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BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20210705T160000
DTEND;TZID=Europe/Berlin:20210705T170000
DTSTAMP:20210531T070017Z
CREATED:20210412T122101Z
LAST-MODIFIED:20210531T070017Z
UID:5498-1625500800-1625504400@alop.uni-trier.de
SUMMARY:ALOP-Colloquium with Frauke Liers\, FAU Erlangen-Nürnberg
DESCRIPTION:On Monday\, July 5\, 2021 at 16:00 c.t.  Prof. Dr. Frauke Liers with FAU Erlangen-Nuernberg will present her recent work at our colloquium. She will speak on the topic of  \n  \nData-Driven Robust Protection for Uncertain Optimization Problems \n  \nOne way of protecting against uncertainties that occur in real-world applications is to apply and to develop methodologies from robust optimization that determine best possible robust solutions that are feasible regardless of how uncertainties manifest themselves within predefined uncertainty sets. However\, it is often non-trivial to construct “suitable” uncertainty sets. In this talk\, we present two methodologies in this area. \nAt first\, we introduce a new iterative approach which uses scenario observations to learn more about the uncertainty over time\, enabling us to improve our solutions. The goal is to incorporate new information when it arrives and to improve our solution without resolving the entire robust counterpart. We illustrate the effectiveness of our procedure by numerical experiments on mixed-integer optimization instances from popular benchmark libraries as well as on a practical network design problem. The proposed algorithm is able to solve the problem significantly faster than solving equivalent reformulations. \nSubsequently\, we show that robust protection can also be used for a robust safe approximation of joint chance constrained in DC Optimal Power Flow problems. We propose an approach that replaces probabilistic constraints by robust constraints where the task consists in constructing uncertainty sets from historical data using the scenario approach by Margellos et al. (IEEE Transactions on Automatic Control\, 59 (2014)). The experimental tests demonstrate the effectiveness of this method and run times are very fast and lead to high-quality solutions. \n  \nThe first part is joint with Kevin Aigner\, Andreas Bärmann\, Kristin Braun\,  Oskar Schneider\, Sebastian Tschuppik (FAU Erlangen-Nürnberg)\, and Kartikey Sharma and Sebastian Pokutta (ZIB\, Berlin). The second part is joint with Kevin Aigner\, Jan-Patrick Clarner\, and Alexander Martin (FAU Erlangen-Nürnberg\, Germany). \nThis presentation will take place via ZOOM. A link will be e-mailed prior to the event. \n 
URL:https://alop.uni-trier.de/event/alop-colloquium-with-prof-dr-frauke-liers-fau-erlangen-nurnberg/
CATEGORIES:Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20210712
DTEND;VALUE=DATE:20210715
DTSTAMP:20210713T153651Z
CREATED:20200210T083835Z
LAST-MODIFIED:20210713T153651Z
UID:3357-1626048000-1626307199@alop.uni-trier.de
SUMMARY:ALOP Workshop on Nonlocal Models
DESCRIPTION:This workshop will be held in a digital format (live). Registration is free. \n  \nThe Research Training Group on Algorithmic Optimization is hosting a workshop on \n \nwhich will take place as a live video conference via Zoom from July 12-14\, 2021. \nPlenary Speakers\nHarbir Antil (George Mason University)\nMarta D’Elia (Sandia National Laboratories)\nMax Gunzburger (Florida State University)\nMoritz Kaßmann (Universität Bielefeld)\nJulio D. Rossi (Universidad de Buenos Aires)\nPablo Seleson (Oak Ridge National Laboratory) \n  \nScope\n\nThe goal of this workshop is to bring together researchers from various fields that intersect with nonlocal spacial modeling and thereby generate fruitful synergistic effects among the participants. The workshop will be focused on models which are nonlocal in space; including fractional equations as well as nonlocal models with a finite range of interactions. Aspects that shall be covered include: \n\nOptimization (optimal distributed control\, interface and parameter identification\, etc.)\nAnalysis and Stochastics (numerical analysis\, jump processes\, etc.)\nImplementation (finite element and mesh-free methods\, Monte-Carlo type methods\, low-rank approaches\, spectral methods\, etc.)\nApplications (finance\, peridynamics\, economic models\, etc.)\n\n \nWorkshop Program\n \nalop-ws-schedule\n \nMore details on the virtual setting and a book of abstracts will soon be emailed to the participants.\n\nLocal Organizers\nLeonhard Frerick\nManuel Klar\nEkkehard Sachs\nVolker Schulz\nChristian Vollmann \n  \n 
URL:https://alop.uni-trier.de/event/workshop-on-nonlocal-models-analysis-optimization-and-implementation/
CATEGORIES:Workshop
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20211004T150000
DTEND;TZID=Europe/Berlin:20211007T210000
DTSTAMP:20211001T124244Z
CREATED:20210315T131828Z
LAST-MODIFIED:20211001T124244Z
UID:5438-1633359600-1633640400@alop.uni-trier.de
SUMMARY:Autumn School on Optimization and Market Design
DESCRIPTION:The Research Training Group on Algorithmic Optimization proudly announces its sixth annual \nAutumn School scheduled to take place from October 4 –  7\, 2021.  \nData intensive firms like Uber\, AirBnB\, Deliveroo and the European Electricity Markets play the role of market makers connecting buyers with sellers. They must\, among other things\, monitor quality\, standardize offerings so as to operate at scale\, determine prices and facilitate search. Optimization plays a fundamental role in the design of the rules of a marketplace. What distinguishes the optimization problems in this setting from classical resource allocation problems is the role of incentives. How should they be incorporated into optimization models? \nThis year’s Autumn School will take place in a digital setting (via ZOOM). \nSpeakers: \n\nMoshe Babaioff\, Senior Principal Researcher\, Microsoft Research Israel\n\nMartin Bichler\, Department of Computer Science: Decision Sciences & Systems\, Technical University of Munich\n\nGarrett van Ryzin\,  Distinguished Scientist\, Amazon Supply Chain Optimization Technologies (SCOT) organization\nRakesh V. Vohra\,  Prof.\, Department of Economics & Department of Electrical and Systems Engineering\, University of Pennsylvania\n\n  \nOrganizer:  \n \nSven de Vries\, Trier University \nFurther Details: \nThis autumn school is scheduled to begin on Monday\, October 4\, 2021 at 15:00 local time (CEST) with an official welcome.  All sessions are scheduled for 15:30 local time (CEST). This event will be held in a digital format (live).\n \nA detailed schedule of the sessions can be downloaded here. \nThere is no registration fee for this event.    \nPlease consider presenting your research in the poster session scheduled on Sunday\, October 3\, 2021.  The poster should be related to the topic.  We ask that you submit a one-paragraph abstract regarding your planned presentation.  The deadline to submit an abstract of your planned presentation has been extended to September 15\, 2021. \nThe poster format should be 16:9 (landscape format).  You should submit two documents\, both either in png or jpg: \n\nMain poster: Minimum width is 1000px (26.46cm)\, Minimum height is 600px (15.88cm). Maximum file size is 3MB\, No transparent background.\nA preview poster: A copy of the main poster document that has been made smaller (Recommended width and height are half of the main document). Try to keep it below 1MB.\n\n  \nThe poster with any further information needs to be sent to wahlen[at]uni-trier.de no later than Sep. 16\, 2021 . \nPlease refer back to this page for additional information and updates.  \nRegistration is now closed. \n 
