Turku Centre for Computer Science

About: Turku Centre for Computer Science is a facility organization based out in Turku, Finland. It is known for research contribution in the topics: Decidability & Word (group theory). The organization has 382 authors who have published 1027 publications receiving 19560 citations.

The Unique Decipherability in the Monoid of Regular Languages is Undecidable

Abstract: We show by a simple reduction that the unique decipherability problem in the language monoid of regular languages over a non-unary alphabet is undecidable.

Fast and parallelized greedy forward selection of genetic variants in Genome-wide association studies

Abstract: We present the application of a regularized least-squares based algorithm, known as greedy RLS, to perform a wrapper-based feature selection on an entire genome-wide association dataset. Wrapper methods were previously thought to be computationally infeasible on these types of studies. The running time of the method grows linearly in the number of training examples, the number of features in the original data set, and the number of selected features. Moreover, we show how it can be further accelerated using parallel computation on multi-core processors. We tested the method on the Wellcome Trust Case Control Consortium's (WTCCC) Type 2 Diabetes - UK National Blood Service dataset consisting of 3,382 subjects and 404,569 single nucleotide polymorphisms (SNPs). Our method is capable of high-speed feature selection, selecting the top 100 predictive SNPs in under five minutes on a high end desktop and outperforms typical filter approaches in terms of predictive performance.

Preventing look-ahead cheating with active objects

Abstract: In a turn-based networked multiplayer computer game, it is possible to cheat by delaying the announcement of one's action for a turn until one has received messages from all the other players. This look-ahead cheating can be prevented with a lockstep protocol, which requires that the player first announces a commitment to an action and later on the action itself, which can be compared with the earlier announced commitment. However, because the lockstep protocol requires separate transmissions for the commitment and the action and a synchronization step before the actions can be announced, it slows down the turns of the game. In this paper, we propose that active objects can be used to prevent look-ahead cheating. Moreover, we can parameterize the probability of catching cheaters: The smaller this probability is, the less bandwidth and transmissions are required. In most cases, the mere threat of getting caught is enough to discourage cheating, and, consequently, this probability can be quite small.

More on the Dynamics of the Symbolic Square Root Map

Abstract: In our paper [A square root map on Sturmian words, Electron. J. Combin. 24.1 (2017)], we introduced a symbolic square root map. Every optimal squareful infinite word s contains exactly six minimal squares and can be written as a product of these squares: \(s = X_1^2 X_2^2 \cdots \). The square root \(\sqrt{s}\) of s is the infinite word \(X_1 X_2 \cdots \) obtained by deleting half of each square. We proved that the square root map preserves the languages of Sturmian words (which are optimal squareful words). The dynamics of the square root map on a Sturmian subshift are well understood. In our earlier work, we introduced another type of subshift of optimal squareful words which together with the square root map form a dynamical system. In this paper, we study these dynamical systems in more detail and compare their properties to the Sturmian case. The main results are characterizations of periodic points and the limit set. The results show that while there is some similarity it is possible for the square root map to exhibit quite different behavior compared to the Sturmian case.

Hierarchical Agent-Based Monitoring Systems for Dynamic Reconfiguration in NoC Platforms: A Formal Approach

Abstract: A Network-On-Chip is a paradigm that tackles limitations of traditional bus-based interconnects. It allows complex applications that demand many resources to be deployed on many-core platforms effectively. To satisfy requirements on dependability, however, a NoC platform requires dynamic monitoring and reconfiguration mechanisms. In this chapter, the authors propose an agent-based management system that monitors the state of the platform and applies various reconfiguration techniques. These techniques aim at enabling uninterruptable execution of applications satisfying dependability requirements. The authors develop the proposed system within Event-B that provides a means for stepwise and correctby-construction specification supported by mathematical proofs. Furthermore, the authors show the mechanism of decomposition of Event-B specifications such that a well-structured and hierarchical agent-based management system is derived.