1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576
//! The EGF (European Go Federation) rating system is a variation of the Elo rating system, adapted for playing Go.
//! Used for calculating Go player ratings in Europe since 1998.
//!
//! The ratings are loosely centred around the Go ranks, ranging from 30 *kyu* (lowest) to 9 *dan* (highest).
//! A rating of 2100 equals a rank of 1 *dan*, and 1 rank up and down equals a gain or loss of around 100 points.
//! So a 2 *dan* rank would equal around 2200 points, and so on. The lowest rank, 30 *kyu*, is equal to -900 points.
//! You start at a rating of 0, around 21 *kyu*.
//! The [full table of ranks/rating can be found here](https://senseis.xmp.net/?GoR),
//! or [here is an unofficial comparison table](https://forums.online-go.com/t/go-ranks-vs-chess-ratings/41594/42)
//! that includes USCF chess ratings.
//!
//! # Quickstart
//!
//! This is the most basic example on how to use the EGF Module.
//! Please take a look at the functions below to see more advanced use cases.
//!
//! ```
//! use skillratings::{
//! egf::{egf, EGFConfig, EGFRating},
//! Outcomes,
//! };
//!
//! // Initialise a new player rating with a rating of 0.
//! let player_one = EGFRating::new();
//!
//! // Or you can initialise it with your own values of course.
//! // Imagine these numbers being pulled from a database.
//! let some_rating = 325.0;
//! let player_two = EGFRating {
//! rating: some_rating,
//! };
//!
//! // The outcome of the match is from the perspective of player one.
//! let outcome = Outcomes::WIN;
//!
//! // The config allows you to specify certain values in the EGF calculation.
//! // We set a handicap of 4.0 here for player one.
//! // This means that player_two starts with 4 handicap stones.
//! // For more details see the "Handicapping in Go" link below.
//! let config = EGFConfig { handicap: 4.0 };
//!
//! // The egf function will calculate the new ratings for both players and return them.
//! let (new_player_one, new_player_two) = egf(&player_one, &player_two, &outcome, &config);
//! ```
//!
//! # More Information
//!
//! - [Wikipedia Article: Go Ratings](https://en.wikipedia.org/wiki/Go_ranks_and_ratings#Elo_ratings_as_used_in_Go)
//! - [Wikipedia Article: EGF](https://en.wikipedia.org/wiki/European_Go_Federation)
//! - [Official EGF Website](https://www.europeangodatabase.eu/EGD/EGF_rating_system.php)
//! - [EGF Rating Calculator](https://www.europeangodatabase.eu/EGD/gor_calculator.php)
//! - [Sensei's library](https://senseis.xmp.net/?GoR)
//! - [Handicapping in Go](https://en.wikipedia.org/wiki/Handicapping_in_Go)
#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};
use crate::{Outcomes, Rating, RatingPeriodSystem, RatingSystem};
#[derive(Copy, Clone, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
/// The EGF (European Go Federation) Rating for a player.
///
/// If the player has a Go rank or similar,
/// you can set the rating value manually approximately according to
/// [this unofficial comparison table](https://forums.online-go.com/t/go-ranks-vs-chess-ratings/41594/42).
/// Keep in mind that here, the lowest possible rating is -900.0.
///
/// The default rating is 0.0.
pub struct EGFRating {
/// The player's EGF rating number, by default 0.0.
pub rating: f64,
}
impl EGFRating {
#[must_use]
/// Initialise a new `EGFRating` with a rating of 0.0.
pub const fn new() -> Self {
Self { rating: 0.0 }
}
}
impl Default for EGFRating {
fn default() -> Self {
Self::new()
}
}
impl Rating for EGFRating {
fn rating(&self) -> f64 {
self.rating
}
fn uncertainty(&self) -> Option<f64> {
None
}
fn new(rating: Option<f64>, _uncertainty: Option<f64>) -> Self {
Self {
rating: rating.unwrap_or(0.0),
}
}
}
impl From<f64> for EGFRating {
fn from(r: f64) -> Self {
Self { rating: r }
}
}
#[derive(Clone, Copy, Debug)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
/// Constants used in the EGF Calculations.
pub struct EGFConfig {
/// The [handicap](https://en.wikipedia.org/wiki/Handicapping_in_Go), of the perspective of player one.
