News | AC Group | TU Wien

New PhD: Alexander Dobler

Thu, 11 Dec 2025 00:00:00 +0000

Alexander Dobler successfully defended his PhD thesis “Algorithmic Aspects of Ordering Problems in Information Visualization” on December 11, 2025. Congratulations, Dr. Dobler!

from left to right: Kathrin Hanauer (external committee member), Alexander Dobler, Martin Nöllenburg, Markus Chimani

Alexander was a PhD student in the Algorithms and Complexity Group and worked in the project Engineering Linear Ordering Algorithms for Optimizing Data Visualizations funded by WWTF . He was supervised by Martin Nöllenburg and his external thesis reviewers were Markus Chimani and Walter Didimo .

What Happens When Computers Go Quantum?

Thu, 04 Dec 2025 00:00:00 +0000

Hartmut Neven (Google Quantum AI) will give a talk titled What Happens When Computers Go Quantum?.

Date & Time: Thu, Dec 04 2025 at 15:30 Location: Luftpavillon, Karlsplatz 13, Hof 2

Click here for more details and registration

Herbert Fleischner (1944-2025)

Wed, 05 Nov 2025 00:00:00 +0000

We are deeply saddened by the passing of Herbert Fleischner, friend and colleague. Herbert was a distinguished graph theorist whose work, including the famous Fleischner’s theorem, shaped the field.

Herbert Fleischner, who passed away on October 7, 2025, in Vienna, was a mathematician whose work shaped our understanding of graph theory. Born in London on January 29, 1944, he moved to Vienna with his parents in 1946 and remained connected to the city throughout his life, even as his career took him across continents.

Herbert studied mathematics and physics at the University of Vienna under Nikolaus Hofreiter and Edmund Hlawka, earning his PhD in 1968. His dissertation focused on Eulerian and Hamiltonian graphs, topics that would define his research for decades. While Hlawka was his official supervisor, Herbert Izbicki provided the actual guidance, being a graph theorist himself.

His most influential contribution came early in his career. In 1971, he submitted a proof showing that the square of every two-connected graph contains a Hamiltonian cycle. Published in 1974, this result became known as Fleischner’s theorem and remains a cornerstone in graph theory. The elegance of the statement, which is simple to understand yet challenging to prove, captured something essential about the structure of graphs.

Another milestone in his research was solving Paul Erdős’s “Cycle plus Triangles” problem, work he accomplished in collaboration with Michael Stiebitz. That paper appeared in 1992 in a special issue honoring Julius Petersen. His Erdős number was 2.

Herbert’s career path was anything but conventional. After positions at SUNY Binghamton and a year at the Institute for Advanced Study in Princeton, he spent most of his professional life at the Austrian Academy of Sciences, from 1973 to 2002. However, he was always on the move, traveling to Memphis, MIT, and making multiple stays in Canada, as well as regularly visiting Texas A&M. In 2003, Herbert joined TU Wien, where he continued his research as the PI of projects from the Austrian Science Funds (FWF) as part of what is now the Algorithms and Complexity Group at the Institute of Logic and Computation. In total, Herbert secured four grants from the Austrian Science Fund (FWF), one while at the Austrian Academy of Sciences, where I collaborated as a PhD student, and three at TU Wien, in collaboration with my colleague Günther Raidl. Herbert worked on graph theoretical problems until his last days.

What set Herbert apart was his commitment to mathematics education in developing countries. From the late 1990s to 2012, he worked extensively with the University of Zimbabwe, serving as the main lecturer and project coordinator for an M.Sc. program in academic staff development (1997-1999, sponsored by UNESCO and the Austrian Development Cooperation), and subsequently making regular visits for teaching and supervision through 2012. He did similar work at the University of Dar es Salaam in Tanzania from 2003 to 2009. From 2001 to 2007, he chaired the Committee for Developing Countries of the European Mathematical Society, working to strengthen mathematical research and education where it was needed most.

He supervised nine PhD students. I was fortunate to be among them. Herbert was genuinely open to ideas and topics. Some of my best memories are standing with him in front of a blackboard, working through an argument together. He’d draw a graph, we’d discuss where it might lead, and he’d push for thoroughness: every case would be considered, and every detail would be checked. Those sessions taught me what mathematical thinking, where intuition meets precision, actually looks like.

He organized workshops on the Matthews-Sumner Conjecture with Zdeněk Ryjáček in the Czech Republic, bringing together researchers who shared his passion for cycle-related problems in graphs.

