@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},
}
@misc{277,
author = {Kothe, Nils},
publisher = {Universität Paderborn},
title = {{Multilevel Netzwerk Spiele mit konstanten Entfernungen im Highspeed-Netzwerk}},
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},
}
@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},
}
@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},
}
@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},
}
@inproceedings{453,
abstract = {In this paper we study the potential function in congestion games. We consider both games with non-decreasing cost functions as well as games with non-increasing utility functions. We show that the value of the potential function $\Phi(\sf s)$ of any outcome $\sf s$ of a congestion game approximates the optimum potential value $\Phi(\sf s^*)$ by a factor $\Psi_{\mathcal{F}}$ which only depends on the set of cost/utility functions $\mathcal{F}$, and an additive term which is bounded by the sum of the total possible improvements of the players in the outcome $\sf s$. The significance of this result is twofold. On the one hand it provides \emph{Price-of-Anarchy}-like results with respect to the potential function. On the other hand, we show that these approximations can be used to compute $(1+\varepsilon)\cdot\Psi_{\mathcal{F}}$-approximate pure Nash equilibria for congestion games with non-decreasing cost functions. For the special case of polynomial cost functions, this significantly improves the guarantees from Caragiannis et al. [FOCS 2011]. Moreover, our machinery provides the first guarantees for general latency functions.},
author = {Feldotto, Matthias and Gairing, Martin and Skopalik, Alexander},
booktitle = {Proceedings of the 10th International Conference on Web and Internet Economics (WINE)},
pages = {30--43},
title = {{Bounding the Potential Function in Congestion Games and Approximate Pure Nash Equilibria}},
doi = {10.1007/978-3-319-13129-0_3},
year = {2014},
}
@inproceedings{395,
abstract = {We consider a multilevel network game, where nodes can improvetheir communication costs by connecting to a high-speed network.The n nodes are connected by a static network and each node can decideindividually to become a gateway to the high-speed network. The goalof a node v is to minimize its private costs, i.e., the sum (SUM-game) ormaximum (MAX-game) of communication distances from v to all othernodes plus a fixed price α > 0 if it decides to be a gateway. Between gatewaysthe communication distance is 0, and gateways also improve othernodes’ distances by behaving as shortcuts. For the SUM-game, we showthat for α ≤ n − 1, the price of anarchy is Θ (n/√α) and in this rangeequilibria always exist. In range α ∈ (n−1, n(n−1)) the price of anarchyis Θ(√α), and for α ≥ n(n − 1) it is constant. For the MAX-game, weshow that the price of anarchy is either Θ (1 + n/√α), for α ≥ 1, orelse 1. Given a graph with girth of at least 4α, equilibria always exist.Concerning the dynamics, both games are not potential games. For theSUM-game, we even show that it is not weakly acyclic.},
author = {Abshoff, Sebastian and Cord-Landwehr, Andreas and Jung, Daniel and Skopalik, Alexander},
booktitle = {Proceedings of the 10th International Conference on Web and Internet Economics (WINE)},
pages = {435--440},
title = {{Multilevel Network Games}},
doi = {10.1007/978-3-319-13129-0_36},
year = {2014},
}
@inproceedings{459,
abstract = {In this survey article, we discuss two algorithmic research areas that emerge from problems that arise when resources are offered in the cloud. The first area, online leasing, captures problems arising from the fact that resources in the cloud are not bought, but leased by cloud vendors. The second area, Distributed Storage Systems, deals with problems arising from so-called cloud federations, i.e., when several cloud providers are needed to fulfill a given task.},
author = {Kniesburges, Sebastian and Markarian, Christine and Meyer auf der Heide, Friedhelm and Scheideler, Christian},
booktitle = {Proceedings of the 21st International Colloquium on Structural Information and Communication Complexity (SIROCCO)},
pages = {1--13},
title = {{Algorithmic Aspects of Resource Management in the Cloud}},
doi = {10.1007/978-3-319-09620-9_1},
year = {2014},
}
@inproceedings{435,
abstract = {We give a polynomial time algorithm to compute an optimal energy and fractional weighted flow trade-off schedule for a speed-scalable processor with discrete speeds.Our algorithm uses a geometric approach that is based on structural properties obtained from a primal-dual formulation of the problem.},
author = {Antoniadis, Antonios and Barcelo, Neal and Consuegra, Mario and Kling, Peer and Nugent, Michael and Pruhs, Kirk and Scquizzato, Michele},
booktitle = {Proceedings of the 31st Symposium on Theoretical Aspects of Computer Science (STACS)},
pages = {63----74},
title = {{Efficient Computation of Optimal Energy and Fractional Weighted Flow Trade-off Schedules}},
doi = {10.4230/LIPIcs.STACS.2014.63},
