@article{GelssKlusKnebeletal.2022, author = {Gelß, Patrick and Klus, Stefan and Knebel, Sebastian and Shakibaei, Zarin and Pokutta, Sebastian}, title = {Low-Rank Tensor Decompositions of Quantum Circuits}, journal = {Journal of Computational Physics}, arxiv = {http://arxiv.org/abs/2205.09882}, year = {2022}, abstract = {Quantum computing is arguably one of the most revolutionary and disruptive technologies of this century. Due to the ever-increasing number of potential applications as well as the continuing rise in complexity, the development, simulation, optimization, and physical realization of quantum circuits is of utmost importance for designing novel algorithms. We show how matrix product states (MPSs) and matrix product operators (MPOs) can be used to express certain quantum states, quantum gates, and entire quantum circuits as low-rank tensors. This enables the analysis and simulation of complex quantum circuits on classical computers and to gain insight into the underlying structure of the system. We present different examples to demonstrate the advantages of MPO formulations and show that they are more efficient than conventional techniques if the bond dimensions of the wave function representation can be kept small throughout the simulation.}, language = {en} } @article{MathieuCardereraPokutta2022, author = {Mathieu, Besan{\c{c}}on and Carderera, Alejandro and Pokutta, Sebastian}, title = {FrankWolfe.jl: a high-performance and flexible toolbox for Frank-Wolfe algorithms and Conditional Gradients}, volume = {34}, journal = {INFORMS Journal on Computing}, number = {5}, doi = {10.1287/ijoc.2022.1191}, pages = {2383 -- 2865}, year = {2022}, abstract = {We present FrankWolfe.jl, an open-source implementation of several popular Frank-Wolfe and conditional gradients variants for first-order constrained optimization. The package is designed with flexibility and high performance in mind, allowing for easy extension and relying on few assumptions regarding the user-provided functions. It supports Julia's unique multiple dispatch feature, and it interfaces smoothly with generic linear optimization formulations using MathOptInterface.jl.}, language = {en} } @article{ŠofranacGleixnerPokutta2022, author = {Šofranac, Boro and Gleixner, Ambros and Pokutta, Sebastian}, title = {Accelerating domain propagation: An efficient GPU-parallel algorithm over sparse matrices}, volume = {109}, journal = {Parallel Computing}, doi = {10.1016/j.parco.2021.102874}, pages = {102874}, year = {2022}, abstract = {• Currently, domain propagation in state-of-the-art MIP solvers is single thread only. • The paper presents a novel, efficient GPU algorithm to perform domain propagation. • Challenges are dynamic algorithmic behavior, dependency structures, sparsity patterns. • The algorithm is capable of running entirely on the GPU with no CPU involvement. • We achieve speed-ups of around 10x to 20x, up to 180x on favorably-large instances.}, language = {en} } @inproceedings{CriadoMartinezRubioPokutta2022, author = {Criado, Francisco and Mart{\´i}nez-Rubio, David and Pokutta, Sebastian}, title = {Fast Algorithms for Packing Proportional Fairness and its Dual}, volume = {36}, booktitle = {Proceedings of the Conference on Neural Information Processing Systems}, year = {2022}, abstract = {The proportional fair resource allocation problem is a major problem studied in flow control of networks, operations research, and economic theory, where it has found numerous applications. This problem, defined as the constrained maximization of sum_i log x_i, is known as the packing proportional fairness problem when the feasible set is defined by positive linear constraints and x ∈ R≥0. In this work, we present a distributed accelerated first-order method for this problem which improves upon previous approaches. We also design an algorithm for the optimization of its dual problem. Both algorithms are width-independent.}, language = {en} } @article{Kerdreuxd'AspremontPokutta2022, author = {Kerdreux, Thomas and d'Aspremont, Alexandre and Pokutta, Sebastian}, title = {Restarting Frank-Wolfe: Faster Rates under H{\"o}lderian Error Bounds}, journal = {Journal of Optimization Theory and Applications}, year = {2022}, language = {en} } @article{KossenHirzelMadaietal.2022, author = {Kossen, Tabea and Hirzel, Manuel A. and Madai, Vince I. and Boenisch, Franziska and Hennemuth, Anja and Hildebrand, Kristian and Pokutta, Sebastian and Sharma, Kartikey and Hilbert, Adam and Sobesky, Jan and Galinovic, Ivana and Khalil, Ahmed A. and Fiebach, Jochen B. and Frey, Dietmar}, title = {Towards Sharing Brain Images: Differentially Private TOF-MRA Images with Segmentation Labels Using Generative Adversarial Networks}, journal = {Frontiers in Artificial Intelligence}, doi = {https://doi.org/10.3389/frai.2022.813842}, year = {2022}, abstract = {Sharing labeled data is crucial to acquire large datasets for various Deep Learning applications. In medical imaging, this is often not feasible due to privacy regulations. Whereas anonymization would be a solution, standard techniques have been shown to be partially reversible. Here, synthetic data using a Generative Adversarial Network (GAN) with differential privacy guarantees could be a solution to ensure the patient's privacy while maintaining the predictive properties