Herbert wrote two volumes on Eulerian graphs, published in 1990 and 1991, that became standard references. They were translated into Russian and Chinese, a testament to their lasting value. Over his career, he published more than 90 papers. He also found an unexpected connection between mathematics and art through his friendship with painter Robert Lettner. They collaborated on a series called “mutations,” where mathematical graphs were transformed into paintings.

Herbert spoke German, English, and Russian fluently. Beyond his professional achievements, he raised his son, Michael, born in 1974, as a single father during a time when this was uncommon. Later in life, he found happiness with his wife Renata, whom he married in 2005.

Herbert Fleischner spent his life building structures: mathematical structures in graph theory, educational structures in developing countries, collaborative structures across continents. He understood that mathematics isn’t just about theorems; it’s about creating communities where ideas can grow.

We’ll miss him.

Algorithms and Complexity Group, TU Wien

Three Contest Awards for Graph Drawing Student Teams

Fri, 26 Sep 2025 00:00:00 +0000

From September 24 to 26, the 33rd International Symposium on Graph Drawing and Network Visualization took place in Norrköping, Sweden. As every year, the conference hosted the Graph Drawing Contest , in which student teams from TU Wien participated in several categories as part of the Master course Graph Drawing Algorithms taught by Martin Nöllenburg .

Winning Team in the Creative Contest 2025: Guilherme Monteiro Oliveira, Florian Saß, Jakob Speitkamp (from left to right)

In the creative contest, participants were given a network and asked to design an appealing visualization that also reveals interesting insights into the underlying data. This year’s topic centered on the Netflix series Dark: Nodes in the graph represented events in the series with their involved characters, and edges captured the cause-and-effect relationships among them. In contrast to previous years, participants had the unique opportunity to design a 360° visualization that was displayed in Norrköping’s decision arena , a cylindrical 360-degree high-resolution display with a diameter of 6 meters. In this category, our student team of Florian Saß, Jakob Speitkamp, and Guilherme Monteiro Oliveira (supervised by Thomas Depian ) won the first prize for their submission “Journey of a Time Machine”.

“Journey of a Time Machine” displayed on the 360° screen of the decision arena

In the automatic live challenge, the task was to compute layouts for several different graphs of increasing size and complexity within a timeframe of one hour. The produced layouts had to use straight edges with the aim of minimizing the maximum number of crossings on any single edge. The participating teams designed and implemented their own highly efficient algorithms for this task prior to the contest and competed against each other in the live challenge. Again, our student teams (supervised by Simon D. Fink ) excelled with their respective software developed in the Graph Drawing Algorithms course: Christoph Weber won the second prize, and the team of Stefan Brandmair and Luca Marius Cobzaru reached third place.

Congratulations to all our successful students!

Winners of the 3rd place in the automatic live challenge: Stefan Brandmair and Luca Marius Cobzaru

Second Place in the PACE Challenge for a Team of AC Group Researchers

Fri, 19 Sep 2025 00:00:00 +0000

The Parameterized Algorithms and Computational Experiments (PACE) Challenge takes place annually as part of the International Symposium on Parameterized and Exact Computation (IPEC) to deepen the relationship between parameterized algorithms and practice. The results of the 2025 iteration were presented in Warsaw, Poland, as part of ALGO 2025 from September 15-19. PACE 2025 featured two classic algorithmic problems, Dominating Set and Hitting Set . In a total of four tracks, an exact as well as a heuristic one , practical solutions to these two NP-hard problems were solicited.

Second-place winners Simon D. Fink, Alexander Dobler, and Mathis Rocton (from left to right)

The solver submitted by Alexander Dobler , Simon D. Fink and Mathis Rocton made a very close second place in both exact tracks. Their code and more information on their solver can be found on GitHub, and the full standings can be found here .

Congratulations to our successful team!

COMSOC 2025 Begins - Computational Social Choice

Wed, 17 Sep 2025 00:00:00 +0000

September 17-19, 2025 · TU Wien, Vienna, Austria

Quick Facts

Find the full program and registration details on the official site:

Visit COMSOC 2025 Website Contact

Learning and Belief Revision: an Overview

Tue, 16 Sep 2025 00:00:00 +0000

Nina Gierasimczuk will give a talk titled Learning and Belief Revision: an Overview.

