Overview

Welcome to IJCAI 2025 Mahjong AI Competition. In this competition, you will develop a Mahjong AI that is able to compete with other agents and human players on Botzone, an online AI platform. The Mahjong Competition Rules (MCR) are based on Chinese Mahjong Competition Rules, also known as Chinese Official Mahjong. For learning MCR and debugging purposes, you are provided with a sample game-playing agent and a sample judge program used during the competition. The winner and the rankings will be determined after two rounds of competitions.

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Mahjong is a four-player imperfect information game that originated in China over 3000 years ago. In 1998, the General Administration of Sport of China formalized Chinese Mahjong Competition Rules, the rules upon which this competition is based. In addition to game-playing strategies, luck is required to win a round of Mahjong, and exactly this uncertainty factor brought tremendous fun and challenges to Mahjong. Unlike other Asian mahjong variants, such as Japanese Riichi Mahjong, Chinese Official Mahjong encourages more aggressive game-playing strategies, thus it is more entertaining and attractive for both contestants and game watchers.

In Chinese Official Mahjong, players need to continuously analyze holding tiles, calculate possible winning hands, and pick a discarding tile for each turn. To make substantial progress in this competition, competitors may benefit from combining different AI methods, such as planning, game theory, heuristic search, Monte Carlo Tree Search, opponent modeling, machine learning, etc. Indeed, successfully integrating different kinds of methods remains one of the great challenges of AI nowadays. Best of luck with all your efforts and endeavors in this competition!

Pseudocode of the tournament

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Registration

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Timeline

Committee

Wenxin Li

Professor in Peking University

Xiaotie Deng

Professor in Peking University

Yaodong Yang

Assistant Professor in Peking University

Junliang Xing

Professor in Tsinghua University

Xianping Tao

Professor in Nanjing University

Haifeng Zhang

Associate professor, Institute of Automation, Chinese Academy of Sciences (CASIA)

Wenlong Li

General Secretary of Mahjong International League

Yutian Chen

Staff Research Scientist in Google DeepMind

LanZhou Zheng

CTO & Co-Founder of WEIZHIYU (Beijing) Technology co., LTd.

Haobo Fu

Principal Researcher in Tencent AI Lab

Organizers

AI Lab, Institute of Network and Energy-Efficient Computing, School of Computer Science, Peking University, is led by Professor Wenxin Li, AI Lab is dedicated to artificial intelligence in games, as well as computer education, biometric recognition and related fields.

WEIZHIYU (Beijing) Technology Co., Ltd. is a company focusing on artificial intelligence and application of games. With advanced game AI technology and leading industrial share, WEIZHIYU has long-term cooperation with many academic institutes, including Tsinghua University, Peking University, Chinese Academy of Science and Beijing Information Science & Technology University, for cutting-edge artificial intelligence research. The company has a technical team with over 30 people and the core members graduate from famous universities like Tsinghua University and Peking University.

Technical support

MIL (Mahjong International League) is a global Mahjong organization conducted by the International Mind Sports Association, including formal Mahjong associations from more than 50 countries and regions of five continents. MIL initiates the duplicate format for the Mahjong competitions, which decrease the lucky factors effectively among the traditional Mahjong games. It is an important innovation to show a fair game and sublimate Mahjong from a game for fun to a real mind sport. By inheriting the idea of mind sports, MIL standardizes Mahjong as a competitive sport to bring Mahjong into mind sports games or even the Olympic Games.