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About
Mahjong AI Utilities is a free, browser-based platform built for Riichi Mahjong players who want to elevate their game through AI-powered analysis and practice. It offers two core features: game log review and live AI-opponent matches. For game reviews, players submit logs from Tenhou, Mahjong Soul, Riichi City, or Hime Mahjong. These logs are processed by either the Mortal neural network engine or the akochan engine, which evaluate every tile discard and action against statistically optimal play. Mortal comes in five network versions — ranging from aggressive (4.1c) to a more human-like style (3.0) — letting users compare AI perspectives. Advanced options include round (kyoku) filtering, a temperature parameter to adjust displayed probability values, and an optional performance rating, though the developer explicitly cautions that the rating metric has high variance and should not be over-relied upon. The 'Play with you' feature allows summoning one to three Mortal AI bots into a private Tenhou lobby at configurable speeds and with selectable personalities (aggressive, balanced, or defensive), enabling realistic full-game practice against bots at any time. The platform supports English, Simplified Chinese, Japanese, Korean, and Russian, making it accessible to the global Riichi Mahjong community. It is especially well-suited for competitive players studying their decision-making patterns, beginners learning optimal strategy, and enthusiasts who want a consistent AI sparring partner. No account or installation is required — everything runs in the browser for free.
Key Features
- AI Game Log Review: Submit game logs from Tenhou, Mahjong Soul, Riichi City, or Hime Mahjong and receive a move-by-move AI analysis comparing your decisions against optimal play.
- Multiple AI Engines & Styles: Choose between the Mortal engine (five personality variants from aggressive to human-like) or the akochan engine for different analytical perspectives.
- Play Against AI Bots: Summon up to three Mortal AI instances into a private Tenhou lobby with configurable speed and personality settings for live practice games.
- Advanced Filtering & Options: Filter analysis to specific rounds (kyoku), adjust the Mortal temperature parameter, and optionally view a performance rating for deeper self-assessment.
- Multi-Language Support: The interface is fully available in English, Simplified Chinese, Japanese, Korean, and Russian, catering to the global Riichi Mahjong community.
Use Cases
- Post-game review: A competitive Riichi Mahjong player uploads a ranked Tenhou hanchan log to identify suboptimal discards and learn the AI-recommended moves for each situation.
- Targeted study: A player filters analysis to specific problematic rounds (e.g., South-3 only) to focus their review session on the hands where they made the most errors.
- AI sparring practice: A beginner summons three Mortal AI bots to a private Tenhou lobby to simulate a full four-player game and practice reading opponents and tile efficiency.
- Strategy comparison: An intermediate player reviews the same game log under both the aggressive (4.1c) and defensive (4.1a) Mortal networks to understand how different strategies would have played out.
- Learning optimal play: A student of the game uses repeated game reviews to internalize AI-recommended decisions and gradually improve their intuition for tenpai shapes and discard priority.
Pros
- Completely Free: No subscription, account, or installation required — the full feature set is accessible directly in the browser at no cost.
- Broad Platform Support: Accepts logs from all major Riichi Mahjong platforms including Tenhou, Mahjong Soul, Riichi City, and Hime Mahjong.
- Flexible AI Personalities: Multiple Mortal network versions let users study against or be reviewed by aggressive, balanced, defensive, or human-like AI styles.
- Accessible Globally: Multi-language support in five languages makes the tool usable by players across East Asia, Russia, and English-speaking countries.
Cons
- akochan Engine Is Very Slow: Requests processed by the akochan engine are queued, which can result in significant wait times before results are returned.
- Limited to Standard Four-Player Games: The review feature only supports standard four-player Riichi Mahjong games with common rules; three-player and non-standard variants are not supported.
- Rating Metric Can Be Misleading: The performance rating has high variance, is tied to specific Mortal hyperparameters, and lacks confidence intervals — requiring careful interpretation to avoid misuse.
Frequently Asked Questions
Which Mahjong platforms are supported for game log review?
The tool accepts game logs from Tenhou, Mahjong Soul, Riichi City, and Hime Mahjong. You can input a game URL directly or paste a custom Tenhou JSON log.
What is the difference between the Mortal and akochan engines?
Mortal is a neural network-based engine with multiple personality variants (aggressive, balanced, defensive, legacy, and human-like). akochan is an alternative analytical engine but is notably slower due to request queuing.
How do I play against AI opponents?
Use the 'Play with you' feature: enter your Tenhou private lobby ID, choose a game speed, select personality settings for up to three Mortal AI bots, and submit. The bots will join your lobby and wait up to 2 minutes for the game to start.
Should I rely on the performance rating to measure my skill?
The developer strongly advises caution. The rating is an average min-max scaled value with no calibration or confidence intervals, tied to specific Mortal hyperparameters. It is placed in 'Advanced Options' intentionally and should not be treated as a definitive skill metric.
What does the 'Temperature' option do in the Mortal engine?
The temperature parameter only affects the displayed probability values in the analysis output. It does not change action orders or ratings, and has no impact on the underlying AI decision-making.