Date & Time: Tue, Sep 16 2025 at 17:30 Location: Online via Zoom

Click here for more details and registration

Axioms as rules in intuitionistic logic

Mon, 23 Jun 2025 00:00:00 +0000

Sara Negri will give a talk titled Axioms as rules in intuitionistic logic.

Date & Time: Mon, Jun 23 2025 at 17:00 Location: Online via Zoom

Click here for more details and registration

Best Paper Award and Honourable Mention at EuroVis 2025

Fri, 13 Jun 2025 00:00:00 +0000

Two papers co-authored by our ESPRIT fellow Sara Di Bartolomeo received awards during the EuroVis 2025 conference, held June 2-6 in Luxembourg. The Best Paper Award went to the paper " NODKANT: Exploring Constructive Network Physicalization " written by Sara together with her co-authors Daniel Paar, Henry Ehlers, Velitchko Filipov, Christina Stoiber, Wolfgang Aigner, Hsiang-Yun Wu, and Renata Raidou. This paper explores how constructing physical models of graph data can improve people’s understanding of complex information.

A second paper, " Optimizing Staircase Motifs in Biofabric Network Layouts ", written by Sara Di Bartolomeo , Markus Wallinger , and Martin Nöllenburg received an Honourable Mention Award as one of the top-3 full papers. This paper explores exact optimization algorithms for highlighting certain subgraph motifs in the novel BioFabric network visualization style.

Congratulations to all the award recipients!

Copyrights: Lugdivine Unfer

Markus Wallinger receives EuroVis PhD Award

Fri, 13 Jun 2025 00:00:00 +0000

Markus Wallinger , who did his PhD in the Algorithms and Complexity group in 2024, received the EuroVis PhD Award for his thesis " Exploring Graph-based Concepts for Balanced Information Density in Data Visualizations " last week during the EuroVis conference in Luxembourg. This year’s EuroVis PhD Award was awarded to three young researchers and recognizes outstanding dissertations in academic research and development on topics relevant to visualization. Markus’ thesis was supervised by Martin Nöllenburg and supported by the WWTF grant " Engineering Linear Ordering Algorithms for Optimizing Data Visualizations “. Markus is now a postdoctoral researcher at TU Munich . Congratulations!

Copyrights: Lugdivine Unfer

Towards Formalizing Cyclic Tableaux and Interpolation for PDL in Lean

Wed, 11 Jun 2025 00:00:00 +0000

Malvin Gattinger will give a talk titled Towards Formalizing Cyclic Tableaux and Interpolation for PDL in Lean.

Date & Time: Wed, Jun 11 2025 at 16:00 Location: Gußhausstraße 27-29, Seminar Room 127 (third floor)

Click here for more details and registration

Logic and Computation of Social Behavior

Wed, 19 Mar 2025 00:00:00 +0000

Sonja Smets will give a talk titled Logic and Computation of Social Behavior.

Date & Time: Wed, Mar 19 2025 at 17:00 Location: Online via Zoom

Click here for more details and registration

Codd’s Theorem for Databases over Semirings

Thu, 27 Feb 2025 00:00:00 +0000

Guillermo Badia will give a talk titled Codd’s Theorem for Databases over Semirings.

Date & Time: Thu, Feb 27 2025 at 17:00 Location: Favoritenstrasse 9-11, FAV Lecture Hall 2 (ground floor)

Click here for more details and registration

Classical versus Constructive: An Ecumenical Approach

Wed, 05 Feb 2025 00:00:00 +0000

Elaine Pimentel will give a talk titled Classical versus Constructive: An Ecumenical Approach.

Date & Time: Wed, Feb 05 2025 at 16:00 Location: Online via Zoom - link for registration below

Click here for more details and registration

Explanatory Proofs: From Logic to Mathematics

Fri, 24 Jan 2025 00:00:00 +0000

A talk titled Explanatory Proofs: From Logic to Mathematics.

Date & Time: Fri, Jan 24 2025 at 17:00 Location: Online via Zoom

Click here for more details and registration

Best Paper Award at SOFSEM 2025

Thu, 23 Jan 2025 00:00:00 +0000

Thomas Depian , Simon D. Fink , Alexander Firbas , Robert Ganian , and Martin Nöllenburg received the Best Paper Award for their paper Pathways to Tractability for Geometric Thickness [ arXiv ] at the 50th International Conference on Current Trends in Theory and Practice of Computer Science (SOFSEM) held in Bratislava, Slovakia from January 20-23, 2025.

