Complete Implementation of WXF Chinese Chess Rules

TL;DR

This paper presents a comprehensive algorithm for accurately implementing Chinese Chess rules, including all repetition scenarios, with optimizations that improve engine strength and correctness.

Contribution

The paper introduces a complete algorithm for Chinese Chess repetition rules, covering all cases and optimized for speed, enhancing game correctness and engine performance.

Findings

Increased engine strength by +10 rating points.

Achieved a 5% increase in win rate.

Successfully handled all 110 WXF manual cases.

Abstract

Unlike repetitions in Western Chess where all repetitions are draws, repetitions in Chinese Chess could result in a win, draw, or loss depending on the kind of repetition being made by both players. One of the biggest hurdles facing Chinese Chess application development is a proper system for judging games correctly. This paper introduces a complete algorithm for ruling the WXF rules correctly in all 110 example cases found in the WXF manual. We introduce several novel optimizations for speeding up the repetition handling without compromising the program correctness. This algorithm is usable in engines, and we saw a total increase in playing strength by +10 point rating increase, or an increased 5% winrate when integrating this approach into our prototype engine.