Computer Science Seminars
Distinguished Lecture Series

Université Libre de Bruxelles
Computer Science Department

Practical information

The seminars are usually held on Thursdays or Fridays between 12:15 and 1:15PM, Campus de la Plaine.

You can receive seminar announcements by subscribing to the 'computerscience' mailing list. Help on ULB/VUB mailing lists can be found here. For more information, please contact Stefan Langerman (slanger at ulb dot ac dot be).

Monday May 28, 2018, 12:00 PM, room: NO5, Solvay Room
Social norm complexity and human cooperation
Francisco C. Santos (Department of Computer Science and Engineering of Instituto Superior Técnico (IST), University of Lisbon, Portugal)

Explaining the emergence of cooperation is one of the biggest challenges science faces today. Indeed, cooperation dilemmas occur at all scales and levels of complexity, from cells to global governance. Theoretical and experimental works have shown that status and reputations can provide solutions to the cooperation conundrum. These features are often framed in the context of indirect reciprocity, which constitutes one of the most elaborate mechanisms of cooperation discovered so far. By helping someone, individuals may increase their reputation, which can change the predisposition of others to help them in the future. The reputation of an individual depends, in turn, on the social norms that establish what characterises a good or bad action. Such norms are often so complex that an individual’s ability to follow subjective rules becomes important. In this seminar, I will discuss a simple evolutionary game capable of identifying the key pattern of the norms that promote cooperation, and those that do so at a minimum complexity. This combination of high cooperation and low complexity suggests that simple moral principles, and informal institutions based on reputations, can elicit cooperation even in complex environments.

Short bio:
Francisco C. Santos is an Associate Professor of the Department of Computer Science and Engineering of IST, University of Lisbon (Portugal). He is interested in applying scientific computing and modelling tools to understand collective dynamics in social and life sciences. He has been working on problems related to the evolution of cooperation, the origins of social norms, network science, and environmental governance, among others. He obtained a PhD in computer science from the Université Libre de Bruxelles in 2007.

The speaker is hosted by MLG.

Past Seminars

Tuesday March 27, 2018, 12:15 PM, room: Forum F
Hub Location Problems: Applications, Models and Solution Methods
Hande Yaman (Bilkent University)

Hubbing is commonly used in airlines, cargo delivery and telecommunications networks where traffic from many origins to many destinations are consolidated at hubs and are routed together to benefit from economies of scale. Each application area has its own specific features and the associated hub location problems are of complex nature. In the first part of this talk, I will introduce the basic hub location problems, summarize important models and results and mention the shortcomings of these in addressing real life situations. In the second part, I will introduce new variants of the hub location problem that incorporate features such as hierarchical and multimodal networks, service of quality constraints, generalized allocation strategies and demand uncertainty. I will conclude the talk with an ongoing work on a joint problem of hub location, network design and dimensioning.

Short bio:
Hande Yaman received her B.S. and M.S. degrees in Industrial Engineering from Bilkent University, and her Ph.D. degree in Operations Research from Universite Libre de Bruxelles. She joined the Department of Industrial Engineering at Bilkent University in 2003. She spent a year as a visiting researcher at CORE, Universite catholique de Louvain. Her research interests are in exact methods for mixed integer programming with applications in production planning, logistics, and network design.

The speaker is hosted by GOM.

Thursday April 26, 2018, 13:30PM, room: NO5, Solvay Room
Column-parity mixing layers in cryptography
Joan Daemen (Institute for Computing and Information Sciences at the Radboud University and STMicroelectronics)

Mixing layers, such as MixColumns in the AES, are an essential ingredient that can be found in the round function of most modern block ciphers and permutations. We study a generalization of the mixing layer in Keccak-f, the permutation underlying the NIST standard SHA-3 and the authenticated encryption schemes Keyak and Ketje. We call this generalization column-parity mixing layers and investigate their algebraic and diffusion properties and implementation cost. We demonstrate their competitiveness by presenting a fully specified 256-bit permutation with strong bounds for differential and linear trails.

Short bio:
Joan Daemen, who obtained his PhD in cryptography at the COSIC research group of the KULeuven, is a Belgian cryptographer who co-designed the Rijndael encryption scheme which was selected by the NIST as the Advanced Encryption Standard (AES), as well as the Keccak cryptographic hashing algorithm which was selected also by the NIST as the new SHA-3 standard hash function. He is also the author of many other symmetric cryptographic primitives. In 2017 Joan Daemen won the Levchin Prize for Real World Cryptography. Joan Daemen divides his time between the Institute for Computing and Information Sciences at the Radboud University and STMicroelectronics in Belgium.

The speaker is hosted by QualSEC.

Thursday October 12, 2017, 12:15 PM, room: Forum G
The Cache Oblivious Model of Computation
John Iacono (New York University / ULB)

Abstract: In the standard model of computation often taught in computer science courses one identifies elementary operations and counts them in order to obtain the runtime. However, given the complexity of computing hardware, this measure often does not correlate well with actual observed runtime on a computer; accessing n items sequentially or randomly typically have runtimes that differ by several orders of magnitude. In this talk I will present the cache-oblivious model of computation, a model that was introduced by Prokop in 1999 and is relatively easy to reason with, by modeling the multilevel caches that are a defining feature of the cost of modern computation. After presenting the model, several data structure and algorithms that illustrate design techniques to develop cache-obliviously optimal structures will be presented.

The speaker is hosted by the Algorithms Group.