Trustable Explainable AI -- A Redemption by Logic

Tue, 14 Jan 2025 00:00:00 +0000

Joao Marques-Silva will give a talk titled Trustable Explainable AI – A Redemption by Logic.

Date & Time: Tue, Jan 14 2025 at 17:00 Location: zoom and youtube

Click here for more details and registration

NL interface of PROLEG system and extracting normative sentences from German traffic judgements

Mon, 09 Dec 2024 00:00:00 +0000

Ken Satoh (NII Tokyo) will give a talk titled NL interface of PROLEG system and extracting normative sentences from German traffic judgements.

Date & Time: Mon, Dec 09 2024 at 14:30 Location: Favoritenstrasse 9-11, Seminar Room FAV 3 Zemanek

Click here for more details and registration

Markus Wallinger receives Award of Excellence for his PhD Thesis

Thu, 05 Dec 2024 00:00:00 +0000

Our former group member Markus Wallinger won the Award of Excellence by the Federal Ministry for Education, Science and Research . This state prize is awarded annually to 40 outstanding dissertations completed at all Austrian universities and in all subjects. Markus, as one of only four researchers of TU Wien, received this prestigious award on December 5, 2024 for his dissertation " Exploring Graph-based Concepts for Balanced Information Density in Data Visualizations “, supervised by Martin Nöllenburg . Markus is now a postdoctoral researcher at the Chair of Efficient Algorithms at TU Munich. Congratulations, Markus!

Thomas Depian receives State Prize for his Master's Thesis

Thu, 21 Nov 2024 00:00:00 +0000

Our group member Thomas Depian won the Appreciation Award given by the Federal Ministry for Education, Science and Research . This state prize is awarded annually to the best 55 Master graduates among each year’s about 16.000 graduates of all Austrian universities. In 2024 Thomas, as one of only two students of TU Wien, received this prestigious award for his Master’s thesis " Grouping and Ordering Constraints in Boundary Labeling “, supervised by Martin Nöllenburg . Thomas will present the results of his thesis at the 35th International Symposium on Algorithms and Computation (ISAAC'24) in Sydney, Australia in December 2024. Congratulations, Thomas!

Best Paper Award at GECCO 2024 for M. Bresich, G. Raidl, and S. Limmer

Wed, 24 Jul 2024 00:00:00 +0000

Maria Bresich, Günther Raidl, and Steffen Limmer received the best paper award at the 2024 Genetic and Evolutionary Computation Conference (GECCO 2024) for their contribution Letting a Large Neighborhood Search for an Electric Dial-A-Ride Problem Fly: On-The-Fly Charging Station Insertion . The conference took place in Melbourne, Australia, July 14-18, 2024.

Welcome to our Feodor Lynen Fellow Dr. Frank Sommer

Fri, 14 Jun 2024 00:00:00 +0000

On June 1, 2024, Dr. Frank Sommer has joined the Algorithms and Complexity group with a prestigious Feodor Lynen postdoc fellowship from the Alexander von Humboldt Foundation .

Frank has received his PhD in 2022 from Philipps-Universität Marburg in Germany, and has worked as a postdoc researcher at Friedrich-Schiller-Universität Jena in Germany. In his one-year project at TU Wien he will investigate machine learning models such as decision trees and neural networks by exploiting specific input structures leading to input parameters which can be assumed to be small in practice. Together with his host Dr. Manuel Sorge , they will initially tackle these problems in theory by studying the parameterized complexity of these problems. Afterwards, they plan to implement the most promising algorithms they discovered.

We thank TU Wien for supporting a part of Frank’s fellowship.

Esra Ceylan won the OCG Award 2024

Fri, 31 May 2024 00:00:00 +0000

Our best Master thesis awardee last year, Esra Ceylan , won the OCG award 2024 for her Master’s thesis, supervised by Jiehua Chen ! Congratulations!

The ceremony will take place at the Austrian Computer Science Day on June 14th:

https://acsd2024.univie.ac.at/program/

New PhD: Markus Wallinger

Fri, 26 Apr 2024 00:00:00 +0000

Markus Wallinger successfully defended his PhD thesis “Exploring Graph-based Concepts for Balanced Information Density in Data Visualizations” on April 26, 2024. Congratulations, Dr. Wallinger!