URL:https://alop.uni-trier.de/event/autumn-school-on-optimization-and-market-design/
CATEGORIES:Autumn School
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20211108T160000
DTEND;TZID=Europe/Berlin:20211108T170000
DTSTAMP:20210811T093446Z
CREATED:20210519T085020Z
LAST-MODIFIED:20210811T093446Z
UID:5606-1636387200-1636390800@alop.uni-trier.de
SUMMARY:ALOP-Colloquium with Daniel Aloise\, Polytechnique Montréal
DESCRIPTION:On Monday\, November 8\, 2021 at 16:00 c.t.  Dr. Daniel Aloise\, Polytechnique Montréal will present his recent work at our colloquium.  \nTitle: Convex fuzzy k-medoids clustering \nAbstract: \nK-medoids clustering is among the most popular methods for cluster analysis\, but it carries several assumptions about the nature of the latent clusters. In this work\, we introduce the Convex Fuzzy k -Medoids (CFKM) model\, whose underlying formulation not only relaxes the assumption that objects must be assigned entirely to one and only one medoid\, but also that medoids must be assigned entirely to one and only one cluster. Moreover\, due to its convexity\, CFKM resolution is completely robust to initialization. We compare our model with two fuzzy k-medoids clustering models found in the literature: the Fuzzy k -Medoids (FKM) and the Fuzzy Clustering with Multi-Medoids (FMMdd)\, both solved approximately by heuristics because of their hard computational complexity. Our experiments in synthesized and real-world data sets reveal that our model can uniquely discover important aspects of clustered data which are inherently fuzzy in nature\, besides being more robust regarding the hyperparameters of the fuzzy clustering task. \nThis presentation will take place via ZOOM. A link will be e-mailed prior to the event.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-daniel-alois-polytechnique-montreal/
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20211115T160000
DTEND;TZID=Europe/Berlin:20211115T170000
DTSTAMP:20210521T050924Z
CREATED:20210519T085624Z
LAST-MODIFIED:20210521T050924Z
UID:5608-1636992000-1636995600@alop.uni-trier.de
SUMMARY:ALOP-Colloquium with Sungho Shin\, University of Wisconsin-Madison
DESCRIPTION:On Monday\, November 15\, 2021\, at 16:00 c.t.\, Ph.D. candidate Sungho Shin\, University of Madison-Wisonsin will speak about his recent work: \n  \nTitle: Graph-Structured Nonlinear Programming: Properties and Algorithms \n  \nA graph-structured nonlinear program (NLP) is a nonlinear optimization problem whose algebraic structure is induced by a graph. These problems arise in diverse applications such as dynamic optimization (model predictive control and moving horizon estimation)\, network optimization (energy systems and supply chain)\, optimization with embedded discretized partial differential equations\, and multi-stage stochastic programming. Building upon the existing NLP sensitivity theory\, we show that the nodal solution sensitivity against parametric perturbation decays exponentially with respect to the distance from the perturbation point. Remarkably\, this result (which we call exponential decay of sensitivity; EDS) holds under fairly standard regularity assumptions used in classical NLP sensitivity theory: second-order sufficiency conditions and the linear independence constraint qualification. EDS allows the creation of novel computing strategies\, the overlapping Schwarz decomposition method (also known as domain decomposition). This method decomposes a graph-structured NLP into multiple smaller subproblems over overlapping subdomains and solves the subproblems in parallel and iteratively with the exchange of information at boundries. Based on the EDS result\, we prove that for a certain class of problems satisfying the regularity assumptions\, the convergence rate of the overlapping Schwarz method improves exponentially with the size of overlap; thus\, overlap accelerates the convergence. With real-world case studies on gas and electric networks\, we demonstrate the effectiveness of the overlapping Schwarz method. \n  \nThis presentation will take place via ZOOM. A link will be e-mailed prior to the event
URL:https://alop.uni-trier.de/event/alop-colloquium-with-sungho-shin-university-of-wisconsin-madison/
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20220110T160000
DTEND;TZID=Europe/Berlin:20220110T170000
DTSTAMP:20211130T112128Z
CREATED:20211117T073819Z
LAST-MODIFIED:20211130T112128Z
UID:6266-1641830400-1641834000@alop.uni-trier.de
SUMMARY:ALOP-Colloquium with Prof. Samuel Amstutz\, CMAP - Ecole Polytechnique
DESCRIPTION:On Monday\, January 10\, 2022\, at 16:00 c.t.\, Prof. Samuel Amstutz of CMAP – Ecole Polytechnique will speak about his recent work regarding  \nTopology optimization and optimal partitioning with non-local perimeter approximation \n\nTopology optimization deals with the optimal design of shapes of unknown topology. For such problems\, the perimeter may be considered as penalization to regularize the boundaries and ultimately favor the existence of optimal shapes\, but it is difficult to handle directly within algorithms because it is highly sensitive to topology changes. A classical remedy is to use approximate versions of the perimeter in the sense of Gamma-convergence. In this talk\, after reviewing the context\, I will present a (relative or total) perimeter approximation which is built upon the solution of an elliptic boundary value problem. I will discuss the advantages and drawbacks of this approach compared with alternative functionals\, and show in particular how the variational formulation of the boundary value problem can be exploited to design alternating minimizations schemes. Then I will explain how those results and methods\, through combinatorial and convex analysis techniques\, can be adapted to multiphase optimal partitioning problems with an energy term consisting of a weighted sum of Hausdorff measures of interfaces. Problems of image classification and of hydrostatics with surface tensions will be shown as examples. If time allows\, I will also discuss anisotropic variants. \n  \nThis presentation will take place via ZOOM. A link will be e-mailed prior to the event.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-samuel-amstutz-cmap-ecole-polytechnique/
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20220207T160000
DTEND;TZID=Europe/Berlin:20220207T170000
DTSTAMP:20220110T113307Z
CREATED:20211102T120107Z
LAST-MODIFIED:20220110T113307Z
UID:6260-1644249600-1644253200@alop.uni-trier.de
SUMMARY:ALOP-Colloquium with Prof. Geunyeong Byeon\, Arizona State University
