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Mortal (凡夫) is a free and open source AI for Japanese mahjong, powered by deep reinforcement learning.

The development of Mortal is hosted on GitHub at


  • A strong mahjong AI that is compatible with Tenhou's standard ranked rule for four-player mahjong.
  • A blazingly fast mahjong emulator written in Rust with a Python interface. Up to 40K hanchans per hour1 can be achieved using the Rust emulator combined with Python neural network inference.
  • An easy-to-use mjai interface.
  • Serve as a backend for mjai-reviewer (previously known as akochan-reviewer).
  • Free and open source.

About this doc

This doc is work in progress, so most pages are empty right now.

Okay cool now give me the weights!

Read this post for details regarding this topic.




Copyright (C) 2021-2022 Equim

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License along with this program. If not, see

Logo and Other Assets

CC BY-SA 4.0


Evaluated on NVIDIA GeForce RTX 4090 with AMD Ryzen 9 7950X, game batch size 2000.