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Whole History Rating

A system for ranking game players by skill, based on Rémi Coulom's Whole History Rating algorithm, with modifications to support handicaps.

Developed for use on GoShrine, but the code is not go specific. It can support any two player game, as long as the outcome is a simple win/loss.


  • gem install whole_history_rating


require 'whole_history_rating'

@whr =

# WholeHistoryRating::Base#create_game arguments: black player name, white player name, winner, day number, handicap
# Handicap should generally be less than 500 elo
@whr.create_game("shusaku", "shusai", "B", 1, 0)
@whr.create_game("shusaku", "shusai", "W", 2, 0)
@whr.create_game("shusaku", "shusai", "W", 3, 0)

# Iterate the WHR algorithm towards convergence with more players/games, more iterations are needed.

# Results are stored in one triplet for each day: [day_number, elo_rating, uncertainty]
@whr.ratings_for_player("shusaku") => 
  [[1, -43, 84], 
   [2, -45, 84], 
   [3, -45, 84]]
@whr.ratings_for_player("shusai") => 
  [[1, 43, 84], 
   [2, 45, 84], 
   [3, 45, 84]]

Optional Configuration

One of the meta parameters to WHR is the variance of rating change over one time step, :w2, which determines how much that a player's rating is likely change in one day. Higher numbers allow for faster progress. The default value is 300, which is fairly high.

@whr = => 17)