Improving Portfolio Optimization Results with Bandit Networks

TL;DR

This paper introduces novel bandit algorithms and architectures, including Bandit Networks, to improve portfolio optimization in non-stationary environments, demonstrating superior performance over classical methods in financial data experiments.

Contribution

The paper develops Adaptive Discounted Thompson Sampling and its extension for portfolio optimization, along with Bandit Networks that integrate these algorithms for better dynamic decision-making.

Findings

Bandit Networks outperform classical portfolio methods in financial data.

Proposed algorithms adapt effectively to non-stationary reward environments.

Best network achieves 20% higher out-of-sample Sharpe Ratio.

Abstract

In Reinforcement Learning (RL), multi-armed Bandit (MAB) problems have found applications across diverse domains such as recommender systems, healthcare, and finance. Traditional MAB algorithms typically assume stationary reward distributions, which limits their effectiveness in real-world scenarios characterized by non-stationary dynamics. This paper addresses this limitation by introducing and evaluating novel Bandit algorithms designed for non-stationary environments. First, we present the Adaptive Discounted Thompson Sampling (ADTS) algorithm, which enhances adaptability through relaxed discounting and sliding window mechanisms to better respond to changes in reward distributions. We then extend this approach to the Portfolio Optimization problem by introducing the Combinatorial Adaptive Discounted Thompson Sampling (CADTS) algorithm, which addresses computational challenges within Combinatorial Bandits and improves dynamic asset allocation. Additionally, we propose a novel architecture called Bandit Networks, which integrates the outputs of ADTS and CADTS, thereby mitigating computational limitations in stock selection. Through extensive experiments using real financial market data, we demonstrate the potential of these algorithms and architectures in adapting to dynamic environments and optimizing decision-making processes. For instance, the proposed bandit network instances present superior performance when compared to classic portfolio optimization approaches, such as capital asset pricing model, equal weights, risk parity, and Markovitz, with the best network presenting an out-of-sample Sharpe Ratio 20% higher than the best performing classical model.