year = {2014},
}
@misc{373,
author = {Pahl, David},
publisher = {Universität Paderborn},
title = {{Reputationssysteme für zusammengesetzte Dienstleistungen}},
year = {2014},
}
@inproceedings{380,
abstract = {Network creation games model the creation and usage costs of networks formed by n selfish nodes. Each node v can buy a set of edges, each for a fixed price α > 0. Its goal is to minimize its private costs, i.e., the sum (SUM-game, Fabrikant et al., PODC 2003) or maximum (MAX-game, Demaine et al., PODC 2007) of distances from v to all other nodes plus the prices of the bought edges. The above papers show the existence of Nash equilibria as well as upper and lower bounds for the prices of anarchy and stability. In several subsequent papers, these bounds were improved for a wide range of prices α. In this paper, we extend these models by incorporating quality-of-service aspects: Each edge cannot only be bought at a fixed quality (edge length one) for a fixed price α. Instead, we assume that quality levels (i.e., edge lengths) are varying in a fixed interval [βˇ,β^] , 0 series = {LNCS}},
author = {Cord-Landwehr, Andreas and Mäcker, Alexander and Meyer auf der Heide, Friedhelm},
booktitle = {Proceedings of the 10th International Conference on Web and Internet Economics (WINE)},
pages = {423--428},
title = {{Quality of Service in Network Creation Games}},
doi = {10.1007/978-3-319-13129-0_34},
year = {2014},
}
@inproceedings{412,
abstract = {In this paper we present and analyze HSkip+, a self-stabilizing overlay network for nodes with arbitrary heterogeneous bandwidths. HSkip+ has the same topology as the Skip+ graph proposed by Jacob et al. [PODC 2009] but its self-stabilization mechanism significantly outperforms the self-stabilization mechanism proposed for Skip+. Also, the nodes are now ordered according to their bandwidths and not according to their identifiers. Various other solutions have already been proposed for overlay networks with heterogeneous bandwidths, but they are not self-stabilizing. In addition to HSkip+ being self-stabilizing, its performance is on par with the best previous bounds on the time and work for joining or leaving a network of peers of logarithmic diameter and degree and arbitrary bandwidths. Also, the dilation and congestion for routing messages is on par with the best previous bounds for such networks, so that HSkip+ combines the advantages of both worlds. Our theoretical investigations are backed by simulations demonstrating that HSkip+ is indeed performing much better than Skip+ and working correctly under high churn rates.},
author = {Feldotto, Matthias and Scheideler, Christian and Graffi, Kalman},
booktitle = {Proceedings of the 14th IEEE International Conference on Peer-to-Peer Computing (P2P)},
pages = {1--10},
title = {{HSkip+: A Self-Stabilizing Overlay Network for Nodes with Heterogeneous Bandwidths}},
doi = {10.1109/P2P.2014.6934300},
year = {2014},
}
@phdthesis{431,
abstract = {In meiner Dissertation besch{\"a}ftige ich mich mit dem Entwurf und der Analyse energieeffizienter Schedulingalgorithmen, insbesondere f{\"u}r sogenannte Speed-Scaling Modelle. Diese stellen das theoretische Pendant von Techniken wie AMDs PowerNOW! und Intels SpeedStep dar, welche es erlauben die Geschwindigkeit von Prozessoren zur Laufzeit an die derzeitigen Bedingungen anzupassen. Theoretische Untersuchungen solcher Modelle sind auf eine Arbeit von Yao, Demers und Shenker (FOCS'95) zur{\"u}ckzuf{\"u}hren. Hier kombinieren die Autoren klassisches Deadline-Scheduling mit einem Prozessor der Speed-Scaling beherrscht. Es gilt Jobs verschiedener Gr{\"o}ße fristgerecht abzuarbeiten und die dabei verwendete Energie zu minimieren. Der Energieverbrauch des Prozessors wird durch eine konvexe Funktion $\POW\colon\R_{\geq0}\to\R_{\geq0}$ modelliert, welche die Geschwindigkeit auf den Energieverbrauch abbildet.Meine Dissertation betrachtet verschiedene Varianten des urspr{\"u}nglichen Speed-Scaling Modells. Forschungsrelevante Ergebnisse sind in den Kapiteln 3 bis 6 zu finden und erstrecken sich {\"u}ber die im Folgenden beschriebenen Aspekte:- Kapitel 3 und 4 betrachten verschiedene \emph{Price-Collecting} Varianten des Originalproblems. Hier d{\"u}rfen einzelne Deadlines verfehlt werden, sofern eine jobabh{\"a}ngige Strafe gezahlt wird. Ich entwerfe insbesondere Online-Algorithmen mit einer beweisbar guten Competitiveness. Dabei liefern meine Ergebnisse substantielle Verbesserungen bestehender Arbeiten und erweitern diese unter Anderem auf Szenarien mit mehreren Prozessoren.- In Kapitel 5 wird statt des klassischen Deadline-Schedulings eine Linearkombination der durchschnittlichen Antwortzeit und des Energieverbrauchs betrachtet. Die Frage, ob dieses Problem NP-schwer ist, stellt eine der zentralen Forschungsfragen in diesem Gebiet dar. F{\"u}r eine relaxierte Form dieser Frage entwerfe ich einen effizienter Algorithmus und beweise seine Optimalit{\"a}t.- Das letzte Kapitel betrachtet ein Modell, welches – auf den ersten Blick – nicht direkt zur Speed-Scaling Literatur z{\"a}hlt. Hier geht es stattdessen um ein allgemeines Resource-Constrained Scheduling, in dem sich die Prozessoren zusammen eine gemeinsame, beliebig aufteilbare Ressource teilen. Ich untersuche die Komplexit{\"a}t des Problems und entwerfe verschiedene Approximationsalgorithmen.},
