Evènement pour le groupe Probabilité et informatique


Date 2011-01-10  11:00-12:00
TitreOptimal positional strategies in stochastic games 
Résumé(Exposé en Français) We consider Markov decision processes with finitely many states and actions. Roughly speaking, a Markov decision process is a Markov chain whose execution is influenced by a player: at each step, depending on the current state of the Markov chain, the player is allowed to choose which probability distribution will be used to make the transition to the next state. His choices are restricted to a finite set of distributions, also called *actions*. The goal of the player is to maximize his expected payoff, which is computed by a payoff function. Such a function associates to each infinite sequence of states and actions a real number. For arbitrary payoff function, the player may have to play very complex strategies to maximize his expected payoff. We are interested in *positional* payoff functions that make the job very simple for the player: whatever is the Markov decision process, the player is able to play *optimally* with *no memory at all*. More precisely, for each state, the player can choose again and again the same action each time the process reaches this state. We will present a theorem about positional payoff functions which provides a unified proof of several results previously known, as well as new examples of Markov decision processes in which simple optimal strategies are guaranteed to exist.  
Lieu076 
OrateurHugo Gimbert 



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