Riichi Rust library

Small library to calculate hands and yaku for japanese (riichi) mahjong.

For WebAssembly sources and builds, see the repo and npm packages for node and bundlers.

Build

cargo build --release

Usage

Install the library by adding the following in your Cargo.toml:

[dependencies]
# write last version from https://github.com/MahjongPantheon/riichi-rust/blob/main/Cargo.toml
riichi-rust = { git = "https://github.com/MahjongPantheon/riichi-rust.git", version = "2.1.0" } 

Use the library:

use riichi_rust::{calc_riichi, RiichiHand, RiichiOptions, Tiles, Yaku};

pub fn main() {
  let mut options = RiichiOptions {
    dora: vec![Tiles::M3 as i8], // actual dora tiles (not indicators value)
    aka_count: 0, // count of akadora in hand
    first_take: false, // if this hand is completed on first take
    riichi: false, // if there was riichi declared
    ippatsu: false, // if ippatsu happened
    double_riichi: false, // if there was riichi declared on first turn.
    // Note that ankans are allowed, but checking if the ankan was declared before double riichi
    // (and voiding double riichi consequently) is responsibility of external code.

    after_kan: false, // chankan (on ron) or rinshan (on tsumo)
    tile_discarded_by_someone: -1, // Tile the hand won on. If tsumo, pass -1
    bakaze: Tiles::S as i8, // Round wind
    jikaze: Tiles::E as i8, // Seat wind
    allow_aka: true, // if akadora is allowed
    allow_kuitan: true, // if open tanyao is allowed
    with_kiriage: false, // if 4/30 and 3/60 hands are treated as mangan
    disabled_yaku: vec![Yaku::Renhou as i8], // List of yaku to be disabled
    local_yaku_enabled: vec![Yaku::Daisharin as i8], // List of local yaku to be enabled
    all_local_yaku_enabled: false, // pass true here to enable all supported local yaku
    allow_double_yakuman: false, // if double yakuman is allowed
    last_tile: false, // haitei or houtei
  };

  let result = calc_riichi(
    RiichiHand {
      open_part: vec![
        (false, vec![Tiles::M1 as i8]),
        (false, vec![Tiles::M2 as i8]),
        (false, vec![Tiles::M3 as i8]),
        (false, vec![Tiles::M4 as i8]),
        (false, vec![Tiles::M5 as i8]),
        (false, vec![Tiles::M6 as i8]),
        (false, vec![Tiles::P9 as i8]),
        (false, vec![Tiles::P9 as i8])
      ],
      closed_part: vec![
        Tiles::M7 as i8,
        Tiles::M8 as i8,
        Tiles::M9 as i8,
        Tiles::P5 as i8,
        Tiles::P5 as i8,
        Tiles::P5 as i8,
      ],
    },
    &mut options,
    false, // calc_hairi:  if completions and discard variants should be calculated
  );

  match result {
    Ok(data) => {
      /*  do something with data; format of output matches RiichiResult struct */
      println!("{}", data.han)
    }
    Err(e) => println!("{}", e)
  }
}

Performance and benchmarks

Performance testing setup:

• Comparing riichi-ts library (Typescript-only) and riichi-rust library compiled to WebAssembly.
  • See code and details here and here.
• Both tests use same logs archive containing 300k+ game logs with 1.5M+ hands. Archive size: 1.9GB.
• Both tests were single-threaded.
• CPU: Intel Core i7-11700 desktop
• Test runner: Jest
• We executed third run without any calculations to subtract time required for archive processing and data preparation.

Examined code	Time to complete, sec	Calculation time, sec	Speedup	Failures
Jest tests without calculation	71	0*	-	-
Jest tests using riichi-ts	600	529	-	0
Jest tests using riichi-rust	120	49	1079%	0

As we can see, WebAssembly version shows performance increase around 10x, and we may expect even better performance with native code target (this was not measured though).

Credits

Inspired by and partially taken from following repositories:

• https://github.com/takayama-lily/riichi
• https://github.com/takayama-lily/syanten
• https://github.com/takayama-lily/agari

Testing on real games data

The library was tested against over 19 million of hands from real-life game logs from Tenhou.net phoenix lobby. Though we don't supply these logs in the repo, you can still download it on Tenhou.net and use it for testing. Please refer to this external file which uses wasm-compiled version of this library for testing.