/// As a general rule, one handicap point is about equal to a 100 rating point difference.
///
/// If player one has a handicap in the game,
/// you can set this number to the amount of handicap stones given to the opponent.
/// If player two is the one with the handicap, set this number to the negative amount of stones given.
/// If an equal game is played, this value should be 0.0.
/// For example, if player two has a handicap of 4 points (player one starts with 4 stones), set this number to -4.0.
///
/// The maximum number should not exceed 9.0 or -9.0.
/// By default set to 0.0.
pub handicap: f64,
}
impl EGFConfig {
#[must_use]
/// Initialises a new `EGFConfig` with a handicap value of `0.0`.
pub const fn new() -> Self {
Self { handicap: 0.0 }
}
}
impl Default for EGFConfig {
fn default() -> Self {
Self::new()
}
}
/// Struct to calculate ratings and expected score for [`EGFRating`]
pub struct EGF {
config: EGFConfig,
}
impl RatingSystem for EGF {
type RATING = EGFRating;
type CONFIG = EGFConfig;
fn new(config: Self::CONFIG) -> Self {
Self { config }
}
fn rate(
&self,
player_one: &EGFRating,
player_two: &EGFRating,
outcome: &Outcomes,
) -> (EGFRating, EGFRating) {
egf(player_one, player_two, outcome, &self.config)
}
fn expected_score(&self, player_one: &EGFRating, player_two: &EGFRating) -> (f64, f64) {
expected_score(player_one, player_two, &self.config)
}
}
impl RatingPeriodSystem for EGF {
type RATING = EGFRating;
type CONFIG = EGFConfig;
fn new(config: Self::CONFIG) -> Self {
Self { config }
}
fn rate(&self, player: &EGFRating, results: &[(EGFRating, Outcomes)]) -> EGFRating {
// Need to add a config to the results.
let new_results: Vec<(EGFRating, Outcomes, EGFConfig)> =
results.iter().map(|r| (r.0, r.1, self.config)).collect();
egf_rating_period(player, &new_results[..])
}
fn expected_score(&self, player: &Self::RATING, opponents: &[Self::RATING]) -> Vec<f64> {
let new_opponents: Vec<(EGFRating, EGFConfig)> =
opponents.iter().map(|o| (*o, self.config)).collect();
expected_score_rating_period(player, &new_opponents)
}
}
#[must_use]
/// Calculates the [`EGFRating`]s of two players based on their old ratings and the outcome of the game.
///
/// Takes in two players as [`EGFRating`]s, an [`Outcome`](Outcomes) and an [`EGFConfig`], where you can set up handicaps.
///
/// The outcome of the match is in the perspective of `player_one`.
/// This means [`Outcomes::WIN`] is a win for `player_one` and [`Outcomes::LOSS`] is a win for `player_two`.
///
/// # Examples
///
/// ```
/// use skillratings::{
/// egf::{egf, EGFConfig, EGFRating},
/// Outcomes,
/// };
///
/// let player_one = EGFRating { rating: 950.0 };
/// let player_two = EGFRating { rating: 1200.0 };
///
/// let outcome = Outcomes::WIN;
///
/// let config = EGFConfig::new();
///
/// let (new_one, new_two) = egf(&player_one, &player_two, &outcome, &config);
///
/// assert!((new_one.rating.round() - 989.0).abs() < f64::EPSILON);
/// assert!((new_two.rating.round() - 1173.0).abs() < f64::EPSILON);
/// ```
pub fn egf(
player_one: &EGFRating,
player_two: &EGFRating,
outcome: &Outcomes,
config: &EGFConfig,
) -> (EGFRating, EGFRating) {
let con1 = con(player_one.rating);
let con2 = con(player_two.rating);
let bonus1 = bonus(player_one.rating);
let bonus2 = bonus(player_two.rating);
let (exp1, exp2) = expected_score(player_one, player_two, config);
let outcome1 = outcome.to_chess_points();
let outcome2 = 1.0 - outcome1;
let new_rating1 = new_rating(player_one.rating, con1, outcome1, exp1, bonus1);
let new_rating2 = new_rating(player_two.rating, con2, outcome2, exp2, bonus2);
(
EGFRating {
rating: new_rating1,
},
EGFRating {
rating: new_rating2,
},
)
}
#[must_use]
/// Calculates an [`EGFRating`] in a traditional way using a rating period, commonly used for tournaments.
