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, real-world 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 problem-specific 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 real-world problems. We are always interested in new algorithmic challenges arising in real-world 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

CWI co-organizes international trimester program at Bonn University
CWI is co-organizing an international trimester program on Discrete Optimization at the Hausdorff Research Institute for Mathematics in Bonn. Goal of this community service is to collaborate and make progress on long-standing open problems.

Monique Laurent elected as EUROPT Fellow 2021
Monique Laurent (CWI and Tilburg University) was elected EUROPT Fellow 2021 for being an outstanding researcher in continuous optimization.

Strong Contribution of Networks and Optimization at IPCO 2021
Research carried out by CWI's Networks and Optimization (N&O) group has resulted in several contributions to the 22nd Conference on Integer Programming and Combinatorial Optimization, IPCO 2021: three presentations of research papers and the award in the Student Poster Competition.

NETWORKS consortium awarded €1M from EU COFUND for postdoc programme
After receiving the COFUND grant from the Horizon 2020 programme for 14 PhD positions, NETWORKS has been granted a COFUND grant of €1.0 million to appoint 14 postdoctoral researchers for 2 years.
Current events
Dutch Seminar on Optimization (online series) with Jasper van Doornmalen (TU/e) and Daniel Brosch (Tilburg University)
- 2022-05-24T16:00:00+02:00
- 2022-05-24T17:00:00+02:00
Dutch Seminar on Optimization (online series) with Jasper van Doornmalen (TU/e) and Daniel Brosch (Tilburg University)
Start: 2022-05-24 16:00:00+02:00 End: 2022-05-24 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 PhD-students:
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 branch-and-bound 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 propagation-based 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 symmetry-based 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 Flag-Algebras
Date: Tuesday 24th May, 4:30pm CET
Abstract:
Flag-Algebras, 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 Flag-Sums-of-Squares 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 graph-profiles, which model various open problems from extremal combinatorics.
N&O seminar: Stefan Schmid (TU Berlin)
- 2022-06-15T11:00:00+02:00
- 2022-06-15T12:00:00+02:00
N&O seminar: Stefan Schmid (TU Berlin)
Start: 2022-06-15 11:00:00+02:00 End: 2022-06-15 12:00:00+02:00
Everyone is welcome to attend the next N&O seminar with Stefan Schmid with the title 'Self-Adjusting 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 e-mail, 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 self-adjusting networks: communication networks whose physical topology adapts to the traffic pattern it serves, in a demand-aware manner. Such networks are enabled by emerging reconfigurable optical technologies. It will be shown that the benefit of self-adjusting networks depends on the amount of “structure” there is in the demand, and an information-theoretical approach to measure the complexity of traffic traces will be presented to derive entropy-based metrics accordingly. Optimal offline and online algorithms to design self-adjusting networks whose performance matches the derived metrics asymptotically will be discussed.
Dutch Seminar on Optimization (online series) with Vera Traub (ETH Zürich)
- 2022-06-30T16:00:00+02:00
- 2022-06-30T17:00:00+02:00
Dutch Seminar on Optimization (online series) with Vera Traub (ETH Zürich)
Start: 2022-06-30 16:00:00+02:00 End: 2022-06-30 17:00:00+02:00
Speaker: Vera Traub (ETH Zürich)
Title:
Better-Than-2 Approximations for Weighted Tree Augmentation and Forest Augmentation
Zoom link:
https://cwi-nl.zoom.us/j/84909645595?pwd=b1M4QnNKVzNMdmNSVFNaZUJmR1kvUT09
(Meeting ID: 849 0964 5595, Passcode: 772448)
Abstract:
Workshop on Semidefinite and Polynomial Optimization (Semester Programme)
- 2022-08-29T00:00:00+02:00
- 2022-10-02T23:59:59+02:00
Workshop on Semidefinite and Polynomial Optimization (Semester Programme)
Start: 2022-08-29 00:00:00+02:00 End: 2022-10-02 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 co-orgnized 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)
- 2022-10-05T00:00:00+02:00
- 2022-10-07T23:59:59+02:00
Workshop on Solving Polynomial Equations and Applications (Semester Programme)
Start: 2022-10-05 00:00:00+02:00 End: 2022-10-07 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 co-organized 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)
- 2022-11-16T00:00:00+01:00
- 2022-11-18T23:59:59+01:00
Workshop on Polynomial Optimization and Applications in Control and Energy (Semester Programme)
Start: 2022-11-16 00:00:00+01:00 End: 2022-11-18 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 well-known moment/sum-of-squares 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 co-organized 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
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Laurent, M, & Vargas, L.F. (2022). Finite convergence of sum-of-squares hierarchies for the stability number of a graph. SIAM Journal on Optimization, 32(2), 491–518. doi:10.1137/21M140345X
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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/s00453-022-00946-8
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Schäfer, G, & Zweers, B.G. (2021). Maximum coverage with cluster constraints: An LP-based approximation technique. In Proceedings of the 19th International Workshop on Approximation and Online Algorithms (pp. 63–80). doi:10.1007/978-3-030-80879-2_5
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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
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Bansal, N, Naor, J, & Talmon, O. (2021). Efficient online weighted multi-level paging. In Proceedings of the ACM Symposium on Parallelism in Algorithms and Architectures (pp. 94–104). doi:10.1145/3409964.3461801
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Coester, C.E, & Koutsoupias, E. (2021). Towards the k-server 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
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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
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Slot, L.F.H, & Laurent, M. (2021). Sum-of-squares hierarchies for binary polynomial optimization. In Lecture Notes in Computer Science/Lecture Notes in Artificial Intelligence (pp. 43–57). doi:10.1007/978-3-030-73879-2_4
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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:10.1007/978-3-030-73879-2_30
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Buchbinder, N, Coester, C.E, & Naor, J. (2021). Online k-taxi via double coverage and time-reverse primal-dual. In Proceedings of the 22nd Conference on Integer Programming and Combinatorial Optimization. doi:10.1007/978-3-030-73879-2_2
Current projects with external funding
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Smart Heuristic Problem Optimization ()
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Mixed-Integer Non-Linear Optimisation Applications (MINOA)
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New frontiers in numerical nonlinear algebra (None)
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Optimization for and with Machine Learning (OPTIMAL)
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Polynomial Optimization, Efficiency through Moments and Algebra (POEMA)
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Towards a Quantitative Theory of Integer Programming (QIP)
Related partners
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Alma Mater Studiorum-Universita di Bologna
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Alpen-Adria-Universität Klagenfurt
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CNR Pisa
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CNRS
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Dassault Systèmes B.V.
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IBM
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INRIA
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Rheinische Friedrich-Wilhelmus Universitaet Bonn
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Technische Universität Dortmund
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Tilburg University
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Tromsø, Norway
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Universita degli Studi di Firenze
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Universität Konstanz
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University of Birmingham
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Universiteit van Tilburg