@inproceedings{19960, abstract = {{Besides the life-as-it-could-be driver of artificial life research there is also the concept of extending natural life by creating hybrids or mixed societies that are built from natural and artificial components. In this paper we motivate and present the research program of the project flora robotica. Our objective is to develop and to investigate closely linked symbiotic relationships between robots and natural plants and to explore the potentials of a plant-robot society able to produce architectural artifacts and living spaces. These robot-plant bio-hybrids create synergies that allow for new functions of plants and robots. They also create novel design opportunities for an architecture that fuses the design and construction phase. The bio-hybrid is an example of mixed societies between 'hard' artificial and 'wet' natural life, which enables an interaction between natural and artificial ecologies. They form an embodied, self-organizing, and distributed cognitive system which is supposed to grow and develop over long periods of time resulting in the creation of meaningful architectural structures. A key idea is to assign equal roles to robots and plants in order to create a highly integrated, symbiotic system. Besides the gain of knowledge, this project has the objective to create a bio-hybrid system with a defined function and application -- growing architectural artifacts.}}, author = {{Hamann, Heiko and Wahby, Mostafa and Schmickl, Thomas and Zahadat, Payam and Hofstadler, Daniel and Stoy, Kasper and Risi, Sebastian and Faina, Andres and Veenstra, Frank and Kernbach, Serge and Kuksin, Igor and Kernbach, Olga and Ayres, Phil and Wojtaszek, Przemyslaw}}, booktitle = {{Proceedings of the 2015 IEEE Symposium on Artificial Life (IEEE ALIFE'15)}}, isbn = {{9781479975600}}, title = {{{Flora Robotica - Mixed Societies of Symbiotic Robot-Plant Bio-Hybrids}}}, doi = {{10.1109/ssci.2015.158}}, year = {{2015}}, } @article{19962, abstract = {{Recent approaches in evolutionary robotics (ER) propose to generate behavioral diversity in order to evolve desired behaviors more easily. These approaches require the definition of a behavioral distance, which often includes task-specific features and hence a priori knowledge. Alternative methods, which do not explicitly force selective pressure towards diversity (SPTD) but still generate it, are known from the field of artificial life, such as in artificial ecologies (AEs). In this study, we investigate how SPTD is generated without task-specific behavioral features or other forms of a priori knowledge and detect how methods of generating SPTD can be transferred from the domain of AE to ER. A promising finding is that in both types of systems, in systems from ER that generate behavioral diversity and also in the investigated speciation model, selective pressure is generated towards unpopulated regions of search space. In a simple case study we investigate the practical implications of these findings and point to options for transferring the idea of self-organizing SPTD in AEs to the domain of ER.}}, author = {{Hamann, Heiko}}, issn = {{1064-5462}}, journal = {{Artificial Life}}, pages = {{464--480}}, title = {{{Lessons from Speciation Dynamics: How to Generate Selective Pressure Towards Diversity}}}, doi = {{10.1162/artl_a_00186}}, year = {{2015}}, } @inproceedings{19966, abstract = {{Aggregation is a crucial task in swarm robotics to ensure cooperation. We investigate the task of aggregation on an area specified indirectly by certain environmental features, here it is a light distribution. We extend the original BEECLUST algorithm, that implements an aggregation behavior, to an adaptive variant that automatically adapts to any light conditions. We compare these two control algorithms in a number of swarm robot experiments with different light conditions. The improved, adaptive variant is found to be significantly better in the tested setup.}}, author = {{Wahby, Mostafa and Weinhold, Alexander and Hamann, Heiko}}, booktitle = {{Proceedings of the 9th EAI International Conference on Bio-inspired Information and Communications Technologies (formerly BIONETICS)}}, isbn = {{9781631901003}}, title = {{{Revisiting BEECLUST: Aggregation of Swarm Robots with Adaptiveness to Different Light Settings}}}, doi = {{10.4108/eai.3-12-2015.2262877}}, year = {{2015}}, } @inproceedings{19967, author = {{Wahby, Mostafa and Divband Soorati, Mohammad and von Mammen, Sebastian and Hamann, Heiko}}, booktitle = {{Proceedings. 25. Computational Intelligence Workshop}}, title = {{{Evolution of Controllers for Robot-Plant Bio-Hybdrids: A Simple Case Study Using a Model of Plant Growth and Motion}}}, year = {{2015}}, } @inproceedings{19980, abstract = {{Fitness function design is known to be a critical feature of the evolutionary-robotics approach. Potentially, the complexity of evolving a successful controller for a given task can be reduced by integrating a priori knowledge into the fitness function which complicates the comparability of studies in evolutionary robotics. Still, there are only few publications that study the actual effects of different fitness functions on the robot's performance. In this paper, we follow the fitness function classification of Nelson et al. (2009) and investigate a selection of four classes of fitness functions that require different degrees of a priori knowledge. The robot controllers are evolved in simulation using NEAT and we investigate different tasks including obstacle avoidance and (periodic) goal homing. The best evolved controllers were then post-evaluated by examining their potential for adaptation, determining their convergence rates, and using cross-comparisons based on the different fitness function classes. The results confirm that the integration of more a priori knowledge can simplify a task and show that more attention should be paid to fitness function classes when comparing different studies.