///
/// Takes in a player as an [`EGFRating`], their results as a Slice of tuples containing the opponent as an [`EGFRating`],
/// the outcome of the game as an [`Outcome`](Outcomes), and an [`EGFConfig`] where you can specify handicaps for the players.
///
/// ---
///
/// 📌 _**Important note:**_ The parameters intentionally work different from other rating_period functions here.
/// In most cases the config is a separate parameter, because it holds static values that should not change from game-to-game.
/// Here, the config is in the tuple together with the results, because the handicaps will likely change each game, if used.
/// Thus it would not make sense to have the config as its own separate parameter, disconnected from the game results.
///
/// ---
///
/// All of the outcomes are from the perspective of the player.
/// This means [`Outcomes::WIN`] is a win for the player and [`Outcomes::LOSS`] is a win for the opponent.
///
/// Keep in mind that [according to EGF](https://www.europeangodatabase.eu/EGD/EGF_rating_system.php#Remarks),
/// the rating will not update in between games of a tournament, in contrast to the other rating_period algorithms.
/// That means that for example, in game 5 of a tournament,
/// the ratings will still be calculated with the ratings *before* game 1,
/// and not with the ratings after game 4, as you might expect.
///
/// # Examples
/// ```
/// use skillratings::{
/// egf::{egf_rating_period, EGFConfig, EGFRating},
/// Outcomes,
/// };
///
/// let player = EGFRating { rating: 220.0 };
///
/// let opponent1 = EGFRating { rating: 420.0 };
/// let opponent2 = EGFRating { rating: 40.0 };
/// let opponent3 = EGFRating { rating: 1320.0 };
///
/// let config = EGFConfig::new();
///
/// let new_player = egf_rating_period(
/// &player,
/// &vec![
/// // Make sure to include the configs in each game!
/// (opponent1, Outcomes::LOSS, config),
/// (opponent2, Outcomes::WIN, config),
/// (opponent3, Outcomes::DRAW, config),
/// ],
/// );
///
/// assert!((new_player.rating.round() - 273.0).abs() < f64::EPSILON);
/// ```
pub fn egf_rating_period(
player: &EGFRating,
results: &[(EGFRating, Outcomes, EGFConfig)],
) -> EGFRating {
// According to the EGF, the rating values are not updated in between games.
// Only the change in rating is kept track of.
// Reference: https://www.europeangodatabase.eu/EGD/EGF_rating_system.php#Remarks
let mut rating_change = 0.0;
let con = con(player.rating);
let bonus = bonus(player.rating);
for (opponent, result, config) in results {
let (exp1, _) = expected_score(player, opponent, config);
let outcome = result.to_chess_points();
rating_change += new_rating(player.rating, con, outcome, exp1, bonus) - player.rating;
}
EGFRating {
rating: player.rating + rating_change,
}
}
#[must_use]
/// Calculates the expected score of two players based on their EGF rating.
///
/// Takes in two players as [`EGFRating`]s and returns the probability of victory for each player as an [`f64`] between 1.0 and 0.0.
/// 1.0 means a certain victory for the player, 0.0 means certain loss.
/// Values near 0.5 mean a draw is likely to occur, if draws are possible.
///
/// # Examples
/// ```
/// use skillratings::{
/// egf::{expected_score, EGFConfig, EGFRating},
/// Outcomes,
/// };
///
/// let player_one = EGFRating { rating: 1320.0 };
/// let player_two = EGFRating { rating: 1217.0 };
///
/// let config = EGFConfig::new();
///
/// let (exp1, exp2) = expected_score(&player_one, &player_two, &config);
///
/// assert!(((exp1 * 100.0).round() - 59.0).abs() < f64::EPSILON);
/// assert!(((exp2 * 100.0).round() - 41.0).abs() < f64::EPSILON);
/// ```
pub fn expected_score(
player_one: &EGFRating,
player_two: &EGFRating,
config: &EGFConfig,
) -> (f64, f64) {
let (h1, h2) = if config.handicap.is_sign_negative() {
(config.handicap.abs(), 0.0)
} else {
(0.0, config.handicap.abs())
};
let exp_one = (1.0 + (beta(player_two.rating, h2) - beta(player_one.rating, h1)).exp()).recip();
(exp_one, 1.0 - exp_one)
}
#[must_use]
/// Calculates the expected outcome of a player in a rating period or tournament.