Markus was a PhD student in the Algorithms and Complexity Group and worked in the project Engineering Linear Ordering Algorithms for Optimizing Data Visualizations funded by WWTF . He was supervised by Martin Nöllenburg and his external thesis reviewers were Christophe Hurter and Stephen Kobourov . Markus will continue his academic path as a postdoc at TU Munich.

PhD completed by Soeren Terziadis

Tue, 09 Jan 2024 00:00:00 +0000

Soeren Terziadis successfully defended his PhD thesis “Algorithms for Schematic Representations” on January 9, 2024. Congratulations, Dr. Terziadis!

Soeren was a PhD student in the Algorithms and Complexity Group and was supervised by Martin Nöllenburg . His external thesis reviewers were Will Evans and Sabine Storandt . He is now a postdoctoral researcher at TU Eindhoven .

Informatics Awards 2023

Wed, 06 Dec 2023 00:00:00 +0000

The Algorithms and Complexity group was very successful at the Informatics Awards 2023 :

André Schidler won the Best Dissertation Award for his thesis Scalability for SAT-based Combinatorial Problem Solving (supervised by Stefan Szeider ).

Esra Ceylan won the Best Master Thesis Award for her thesis Optimal Seat Arrangement: Structure, Algorithms, and Complexity (supervised by Jiehua Chen).

Among the thirteen students who received a Bachelor of Honors award, five were supervised by professors of the Algorithms and Complexity group: Thomas Depian, Jakob Greilhuber, Michael Kiran Huber, Sophia Schober , and Florentina Voboril .

Congratulations to all awardees!

Jiehua Chen: promotion to tenured Associate Professor

Wed, 18 Oct 2023 00:00:00 +0000

After her successful tenure evaluation, our colleague Jiehua Chen has been promoted to an Associate Professor.

Hua joined the Algorithms and Complexity group at TU Wien in 2019. Her research interests include the (parameterized) complexity of, and the design and analysis for, combinatorial problems arising in contexts such as optimization problems related to graphs and hypergraphs and Computational Social Choice (computational problems around voting, domain restrictions, and preference-based stable matching problems).

Congratulations!

Successful Graph Drawing conference 2023 in Palermo

Sat, 23 Sep 2023 00:00:00 +0000

The 31st edition of the International Symposium on Graph Drawing and Network Visualization in Palermo, Italy, ended on September 22, 2023, with a large number of awards and prizes for members and students of the Algorithms and Complexity Group.

We congratulate Markus Wallinger and his co-authors Felix Klesen, Jacob Miller, Fabrizio Montecchiani, and Martin Nöllenburg for the best poster award 2023 on their poster “What happens at Dagstuhl? Uncovering Patterns through Visualization”.

Markus Chimani (PC co-chair), Jacob Miller, Felix Klesen, Martin Nöllenburg, Markus Wallinger, Fabrizio Montecchiani, and Michalis Bekos (PC co-chair).

Furthermore, the annual Graph Drawing Contest honored multiple contributions in the following categories:

Congratulations to all our successful students and team members!

PhD completed by Anaïs Villedieu

Mon, 24 Jul 2023 00:00:00 +0000

Anaïs Villedieu successfully defended her PhD thesis “Engineering Human-in-the-loop Graph Drawing Algorithms” on July 24, 2023. Congratulations, Dr. Villedieu!

Anaïs was a PhD student in the FWF project " Human-centered Algorithm Engineering " and was supervised by Martin Nöllenburg . Her external thesis reviewers were Seokhee Hong and Philipp Kindermann .

PhD completed by Andre Schidler

Wed, 31 May 2023 00:00:00 +0000

Congratulations to André Schidler , who successfully defended his PhD thesis " Scalability for SAT-based combinatorial problem solving " today.

Thanks to the evaluation committee: Armin Biere, Daniel Le Berre, João Marques-Silva, and Nysret Musliu.

PhD completed by Vaidyanathan P.R.

Fri, 12 May 2023 00:00:00 +0000

Congratulations to Vaidyanathan P.R. , who successfully defended his PhD thesis Scalable Bayesian Network Structure Learning using SAT-based Methods today.

Thanks to the evaluation committee (Christian Fermüller, Pekka Parviainen, Martina Seidl, and Sebastian Ordyniak).

PhD completed by Nikolaus Frohner

Thu, 11 May 2023 00:00:00 +0000

Congratulations to Nikolaus Frohner , who successfully defended his PhD thesis " Advancing State Space Search for Static and Dynamic Optimization by Parallelization and Learning " today.

