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Price of Anarchy for Machines Models

2002; Czumaj, Vöcking

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Encyclopedia of Algorithms
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Keywords and Synonyms

Worst-case coordination ratio ; Selfish routing                

Problem Definition

Notations

This entry considers a selfish routing model formally introduced by Koutsoupias and Papadimitriou [11], in which the goal is to route the traffic on parallel links with linear latency functions. One can describe this model as a scheduling problem with m independent machines with speeds \( { s_1, \dots, s_m } \) and n independent tasks with weights \( { w_1, \dots, w_n } \). The goal is to allocate the tasks to the machines to minimize the maximum load of the links in the system.

It is assumed that all tasks are assigned by non-cooperative agents. The set of pure strategies for task i is the set \( { \{1, \dots, m\} } \) and a mixed strategy is a distribution on this set.

Given a combination \( { (j_1, \dots, j_n) \in \{1, \dots, m\}^n } \) of pure strategies, one for each task, the cost for task i is \( { \sum_{j_k = j_i} \frac{w_k}{s_{j_i}} } \), which is the time needed for machine j...

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Notes

  1. 1.

    To simplify the notation, for any real \( { x \ge 0 } \), let \( { \log x } \) denote \( { \log x = \max \{\log_2 x, 1\} } \). Also, following standard convention, \( { \Gamma(N) } \) is used to denote the Gamma (factorial) function, which for any natural N is defined by \( { \Gamma(N+1) = N! } \) and for an arbitrary real \( { x > 0 } \) is \( { \Gamma(x)= \int_0^{\infty} t^{x-1} \mskip2mu\mathrm{e}^{-t} \mskip2mu\mathrm{d} t } \). For the inverse of the Gamma function, \( { \Gamma^{(-1)}(N) } \), it is known that \( { \Gamma^{(-1)} (N) = x } \) such that \( { \lfloor x \rfloor! \le N-1 \le \lceil x \rceil! } \). It is well known that \( { \Gamma^{(-1)} (N) = (\log N )/(\log\log N) (1+o(1)) } \).

Recommended Reading

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Czumaj, A., Vöcking, B. (2008). Price of Anarchy for Machines Models. In: Kao, MY. (eds) Encyclopedia of Algorithms. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-30162-4_300

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