Rating System

A simple implementation of a modified Elo-based Rating System for Multiplayer Games and tournaments, which is currently used by Codeforces. This implementation is based on: MikeMirzayanov's Submission.

Features

• Calculates new ratings for players based on their performance in a tournament.
• Modified Elo rating system adapted for multiplayer games.

Installation

Add this line to your application's Gemfile:

gem 'rating_system'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rating_system

Usage

In a tournament, player A, with a rating of 1500, plays against opponents with the following ratings: 1500, 1658, 1256, 1353.

Let's assume the rankings of players after the tournament ends are:

• A -> 1
• B -> 2
• C -> 3
• D -> 4
• E -> 5

So, to calculate the new ratings based on the lastest ranks, we would use this gem like this:

contestants = [
  {
    position: 1,
    user_id: 'A',
    previous_rating: 1500
  },
  {
    position: 2,
    user_id: 'B',
    previous_rating: 1500
  },
  {
    position: 3,
    user_id: 'C',
    previous_rating: 1658
  },
  {
    position: 4,
    user_id: 'D',
    previous_rating: 1256
  },
  {
    position: 5,
    user_id: 'E',
    previous_rating: 1353
  }
]

RatingSystem::RatingCalculator.get_new_ratings(contestants) # Gets new ratings array

OUTPUT:

[
  {:position=>1, :user_id=>"A", :previous_rating=>1500, :delta=>125, :new_rating=>1625},
  {:position=>2, :user_id=>"B", :previous_rating=>1500, :delta=>31, :new_rating=>1531},
  {:position=>3, :user_id=>"C", :previous_rating=>1658, :delta=>-72, :new_rating=>1586},
  {:position=>4, :user_id=>"D", :previous_rating=>1256, :delta=>0, :new_rating=>1256},
  {:position=>5, :user_id=>"E", :previous_rating=>1353, :delta=>-93, :new_rating=>1260}
]

Benchmarks

Benchmarks for the rating system are coming soon. Stay tuned for performance metrics and comparisons!

License

The code is available as open source under the terms of the MIT License.