Strength Estimation and Human-Like Strength Adjustment in Games

TL;DR

This paper presents a novel strength estimation system and a Monte Carlo tree search method that adjusts AI strength to match human styles in games, demonstrated in Go and chess with high accuracy.

Contribution

The paper introduces a new strength estimator and an SE-MCTS method for predicting and adjusting AI strength in games, improving accuracy and human-like play.

Findings

Over 80% accuracy in rank prediction with 15 game observations

SE-MCTS achieves 51.33% accuracy in human action alignment

Method generalizes well from Go to chess

Abstract

Strength estimation and adjustment are crucial in designing human-AI interactions, particularly in games where AI surpasses human players. This paper introduces a novel strength system, including a strength estimator (SE) and an SE-based Monte Carlo tree search, denoted as SE-MCTS, which predicts strengths from games and offers different playing strengths with human styles. The strength estimator calculates strength scores and predicts ranks from games without direct human interaction. SE-MCTS utilizes the strength scores in a Monte Carlo tree search to adjust playing strength and style. We first conduct experiments in Go, a challenging board game with a wide range of ranks. Our strength estimator significantly achieves over 80% accuracy in predicting ranks by observing 15 games only, whereas the previous method reached 49% accuracy for 100 games. For strength adjustment, SE-MCTS successfully adjusts to designated ranks while achieving a 51.33% accuracy in aligning to human actions, outperforming a previous state-of-the-art, with only 42.56% accuracy. To demonstrate the generality of our strength system, we further apply SE and SE-MCTS to chess and obtain consistent results. These results show a promising approach to strength estimation and adjustment, enhancing human-AI interactions in games. Our code is available at https://rlg.iis.sinica.edu.tw/papers/strength-estimator.