Investigation of progress and application related to Multi-Armed Bandit algorithms

Abstract

This paper discusses four Multi-armed Bandit algorithms: Explore-then-Commit (ETC), Epsilon-Greedy, Upper Confidence Bound (UCB), and Thompson Sampling algorithm. ETC algorithm aims to spend the majority of rounds on the best arm, but it can lead to a suboptimal outcome if the environment changes rapidly. The Epsilon-Greedy algorithm is designed to explore and exploit simultaneously, while it often tries sub-optimal arm even after the algorithm finds the best arm. Thus, the Epsilon-Greedy algorithm performs well when the environment continuously changes. UCB algorithm is one of the most used Multi-armed Bandit algorithms because it can rapidly narrow the potential optimal decisions in a wide range of scenarios; however, the algorithm can be influenced by some specific pattern of reward distribution or noise presenting in the environment. Thompson Sampling algorithm is also one of the most common algorithms in the Multi-armed Bandit algorithm due to its simplicity, effectiveness, and adaptability to various reward distributions. The Thompson Sampling algorithm performs well in multiple scenarios because it explores and exploits simultaneously, but its variance is greater than the three algorithms mentioned above. Today, Multi-armed bandit algorithms are widely used in advertisement, health care, and website and app optimization. Finally, the Multi-armed Bandit algorithms are rapidly replacing the traditional algorithms; in the future, the advanced Multi-armed Bandit algorithm, contextual Multi-armed Bandit algorithm, will gradually replace the old one.