Thanks to the evaluation committee: Christian Blum, Luca di Gaspero, Sophie Parragh, and Nysret Musliu.

Best paper award at IEEE PacificVis 2023

Sat, 22 Apr 2023 00:00:00 +0000

Markus Wallinger , Alexander Dobler , and Martin Nöllenburg received the Best Paper Award for their paper LinSets.zip: Compressing Linear Set Diagram s at the 16th IEEE Pacific Visualization Symposium held in Seoul, Korea from April 18-21.

Best paper award at EvoCOP 2023

Fri, 14 Apr 2023 00:00:00 +0000

Rupert Ettrich, Marc Huber , and Günther Raidl received the Best Paper Award for their paper A Policy-Based Learning Beam Search for Combinatorial Optimization at the 23rd Europen Conference on Evolutionary Computation in Combinatorial Optimization held in Brno, Czech Republic, from April 12-14.

New FWF ESPRIT Postdocs

Wed, 09 Nov 2022 00:00:00 +0000

Leroy Chew and Alexis de Colnet just joined the Algorithms and Complexity group as PIs of their own FWF ESPRIT Projects:

Congratulations to Leroy and Alexis for winning these competitively awarded project grants!

Best student paper award at DIAGRAMS 2022

Sat, 01 Oct 2022 00:00:00 +0000

Alexander Dobler received the Best Student Paper Award at the 13th International Conference on the Theory and Application of Diagrams (DIAGRAMS 2022) in Rome in September 2022 for his paper " On Computing Optimal Linear Diagrams “, co-authored with his PhD advisor Martin Nöllenburg .

Robert Ganian promoted to Associate Professor

Fri, 01 Jul 2022 00:00:00 +0000

Effective as of today, Robert Ganian is promoted to a tenured Associate Professor at the Algorithms and Complexity group. Congratulations, Robert!

Best paper award at EvoCOP 2022

Tue, 24 May 2022 00:00:00 +0000

Jonas Mayerhofer, Markus Kirchweger, Marc Huber, and Günther Raidl received the best paper award for their work A Beam Search for the Shortest Common Supersequence Problem Guided by an Approximate Expected Length Calculation at the 22nd European Conference on Evolutionary Computation in Combinatorial Optimization being held in Madrid, Spain, in April 2022.

New PhD: Guangping Li

Fri, 13 May 2022 00:00:00 +0000

Guangping Li successfully defended her PhD thesis “An Algorithmic Study of Practical Map Labeling” on May 13, 2022. Congratulations, Dr. Li!

Guangping was a PhD student in the FWF project " Human-centered Algorithm Engineering " and was supervised by Martin Nöllenburg . Her external thesis reviewers were Kevin Buchin and Christian Schulz . Guangping has already started a postdoc position at TU Dortmund , Germany.

Outstanding results for TU Wien students at the 2021 Graph Drawing Contest

Fri, 24 Sep 2021 00:00:00 +0000

The 28th Annual Graph Drawing Contest , a long running tradition of the graph drawing research community, was held in conjunction with the 29th International Symposium on Graph Drawing and Network Visualization (GD 2021), hosted in Tübingen from the 14th to the 17th of September, 2021. The contest is comprised of various categories. In the creative topics participants are provided with network data and tasked to design an informative but at the same time aesthetically pleasing layout of these networks.

In this category TU Wien was represented by two submissions, both of which were created as part of the coursework for the lecture Graph Drawing Algorithms (taught by Martin Nöllenburg and Soeren Nickel ), with resounding success, winning a first and a joint second prize. Both groups chose the task of visualizing a graph of movie remakes by different directors out of the available data sets.

David Ammer, Thorsten Korpitsch and Simon Pointner won the first prize by choosing a design, which puts the focus of the visualization firmly on the movies and representing directors as spanning trees between movie nodes. Readability was automatically optimized, by minimizing crossings and edge lengths via simulated annealing. The design was praised for being intuitive and highly informative.

Najla Amira Ochoa Leonor and Daniela Martinez Duarte won the second prize with their multi-style visualization, utilizing a clustering of directors based on their influence. It shows high degree directors as meta-nodes depicting their remakes and original movies and an essential list of movies connecting them through a Steiner tree is highlighted. Beyond trying to explore structures not immediately visible in the data set, the design was lauded for being aesthetically pleasing.

