentially. One prominent example for such a sequential process is public transport optimization: One starts with network design, then plans lines and their frequencies. Based on these, the timetable is determined, and later on the vehicles’ and drivers’ schedules.
The sequential procedure sketched above can be regarded as a Greedy approach: in each planning stage one aims at the best one can do. This usually leads to suboptimal solutions. On the other hand, in public transport optimization many of the mentioned single steps are already NP hard such that solving the integrated problem to optimality seems to be out of scope.
We introduce a general framework to analyze integrated versus sequential planning. We define the price of sequentiality to measure how much can be gained by integrated approaches. We present results under which conditions the price of sequentiality is bounded or even zero. We also develop different approaches for integrated optimization, among them partial integration or the Eigenmodel. We illustrate our findings for the case of public transport optimization.

Gerhard Woeginger (RWTH Aachen)

Gerhard Woeginger is Professor for Algorithms and Complexity at RWTH Aachen. He obtained a Diploma from the Graz University of Technology in 1987, and completed his PhD at Graz University of Technology 1991 under the supervision of Franz Rendl. Since completing his Habilitation in Graz in 1995, Gerhard Woeginger has held professorships at the University of Twente from 2001 to 2004 and at TU Eindhoven from 2004 onwards, before moving to Aachen in 2016. Among the prizes he has won for his research is the Humboldt Research Award (2013). His main research interests are randomized algorithms, approximation algorithms, graph algorithms and algorithmic game theory.

Complexity-theoretic aspects of bilevel and of robust optimization