}}, author = {{Hamann, Heiko and Divband Soorati, Mohammad}}, booktitle = {{Proceedings of the Genetic and Evolutionary Computation Conference (GECCO 2015)}}, pages = {{153--160}}, publisher = {{ACM}}, title = {{{The Effect of Fitness Function Design on Performance in Evolutionary Robotics: The Influence of a Priori Knowledge}}}, doi = {{10.1145/2739480.2754676}}, year = {{2015}}, } @inproceedings{19988, author = {{Hamann, Heiko and Schmickl, Thomas and Zahadat, Payam}}, booktitle = {{13th European Conference on Artificial Life (ECAL 2015)}}, pages = {{174}}, publisher = {{MIT Press}}, title = {{{Evolving Collective Behaviors With Diverse But Predictable Sensor States}}}, doi = {{10.7551/978-0-262-33027-5-ch036}}, year = {{2015}}, } @inbook{19989, author = {{Hamann, Heiko and Correll, Nikolaus and Kacprzyk, Janusz and Pedrycz, Witold}}, booktitle = {{Springer Handbook of Computational Intelligence}}, pages = {{1423--1431}}, publisher = {{Springer}}, title = {{{Probabilistic Modeling of Swarming Systems}}}, doi = {{10.1007/978-3-662-43505-2_74}}, year = {{2015}}, } @inproceedings{19990, author = {{Ding, Hongli and Hamann, Heiko}}, booktitle = {{First International Symposium on Swarm Behavior and Bio-Inspired Robotics (SWARM 2015)}}, title = {{{Dependability in Swarm Robotics: Error Detection and Correction}}}, year = {{2015}}, } @inproceedings{19991, author = {{Hamann, Heiko and Schmickl, Thomas and Kengyel, Daniela and Zahadat, Payam and Radspieler, Gerald and Wotawa, Franz}}, booktitle = {{Principles and Practice of Multi-Agent Systems (PRIMA 2015)}}, pages = {{201--217}}, title = {{{Potential of Heterogeneity in Collective Behaviors: A Case Study on Heterogeneous Swarms}}}, year = {{2015}}, } @article{19992, author = {{Valentini, Gabriele and Hamann, Heiko}}, issn = {{1935-3812}}, journal = {{Swarm Intelligence}}, pages = {{153--176}}, title = {{{Time-variant feedback processes in collective decision-making systems: influence and effect of dynamic neighborhood sizes}}}, doi = {{10.1007/s11721-015-0108-8}}, year = {{2015}}, } @inproceedings{20005, author = {{Dorigo, Marco and Hamann, Heiko and Valentini, Gabriele}}, booktitle = {{Proceedings of the 14th Int. Conf. on Autonomous Agents and Multiagent Systems (AAMAS 2015)}}, title = {{{Efficient Decision-Making in a Self-Organizing Robot Swarm: On the Speed Versus Accuracy Trade-Off}}}, year = {{2015}}, } @inproceedings{20006, author = {{Dorigo, Marco and Hamann, Heiko and Valentini, Gabriele}}, booktitle = {{AAAI-15 Video Proceedings}}, title = {{{Self-organized collective decisions in a robot swarm}}}, year = {{2015}}, } @inproceedings{266, abstract = {{Many markets have seen a shift from the idea of buying and moved to leasing instead. Arguably, the latter has been the major catalyst for their success. Ten years ago, research realized this shift and initiated the study of "online leasing problems" by introducing leasing to online optimization problems. Resources required to provide a service in an "online leasing problem" are no more bought but leased for different durations. In this paper, we provide an overview of results that contribute to the understanding of "online resource leasing problems". }}, author = {{Markarian, Christine and Meyer auf der Heide, Friedhelm}}, booktitle = {{Proceedings of the 2015 ACM Symposium on Principles of Distributed Computing (PODC)}}, pages = {{343--344}}, title = {{{Online Resource Leasing}}}, doi = {{10.1145/2767386.2767454}}, year = {{2015}}, } @phdthesis{267, author = {{Markarian, Christine}}, publisher = {{Universität Paderborn}}, title = {{{Online Resource Leasing}}}, year = {{2015}}, } @article{320, abstract = {{We consider structural and algorithmic questions related to the Nash dynamics of weighted congestion games. In weighted congestion games with linear latency functions, the existence of pure Nash equilibria is guaranteed by a potential function argument. Unfortunately, this proof of existence is inefficient and computing pure Nash equilibria in such games is a PLS-hard problem even when all players have unit weights. The situation gets worse when superlinear (e.g., quadratic) latency functions come into play; in this case, the Nash dynamics of the game may contain cycles and pure Nash equilibria may not even exist. Given these obstacles, we consider approximate pure Nash equilibria as alternative solution concepts. A ρ--approximate pure Nash equilibrium is a state of a (weighted congestion) game from which no player has any incentive to deviate in order to improve her cost by a multiplicative factor higher than ρ. Do such equilibria exist for small values of ρ? And if so, can we compute them efficiently?We provide positive answers to both questions for weighted congestion games with polynomial latency functions by exploiting an “approximation” of such games by a new class of potential games that we call Ψ-games. This allows us to show that these games have d!