author = {Kling, Peter},
publisher = {Universität Paderborn},
title = {{Energy-efficient Scheduling Algorithms}},
year = {2014},
}
@inproceedings{462,
abstract = {We discuss a technique to analyze complex infinitely repeated games using techniques from the fields of game theory and simulations. Our research is motivated by the analysis of electronic markets with thousands of participants and possibly complex strategic behavior. We consider an example of a global market of composed IT services to demonstrate the use of our simulation technique. We present our current work in this area and we want to discuss further approaches for the future.},
author = {Feldotto, Matthias and Skopalik, Alexander},
booktitle = {Proceedings of the 4th International Conference on Simulation and Modeling Methodologies, Technologies and Applications (SIMULTECH 2014)},
pages = {625--630},
title = {{A Simulation Framework for Analyzing Complex Infinitely Repeated Games}},
doi = {10.5220/0005110406250630},
year = {2014},
}
@inproceedings{455,
abstract = {We study the existence of approximate pure Nash equilibria in weighted congestion games and develop techniques to obtain approximate potential functions that prove the existence of alpha-approximate pure Nash equilibria and the convergence of alpha-improvement steps. Specifically, we show how to obtain upper bounds for approximation factor alpha for a given class of cost functions. For example for concave cost functions the factor is at most 3/2, for quadratic cost functions it is at most 4/3, and for polynomial cost functions of maximal degree d it is at at most d + 1. For games with two players we obtain tight bounds which are as small as for example 1.054 in the case of quadratic cost functions.},
author = {Hansknecht, Christoph and Klimm, Max and Skopalik, Alexander},
booktitle = {Proceedings of the 17th. International Workshop on Approximation Algorithms for Combinatorial Optimization Problems (APPROX)},
pages = {242 -- 257},
title = {{Approximate pure Nash equilibria in weighted congestion games}},
doi = {10.4230/LIPIcs.APPROX-RANDOM.2014.242},
year = {2014},
}
@inproceedings{379,
abstract = {In the leasing variant of Set Cover presented by Anthony et al.[1], elements U arrive over time and must be covered by sets from a familyF of subsets of U. Each set can be leased for K different periods of time.Let |U| = n and |F| = m. Leasing a set S for a period k incurs a cost ckS and allows S to cover its elements for the next lk time steps. The objectiveis to minimize the total cost of the sets leased, such that elements arrivingat any time t are covered by sets which contain them and are leased duringtime t. Anthony et al. [1] gave an optimal O(log n)-approximation forthe problem in the offline setting, unless P = NP [22]. In this paper, wegive randomized algorithms for variants of Set Cover Leasing in the onlinesetting, including a generalization of Online Set Cover with Repetitionspresented by Alon et al. [2], where elements appear multiple times andmust be covered by a different set at each arrival. Our results improve theO(log2(mn)) competitive factor of Online Set Cover with Repetitions [2]to O(log d log(dn)) = O(logmlog(mn)), where d is the maximum numberof sets an element belongs to.},
author = {Abshoff, Sebastian and Markarian, Christine and Meyer auf der Heide, Friedhelm},
booktitle = {Proceedings of the 8th Annual International Conference on Combinatorial Optimization and Applications (COCOA)},
pages = {25--34},
title = {{Randomized Online Algorithms for Set Cover Leasing Problems}},
doi = {10.1007/978-3-319-12691-3_3},
year = {2014},
}
@inproceedings{451,
abstract = {We introduce the concept of budget games. Players choose a set of tasks and each task has a certain demand on every resource in the game. Each resource has a budget. If the budget is not enough to satisfy the sum of all demands, it has to be shared between the tasks. We study strategic budget games, where the budget is shared proportionally. We also consider a variant in which the order of the strategic decisions influences the distribution of the budgets. The complexity of the optimal solution as well as existence, complexity and quality of equilibria are analysed. Finally, we show that the time an ordered budget game needs to convergence towards an equilibrium may be exponential.},
author = {Drees, Maximilian and Riechers, Sören and Skopalik, Alexander},
booktitle = {Proceedings of the 7th International Symposium on Algorithmic Game Theory (SAGT)},
editor = {Lavi, Ron},
pages = {110--121},
title = {{Budget-restricted utility games with ordered strategic decisions}},
doi = {10.1007/978-3-662-44803-8_10},
year = {2014},
}