DESCRIPTION:On Monday\, February 7\, 2022\, at 16:00 c.t.\, Prof. Geunyeong Byeon\, Arizona State University will speak about her recent work. \nDecomposition Methods for Bilevel Problems with Convex Follower \nAbstract: Bilevel optimization formulates hierarchical decision-making processes that arise in many real-world applications such as in pricing\, network design\, and infrastructure defense planning. This work considers a class of bilevel optimization problems where the upper level problem features some integer variables while the lower level problem enjoys strong duality. We propose a dedicated Benders decomposition method for solving this class of bilevel problems\, which decomposes the Benders subproblem into two more tractable\, sequentially solvable problems that can be interpreted as the upper and the lower level problems. We show that the Benders subproblem decomposition carries over to an interesting extension of bilevel problems\, which connects the upper level solution with the lower level dual solution\, and discuss some special cases of bilevel problems that allow sequence-independent subproblem decomposition. Several novel schemes for generating numerically stable cuts\, finding a good incumbent solution\, and accelerating the search tree are discussed. A computational study demonstrates the computational benefits of the proposed method over a state-of-the-art bilevel-tailored branch-and-cut method\, a commercial solver\, and the standard Benders method on standard test cases and the motivating applications in sequential energy markets. \nThis presentation will take place via ZOOM. A link will be e-mailed prior to the event
URL:https://alop.uni-trier.de/event/alop-colloquium-with-prof-geunyeong-byeon-arizona-state-university/
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20220411T160000
DTEND;TZID=Europe/Berlin:20220411T170000
DTSTAMP:20220301T152303Z
CREATED:20220228T102256Z
LAST-MODIFIED:20220301T152303Z
UID:6344-1649692800-1649696400@alop.uni-trier.de
SUMMARY:ALOP-Colloquium with Dr. Akhil Vohra\, University of Cambridge
DESCRIPTION:On Monday\, April 11\, 2022\, at 16:00 c.t.\, Dr. Akhil Vohra\, University of Cambridge will speak on the topic of Bayesian Persuasion: Reduced Form Approach. \nAbstract: \nWe illustrate the usefulness of reduced form representations of Bayesian persuasion problems with two applications. In one\, the reduced form representation yields a simple algorithm to determine the support of the optimal solution. In the second\, the reduced form leads to a simple greedy algorithm to determine the maximum value a sender can achieve in any cheap talk equilibrium. \nThis presentation will take place in HS 9.  Please join us for coffee and an informal meeting with the lecturer prior to the presentation in E 10 at 15:45.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-dr-akhil-vohra-university-of-cambridge/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20220613T160000
DTEND;TZID=Europe/Berlin:20220613T170000
DTSTAMP:20220608T143440Z
CREATED:20220608T101314Z
LAST-MODIFIED:20220608T143440Z
UID:6548-1655136000-1655139600@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Paul Swoboda
DESCRIPTION:On Monday\, June 13\, 2022\, at 16.00 c.t. Dr. Paul Swoboda\, Max-Planck-Institut für Informatik\, Saarland Informatics Campus will present his recent work titled \nSolving 0-1 ILPs with Binary Decision Diagrams \nAbstract: \nWe present a Lagrange decomposition method for solving 0–1 integer linear programs occurring in structured prediction. We propose a sequential and a massively min-marginal averaging schemes for solving the Lagrangean dual and a perturbation technique for decoding primal solutions. For representing subproblems we use binary decision diagrams (BDDs)\, which support efficient computation of subproblem solutions and update steps. We present experimental results on combinatorial problems from MAP inference for Markov Random Fields\, quadratic assignment and cell tracking for developmental biology. Our highly parallel GPU implementation improves comes close to or outperform some state-of-the-art specialized heuristics while being problem agnostic. We additionally showcase improvement that can be obtained by integrating machine learning into our solver. \n  \nThe presentation will take place in HS 9.  Please join us for coffee in E 10 at 15:45.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-paul-swoboda/
LOCATION:Trier University E Building\, Universitätsring 15\, Trier\, 54296\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20220720T080000
DTEND;TZID=Europe/Berlin:20220722T150000
DTSTAMP:20220721T101135Z
CREATED:20220215T104112Z
LAST-MODIFIED:20220721T101135Z
UID:6294-1658304000-1658502000@alop.uni-trier.de
SUMMARY:ALOP Workshop on Algorithmic Optimization and Data Science
DESCRIPTION:The Research Training Group on Algorithmic Optimization is hosting a workshop on \nAlgorithmic Optimization and Data Science\,  July 20 – July 22\, 2022. \n  \nConfirmed Invited Speakers\nProf. Dr. Gitta Kutyniok (Ludwig-Maximilians-Universität München) \nProf. Dr. Sebastian Pokutta (Zuse Institute Berlin) \nProf. Dr. Suvrit Sra (MIT Institute for Data\, Systems\, and Society) \nProf. Dr. Enrique Zuazua (Friedrich-Alexander-Universität Erlangen-Nürnberg) \nScope\n\nOptimization algorithms are a key part of almost every solution approach in data science. On the other hand\, data science or machine learning concepts can be utilized as components of optimization methods to improve state-of-the-art optimization technologies.  These viewpoints will be addressed in lively discussions during the workshop\, which will bring together experts in the fields of data science\, machine learning\, algorithmic optimization\, and everything related to these fields. \nThe topics of the workshop will include but are not limited to \n\n optimization strategies for machine learning\,\n machine learning strategies for optimization\,\n data science models based on optimization and optimal control\,\n the interplay of reinforcement learning and optimal control\,\n as well as implementations and applications.\n\nWorkshop Program\nThe workshop will begin on Wednesday\, July 20\, 2022\, at 8:00 am with registration followed by an official welcome at 9:00 am.  The workshop is scheduled to close on Friday\, July 22\, 2022\, at 3:00 pm. A detailed program may be downloaded here. \nHotel Room Reservations\nWe have a reserved a hotel room contingent at the Friedrich Hotels Trier\, Am Porta Nigra Platz\, 54292 Trier. Please contact them directly via Email: Rezeption@friedrich-hotels.de or phone +49 (651) 9770 10 0 to make your reservations referencing ALOP and Data Science. \nThe contingent will be available for reservation until July 1\, 2022\, or until all available rooms have been booked. \nConference Fee\nA conference of 50 €  is due for in-presence participants and includes refreshments\, the conference dinner complete with a wine tasting\, and a city tour of Trier. \nA conference fee of 10 € is due for remote participation via Zoom. \nSome Covid restrictions have been lifted at this time and participation in presence is unlimited.  Be sure to sign up for participation in person and use the opportunity by presenting a talk.\nRemote participation via Zoom is possible for all participants who do not plan on making a presentation\nPlease follow this page for updates in regards to restrictions due to the pandemic.  \nLocal Organizers\nRalph Bergmann\nNicole Marheineke\nRalf Münnich\nAchim Rettinger\nMartin Schmidt\nVolker Schulz \n________________________________________________________________________________________________________________________\nRegistration is now closed. \nAcceptance of your talk/presentation will be sent no later than June 30\, 2022. \n 
