Elo Rating

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Pasted from page Darkcanuck/RRServer/Ratings

• New competitors start at a rating of 1600
• The expected % score outcome of a pairing between bots A and B is given by E(A,B) = 1.0 / (1 + 20^(ratingA-ratingB)/800))
• When a new pairing result is submitted to the server:
  1. The new % score for bot A vs bot B New(A,B) = scoreA / (scoreA + scoreB)
  2. The running pairing score of A vs B Pair(A,B)' = 0.7 * Pair(A,B) + 0.3 * New(A,B)
  3. Then calculate the rating change for A by iterating over all ranked bots Ri:
     • deltaRatingA += 3.0 * (Pair(A,Ri) - E(A,Ri)
  4. Do the same for B
  5. Update the ratings for A and B by adding the new delta to their current rating.

As mentioned above, this server uses the true average for Pair(A,B); otherwise the calculations are the same.