///
/// Takes in a players as [`EGFRating`] and a list of opponents as a slice of Tuples of [`EGFRating`]s and [`EGFConfig`]s
/// and returns the probability of victory for each match as an Vec of [`f64`] between 1.0 and 0.0 from the perspective of the player.
/// 1.0 means a certain victory for the player, 0.0 means certain loss.
/// Values near 0.5 mean a draw is likely to occur.
///
/// ---
///
/// 📌 _**Important note:**_ The parameters intentionally work different from other expected_score_rating_period functions here.
/// In most cases the config is not used, however it is required here, because of the handicaps that can change from game-to-game.
///
/// ---
///
/// # Examples
/// ```
/// use skillratings::egf::{expected_score_rating_period, EGFConfig, EGFRating};
///
/// let player = EGFRating { rating: 900.0 };
///
/// let opponent1 = (EGFRating { rating: 930.0 }, EGFConfig::new());
///
/// let opponent2 = (EGFRating { rating: 730.0 }, EGFConfig::new());
///
/// let exp = expected_score_rating_period(&player, &[opponent1, opponent2]);
///
/// assert_eq!((exp[0] * 100.0).round(), 48.0);
/// assert_eq!((exp[1] * 100.0).round(), 62.0);
/// ```
pub fn expected_score_rating_period(
player: &EGFRating,
opponents: &[(EGFRating, EGFConfig)],
) -> Vec<f64> {
opponents
.iter()
.map(|o| {
let (h1, h2) = if o.1.handicap.is_sign_negative() {
(o.1.handicap.abs(), 0.0)
} else {
(0.0, o.1.handicap.abs())
};
(1.0 + (beta(o.0.rating, h2) - beta(player.rating, h1)).exp()).recip()
})
.collect()
}
fn new_rating(rating: f64, con: f64, score: f64, exp_score: f64, bonus: f64) -> f64 {
// The absolute minimum rating is set to be -900.
(con.mul_add(score - exp_score, rating) + bonus).max(-900.0)
}
/// This factor determines the rating volatility.
/// Think of it like the k-value in Elo, but dynamic to your rating.
fn con(rating: f64) -> f64 {
((3300.0 - rating) / 200.0).powf(1.6)
}
/// The bonus parameter counters rating deflation over time.
fn bonus(rating: f64) -> f64 {
((2300.0 - rating) / 80.0).exp().ln_1p() / 5.0
}
fn beta(rating: f64, handicap: f64) -> f64 {
// The explanation of the handicap formula can be found here:
// https://www.europeangodatabase.eu/EGD/EGF_rating_system_old.php#System
// The new system doesn't really mention this, but it stayed the same between transitions.
// You can verify this with the calculator: https://www.europeangodatabase.eu/EGD/gor_calculator.php
let h = if handicap == 0.0 {
0.0
} else {
100.0 * (handicap - 0.5)
};
-7.0 * (3300.0 - h - rating).ln()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_handicap() {
let config = EGFConfig { handicap: 0.0 };
let player_one = EGFRating { rating: 1000.0 };
let player_two = EGFRating { rating: 1300.0 };
let (new_one, new_two) = expected_score(&player_one, &player_two, &config);
assert!((new_one - 0.273_222_559_619_518_8).abs() < f64::EPSILON);
assert!((new_two - 0.726_777_440_380_481_2).abs() < f64::EPSILON);
assert!((new_one + new_two - 1.0).abs() < f64::EPSILON);
let handicap_config = EGFConfig { handicap: 1.0 };
let (new_one, new_two) = expected_score(&player_one, &player_two, &handicap_config);
assert!((new_one - 0.239_475_310_432_178_62).abs() < f64::EPSILON);
assert!((new_two - 0.760_524_689_567_821_4).abs() < f64::EPSILON);
assert!((new_one + new_two - 1.0).abs() < f64::EPSILON);
let other_handicap_config = EGFConfig { handicap: -1.0 };
let (new_one, new_two) = expected_score(&player_one, &player_two, &other_handicap_config);
assert!((new_one - 0.304_813_243_836_844_05).abs() < f64::EPSILON);