URL:https://alop.uni-trier.de/event/alop-workshop-on-algorithmic-optimization-and-data-science/
LOCATION:Trier University E Building\, Universitätsring 15\, Trier\, 54296\, Germany
CATEGORIES:Workshop
ATTACH;FMTTYPE=image/jpeg:https://alop.uni-trier.de/wp-content/uploads/2022/02/WS-AlgOpt-Data-Sci-scaled.jpg
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20220804T160000
DTEND;TZID=Europe/Berlin:20220804T170000
DTSTAMP:20220721T081156Z
CREATED:20220718T130428Z
LAST-MODIFIED:20220721T081156Z
UID:6654-1659628800-1659632400@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Kendra Reiter
DESCRIPTION:On Thursday\, August 4 2022 at 16:00 c.t. Kendra Reiter\, MTU Maintenance (Hannover)\, will speak at the ALOP Colloquium about her recent work: \n  \nBuilding a geo-referenced microsimulation model with discrete optimization* \n*joint work with Dr. Ulf Friedrich\, OVGU Magdeburg and Prof. Dr. Ralf Münnich\, Trier University \nAbstract: \nMicrosimulation is an important tool to support evidence-based policies. To produce a fully geo-coded dataset\, where information is generally available on aggregate levels of different hierarchies\, micro units (households and persons) have to be placed into geo-coded dwellings. The microsimulation model involves mathematical optimization problems with integrality constraints on some of the optimization variables. It is therefore necessary to employ combinatorial optimization techniques to handle these discrete structures efficiently. More specifically\, fast algorithms for the sub-problem of address selection are needed: Given a population generated in the first step of the microsimulation process and a target region\, the households in the population have to be assigned to actual addresses within the region\, i.e.\, an address has to be selected for each household in the population. \nWhile the computation time is often not crucial when considering only a subset of the population\, e.g.\, for the simulation of a certain region or city\, the big-data setting of a complete model typically requires specialized\, fast algorithms and techniques from data science. For example\, in the address selection model for Germany more than 40 million households are assigned to over 25 million addresses while using several statistical variables to measure the quality of the assignment. General purpose heuristics such as simulated annealing do generally not solve this instance within an acceptable time limit and do not provide quality certificates. In addition\, large data sets from several sources (e.g.\, Open Street Map\, city registers\, grid-based census data) have to be combined and pre-processed in an efficient and secure way. \nPlease join us at 16:00 c.t. in HS 9.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-ulf-friedrich-and-kendra-reiter/
LOCATION:Trier University E Building\, Universitätsring 15\, Trier\, 54296\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20221004T074500
DTEND;TZID=Europe/Berlin:20221007T160000
DTSTAMP:20221130T083202Z
CREATED:20220303T080325Z
LAST-MODIFIED:20221130T083202Z
UID:6333-1664869500-1665158400@alop.uni-trier.de
SUMMARY:Autumn School on Model Reduction and Model Predictive Control with Differential Equations
DESCRIPTION:The Research Training Group on Algorithmic Optimization proudly announces its seventh annual \nAutumn School from October 4 – 7\, 2022. \nThis year’s focus will be on Model Reduction and Model Predictive Control with Differential Equations\n \nOptimal control problems have numerous applications in engineering and industry. One strategy for approaching them is model predictive control\, which is based on solving a series of online problems over small time periods. A major advantage of this approach is that constraints can be easily incorporated. However\, the computational complexity can become very high for certain real-time problems\, for example\, when the underlying dynamical system is a discretized partial differential equation. In such cases\, model order reduction becomes necessary to reduce the computational costs. The idea is to construct a low-dimensional surrogate model -typically in an offline phase- to replace the overly computationally expensive system underlying the optimization problem in the online phase. \n  \nThe ALOP Autumn School will feature introductory lectures on model order reduction\, model predictive control\, and related topics\, especially from the systems and control perspective \nConfirmed speakers: \nTobias Breiten (TU Berlin) \nTobias Damm (TU Kaiserslautern) \nJan Heiland (OVGU Magdeburg\, Max Planck Institute for Dynamics of Complex Technical Systems) \nBenjamin Unger (University Stuttgart\, Independent Junior Research Group Leader for Dynamic Systems) \nOrganizers:  \n \nNicole Marheineke (Trier University)  \nBjörn Liljegren-Sailer (Trier University) \nSchedule\, Location and Travel Information:  \n \nThe workshop is scheduled to begin on Tuesday\, October 4\, 2022\, with registration starting at 7:45 am\, and ending on Friday\, October 7\, 2022\, in the afternoon. \nThe workshop schedule can be found here. \nThe workshop will take place in Building E located on Campus I at Trier University. \nFor travel tips on how to get to Trier\, please check  here;\nInstructions on how to find Campus I are located here. \n \nDue to Covid restrictions\,  participation in the workshop may be limited \nThere may be other restrictions due to the pandemic.  Please be sure to follow up on this page for new developments. \nHotel Room Reservations \nWe have reserved a hotel room contingent at the Hotel Römischer Kaiser\, Am Porta Nigra Platz\, 54292 Trier. The cost for a single room is 79 € per night and includes breakfast. Please contact them directly to make your reservations referencing the AUTUMN SCHOOL 2022. \nThe contingent will be available for reservation until August 15\, 2022\, or until all available rooms have been booked. \nRegistration information: \nThe registration fee of 70 € includes a welcome reception\, the conference dinner\, refreshments\, and extra-curricular activities. Detailed payment information will be communicated upon registration.  \nTravel Stipend: \nQualified participants may be eligible for a stipend to assist with travel expenses. In order to be considered for the stipend\, please submit a CV (which should include the names and contact information of two professional references) along with a one-page letter of motivation.  You should also be prepared to submit a poster for the Poster Session. \nThe application for stipends has closed. \nRegistration is closed.
