Mean Field Equilibria of MultiArmed Bandit Games Ramki
Mean Field Equilibria of Multi-Armed Bandit Games Ramki Gummadi (Stanford) Joint work with: Ramesh Johari (Stanford) Jia Yuan Yu (IBM Research, Dublin)
Motivation • Classical MAB models have a single agent. • What happens when other agents influence arm rewards? • Do standard learning algorithms lead to any equilibrium?
Examples • Wireless transmitters learning unknown channels with interference • Sellers learning about product categories: e. g. e. Bay • Positive externalities: social gaming.
Example: Wireless Transmitters Channel A ? 0. 8 Channel B 0. 6
Example: Wireless Transmitters Channel A ? 0. 8 ; 0. 9 Channel B 0. 6 ; 0. 1
Modeling the Bandit Game • Perfect bayesian equilibrium – Implausible agent behavior. • Mean field model – Agents behave under an assumption of stationarity.
Outline • • Model The equilibrium concept Existence Dynamics Uniqueness and convergence From finite system to limit model Conclusion
Mean Field Model of MAB Games •
Mean Field Model of MAB Games •
A Single Agent’s Evolution •
Examples of Reward Functions •
The Equilibrium Concept •
Optimality in Equilibrium •
Existence of MFE •
Beyond Existence • MFE exists, but when is it unique? • Can agent dynamics find such an equilibrium even if it is unique? • How does the mean field model approximate a system with finitely many agents?
Dynamics Arms 1 2 3. i. n
Dynamics Arms 1 2 3. i. n
Dynamics Arms 1 2 3. i. n
Dynamics Arms 1 2 3. i. n
Dynamics •
Uniqueness and Convergence •
Finite Systems to Limit Model •
Approximation Property •
Conclusion • Agent populations converge to a mean field equilibrium using classical bandit algorithms. • Large agent population effectively mitigates non-stationarity in MAB games. • Interesting theoretical results beyond existence: uniqueness, convergence and approximation. • Insights are more general than theorem conditions strictly imply.
- Slides: 24