Matthias Gehnen

E-mail:	gehnen@cs.rwth-aachen.de
Office:	Room 4105b, Erweiterungsbau E1 of the Computer Science Center (2353|105b)
Office hours:	Usually Tuesday 12:00-13:00, check this calender to see wheather it takes place
Phone:	+49-241-80-21132

Currently, I am a PhD Student and research assistant in the Theoretical Computer Science group.

Teaching

In summer 2025, I am organizing an seminar on Online Algorithms and supervise the lab course Competitive Programming.

In the past, I worked in various ways for the following courses:

• Algorithmic Battle in Winter 2021, 2022, 2023 and 2024,
• Datastructures and Algorithms in Summer 2021 and 2024,
• Decision Theory in Summer 2023,
• Formal systems, automatons and processes in Summer 2022 and 2023,
• Dynamic Algorithms in Summer 2022,
• Certifying Algorithms in Summer 2022,
• Competitive Programming in Teams in Summer 2022 and 2023,
• Proof from the Book in Winter 2021,
• Helping Donald Knuth in Winter 2021,
• Datastructures and Algorithms in Summer 2021 and 2024,
• Current Topics in Online Algorithms in Summer 2021,
• Complexity Theory in Winter 2020,
• Microeconomics in Summer 2018, 2019 and 2020,
• Analysis for Computer Scientists in Winter 2017.

In 2022 and 2023 I was the leader of the RWTH-team at the International Mathematics Competition. Furthermore, I was an organizer of the Competitive Programming Contest at RWTH Aachen.

Supervised Theses

The following thesis projects were completed already:

• "A Variant of the Online Travelling Salesperson Problem" by Anna Hansson
• "Online Broadcast with and without Advice" by Jannis Grosse-Verspohl
• "Time Analysis of Space Efficient Uniform Partitioning in Population Protocols " by Pascal Sahner
• "Online Knapsack with Removal and Predictions " by Kübra Güven
• "Balancing Risk and Reward - a Secretary Problem Variant with Reservations and cost-free Option" by David Frason
• "Online Tetris" by Luca Venier
• "Online Bin Packing with Estimated Item Sizes" by Andreas Usdenski
• "The Postdoc Problem with Reservation Costs " by Christian Mürtz
• "The Secretary Problem with Reservation Costs and Accepting one of the two best Candidates" by Jakob Junck
• "The Postdoc Variant of the Secretary Problem with Reservation Costs" by Mats Bierwirth
• "Pitch Detection Methods for Automatic Music Transcription" by Magnus Groß: here you can access the code of his practical part

Publications and Talks

• Online Tetris is not competitive at FUN 2024.
• Online Simple Knapsack with Bounded Predictions at STACS 2024.
• Delaying Decisions and Reservation Costs at COCOON 2023.
• The Online Simple Knapsack Problem with Reservation and Removability at MFCS 2023.
• Transitive Avoidance Games on Boards of Odd Size in The Electronic Journal of Combinatorics, Issue 4 (2021).
• The Secretary Problem with Reservation Costs at COCOON 2021.

In addition, you might have seen my talks at the Workshop on Recent Trends in Online Algorithms (ICALP 2023), the Dutch Day on Optimization 2023, the Seminar on Graphs and Optimization at LaBRI or here in Aachen.

Scholarships and Awards

• Idea League Research Grant for a research stay at the Group for Algorithms and Didactics at ETH Zürich in February and March 2023.
• Springorum-Denkmünze in 2021.
• Part of the Dean's List of the faculty for my studies in mathematics.
• Funding of my studies by the Studienstiftung des deutschen Volkes starting in 2016.

Studies

Before starting in the Theory Group, I studied mathematics with minors in economics and computer science at RWTH Aachen University. I obtained my masters degree with honors in december 2020.

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