URL:https://alop.uni-trier.de/event/autumn-school-on-model-reduction-and-model-predictive-control-with-differential-equations/
LOCATION:Trier University E Building\, Universitätsring 15\, Trier\, 54296\, Germany
CATEGORIES:Autumn School
ATTACH;FMTTYPE=image/jpeg:https://alop.uni-trier.de/wp-content/uploads/2022/10/Gruppenfoto-bearbeitet.jpg
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20221128T160000
DTEND;TZID=Europe/Berlin:20221128T170000
DTSTAMP:20221216T110700Z
CREATED:20221025T102708Z
LAST-MODIFIED:20221216T110700Z
UID:6801-1669651200-1669654800@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Martina Cerulli
DESCRIPTION:On Monday\, November 28 2022 at 16:00 c.t. Martina Cerulli\, ESSEC Business School of Paris\, will speak at the ALOP Colloquium about her recent work: \n  \nOn the dualization of the inner problems of Semi-Infinite programs \nAbstract: \nIn this talk\, we will discuss a solution approach for Semi-Infinite programs (SIPs) based on the dualization of the inner problem\, i.e.\, the problem of finding the constraint that is the most violated by a given point. After a brief introduction to SIPs and the classical solution techniques for these optimization programs\, we will consider two practical problems that can be modeled as SIPs: the aircraft conflict resolution and the collapsed k-core problem. Then\, we will present the results of the paper “Convergent algorithms for a class of convex semi-infinite programs” by M. Cerulli\, A. Oustry\, C. D’Ambrosio\, L. Liberti\, accepted for publication on SIAM Journal on Optimization. In this paper\, we focus on convex SIPs with an infinite number of quadratically parametrized constraints\, not necessarily convex w.r.t. the parameter. A new convergent approach to solve these SIPs is proposed\, leveraging the dualization technique. Based on the Lagrangian dual of the inner problem\, a convex and tractable restriction of the considered SIP is derived. We state sufficient conditions for the optimality of this restriction. If these conditions are not met\, the restriction is enlarged through an Inner-Outer Approximation Algorithm\, and its value converges to the value of the original semi-infinite problem. This new algorithmic approach is compared with the classical Cutting Plane algorithm. We propose a new rate of convergence of the Cutting Plane algorithm\, directly related to the iteration index\, derived when the objective function is strongly convex\, and under a strict feasibility assumption. We successfully test the two methods on two applications: the constrained quadratic regression and a zero-sum game with cubic payoff.  \nPlease join us at 16:00 c.t. in HS 9.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-martina-cerulli/
LOCATION:Trier University E Building\, Universitätsring 15\, Trier\, 54296\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230123T160000
DTEND;TZID=Europe/Berlin:20230123T170000
DTSTAMP:20221216T110910Z
CREATED:20221130T084745Z
LAST-MODIFIED:20221216T110910Z
UID:6893-1674489600-1674493200@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Jannis Kurtz
DESCRIPTION:On Monday\, January 23\, 2023 at 16:00 c.t. Dr. Jannis Kurtz\, University of Amsterdam\, will speak at the ALOP Colloquium about his recent work: \n  \nDeriving Robust Counterfactual Explanations for Machine Learning Models via Two-Stage Robust Optimization \nAbstract: \nNowadays machine learning models are often used to make decisions based on personal data which significantly affect individuals\, e.g. the decision of granting a loan to a person or not. However many machine learning models behave like black-boxes and can incorporate biases contained in the data into their decision which is why in 2016 the European Union enacted the “right to explanation”.   \nCounterfactual explanations (CE) play an important role in providing such explanations and hence improving explainability. The idea is to find the smallest changes which have to be made to a data point such that the model would have changed its decision. Unfortunately most of the common methods can only provide one CE which can be unrealistic to reach for the user. \nIn this work we present a model to calculate robust CEs\, i.e. CEs where after changing each attribute in a certain range the perturbed data point still remains a CE. Hence our method provides a whole set of CEs and the user can choose the one which is most reasonable. We use algorithmic ideas from two-stage robust optimization to calculate robust CEs for the most popular ML methods including logistic regression\, decision trees and neural networks. We show that our method is able to calculate CEs efficiently for common data sets. \n  \nPlease join us at 16:00 c.t. in HS 9. \n 
URL:https://alop.uni-trier.de/event/alop-colloquium-with-jannis-kurtz/
LOCATION:Trier University E Building\, Universitätsring 15\, Trier\, 54296\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230130T160000
DTEND;TZID=Europe/Berlin:20230130T170000
DTSTAMP:20230124T080128Z
CREATED:20230116T141030Z
LAST-MODIFIED:20230124T080128Z
UID:6991-1675094400-1675098000@alop.uni-trier.de
SUMMARY:CANCELED - ALOP Colloquium with Mark Vogelsberger
DESCRIPTION:Unfortunately\, the talk has to be rescheduled. \nAs soon as there is a new date\, we will announce it here.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-mark-vogelsberger/
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230206T164500
DTEND;TZID=Europe/Berlin:20230206T174500
DTSTAMP:20230126T125829Z
CREATED:20221130T082641Z
LAST-MODIFIED:20230126T125829Z
UID:6913-1675701900-1675705500@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Hanno Gottschalk
DESCRIPTION:On Monday\, February 6 2023 at 16:00 c.t. Prof. Dr. Hanno Gottschalk\, University of Wuppertal\, will speak at the ALOP Colloquium about his recent work: \n  \nTheory and Applications of Generative Adversarial Learning \nAbstract: \nGenerative learning is the machine learning task of learning to synthesize new examples that assimilate a given distribution. Since the introduction of generative adversarial networks in the year 2014\, generative learning underwent a rapid development and reached a considerable technological level. \nIn this talk\, generative adversarial learning is studied from a mathematical point of view. However\, we also give applications on domain transfer and sampling from the invariant measure of ergodic processes. \n  \nPlease join us at 16:45 c.t. in HS 10.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-prof-dr-hanno-gottschalk-2/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230213T160000
DTEND;TZID=Europe/Berlin:20230213T170000
DTSTAMP:20230202T125328Z
CREATED:20221129T151056Z
LAST-MODIFIED:20230202T125328Z
UID:6897-1676304000-1676307600@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Marc Goerigk