of the data. In this study, we implemented a Wasserstein GAN (WGAN) with and without differential privacy guarantees to generate privacy-preserving labeled Time-of-Flight Magnetic Resonance Angiography (TOF-MRA) image patches for brain vessel segmentation. The synthesized image-label pairs were used to train a U-net which was evaluated in terms of the segmentation performance on real patient images from two different datasets. Additionally, the Fr{\´e}chet Inception Distance (FID) was calculated between the generated images and the real images to assess their similarity. During the evaluation using the U-Net and the FID, we explored the effect of different levels of privacy which was represented by the parameter ϵ. With stricter privacy guarantees, the segmentation performance and the similarity to the real patient images in terms of FID decreased. Our best segmentation model, trained on synthetic and private data, achieved a Dice Similarity Coefficient (DSC) of 0.75 for ϵ = 7.4 compared to 0.84 for ϵ = ∞ in a brain vessel segmentation paradigm (DSC of 0.69 and 0.88 on the second test set, respectively). We identified a threshold of ϵ <5 for which the performance (DSC <0.61) became unstable and not usable. Our synthesized labeled TOF-MRA images with strict privacy guarantees retained predictive properties necessary for segmenting the brain vessels. Although further research is warranted regarding generalizability to other imaging modalities and performance improvement, our results mark an encouraging first step for privacy-preserving data sharing in medical imaging.}, language = {en} } @inproceedings{WirthPokutta2022, author = {Wirth, Elias and Pokutta, Sebastian}, title = {Conditional Gradients for the Approximately Vanishing Ideal}, volume = {151}, booktitle = {Proceedings of The 25th International Conference on Artificial Intelligence and Statistics}, pages = {2191 -- 2209}, year = {2022}, abstract = {The vanishing ideal of a set of points X is the set of polynomials that evaluate to 0 over all points x in X and admits an efficient representation by a finite set of polynomials called generators. To accommodate the noise in the data set, we introduce the Conditional Gradients Approximately Vanishing Ideal algorithm (CGAVI) for the construction of the set of generators of the approximately vanishing ideal. The constructed set of generators captures polynomial structures in data and gives rise to a feature map that can, for example, be used in combination with a linear classifier for supervised learning. In CGAVI, we construct the set of generators by solving specific instances of (constrained) convex optimization problems with the Pairwise Frank-Wolfe algorithm (PFW). Among other things, the constructed generators inherit the LASSO generalization bound and not only vanish on the training but also on out-sample data. Moreover, CGAVI admits a compact representation of the approximately vanishing ideal by constructing few generators with sparse coefficient vectors.}, language = {en} } @article{ŠofranacGleixnerPokutta2022, author = {Šofranac, Boro and Gleixner, Ambros and Pokutta, Sebastian}, title = {An Algorithm-independent Measure of Progress for Linear Constraint Propagation}, volume = {27}, journal = {Constraints}, doi = {10.1007/s10601-022-09338-9}, pages = {432 -- 455}, year = {2022}, language = {en} } @inproceedings{ParczykPokuttaSpiegeletal.2022, author = {Parczyk, Olaf and Pokutta, Sebastian and Spiegel, Christoph and Szab{\´o}, Tibor}, title = {New Ramsey Multiplicity Bounds and Search Heuristics}, booktitle = {Discrete Mathematics Days}, year = {2022}, abstract = {We study two related problems concerning the number of monochromatic cliques in two-colorings of the complete graph that go back to questions of Erdős. Most notably, we improve the 25-year-old upper bounds of Thomason on the Ramsey multiplicity of K4 and K5 and we settle the minimum number of independent sets of size 4 in graphs with clique number at most 4. Motivated by the elusiveness of the symmetric Ramsey multiplicity problem, we also introduce an off-diagonal variant and obtain tight results when counting monochromatic K4 or K5 in only one of the colors and triangles in the other. The extremal constructions for each problem turn out to be blow-ups of a finite graph and were found through search heuristics. They are complemented by lower bounds and stability results established using Flag Algebras, resulting in a fully computer-assisted approach. More broadly, these problems lead us to the study of the region of possible pairs of clique and independent set densities that can be realized as the limit of some sequence of graphs.}, language = {en} } @article{HunkenschroederPokuttaWeismantel2022, author = {Hunkenschr{\"o}der, Christoph and Pokutta, Sebastian and Weismantel, Robert}, title = {Optimizing a low-dimensional convex function over a high-dimensional cub}, journal = {SIAM Journal on Optimization}, year = {2022}, language = {en} } @inproceedings{MacDonaldBesanconPokutta2022, author = {MacDonald, Jan and Besan{\c{c}}on, Mathieu and Pokutta, Sebastian}, title = {Interpretable Neural Networks with Frank-Wolfe: Sparse Relevance Maps and Relevance Orderings}, booktitle = {Proceedings of the International Conference on Machine Learning}, year = {2022}, language = {en} }