In the manual live challenge category, contestants tried to optimize the polyline edge-length ratio of planar drawings on a fixed grid, wherein the group of Soeren Nickel , Anaïs Villedieu and Jules Wulms of the Algorithms and Complexity group won the third price.

Congratulations to all awardees!

Jan Dreier receives a LICS'21 Distinguished Paper Award

Fri, 02 Jul 2021 00:00:00 +0000

Congratulations to Jan Dreier for his LICS 2021 Distinguished Paper Award for his paper Lacon- and Shrub-Decompositions: A New Characterization of First-Order Transductions of Bounded Expansion Classes.

Here is a link to the video of his presentation.

Lecture at Austrian Parliament

Wed, 16 Jun 2021 00:00:00 +0000

Stefan Szeider and Martin Kronegger gave a lecture on Algorithms and Programming to members of the Austrian Parliament .

The lecture consisted of three parts and concluded with a Q&A session with the MPs and ended with a live programming demonstration.

The Algorithms lecture took place on June 15th, 2021, in the same venue where usually the plenary discussions of the Austrian parliament take place, the “great Redoutensaal,” a beautiful hall located in Vienna’s Hofburg.

This lecture was part of the Faculty of Informatic’s initiative Digitale Kompetenzen (digital competence), consisting of several lectures on computer science topics, to be held in July and September 2021.

Photos at curtesy of Parlamentsdirektion/Thomas Topf

Promotio Sub Auspiciis Praesidentis Rei Publica

Mon, 14 Jun 2021 00:00:00 +0000

Congratulations to our former students Martin Riedler and Tomas Peitl for receiving this outstanding award of a Promotio Sub Auspiciis Praesidentis Rei Publica (Doctoral graduation under the auspices of the Federal President). Each year, only a handful of doctoral students from Austria receive this special award, which requires excellent grades throughout secondary school, undergraduate and graduate studies.

We are specially proud that two students from our group receive this honour this year.

The ceremony took place with over year’s delay due to the Covid pandemic.

News post at TU Wien’s website.

Martin Nöllenburg: promotion to Full Professor

Thu, 17 Dec 2020 00:00:00 +0000

By December 1st, 2020, our colleague Martin Nöllenburg has been promoted to Full Professor for Graph and Geometric Algorithms.

Martin has joined the Algorithms and Complexity group at TU Wien in September 2015 and was promoted to Associated professor in 2017. His research interests include graph algorithms, in particular for graph drawing and network visualization, computational geometry, in particular algorithms for cartography and geovisualization, as well as algorithm engineering and combinatorial optimization.

See here 5 Questions with … Martin Nöllenburg from last year.

Congratulations!

Martin Kronegger wins the Best Teaching Award 2020

Fri, 23 Oct 2020 00:00:00 +0000

Congratulations to Martin Kronegger who received a Best Teaching Award 2020 from TU Wien.

The Algorithms and Complexity group is very happy about Martin’s engagement in the Algorithms and Data Structures course, which received a nomination for the Best Distance Learning Award 2020 for its digitalisation of the course during the COVID-19 restrictions in Spring 2020.

Welcome to our Feodor Lynen Fellow Dr. Manuel Sorge

Mon, 12 Oct 2020 00:00:00 +0000

On October 1, 2020, Dr. Manuel Sorge has joined the Algorithms and Complexity group with a prestigious Feodor Lynen postdoc fellowship from the Alexander von Humboldt Foundation .

Manuel has received his PhD in 2016 from TU Berlin and has worked as a postdoc researcher at Ben-Gurion University in Beer Sheva, Israel and at Warsaw University, Poland. In his two-year project at TU Wien he will investigate network analysis and visualization problems by exploiting knowledge about inherent structures of complex networks, such as their structural sparsity or properties of overlapping clusters. Together with his host Martin Nöllenburg , they will employ a mix of theoretical and practical methods to understand the fine-grained complexity of the studied computational problems and design, analyze and experimentally evaluate new suitable algorithms.

We thank TU Wien for supporting a part of Manuel’s fellowship.

TU Wien students excel at the 2020 Graph Drawing Contest

Thu, 01 Oct 2020 00:00:00 +0000

The 27th annual Graph Drawing Contest , held (virtually) in conjunction with the 28th International Symposium on Graph Drawing and Network Visualization (GD) in Vancouver on September 15-18, 2020 was a big success for our TU Wien graph drawing students, winning the first prize in both creative categories, as well as one second prize and one third prize. Three out of these four layouts were created as part of the coursework for the lecture Graph Drawing Algorithms (taught by Martin Nöllenburg and Soeren Nickel ).

