Conventional algorithms for solving Markov decision processes (MDPs) become intractable for a large finite state and action spaces. Several studies have been devoted to this issue, but most of them only treat infinite-horizon MDPs. This paper is one of the first works to deal with non-stationary finite-horizon MDPs by proposing a new decomposition approach, which consists in partitioning the problem into smaller restricted finite-horizon MDPs, each restricted MDP is solved independently, in a specific order, using the proposed hierarchical backward induction (HBI) algorithm based on the backward induction (BI) algorithm. Next, the sub-local solutions are combined to obtain a global solution. An example of racetrack problems shows the performance of the proposal decomposition technique.
Research background
Markov Decision Processes (MDPs) are a powerful framework for modeling many real-world problems with finite-horizons that maximize the reward given a sequence of actions. Although many problems such as investment and financial market problems where the value of a reward decreases exponentially with time, require the introduction of interest rates.
Purpose
This study investigates non-stationary finite-horizon MDPs with a discount factor to account for fluctuations in rewards over time.
Research methodology
To consider the fluctuations of rewards with time, the authors define new nonstationary finite-horizon MDPs with a discount factor. First, the existence of an optimal policy for the proposed finite-horizon discounted MDPs is proven. Next, a new Discounted Backward Induction (DBI) algorithm is presented to find it. To enhance the value of their proposal, a financial model is used as an example of a finite-horizon discounted MDP and an adaptive DBI algorithm is used to solve it.
Results
The proposed method calculates the optimal values of the investment to maximize its expected total return with consideration of the time value of money.
Novelty
No existing studies have before examined dynamic finite-horizon problems that account for temporal fluctuations in rewards.
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