DESCRIPTION:On Monday\, February 13\, 2023 at 16:00 c.t. Prof. Dr. Marc Goerigk\, University of Siegen\, will speak at the ALOP Colloquium about his recent work: \n  \nModels for Interpretable Optimization \nAbstract: \nWhile explainability and interpretability has become a major research area in machine learning over the past years\, in operations research and mathematical programming the comprehensibility of solutions is hardly every scrutinized. Likely due to the existence of explicitly stated models and well defined solution processes\, experts have high confidence in the correctness and usefulness of found solutions. However\, even understanding a mathematical model can quickly become a challenging task\, especially for people not familiar with modeling techniques. Users with less mathematical and computer background\, e.g. the planner using the optimization software and the workers in charge of implementing the result\, may consider the solver a black box. We present and experimentally validate a modeling framework that inherently provides an interpretable decision rule\, trying to clarify the causal effect of occurring scenario and selected solution. By restricting the number of eligible solutions and providing an interpretable rule\, e.g. in form of a decision tree\, we shift the focus towards comprehensibility and transparency. Our experiments indicate that the costs of interpretability can be small\, i.e.\, only a small percentage of nominal performance needs to be sacrificed. \n  \nPlease join us at 16:00 c.t. in HS 9. \n 
URL:https://alop.uni-trier.de/event/alop-colloquium-with-marc-goerigk/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230424T160000
DTEND;TZID=Europe/Berlin:20230424T170000
DTSTAMP:20230329T140042Z
CREATED:20230102T135641Z
LAST-MODIFIED:20230329T140042Z
UID:6979-1682352000-1682355600@alop.uni-trier.de
SUMMARY:ALOP Colloquium with René Henrion
DESCRIPTION:On Monday\, April 24\, 2023 at 16:00 c.t. Dr. René Henrion\, WIAS Berlin\, will speak at the ALOP Colloquium about his recent work: \n  \nAbstract: \nChance constraints are widely used in stochastic programming when inequality constraints in an optimization problem are affected by some random parameter. A chance constraint then defines a decision to be feasible whenever the constraint is satisfied at some specified probability. \nOriginally developed in the framework of operations research\, chance constraints attract increasing attention also in risk averse optimal control problems. \nThe talk addresses various aspects of chance constraints related with applications\, numerics and optimality conditions in PDE-constrained optimization. \n  \nPlease join us at 16:00 c.t. in HS 10.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-rene-henrion/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230515T160000
DTEND;TZID=Europe/Berlin:20230515T170000
DTSTAMP:20230509T105746Z
CREATED:20230102T135859Z
LAST-MODIFIED:20230509T105746Z
UID:6981-1684166400-1684170000@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Marc Steinbach
DESCRIPTION:On Monday\, May 15\, 2023 at 16:45 c.t. Prof. Dr. Marc Steinbach\, Leibniz Universität Hannover\, will speak at the ALOP Colloquium about his recent work: \n  \nNLP Models for Generating Synthetic Vascular Trees \nAbstract: \nWe introduce a new framework for generating synthetic vascular trees based on NLP models for optimizing the local and global tree geometry. A second novelty is a metaheuristic optimization step for the tree topology. \nThe talk discusses these optimization models and compares the new algorithm to the standard CCO approach for generating vascular trees. Moreover\, it compares the influence of different model variants on trees with 14 branching levels and roughly two million nodes. \nThe validation against a corrosion cast of a human liver shows that the trees generated by our new framework match the physiological data better than those generated by the standard CCO approach. \n  \nPlease join us at 16:45 c.t. in HS 10. \n 
URL:https://alop.uni-trier.de/event/alop-colloquium-with-marc-steinbach/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230612T160000
DTEND;TZID=Europe/Berlin:20230612T170000
DTSTAMP:20230420T141310Z
CREATED:20230420T141310Z
LAST-MODIFIED:20230420T141310Z
UID:7133-1686585600-1686589200@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Steven Gabriel
DESCRIPTION:On Monday\, June 12\, 2023 at 16:00 c.t. Prof. Steven Gabriel\, University of Maryland\, will speak at the ALOP Colloquium about his recent work: \n  \nBilevel Optimization for Infrastructure Management (energy\, water\, environment\, transportation) \nAbstract: \nIn this talk we present both motivation for and examples of bilevel optimization/mathematical programs with equilibrium constraints (MPECs) as applied to better management of infrastructure.  In this setting\, infrastructure means energy\, water\, transportation\, and the environment.  We focus on a diverse set of application areas\, the need to incentivize users of the related infrastructure networks to participate in an efficiency manner\, and then describe some recent work as applied to the power system in Denmark including theoretical and numerical results and algorithms. \n  \nPlease join us at 16:00 c.t. in HS 10.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-steven-gabriel/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230626T160000
DTEND;TZID=Europe/Berlin:20230626T170000
DTSTAMP:20230620T065239Z
CREATED:20230102T140258Z
LAST-MODIFIED:20230620T065239Z
UID:6983-1687795200-1687798800@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Alexander Martin
DESCRIPTION:On Monday\, June 26\, 2023 at 16:00 c.t. Prof. Dr. Alexander Martin\, Fraunhofer IIS; Technische Universität Nürnberg \, will speak at the ALOP Colloquium about his recent work: \n  \nMixed Integer Optimization Problems on Networks with PDE Constraints \nAbstract: \nMotivated by challenging questions in the transformation and control of our energy system we study mixed integer optimization problems on networks with PDE constraints. Control decisions are typically modeled by integer optimization methods\, while the physical behavior of water\, gas and hydrogen is represented in a continuous nonlinear way\, e.g. by partial differential equations (PDEs). \nThe topic of this talk is to discuss mathematical approaches and insights for the efficient coupling of integer and continuous nonlinear optimization in this context. \nWe will also demonstrate the numerical success using examples from gas network optimization within the framework of the SFB/TR 154. \n  \nPlease join us at 16:00 c.t. in HS 10. \n  \n 
URL:https://alop.uni-trier.de/event/alop-colloquium-with-alexander-martin/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230717T160000
DTEND;TZID=Europe/Berlin:20230717T170000
DTSTAMP:20230704T090825Z
CREATED:20230704T090825Z
LAST-MODIFIED:20230704T090825Z
UID:7238-1689609600-1689613200@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Gabriele Dragotto
DESCRIPTION:On Monday\, July 17\, 2023 at 16:00 c.t. Dr. Gabriele Dragotto\, Princeton University\, will speak at the ALOP Colloquium about his recent work: \n  \nLearn-and-Play: Data\, Agents\, and Interactions \nAbstract: \nHow should an energy company determine its optimal production schedule? How should transport authorities design transportation networks? How should graduate students from medical schools be matched with residency training? In all these contexts\, decision-making is rarely an individual task; on the contrary\, it often involves the mutual interaction of several self-interested decision-makers deciding by solving optimization problems. However\, the agents’ self-driven behavior often conflicts with the greater societal goals; in such cases\, external regulators (e.g.\, governments) can intervene in the agents’ interaction via incentives\, laws\, and regulations. This talk provides a method for learning the agents’ preferences from data to design prescriptive interventions that possibly improve social welfare.  \n  \nPlease join us at 16:00 c.t. in HS 10.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-gabriele-dragotto/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20230724T080000
