Description
Leader of the group Networks and Optimization: Daniel Dadush.
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 (online series) with Jasper van Doornmalen (TU/e) and Daniel Brosch (Tilburg University)
 20220524T16:00:00+02:00
 20220524T17:00:00+02:00
Dutch Seminar on Optimization (online series) with Jasper van Doornmalen (TU/e) and Daniel Brosch (Tilburg University)
Start: 20220524 16:00:00+02:00 End: 20220524 17:00:00+02:00
The Dutch Seminar on Optimization is an initiative to bring together researchers from the Netherlands and beyond, with topics that are centered around Optimization in a broad sense. We would like to invite all researchers, especially also PhD students, who are working on related topics to join the events. We hereby announce the following two talks, given by PhDstudents:
Speaker: Jasper van Doornmalen (TU/e)
Title: Symmetry handling in binary programs through propagation
Date: Tuesday 24th May, 4:00pm CET
Abstract:
Symmetries of binary programs are known to dramatically slow down branchandbound procedures. A classical approach to handle permutation symmetries is to enforce that only one representative of equivalent (symmetric) solutions can be computed. In classical integer programming literature, among others, this is established by introducing symmetry handling constraints. This way, solutions that are not lexicographically maximal among the permuted solutions are cut off.
We present a propagationbased symmetry handling technique. Given a set of fixed variables (e.g., due to branching decisions), this technique identifies further variables that can be fixed to ensure that only lexicographically maximal solutions are computed. We present efficient algorithms to find such additional symmetrybased variable fixings for arbitrary sets of permutations and cyclic groups. In particular, for cyclic groups, we show that all possible fixings can be found in polynomial time even if the cyclic group has exponential order.
Our methods are implemented as a plugin in the academic integer programming solver SCIP, and we discuss the effectiveness of these methods on various symmetrical instances.
Speaker: Daniel Brosch (Tilburg University)
Title: The Symmetries of FlagAlgebras
Date: Tuesday 24th May, 4:30pm CET
Abstract:
FlagAlgebras, first introduced by Razborov in 2007, remain one of the most powerful tools in extremal combinatorics. Recently a connection to polynomial optimization was discovered: We can recover FlagSumsofSquares hierarchies by partially exploiting the symmetries of a polynomial optimization hierarchy. We continue from there and fully exploit the symmetries in this polynomial setting for two different hierarchies, one focusing on a low number of edges, and another focusing on a low number of vertices of appearing Flags. For the first, due to the high initial dimension of the hierarchy, a novel algorithm was needed to decompose modules of the symmetric group into irreducible submodules. We apply the reduced hierarchies to obtain outer approximations of graphprofiles, which model various open problems from extremal combinatorics.
N&O seminar: Stefan Schmid (TU Berlin)
 20220615T11:00:00+02:00
 20220615T12:00:00+02:00
N&O seminar: Stefan Schmid (TU Berlin)
Start: 20220615 11:00:00+02:00 End: 20220615 12:00:00+02:00
Everyone is welcome to attend the next N&O seminar with Stefan Schmid with the title 'SelfAdjusting Networks'.
The talk will take place in L017 at CWI, along with zoom support for remote participants. For more information and registration to get the Zoom link via email, please contact Willem Feijen (willem.feijen at cwi.nl), Samarth Tiwari (samarth.tiwari at cwi.nl) or Sven Polak (sven.polak at cwi.nl).
Abstract: This talk will present the vision of selfadjusting networks: communication networks whose physical topology adapts to the traffic pattern it serves, in a demandaware manner. Such networks are enabled by emerging reconfigurable optical technologies. It will be shown that the benefit of selfadjusting networks depends on the amount of “structure” there is in the demand, and an informationtheoretical approach to measure the complexity of traffic traces will be presented to derive entropybased metrics accordingly. Optimal offline and online algorithms to design selfadjusting networks whose performance matches the derived metrics asymptotically will be discussed.
Dutch Seminar on Optimization (online series) with Vera Traub (ETH Zürich)
 20220630T16:00:00+02:00
 20220630T17:00:00+02:00
Dutch Seminar on Optimization (online series) with Vera Traub (ETH Zürich)
Start: 20220630 16:00:00+02:00 End: 20220630 17:00:00+02:00
Speaker: Vera Traub (ETH Zürich)
Title:
BetterThan2 Approximations for Weighted Tree Augmentation and Forest Augmentation
Zoom link:
https://cwinl.zoom.us/j/84909645595?pwd=b1M4QnNKVzNMdmNSVFNaZUJmR1kvUT09
(Meeting ID: 849 0964 5595, Passcode: 772448)
Abstract:
Workshop on Semidefinite and Polynomial Optimization (Semester Programme)
 20220829T00:00:00+02:00
 20221002T23:59:59+02:00
Workshop on Semidefinite and Polynomial Optimization (Semester Programme)
Start: 20220829 00:00:00+02:00 End: 20221002 23:59:59+02:00
This workshop is dedicated to recent developments in semidefinite and polynomial optimization, and their applications in combinatorial and continuous optimization, discrete geometry and quantum information. The program (under construction) will consist of invited lectures by experts in the field. It will also feature lectures by younger researchers and ample time will be left for free discussions.
This workshop is coorgnized by Jop Briët and Monique Laurent.
Here you can find more information on the program of CWI's Semidefinite and Polynomial Optimization Workshop.
Workshop on Solving Polynomial Equations and Applications (Semester Programme)
 20221005T00:00:00+02:00
 20221007T23:59:59+02:00
Workshop on Solving Polynomial Equations and Applications (Semester Programme)
Start: 20221005 00:00:00+02:00 End: 20221007 23:59:59+02:00
Polynomial equations are at the heart of many problems in pure and applied mathematics. They form a powerful tool for modelling nonlinear phenomena in the sciences. Application areas range from robotics, chemistry and computer vision to quantum physics and statistics. Recent progress has made it possible to reliably solve challenging polynomial equations arising in such practical contexts. This workshop will feature a friendly introduction to existing methods, presentations of the latest software tools and research talks by experts in the field. The focus will be on new trends and methodology, as well as applications in the sciences.
This workshop is coorganized by Monique Laurent and Simon Telen.
Here you can find more information on the program of CWI's Solving Polynomial Equations and Applications workshop.
Workshop on Polynomial Optimization and Applications in Control and Energy (Semester Programme)
 20221116T00:00:00+01:00
 20221118T23:59:59+01:00
Workshop on Polynomial Optimization and Applications in Control and Energy (Semester Programme)
Start: 20221116 00:00:00+01:00 End: 20221118 23:59:59+01:00
This workshop is devoted to the application of polynomial optimization methods in the analysis and control of dynamical systems and energy networks. The polynomial optimization approach offers a powerful framework to model hard nonconvex, nonlinear control problems as infinite dimensional linear optimization problems over measure spaces. The rich interplay between functional analysis and operator theory, and real algebraic geometry, underlies the nowadays wellknown moment/sumofsquares hierarchy of relaxations, that allows to efficiently obtain converging sequences of bounds. This approach has also been recently developed to attack large optimal power flow problems in large electrical networks. The program (under construction) will feature lectures by experts in the field and ample time will be left for discussions.
This workshop is coorganized by Monique Laurent and Bert Zwart.
Here you can find more information on the program of CWI's Polynomial Optimization and Applications in Control and Energy workshop.
Members
Associated Members
Publications

