Crate whr

Whole-History Rating

Implementation of Rémi Coulom’s Whole History Rating (WHR) algorithm as a Rust library.

It notably supports:

• handicaps (first player advantage)
• draws

WHR is used to rate players in competitive games, akin to the Elo or TrueSkill systems. It can estimate the probability of winning between two players even if they have never competed against one another. It is more accurate than say the Elo system, at the cost of requiring more computation.

WHR is notably used in Go, Warcraft 3, Renju, and is even used in some sports!

Future work

I hope to generalize the library further, notably by supporting:

• games with more than two players
• teams

as was stated to be possible in Rémi Coulom’s paper introducing WHR.

Installation

The library can be used in any Cargo project by running:

cargo add whr

or by adding the following to your Cargo.toml:

[dependencies]
whr = "0.1"

Exemple usage

The library works following the builder pattern.

use whr::WhrBuilder;

let whr = WhrBuilder::default()
  .with_iterations(50) // Maximum number of iterations for the algorithm to converge.
  .with_epsilon(1e-5) // Target stability between iterations
  // Register games, with:
  // - two named players,
  // - an optional winner,
  // - a timestep,
  // - and optional handicap (first player advantage)
  .with_game("alice", "bob", Some("bob"), 1, None)
  .with_game("alice", "bob", None, 2, None)
  .with_game("bob", "alice", Some("alice"), 2, None)
  .build();

This returns a Whr object with ratings for each player by timestep.

Structs

Whr

WHR ratings for players, with additional API to access probability of winning and other useful information.

WhrBuilder

Builder API for Whr, with easy ways to add input data and set the number of iterations for refinement.