-approximate pure Nash equilibria, where d is the maximum degree of the latency functions. Our main technical contribution is an efficient algorithm for computing O(1)-approximate pure Nash equilibria when d is a constant. For games with linear latency functions, the approximation guarantee is 3+√5/2 + Oγ for arbitrarily small γ > 0; for latency functions with maximum degree d≥ 2, it is d2d+o(d). The running time is polynomial in the number of bits in the representation of the game and 1/γ. As a byproduct of our techniques, we also show the following interesting structural statement for weighted congestion games with polynomial latency functions of maximum degree d ≥ 2: polynomially-long sequences of best-response moves from any initial state to a dO(d2)-approximate pure Nash equilibrium exist and can be efficiently identified in such games as long as d is a constant.To the best of our knowledge, these are the first positive algorithmic results for approximate pure Nash equilibria in weighted congestion games. Our techniques significantly extend our recent work on unweighted congestion games through the use of Ψ-games. The concept of approximating nonpotential games by potential ones is interesting in itself and might have further applications.}}, author = {{Caragiannis, Ioannis and Fanelli, Angelo and Gravin, Nick and Skopalik, Alexander}}, journal = {{Transactions on Economics and Computation}}, number = {{1}}, publisher = {{ACM}}, title = {{{Approximate Pure Nash Equilibria in Weighted Congestion Games: Existence, Efficient Computation, and Structure}}}, doi = {{10.1145/2614687}}, volume = {{3}}, year = {{2015}}, } @misc{316, author = {{Pautz, Jannis}}, publisher = {{Universität Paderborn}}, title = {{{Budget Games with priced strategies}}}, year = {{2015}}, } @phdthesis{317, author = {{Jähn, Claudius}}, publisher = {{Universität Paderborn}}, title = {{{Bewertung von Renderingalgorithmen für komplexe 3-D-Szenen}}}, year = {{2015}}, } @phdthesis{270, author = {{Abshoff, Sebastian}}, publisher = {{Universität Paderborn}}, title = {{{On the Complexity of Fundamental Problems in Dynamic Ad-hoc Networks}}}, year = {{2015}}, } @inproceedings{271, abstract = {{In \emph{bandwidth allocation games} (BAGs), the strategy of a player consists of various demands on different resources. The player's utility is at most the sum of these demands, provided they are fully satisfied. Every resource has a limited capacity and if it is exceeded by the total demand, it has to be split between the players. Since these games generally do not have pure Nash equilibria, we consider approximate pure Nash equilibria, in which no player can improve her utility by more than some fixed factor $\alpha$ through unilateral strategy changes. There is a threshold $\alpha_\delta$ (where $\delta$ is a parameter that limits the demand of each player on a specific resource) such that $\alpha$-approximate pure Nash equilibria always exist for $\alpha \geq \alpha_\delta$, but not for $\alpha < \alpha_\delta$. We give both upper and lower bounds on this threshold $\alpha_\delta$ and show that the corresponding decision problem is ${\sf NP}$-hard. We also show that the $\alpha$-approximate price of anarchy for BAGs is $\alpha+1$. For a restricted version of the game, where demands of players only differ slightly from each other (e.g. symmetric games), we show that approximate Nash equilibria can be reached (and thus also be computed) in polynomial time using the best-response dynamic. Finally, we show that a broader class of utility-maximization games (which includes BAGs) converges quickly towards states whose social welfare is close to the optimum.}}, author = {{Drees, Maximilian and Feldotto, Matthias and Riechers, Sören and Skopalik, Alexander}}, booktitle = {{Proceedings of the 8th International Symposium on Algorithmic Game Theory (SAGT)}}, pages = {{178--189}}, title = {{{On Existence and Properties of Approximate Pure Nash Equilibria in Bandwidth Allocation Games}}}, doi = {{10.1007/978-3-662-48433-3_14}}, year = {{2015}}, } @inproceedings{274, abstract = {{Consider the problem in which n jobs that are classified into k types are to be scheduled on m identical machines without preemption. A machine requires a proper setup taking s time units before processing jobs of a given type. The objective is to minimize the makespan of the resulting schedule. We design and analyze an approximation algorithm that runs in time polynomial in n,m and k and computes a solution with an approximation factor that can be made arbitrarily close to 3/2.}}, author = {{Mäcker, Alexander and Malatyali, Manuel and Meyer auf der Heide, Friedhelm and Riechers, Sören}}, booktitle = {{Algorithms and Data Structures: 14th International Symposium, WADS 2015, Victoria, BC, Canada, August 5-7, 2015. Proceedings}}, editor = {{Dehne, Frank and Sack, Jörg Rüdiger and Stege, Ulrike}}, pages = {{542----553}}, title = {{{Non-preemptive Scheduling on Machines with Setup Times}}}, doi = {{10.1007/978-3-319-21840-3_45}}, year = {{2015}}, }