DTEND;TZID=Europe/Berlin:20230726T140000
DTSTAMP:20230721T082025Z
CREATED:20230303T115741Z
LAST-MODIFIED:20230721T082025Z
UID:7019-1690185600-1690380000@alop.uni-trier.de
SUMMARY:German SIAM Student Chapters Meet Algorithmic Optimization
DESCRIPTION:The SIAM Student Chapter Trier proudly announces hosting the 6th Symposium of the German SIAM Student Chapters together with the Research Training Group on Algorithmic Optimization (ALOP) in 2023. The meeting is organized as a workshop titled “German SIAM Chapters Meet Algorithmic Optimization.“ This three-day event is scheduled to take place in person at Trier University. \nScope \nThe workshop targets the members of the German SIAM Student Chapters but other interested individuals are also welcome to participate. The goal is to bring together researchers from various fields of mathematical optimization and applied mathematics to exchange ideas from different research groups. In particular\, the aim of the workshop is to strengthen the connection of early career researchers from across Germany as well as to network with experienced invited plenary speakers. \nThe topics shall include but are not limited to \n\nSystem Models (PDE Constrained Optimization\, Model Order Reduction\,…)\nOptimization (Discrete Optimization\, Non-Smooth Optimization\, Shape Optimization\,…)\nStatistics\, Data Analysis\, and Machine Learning\n\nThere will be four plenary talks\, contributed talks by early career researchers\, and a poster session. \nConfirmed speakers: \nRoland Herzog (Heidelberg University) \nDaniel Walter (HU Berlin) \nChristina Brandt (Universität Hamburg) \nLaura Scarabosio (Radboud University Nijmegen) \nOrganizers: \nVolker Schulz (Trier University) \nYasmine Beck (Trier University) \nMaximilian Würschmidt (Trier University) \nProgramm Committee: \nYasmine Beck (Trier University) \nJosie König (University of Potsdam) \nHenrik Wyschka (Universität Hamburg) \nTimo Kreimeier (HU Berlin) \nSchedule\, Location\, and Travel Information:\n \nWorkshop Program - German SIAM Student Chapters meet Algorithmic Optimization \nSchedule can be downloaded here. \nThe workshop will take place in Building E located on Campus I at Trier University. \nFor travel tips on how to get to Trier\, please check  here;\nInstructions on how to find Campus I are located here.  \nYou would like to give a short presentation yourself? Send an e-mail to: sokolowski@uni-trier.de \nHotel Room Reservations: \nWe have reserved a hotel room contingent at the Best Western Hotel Trier City\, Kaiserstraße 29\, 54290 Trier. Please contact them directly to make your reservations under the keyword “ALOP”. \nThe contingent will be available for reservation until June 23\, 2023\, or until all available rooms have been booked. \nRegistration is closed.
URL:https://alop.uni-trier.de/event/german-siam-student-chapters-meet-algorithmic-optimization/
LOCATION:Trier University – E-Building – HS 9\, Universität Trier Gebäude E\, Trier\, Rhineland-Palatinate\, 54296\, Germany
CATEGORIES:Workshop
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20231116T160000
DTEND;TZID=Europe/Berlin:20231116T170000
DTSTAMP:20231113T141958Z
CREATED:20231024T091139Z
LAST-MODIFIED:20231113T141958Z
UID:7310-1700150400-1700154000@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Daniel Walter
DESCRIPTION:On Thursday\, November 16\, 2023 at 16:00 c.t. Prof. Dr. Daniel Walter\, HU Berlin\, will speak at the ALOP Colloquium about his recent work. \nIf you would like to participate via Zoom\, please click here. \n  \nEfficient minimization in spaces of measures: Numerical methods and applications \nAbstract: \nMinimization problems in spaces of (vector) measures naturally emerge in a variety of challenging settings including e.g. inverse problems in acoustics and seismology\, micoscropy\, optimal sensor placement as well as the training of shallow neural networks. \nIn this talk\, we discuss several of these applications\, both from a theoretical and numerical perspective\, highlighting the difficulties posed by the (typical) nonsmoothness of the arising optimization problems as well as the lack of “nice” topological properties in the space of (vector) measures. Different practical solution ansatzes are discussed with a particular focus on generalized conditional gradient methods. \nFinally\, we further underline the practical relevance of “sparse” minimization problems by showing that a huge class of nonsmooth problems can be equivalently rewritten as an optimization problem over  measures on a compact metric space using arguments from convex representation theory. From a practical perspective\, this unification allows the derivation and analysis of an efficient general purpose solution algorithm by “lifting” arguments from the vector measure setting. \n  \nPlease join us at 16:00 c.t. in HS 9.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-daniel-walter/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20231204T160000
DTEND;TZID=Europe/Berlin:20231204T170000
DTSTAMP:20231024T083813Z
CREATED:20230814T123308Z
LAST-MODIFIED:20231024T083813Z
UID:7275-1701705600-1701709200@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Marc Pfetsch
DESCRIPTION:On Monday\, December 4\, 2023 at 16:00 c.t. Prof. Dr. Marc Pfetsch\, TU Darmstadt\, will speak at the ALOP Colloquium about his recent work: \n  \nCombinatorial Aspects of Physical Networks \nAbstract:\n \nThis talk considers combinatorial properties of physical networks like water\, gas\, heat\, and electrical networks. One common model are potential-based flows\, for which\, in general\, the corresponding flows depend in a nonlinear way on potentials (e.g.\, pressures) and are unique. The talk will discuss two different topics. The first is how the fact that flows in physical networks are acyclic can be used to strengthen mixed-integer optimization formulations and to derive combinatorial models. The second concerns the recovery of the structure of the network\, given only information at the entries and exits. The talk will demonstrate positive and negative results in this direction. \n  \nPlease join us at 16:00 c.t. in HS 9.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-marc-pfetsch/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20231207T160000
DTEND;TZID=Europe/Berlin:20231207T170000
DTSTAMP:20231123T093046Z
CREATED:20231123T093046Z
LAST-MODIFIED:20231123T093046Z
UID:7328-1701964800-1701968400@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Falk Hante
DESCRIPTION:On Thursday\, December 7\, 2023 at 16:00 c.t. Prof. Dr. Falk Hante\, will speak at the ALOP Colloquium about his recent work: \n  \nTime-Domain Decomposition for Mixed-Integer Optimal Control Problems \nAbstract:\n \nWe consider mixed-integer optimal control problems\, whose optimality conditions involve global combinatorial optimization aspects for the corresponding Hamiltonian pointwise in time. We propose a time-domain decomposition\, which makes this problem class accessible for mixed-integer programming using parallel-in-time direct discretizations. The approach is based on a decomposition of the optimality system and the interpretation of the resulting subproblems as suitably chosen mixed-integer optimal control problems on subintervals in time. An iterative procedure then ensures continuity of the states at the boundaries of the subintervals via co-state information encoded in virtual controls. We prove convergence of this iterative scheme for discrete-continuous linear-quadratic problems and present numerical results both for linear-quadratic as well as nonlinear problems. \n  \nPlease join us at 16:00 c.t. in HS 9.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-falk-hante/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20231211T160000
