Description
Leader of the group Networks and Optimization: Guido Schäfer.
In today’s society, complex systems surround us. From transport and traffic, to behavioral economics and operations management, realworld applications often demand that we identify simple, optimal solutions among a huge set of possibilities. Our research group Networks and Optimization (N&O) does fundamental research to tackle such challenging optimization problems.
We develop algorithmic methods to solve complex optimization problems efficiently. Our research provides efficient algorithms to some of the most challenging problems, for example, in planning, scheduling and routing. To come up with the best optimization algorithms, we combine and extend techniques from different disciplines in mathematics and computer science.
N&O covers a broad spectrum of optimization aspects. Our expertise ranges from discrete to continuous optimization and applies to centralized and decentralized settings. We focus on both problemspecific methods and universal toolkits to solve different types of optimization problems. The key in our investigations is to understand and exploit combinatorial structures, such as graphs, networks, lattices and matroids. Our research is of high scientific impact and contributes to various fields.
In several cooperations with industry partners, the algorithmic techniques that we develop in our group have proven useful to solve complex realworld problems. We are always interested in new algorithmic challenges arising in realworld applications and are open to new cooperations.
Watch our group video to get a glimpse of our activities.
Video about our collaboration with ProRail (in Dutch)
Vacancies
No vacancies currently.
News
Current events
Dutch Seminar on Optimization: talk by Martin Skutella (TU Berlin)
 20210930T16:00:00+02:00
 20210930T17:00:00+02:00
Dutch Seminar on Optimization: talk by Martin Skutella (TU Berlin)
Start: 20210930 16:00:00+02:00 End: 20210930 17:00:00+02:00
Everyone is welcome to attend the online seminar by Martin Skutella (TU Berlin). The title of his lecture is: A Faster Algorithm for Quickest Transshipments via an Extended Discrete Newton Method.
Abstract:
The Quickest Transshipment Problem is to route flow as quickly as possible from sources with supplies to sinks with demands in a network with capacities and transit times on the arcs. It is of fundamental importance for numerous applications in areas such as logistics, production, traffic, evacuation, and finance. More than 25 years ago, Hoppe and Tardos presented the first (strongly) polynomialtime algorithm for this problem. Their approach, as well as subsequently derived algorithms with strongly polynomial running time, are hardly practical as they rely on parametric submodular function minimization via Megiddo's
method of parametric search. The main contribution of this paper is a considerably faster algorithm for the Quickest Transshipment Problem that instead employs a subtle extension of the Discrete Newton Method.
This improves the previously best known running time of $\tilde{O}(m^4k^{14})$ to $\tilde O(m^2k^5+m^3k^3+m^3n)$, where $n$ is the number of nodes, $m$ the number of arcs, and $k$ the number of sources and sinks.
This is joint work with Miriam Schlöter (ETH Zurich) and Khai Van Tran (TU Berlin).
Members
Associated Members
Publications

Brosch, D, Laurent, M, & Steenkamp, J.A.J. (2021). Optimizing hypergraphbased polynomials modeling joboccupancy in queuing with redundancy scheduling. SIAM Journal on Optimization, 31(3), 2227–2254. doi:10.1137/20M1369592

Dadush, D.N, Végh, L.A, & Zambelli, G. (2021). Geometric rescaling algorithms for submodular function minimization. Mathematics of Operations Research, 46(3), 1081–1108. doi:10.1287/MOOR.2020.1064

Bansal, N, & Sinha, M. (2021). kForrelation optimally separates quantum and classical query complexity. In Proceedings of the Annual ACM SIGACT Symposium on Theory of Computing (pp. 1303–1316). doi:10.1145/3406325.3451040

Saha, A, Brokkelkamp, K.R, Velaj, Y, Khan, A, & Bonchi, F. (2021). Shortest paths and centrality in uncertain networks. In Proceedings of the VLDB Endowment (pp. 1188–1201). doi:10.14778/3450980.3450988

Bansal, N, Batra, J, Farhadi, M, & Tetali, P. (2021). Improved approximations for min sum vertex cover and generalized min sum set cover. In Proceedings of the Annual ACMSIAM Symposium on Discrete Algorithms (pp. 986–1005). doi:10.1137/1.9781611976465.62

Bansal, N, & Batra, J. (2021). Nonuniform geometric set cover and scheduling on multiple machines. In Proceedings of the Annual ACMSIAM Symposium on Discrete Algorithms (pp. 3011–3021).

Brokkelkamp, K.R, van Venetië, R., de Vries, M.J, & Westerdiep, J. (2020). PACE Solver Description: tdULL. In 15th International Symposium on Parameterized and Exact Computation. doi:10.4230/LIPIcs.IPEC.2020.29

Bansal, N, & Spencer, J.H. (2020). Online balancing of random inputs. Random Structures & Algorithms, 57(4), 879–891. doi:10.1002/rsa.20955

Slot, L.F.H, & Laurent, M. (2020). Nearoptimal analysis of Lasserre’s univariate measurebased bounds for multivariate polynomial optimization. Mathematical Programming. doi:10.1007/s1010702001586y

Dadush, D.N, & Tiwari, S.S.K. (2020). On the complexity of branching proofs. In Leibniz International Proceedings in Informatics, LIPIcs. doi:10.4230/LIPIcs.CCC.2020.34
Current projects with external funding

Smart Heuristic Problem Optimization ()

Wiskundecluster DIAMANT ()

MixedInteger NonLinear Optimisation Applications (MINOA)

Optimization for and with Machine Learning (OPTIMAL)

Polynomial Optimization, Efficiency through Moments and Algebra (POEMA)

Vóórkomen en voorkómen van incidenten op het spoor (PPS Prorail)

Towards a Quantitative Theory of Integer Programming (QIP)
Related partners

Alma Mater StudiorumUniversita di Bologna

AlpenAdriaUniversität Klagenfurt

CNR Pisa

CNRS

Dassault Systèmes B.V.

IBM

INRIA

Prorail

Rheinische FriedrichWilhelmus Universitaet Bonn

Technische Universität Dortmund

Tilburg University

Tromsø, Norway

Universita degli Studi di Firenze

Universität Konstanz

University of Birmingham

Universiteit van Tilburg