riichienv 0.1.1

A High-Performance Research Environment for Riichi Mahjong

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High-Performance Research Environment for Riichi Mahjong

[!NOTE] This project is currently under active development. The API and specifications are subject to change before the stable release.

✨ Features

• High Performance: Core logic implemented in Rust for lightning-fast state transitions and rollouts.
• Gym-style API: Intuitive interface designed specifically for reinforcement learning.
• Mortal Compatibility: Seamlessly interface with the Mortal Bot using the standard MJAI protocol.
• Rule Flexibility: Support for diverse rule sets, including no-red-dragon variants and three-player mahjong.
• Game Visualization: Integrated replay viewer for Jupyter Notebooks.

📦 Installation

uv add riichienv
# Or
pip install riichienv

Currently, building from source requires the Rust toolchain.

uv sync --dev
uv run maturin develop --release

🚀 Usage

Gym-style API

from riichienv import RiichiEnv
from riichienv.agents import RandomAgent

agent = RandomAgent()
env = RiichiEnv()
obs_dict = env.reset()
while not env.done():
    actions = {player_id: agent.act(obs)
               for player_id, obs in obs_dict.items()}
    obs_dict = env.step(actions)

scores, points, ranks = env.scores(), env.points(), env.ranks()
print(scores, points, ranks)

env.reset() initializes the game state and returns the initial observations. The returned obs_dict maps each active player ID to their respective Observation object.

>>> from riichienv import RiichiEnv
>>> env = RiichiEnv()
>>> obs_dict = env.reset()
>>> obs_dict
{0: <riichienv._riichienv.Observation object at 0x7fae7e52b6e0>}

Use env.done() to check if the game has concluded.

>>> env.done()
False

By default, the environment runs a single round (kyoku). For game rules supporting sudden death or standard match formats like East-only or Half-round, the environment continues until the game-end conditions are met.

Observation

The Observation object provides all relevant information to a player, including the current game state and available legal actions.

obs.new_events() -> list[str] returns a list of new events since the last step, encoded as JSON strings in the MJAI protocol. The full history of events is accessible via obs.events.

>>> obs = obs_dict[0]
>>> obs.new_events()
['{"id":0,"type":"start_game"}', '{"bakaze":"E","dora_marker":"S", ...}', '{"actor":0,"pai":"6p","type":"tsumo"}']

obs.legal_actions() -> list[Action] provides the list of all valid moves the player can make.

>>> obs.legal_actions()
[Action(action_type=Discard, tile=Some(1), ...), ...]

If your agent communicates via the MJAI protocol, you can easily map an MJAI response to a valid Action object using obs.select_action_from_mjai().

>>> obs.select_action_from_mjai({"type":"dahai","pai":"1m","tsumogiri":False,"actor":0})
Action(action_type=Discard, tile=Some(1), consume_tiles=[])

Supported Game Rules

Switch between different rule sets using the game_type keyword argument in the constructor.

[!NOTE] We plan to provide 12 standard preset rule sets. In the future, we will also allow granular customization (e.g., enabling/disabling red dragons, sudden death, 1-han minimum, etc.).

Rule Set	Players	Duration	Red Dragons	Status
4p-red-single	4	Single	Enabled	✅ Ready (Default)
4p-red-half	4	Hanchan	Enabled	✅ Ready
4p-red-east	4	East	Enabled	✅ Ready
3p-red-single	3	Single	Enabled	🚧 In progress
3p-red-half	3	Hanchan	Enabled	🚧 In progress
3p-red-east	3	East	Enabled	🚧 In progress

Single round modes like 4p-red-single do not feature sudden death, and allow you to specify the score situation, wind direction, number of deposit sticks, and other settings.

Example of initializing a four-player half-round game with red dragons:

from riichienv import RiichiEnv
from riichienv.agents import RandomAgent

agent = RandomAgent()
env = RiichiEnv(game_type="4p-red-half")
obs_dict = env.reset()
while not env.done():
    actions = {player_id: agent.act(obs)
               for player_id, obs in obs_dict.items()}
    obs_dict = env.step(actions)

scores, points, ranks = env.scores(), env.points(), env.ranks()
print(scores, points, ranks)

Compatibility with Mortal

RiichiEnv is fully compatible with the Mortal MJAI bot processing flow. I have confirmed that MortalAgent can execute matches without errors in over 1,000,000+ hanchan games on RiichiEnv.

from riichienv import RiichiEnv, Action
from model import load_model

class MortalAgent:
    def __init__(self, player_id: int):
        self.player_id = player_id
        # Initialize your libriichi.mjai.Bot or equivalent
        self.model = load_model(player_id, "./mortal_v4.pth")

    def act(self, obs) -> Action:
        resp = None
        for event in obs.new_events():
            resp = self.model.react(event)

        action = obs.select_action_from_mjai(resp)
        assert action is not None, "Mortal must return a legal action"
        return action

env = RiichiEnv(game_type="4p-red-half")
agents = {pid: MortalAgent(pid) for pid in range(4)}
obs_dict = env.reset()
while not env.done():
    actions = {pid: agents[pid].act(obs) for pid, obs in obs_dict.items()}
    obs_dict = env.step(actions)

print(env.scores(), env.points(), env.ranks())

Agari Calculation

>>> from riichienv import AgariCalculator
>>> import riichienv.convert as cvt

>>> ac = AgariCalculator.hand_from_text("111m33p12s111666z")
>>> ac.is_tenpai()
True
>>> ac.calc(cvt.mpsz_to_tid("3s"))
Agari(agari=True, yakuman=False, ron_agari=12000, tsumo_agari_oya=0, tsumo_agari_ko=0, yaku=[8, 11, 10, 22], han=5, fu=60)

Tile Conversion & Hand Parsing

Standardize between various tile formats (136-tile, MPSZ, MJAI) and easily parse hand strings.

>>> import riichienv.convert as cvt
>>> cvt.mpsz_to_tid("1z")
108

>>> from riichienv import parse_hand
>>> parse_hand("123m406m789m777z")
([0, 4, 8, 12, 16, 20, 24, 28, 32, 132, 133, 134], [])

See DATA_REPRESENTATION.md for more details.

🛠 Development

For more architectural details and contribution guidelines, see CONTRIBUTING.md and DEVELOPMENT_GUIDE.md.

Further Development Plan

• Add performance benchmarks compared to other packages.
• Add support for more game rules.
• Add example codes for training agents.
• Add high-level mahjong domain API for training agents.
• Optimize training performance (e.g., skip_mjai_logging, batch_act, etc.).
• Add interface for batch training.
• Add arena mode for evaluating agents.

📄 License

Apache License 2.0