@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}}, } @inproceedings{275, abstract = {{We investigate a non-cooperative game-theoretic model for the formation of communication networks by selfish agents. Each agent aims for a central position at minimum cost for creating edges. In particular, the general model (Fabrikant et al., PODC'03) became popular for studying the structure of the Internet or social networks. Despite its significance, locality in this game was first studied only recently (Bilò et al., SPAA'14), where a worst case locality model was presented, which came with a high efficiency loss in terms of quality of equilibria. Our main contribution is a new and more optimistic view on locality: agents are limited in their knowledge and actions to their local view ranges, but can probe different strategies and finally choose the best. We study the influence of our locality notion on the hardness of computing best responses, convergence to equilibria, and quality of equilibria. Moreover, we compare the strength of local versus non-local strategy changes. Our results address the gap between the original model and the worst case locality variant. On the bright side, our efficiency results are in line with observations from the original model, yet we have a non-constant lower bound on the Price of Anarchy.}}, author = {{Cord-Landwehr, Andreas and Lenzner, Pascal}}, booktitle = {{Proceedings of the 40th Conference on Mathematical Foundations of Computer Science (MFCS)}}, pages = {{248----260}}, title = {{{Network Creation Games: Think Global - Act Local}}}, doi = {{10.1007/978-3-662-48054-0_21}}, year = {{2015}}, } @misc{277, author = {{Kothe, Nils}}, publisher = {{Universität Paderborn}}, title = {{{Multilevel Netzwerk Spiele mit konstanten Entfernungen im Highspeed-Netzwerk}}}, year = {{2015}}, } @inproceedings{17425, author = {{Berssenbrügge, Jan and Wiederkehr, Olga and Jähn, Claudius and Fischer, Matthias}}, booktitle = {{12. Paderborner Workshop Augmented & Virtual Reality in der Produktentstehung}}, pages = {{65--78}}, publisher = {{Verlagsschriftenreihe des Heinz Nixdorf Instituts}}, title = {{{Anbindung des Virtuellen Prototypen an die Partialmodelle intelligenter technischer Systeme}}}, volume = {{343}}, year = {{2015}}, } @inproceedings{17427, author = {{Jähn, Claudius and Fischer, Matthias and Gerges, Maria and Berssenbrügge, Jan}}, booktitle = {{12. Paderborner Workshop Augmented & Virtual Reality in der Produktentstehung}}, pages = {{107--120}}, publisher = {{Verlagsschriftenreihe des Heinz Nixdorf Instituts}}, title = {{{Automatische Ableitung geometrischer Eigenschaften von Bauteilen aus dem 3-D-Polygonmodell}}}, volume = {{342}}, year = {{2015}}, } @book{17431, editor = {{Gausemeier, Jürgen and Grafe, Michael and Meyer auf der Heide, Friedhelm}}, publisher = {{Verlagsschriftenreihe des Heinz Nixdorf Instituts}}, title = {{{Augmented & Virtual Reality in der Produktentstehung: Grundlagen, Methoden und Werkzeuge; Interaktions- und Visualisierungstechniken, Virtual Prototyping intelligenter technischer Systeme mit AR/VR}}}, volume = {{342}}, year = {{2015}}, } @article{17657, abstract = {{Inter-datacenter transfers of non-interactive but timely large flows over a private (managed) network is an important problem faced by many cloud service providers. The considered flows are non-interactive because they do not explicitly target the end users. However, most of them must be performed on a timely basis and are associated with a deadline. We propose to schedule these flows by a centralized controller, which determines when to transmit each flow and which path to use. Two scheduling models are presented in this paper. In the first, the controller also determines the rate of each flow, while in the second bandwidth is assigned by the network according to the TCP rules. We develop scheduling algorithms for both models and compare their complexity and performance.}}, author = {{Cohen, R. and Polevoy, Gleb}}, issn = {{2168-7161}}, journal = {{Cloud Computing, IEEE Transactions on}}, keywords = {{Approximation algorithms, Approximation methods, Bandwidth, Cloud computing, Routing, Schedules, Scheduling}}, number = {{99}}, pages = {{1--1}}, title = {{{Inter-Datacenter Scheduling of Large Data Flows}}}, doi = {{10.1109/TCC.2015.2487964}}, volume = {{PP}}, year = {{2015}}, } @article{17658, abstract = {{Abstract We study the problem of bandwidth allocation with multiple interferences. In this problem the input consists of a set of users and a set of base stations. Each user has a list of requests, each consisting of a base station, a frequency demand, and a profit that may be gained by scheduling this request. The goal is to find a maximum profit set of user requests S that satisfies the following conditions: (i) S contains at most one request per user, (ii) the frequency sets allotted to requests in S that correspond to the same base station are pairwise non-intersecting, and (iii) the QoS received by any user at any frequency is reasonable according to an interference model. In this paper we consider two variants of bandwidth allocation with multiple interferences. In the first each request specifies a demand that can be satisfied by any subset of frequencies that is large enough. In the second each request specifies a specific frequency interval. Furthermore, we consider two interference models, multiplicative and additive. We show that these problems are extremely hard to approximate if the interferences