assert!((new_two - 0.695_186_756_163_156).abs() < f64::EPSILON);
assert!((new_one + new_two - 1.0).abs() < f64::EPSILON);
}
#[test]
fn test_egf() {
let player_one = EGFRating { rating: 1000.0 };
let player_two = EGFRating { rating: 1300.0 };
let config = EGFConfig::new();
let (new_one, new_two) = egf(&player_one, &player_two, &Outcomes::WIN, &config);
assert!((new_one.rating.round() - 1039.0).abs() < f64::EPSILON);
assert!((new_two.rating.round() - 1274.0).abs() < f64::EPSILON);
let player_one = EGFRating { rating: 0.0 };
let player_two = EGFRating::default();
let (new_one, new_two) = egf(&player_one, &player_two, &Outcomes::LOSS, &config);
assert!((new_one.rating.round() - -39.0).abs() < f64::EPSILON);
assert!((new_two.rating.round() - 50.0).abs() < f64::EPSILON);
let (new_one, new_two) = egf(&player_one, &player_two, &Outcomes::DRAW, &config);
assert!((new_one.rating.round() - 6.0).abs() < f64::EPSILON);
assert!((new_two.rating.round() - 6.0).abs() < f64::EPSILON);
}
#[test]
fn test_egf_rating_period() {
let player = EGFRating::new();
let config = EGFConfig::default();
let results = vec![
(EGFRating { rating: 20.0 }, Outcomes::WIN, config),
(EGFRating { rating: 40.0 }, Outcomes::DRAW, config),
(EGFRating { rating: 10.0 }, Outcomes::LOSS, config),
(EGFRating { rating: -40.0 }, Outcomes::WIN, config),
];
let new_player = egf_rating_period(&player, &results);
assert!((new_player.rating.round() - 69.0).abs() < f64::EPSILON);
}
#[test]
#[allow(clippy::clone_on_copy)]
fn test_misc_stuff() {
let player_one = EGFRating::new();
let config = EGFConfig::new();
assert_eq!(player_one, player_one.clone());
assert!((config.handicap - config.clone().handicap).abs() < f64::EPSILON);
assert!(!format!("{player_one:?}").is_empty());
assert!(!format!("{config:?}").is_empty());
assert_eq!(player_one, EGFRating::from(0.0));
}
#[test]
fn test_traits() {
let player_one: EGFRating = Rating::new(Some(240.0), Some(90.0));
let player_two: EGFRating = Rating::new(Some(240.0), Some(90.0));
let rating_system: EGF = RatingSystem::new(EGFConfig::new());
assert!((player_one.rating() - 240.0).abs() < f64::EPSILON);
assert_eq!(player_one.uncertainty(), None);
let (new_player_one, new_player_two) =
RatingSystem::rate(&rating_system, &player_one, &player_two, &Outcomes::WIN);
let (exp1, exp2) = RatingSystem::expected_score(&rating_system, &player_one, &player_two);
assert!((new_player_one.rating - 284.457_578_792_560_87).abs() < f64::EPSILON);
assert!((new_player_two.rating - 205.842_421_207_441_73).abs() < f64::EPSILON);
assert!((exp1 - 0.5).abs() < f64::EPSILON);
assert!((exp2 - 0.5).abs() < f64::EPSILON);
let rating_period_system: EGF = RatingPeriodSystem::new(EGFConfig::new());
let exp_rp =
RatingPeriodSystem::expected_score(&rating_period_system, &player_one, &[player_two]);
assert!((exp1 - exp_rp[0]).abs() < f64::EPSILON);
let rating_period_system2: EGF = RatingPeriodSystem::new(EGFConfig { handicap: -0.0 });
let exp_rp =
RatingPeriodSystem::expected_score(&rating_period_system2, &player_one, &[player_two]);
assert!((exp1 - exp_rp[0]).abs() < f64::EPSILON);
let player_one: EGFRating = Rating::new(Some(240.0), Some(90.0));
let player_two: EGFRating = Rating::new(Some(240.0), Some(90.0));
let rating_period: EGF = RatingPeriodSystem::new(EGFConfig::new());
let new_player_one =
RatingPeriodSystem::rate(&rating_period, &player_one, &[(player_two, Outcomes::WIN)]);
assert!((new_player_one.rating - 284.457_578_792_560_87).abs() < f64::EPSILON);
}
}