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RP 2014: Reachability Problems pp 125-137

# Reachability in MDPs: Refining Convergence of Value Iteration

• Serge Haddad
• Benjamin Monmege
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8762)

## Abstract

Markov Decision Processes (MDP) are a widely used model including both non-deterministic and probabilistic choices. Minimal and maximal probabilities to reach a target set of states, with respect to a policy resolving non-determinism, may be computed by several methods including value iteration. This algorithm, easy to implement and efficient in terms of space complexity, consists in iteratively finding the probabilities of paths of increasing length. However, it raises three issues: (1) defining a stopping criterion ensuring a bound on the approximation, (2) analyzing the rate of convergence, and (3) specifying an additional procedure to obtain the exact values once a sufficient number of iterations has been performed. The first two issues are still open and for the third one a “crude” upper bound on the number of iterations has been proposed. Based on a graph analysis and transformation of MDPs, we address these problems. First we introduce an interval iteration algorithm, for which the stopping criterion is straightforward. Then we exhibit convergence rate. Finally we significantly improve the bound on the number of iterations required to get the exact values.

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## Copyright information

© Springer International Publishing Switzerland 2014

## Authors and Affiliations

• Serge Haddad
• 1
• Benjamin Monmege
• 2
1. 1.LSVENS Cachan, CNRS & InriaFrance
2. 2.Université libre de BruxellesBelgium