Awards

Dissertation Award of the University Society for Innovative Data Structures

The Universitätsgesellschaft Ilmenau - Freunde, Förderer, Alumni e. V. (Ilmenau University Society - Friends, Sponsors, Alumni) has once again awarded the 5,000 euro prize for the best dissertation at TU Ilmenau. The award for 2020 was given to Dr. Stefan Walzer for his dissertation "Random Hypergraphs for Hashing-Based Data Structures".

Alexandra Dalek
Awarding of the Dissertation Prize during the PhD Reception of TU Ilmenau on December 1. from left to right: The Chairwoman of the Universitätsgesellschaft, Prof. Dr. Dagmar Schipanski, award winner Dr. Stefan Walzer and the Vice Presidents Prof. Stefan Sinzinger and Prof. Jens Müller.

In his dissertation, Stefan Walzer dealt with the improvement of so-called hash tables and related data structures, especially with regard to their memory consumption.

In view of the enormous amounts of data that accrue in such forms everywhere, progress in this fundamental task is of great importance," said the chairperson of the University Society, Prof. Dr. Dagmar Schipanski, at the award ceremony during TU Ilmenau's PhD reception on December 1, 2021. "With his dissertation, Stefan Walzer has significantly advanced the state of research and known techniques in this field.

Hash functions are common tools to assign a location in memory to any data set. On the one hand, they allow to retrieve this location on request, but on the other hand, they have pseudo-random properties, which favors a uniform distribution of the data load. A key issue here is how to deal with hash collisions, the case where multiple records have been assigned the same location.

Outstanding results

Stefan Walzer investigated a strategy that provides alternative alternate locations in memory for each data set through additional hash functions. This situation can be modeled by random hypergraphs, a generalization of graphs, whose mathematical properties are related to quality measures of the corresponding data structures. In the dissertation, new variants of hypergraphs were designed and analyzed, from which innovative data structures can be inferred. Dr. Walzer's research work is internationally recognized.

The thesis was written at the Department of Computer Science and Automation in the Group of Complexity Theory and Efficient Algorithms and was supervised by Prof. Dr. Martin Dietzfelbinger, the head of the group. The three reviewers, including Prof. Dr. Michael Mitzenmacher from Havard University, Boston, who is one of the world's leading researchers in the field of analysis of randomized structures and algorithms, rated the results achieved as outstanding. All three independently awarded the grade "summa cum laude."

The excellent work particularly demonstrates the high level of research at TU Ilmenau," said the chairwoman of the university society. "I congratulate the university on such outstanding graduates.

Since last year, Stefan Walzer has been working at the University of Cologne and, since October 2021, as part of a third-party funded project funded by the German Research Foundation DFG to continue his work from the dissertation in order to advance applications and further developments. The goal is to develop even more space-efficient data structures for other technically important problems.