Laurent, M, & Vargas, L.F. (2022). Finite convergence of sumofsquares hierarchies for the stability number of a graph. SIAM Journal on Optimization, 32(2), 491–518. doi:10.1137/21M140345X

Borst, S.J, van Iersel, L.J.J, Jones, M.E.L, & Kelk, S.M. (2022). New FPT algorithms for finding the temporal hybridization number for sets of phylogenetic trees. Algorithmica. doi:10.1007/s00453022009468

Schäfer, G, & Zweers, B.G. (2021). Maximum coverage with cluster constraints: An LPbased approximation technique. In Proceedings of the 19th International Workshop on Approximation and Online Algorithms (pp. 63–80). doi:10.1007/9783030808792_5

Dadush, D.N, Koh, Z.K, Natura, B, & Végh, L.A. (2021). An accelerated Newton–Dinkelbach method and its application to two variables per inequality systems. In Annual European Symposium on Algorithms (pp. 36.1–36.15). doi:10.4230/LIPIcs.ESA.2021.36

Bansal, N, Naor, J, & Talmon, O. (2021). Efficient online weighted multilevel paging. In Proceedings of the ACM Symposium on Parallelism in Algorithms and Architectures (pp. 94–104). doi:10.1145/3409964.3461801

Coester, C.E, & Koutsoupias, E. (2021). Towards the kserver conjecture: A unifying potential, pushing the frontier to the circle. In International Colloquium on Automata, Languages, and Programming (pp. 57:1–57:20). doi:10.4230/LIPIcs.ICALP.2021.57

van Apeldoorn, J.T.S, Gribling, S.J, Li, Y, Nieuwboer, H.A, Walter, M, & de Wolf, R.M. (2021). Quantum algorithms for matrix scaling and matrix balancing. In International Colloquium on Automata, Languages, and Programming (pp. 110:1–110:17). doi:10.4230/LIPIcs.ICALP.2021.110

Slot, L.F.H, & Laurent, M. (2021). Sumofsquares hierarchies for binary polynomial optimization. In Lecture Notes in Computer Science/Lecture Notes in Artificial Intelligence (pp. 43–57). doi:10.1007/9783030738792_4

Borst, S.J, Dadush, D.N, Huiberts, S, & Tiwari, S.S.K. (2021). On the integrality gap of binary integer programs with Gaussian data. In Lecture Notes in Computer Science/Lecture Notes in Artificial Intelligence (pp. 427–442). doi:10.1007/9783030738792_30

Buchbinder, N, Coester, C.E, & Naor, J. (2021). Online ktaxi via double coverage and timereverse primaldual. In Proceedings of the 22nd Conference on Integer Programming and Combinatorial Optimization. doi:10.1007/9783030738792_2
Current projects with external funding

Smart Heuristic Problem Optimization ()

MixedInteger NonLinear Optimisation Applications (MINOA)

New frontiers in numerical nonlinear algebra (None)

Optimization for and with Machine Learning (OPTIMAL)

Polynomial Optimization, Efficiency through Moments and Algebra (POEMA)

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

Rheinische FriedrichWilhelmus Universitaet Bonn

Technische Universität Dortmund

Tilburg University

Tromsø, Norway

Universita degli Studi di Firenze

Universität Konstanz

University of Birmingham

Universiteit van Tilburg