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- Dimitris Fotakis, Spyros C. Kontogiannis, Paul G. Spirakis
- Theor. Comput. Sci.
- 2004

What is the price of anarchy when unsplittable demands are routed selfishly in general networks with load-dependent edge delays? Motivated by this question we generalize the model of [14] to the case of weighted congestion games. We show that varying demands of users crucially affect the nature of these games, which are no longer isomorphic to exact… (More)

- Dimitris Fotakis, Rasmus Pagh, Peter Sanders, Paul G. Spirakis
- Theory of Computing Systems
- 2003

We generalize Cuckoo Hashing to d-ary Cuckoo Hashing and show how this yields a simple hash table data structure that stores n elements in (1 + ε)n memory cells, for any constant ε > 0. Assuming uniform hashing, accessing or deleting table entries takes at most d=O (ln (1/ε)) probes and the expected amortized insertion time is constant. This is the first… (More)

In this work, we study the combinatorial structure and the computational complexity of Nash equilibria for a certain game that models selfish routing over a network consisting of m parallel links. We assume a collection of n users, each employing a mixed strategy, which is a probability distribution over links, to control the routing of its own assigned… (More)

- Dimitris Fotakis
- Algorithmica
- 2003

We consider the problem of Online Facility Location, where the demand points arrive online and must be assigned irrevocably to an open facility upon arrival. The objective is to minimize the sum of facility and assignment costs. We prove that the competitive ratio for Online Facility Location is Θ $(\frac{\log n}{\log\log n})$ . On the negative side, we… (More)

- Foto N. Afrati, Dimitris Fotakis, Jeffrey D. Ullman
- 2013 IEEE 29th International Conference on Data…
- 2013

The theme of this paper is how to find all instances of a given “sample” graph in a larger “data graph,” using a single round of map-reduce. For the simplest sample graph, the triangle, we improve upon the best known such algorithm. We then examine the general case, considering both the communication cost between mappers and… (More)

- Dimitris Fotakis
- Theory of Computing Systems
- 2007

We investigate the effectiveness of Stackelberg strategies for atomic congestion games with unsplittable demands. In our setting, only a fraction of the players are selfish, while the rest are willing to follow a predetermined strategy. A Stackelberg strategy assigns the coordinated players to appropriately selected strategies trying to minimize the… (More)

- Dimitris Fotakis
- Theory of Computing Systems
- 2008

We investigate the effect of linear independence in the strategies of congestion games on the convergence time of best improvement sequences and on the pure Price of Anarchy. In particular, we consider symmetric congestion games on extension-parallel networks, an interesting class of networks with linearly independent paths, and establish two remarkable… (More)

- Dimitris Fotakis, Spyros C. Kontogiannis, Paul G. Spirakis
- ACM Trans. Algorithms
- 2006

We consider algorithmic questions concerning the existence, tractability, and quality of Nash equilibria, in atomic congestion games among users participating in selfish coalitions.
We introduce a coalitional congestion model among atomic players and demonstrate many interesting similarities with the noncooperative case. For example, there exists a… (More)

- Dimitris Fotakis, Christos Tzamos
- Theor. Comput. Sci.
- 2010

We study Facility Location games, where a number of facilities are placed in a metric space based on locations reported by strategic agents. A mechanism maps the agents’ locations to a set of facilities. The agents seek to minimize their connection cost, namely the distance of their true location to the nearest facility, and may misreport their location. We… (More)

- Dimitris Fotakis, Paul G. Spirakis
- FSTTCS
- 1998

The problem of Radio Labelling is to assign distinct integer labels to all the vertices of a graph, such that adjacent vertices get labels at distance at least two. The objective is to minimize the label span. Radio labelling is a combinatorial model for frequency assignment in case that the transmitters are not allowed to operate at the same channel. We… (More)