First database update: 2006-10-27 17:10:03 UTC
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Common information about the new ELO rating
The new ZELO rating system is the successor of the old one for the '1vs1 League'. It bases on the ELO system but doesn't allow a tie game and takes the players'game scores into account (ratio of the scores). The intention is to motivate even obviously weaker players to fight for every point for the final score.

Relevance for BZFlag
This ranking method is irrelevant for the game itself. But the new ZELO system is used by the '1vs1 League' for calculating player strength indexes. Such a strength index depends on the own and the opponent's strength index. As initial rating, players get 1000 points by default and a match ends when the first player died 10 times.

ZELO rating calculator & formula
Player A: 
Player B: 
Weighting factor*: 
Score influence**: 
Score winner***: 
Score loser****: 

Player A Player B
Chance to win 50% 50%
Player A wins 1025 975
Player B wins 975 1025

E_A = 1 / ( 1 + pow( 10, ( ( R_B - R_A ) / 400 ) ) )
R_A_N = R_A + round( K * ( ( 1 - S_R ) + S_R * ( ( S_W - S_L ) / S_W ) ) * ( S_A - E_A ) )
E_A:  expected score for player A
R_A:  real/current ZELO-score of player A
R_B:  real/current ZELO-score of player B
*K:  weighting factor - normally 15, for top-players 10, for beginners 25
The '1vs1 League' uses a value of 50 to get more significant changes for the scores after a match!
**S_R:  influence factor for ratio of winner and loser scores (0 <= S_R <= 1)
The '1vs1 League' uses a value of 0.25 (25%).
***S_W:  match score winner
****S_L:  match score loser
R_A_N:  new ZELO-rating of player A
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