The 2020 contest comprised two creative topics: the first data set was a small-scale social network of 43 chieftains and farmers and their interactions from the Icelandic Hrafnkel Saga, the second data set a larger relationship network of thousands of artists, bands, and record labels in K-Pop music. Participants were free to design an informative but at the same time aesthetically pleasing layout of these networks.

Tamara Drucks, Moritz Leidinger, and Giulio Pace won the first prize with their idea of showing the Hrafnkel Saga as a spiral-shaped storyline layout embedded on a map of Iceland. The second place went to the team of Fabian Jogl, Melanie Paschinger, and Adrian Chmurovic, who used a layered graph layout on concentric half circles to show the actors and events of the saga.

In the second category, Rupert Ettrich, Julian Haumer, and Samantha Fuchs won the first prize for their Map of K-Pop Stars as a collaboration network of artists and bands grouped by their record labels in the visual style of a celestial chart (or star map). The third place went to Markus Wallinger and Hsiang-Yun Wu who used a matrix of hive plots to highlight several different aspects of the data set.

Congratulations to all awardees!

Best Paper Award at CP'2020

Fri, 11 Sep 2020 00:00:00 +0000

Tomáš Peitl and Stefan Szeider won the Best Paper Award at the main track of CP'2020 , the 26th International Conference on Principles and Practice of Constraint Programming, for their paper: " Finding the Hardest Formulas for Resolution “.

Congratulations!

In the paper, a resolution -based method (CDCL SAT solver) is used to find the hardest formulas for resolution , which constitutes a self reference as greatly illustrated by MC Escher in his lithograph “Drawing Hands (1948).

Abstract: A CNF formula is harder than another CNF formula with the same number of clauses if it requires a longer resolution proof. The resolution hardness numbers give for m=1,2,…m=1,2,… the length of a shortest proof of a hardest formula on m clauses. We compute the first ten resolution hardness numbers, along with the corresponding hardest formulas. We achieve this by a candidate filtering and symmetry breaking search scheme for limiting the number of potential candidates for formulas and an efficient SAT encoding for computing a shortest resolution proof of a given candidate formula.

An open access version of the paper is available as a technical report

Robert Ganian receives an FWF START prize

Wed, 17 Jun 2020 00:00:00 +0000

Robert Ganian who receives an FWF START Prize for his project Parameterized Analysis in Artificial Intelligence .

The FWF START prize is comparable in competitiveness and funding to an ERC starting grant.

Out of 111 applications over all scientific disciplines, 7 START prizes where awarded.

Congratulations!

New PhD: Fabian Klute

Mon, 16 Mar 2020 00:00:00 +0000

Fabian Klute successfully defended his PhD thesis " Avoiding Crossings in Non-Planar Graph Layouts " on March 13, 2020. Congratulations!

Fabian was supervised by Martin Nöllenburg . His thesis reviewers were Fabrizio Frati and Stephen Kobourov . Fabian is now a postdoc at Utrecht University .

New PhD: Benedikt Klocker

Tue, 03 Mar 2020 00:00:00 +0000

Benedikt Klocker successfully defended his PhD thesis “Combinatorial Optimization Approaches for Graph Construction Problems” on March 25, 2020. Congratulations!

Benedikt was supervised by Günther Raidl and co-supervised by Herbert Fleischner.

Soeren Nickel wins the Distinguished Young Alumn Award

Mon, 27 Jan 2020 00:00:00 +0000

Soeren Nickel , who recently joined the Algorithms and Complexity Group as a PhD student, won the Distinguished Young Alumn Award at the 29th EPILOG event of the Faculty of Informatics. With this award the Faculty of Informatics honors Soeren’s outstanding Master thesis " Generating Stable Demers and Iso-Hexagon Cartograms " as well as his excellent EPILOG presentation.

Martin Nöllenburg, Awardee Soeren Nickel, Vice Dean of Academic Affairs Stefan Woltran, and Dean Gerti Kappel. Photo credits: © Amélie Chapalain

Soeren’s thesis, supervised by Martin Nöllenburg , presents algorithms and complexity results for computing value-by-area square and hexagon cartograms to display spatiotemporal data as a highly abstract map. It has already been presented at the International Symposium on Graph Drawing and Network Visualization (GD) 2019.

Congratulations to Soeren for this prestigious award!