depend on both the interfered and the interfering base stations. On the other hand, we provide constant factor approximation algorithms for both variants of bandwidth allocation with multiple interferences for the case where the interferences depend only on the interfering base stations. We also consider a restrictive special case that is closely related to the Knapsack problem. We show that this special case is NP-hard and that it admits an FPTAS. }}, author = {{Bar-Yehuda, Reuven and Polevoy, Gleb and Rawitz, Dror}}, issn = {{0166-218X}}, journal = {{Discrete Applied Mathematics }}, keywords = {{Local ratio}}, pages = {{23 -- 36}}, publisher = {{Elsevier}}, title = {{{Bandwidth allocation in cellular networks with multiple interferences}}}, doi = {{http://dx.doi.org/10.1016/j.dam.2015.05.013}}, volume = {{194}}, year = {{2015}}, } @inproceedings{240, abstract = {{We consider online leasing problems in which demands arrive over time and need to be served by leasing resources. We introduce a new model for these problems such that a resource can be leased for K different durations each incurring a different cost (longer leases cost less per time unit). Each demand i can be served anytime between its arrival ai and its deadline ai+di by a leased resource. The objective is to meet all deadlines while minimizing the total leasing costs. This model is a natural generalization of Meyerson’s ParkingPermitProblem (FOCS 2005) in which di=0 for all i. We propose an online algorithm that is Θ(K+dmaxlmin)-competitive where dmax and lmin denote the largest di and the shortest available lease length, respectively. We also extend the SetCoverLeasing problem by deadlines and give a competitive online algorithm which also improves on existing solutions for the original SetCoverLeasing problem.}}, author = {{Li, Shouwei and Mäcker, Alexander and Markarian, Christine and Meyer auf der Heide, Friedhelm and Riechers, Sören}}, booktitle = {{Proceedings of the 21st Annual International Computing and Combinatorics Conference (COCOON)}}, pages = {{277----288}}, title = {{{Towards Flexible Demands in Online Leasing Problems}}}, doi = {{10.1007/978-3-319-21398-9_22}}, year = {{2015}}, } @unpublished{16449, abstract = {{We consider the following variant of the two dimensional gathering problem for swarms of robots: Given a swarm of $n$ indistinguishable, point shaped robots on a two dimensional grid. Initially, the robots form a closed chain on the grid and must keep this connectivity during the whole process of their gathering. Connectivity means, that neighboring robots of the chain need to be positioned at the same or neighboring points of the grid. In our model, gathering means to keep shortening the chain until the robots are located inside a $2\times 2$ subgrid. Our model is completely local (no global control, no global coordinates, no compass, no global communication or vision, \ldots). Each robot can only see its next constant number of left and right neighbors on the chain. This fixed constant is called the \emph{viewing path length}. All its operations and detections are restricted to this constant number of robots. Other robots, even if located at neighboring or the same grid point cannot be detected. Only based on the relative positions of its detectable chain neighbors, a robot can decide to obtain a certain state. Based on this state and their local knowledge, the robots do local modifications to the chain by moving to neighboring grid points without breaking the chain. These modifications are performed without the knowledge whether they lead to a global progress or not. We assume the fully synchronous $\mathcal{FSYNC}$ model. For this problem, we present a gathering algorithm which needs linear time. This result generalizes the result from \cite{hopper}, where an open chain with specified distinguishable (and fixed) endpoints is considered.}}, author = {{Abshoff, Sebastian and Cord-Landwehr, Andreas and Fischer, Matthias and Jung, Daniel and Meyer auf der Heide, Friedhelm}}, booktitle = {{arXiv:1510.05454}}, title = {{{Gathering a Closed Chain of Robots on a Grid}}}, year = {{2015}}, } @unpublished{16452, abstract = {{We consider the problem of dominating set-based virtual backbone used for routing in asymmetric wireless ad-hoc networks. These networks have non-uniform transmission ranges and are modeled using the well-established disk graphs. The corresponding graph theoretic problem seeks a strongly connected dominating-absorbent set of minimum cardinality in a digraph. A subset of nodes in a digraph is a strongly connected dominating-absorbent set if the subgraph induced by these nodes is strongly connected and each node in the graph is either in the set or has both an in-neighbor and an out-neighbor in it. Distributed algorithms for this problem are of practical significance due to the dynamic nature of ad-hoc networks. We present a first distributed approximation algorithm, with a constant approximation factor and O(Diam) running time, where Diam is the diameter of the graph. Moreover we present a simple heuristic algorithm and conduct an extensive simulation study showing that our heuristic outperforms previously known approaches for the problem.}}, author = {{Abu-Khzam, Faisal N. and Markarian, Christine and Meyer auf der Heide, Friedhelm and Schubert, Michael}}, booktitle = {{arXiv:1510.01866}}, title = {{{Approximation and Heuristic Algorithms for Computing Backbones in Asymmetric Ad-Hoc Networks}}}, year = {{2015}}, }