DTEND;TZID=Europe/Berlin:20231211T170000
DTSTAMP:20230906T085744Z
CREATED:20230814T123248Z
LAST-MODIFIED:20230906T085744Z
UID:7277-1702310400-1702314000@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Mathias Staudigl
DESCRIPTION:On Monday\, December 11\, 2023 at 16:00 c.t. Prof. Dr. Mathias Staudigl\, University of Mannheim\, will speak at the ALOP Colloquium about his recent work: \n  \nA regularized variance-reduced modified extragradient method for stochastic hierarchical games \nAbstract:\n \nThe theory of learning in games has so far focused mainly on games with simultaneous moves. Recently\, researchers in machine learning have started investigating learning dynamics in games involving hierarchical decision-making. We consider an N-player hierarchical game in which the ith player’s objective comprises of an expectation-valued term\, parametrized by rival decisions\, and a hierarchical term. Such a framework allows for capturing a broad range of stochastic hierarchical optimization problems\, Stackelberg equilibrium problems\, and leader-follower games. We develop an iteratively regularized and smoothed variance-reduced modified extragradient framework for learning hierarchical equilibria in a stochastic setting. We equip our analysis with rate statements\, complexity guarantees\, and almost-sure convergence claims. We then extend these statements to settings where the lower-level problem is solved inexactly and provide the corresponding rate and complexity statements. \n  \nPlease join us at 16:00 c.t. in HS 9.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-mathias-staudigl/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
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BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20240212T160000
DTEND;TZID=Europe/Berlin:20240212T170000
DTSTAMP:20231221T143522Z
CREATED:20231221T094533Z
LAST-MODIFIED:20231221T143522Z
UID:7334-1707753600-1707757200@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Dorothee Henke
DESCRIPTION:On Monday\, February 12\, 2024 at 16:00 c.t. Dorothee Henke\, University of Passau\, will speak at the ALOP Colloquium about her recent work: \n  \nOn the Complexity of the Bilevel Shortest Path Problem \nAbstract: \nWe introduce a new bilevel version of the classical shortest path problem and completely characterize its computational complexity with respect to several problem variants. In our problem\, the leader and the follower each control a subset of the edges of a graph and together aim at building a path between two given vertices\, while each of the two players minimizes the length of the resulting path according to their own edge lengths. We investigate both directed and undirected graphs\, as well as the special case of acyclic directed graphs. Moreover\, we distinguish two versions of the follower’s problem: Either he has to complete the edge set selected by the leader such that the joint solution is exactly a path\, without any additional edges\, or he is allowed to include only a subset of the leader’s selection into the final path. In general\, the bilevel problem turns out to be much harder in the former case: We show that the follower’s problem is already NP-hard here and the leader’s problem is even hard for the second level of the polynomial hierarchy\, while both problems are one level easier in the latter case. Interestingly\, for acyclic directed graphs\, this difference turns around\, as we give a polynomial-time algorithm for the first version of the bilevel problem\, but it stays NP-hard in the second case. \nThis is joint work with Lasse Wulf. \n  \nPlease join us at 16:00 c.t. in HS 9.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-dorothee-henke/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
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BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20240226T160000
DTEND;TZID=Europe/Berlin:20240226T170000
DTSTAMP:20240118T072334Z
CREATED:20231019T094016Z
LAST-MODIFIED:20240118T072334Z
UID:7307-1708963200-1708966800@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Boris Detienne
DESCRIPTION:On Monday\, February 26\, 2024 at 16:00 c.t. Prof. Boris Detienne\, University of Bordeaux\, will speak at the ALOP Colloquium about his recent work. \n  \nThe Benders-by-batch algorithm to solve two-stage stochastic linear programs \nAbstract: \nIn this talk\, we will introduce a new exact algorithm to solve two-stage stochastic linear programs. Based on the multicut Benders reformulation of such problems\, with one subproblem for each scenario\, this method relies on a partition of the subproblems into batches. The key idea is to solve at most iterations only a small proportion of the subproblems by detecting as soon as possible that a first-stage candidate solution cannot be proven optimal. We also propose a general framework to stabilize our algorithm\, and show its finite convergence and exact behavior. We report an extensive computational study on large-scale instances of stochastic optimization literature that shows the efficiency of the proposed algorithm compared to nine alternative algorithms from the literature. We also obtain significant additional computational time savings using the primal stabilization schemes \n  \nPlease join us at 16:00 c.t. in HS 9. \n 
URL:https://alop.uni-trier.de/event/alop-colloquium-with-boris-detienne/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
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BEGIN:VEVENT
DTSTART;TZID=Europe/Berlin:20240506T160000
DTEND;TZID=Europe/Berlin:20240506T170000
DTSTAMP:20240418T125616Z
CREATED:20240418T123625Z
LAST-MODIFIED:20240418T125616Z
UID:7414-1715011200-1715014800@alop.uni-trier.de
SUMMARY:ALOP Colloquium with Laura Vargas Koch
DESCRIPTION:On Monday\, May 6\, 2024 at 16:00 c.t. Prof. Dr. Laura Vargas Koch\, University of Bonn\, will speak at the ALOP Colloquium about her recent work. \n  \nMathematics in Traffic Modeling: Nash Flows over Time \nAbstract: \nIn traffic planning\, traffic simulations are widely used. However\, effective practical traffic simulations require good mathematical models as a foundation\, and one such model is Nash flows over time. Traffic is not a centrally controlled system. Instead\, each participant in traffic decides individually which route is best for them. When all participants do this\, so-called equilibrium states emerge. In our research\, we focus on these equilibria and their properties. Unlike static\, classical models\, the unique aspect of Nash flows over time is that temporal changes can be depicted. This means that a flow\, which models traffic\, moves through the network over time\, and the situation in the network can dynamically change. In this presentation\, we will learn about the model of Nash flows over time\, understand its close connection to the traffic simulation software MATSim and see what properties of the equilibria have already been understood\, and what questions are still open. \n  \nPlease join us at 16:00 c.t. in HS 9. \n 
URL:https://alop.uni-trier.de/event/alop-colloquium-with-laura-vargas-koch/
LOCATION:Trier University\, E Building\, Universitätsring 15\, Trier\, Germany
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
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