Author: Uri Blass
Date: 12:52:39 08/26/00
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On August 26, 2000 at 14:46:08, Stephen A. Boak wrote: >In below threads, there is discussion about comparing performances of various >programs using 1) Ranking or average Ranking (for 'teams') or 2) TPR - >Tournament Performance Rating or average TPR (for 'teams'). > >I suggest that using 2) TPR as a measure of which program (or team) is best is >inappropriate under many circumstances, including the circumstances of the just >concluded WMCC competition where the ratings of the participants varied >greatly. > >Examples: > >My rating is approx 1900. Let's say I play in a 4-round tournament in an >appropriate class section (Under 2000 rating--which typically includes mostly >1800 to 1999 rated players) that happens to several very weak entrants--possibly >up and coming young players that wish to get tougher competition to foster their >chess development. > >Example 1: > >Assume I play the following opponents, and have the following results: > Ro Pts GPR (Game Perf Rtg--using +/- 400 rule for TPR calc) >1300 1 1700 >1950 0 2350 >1975 1 1575 >1960 0.5 1960 > TPR 1896 I think this way to calculate performance is wrong. You should calculate the rating that you need in order not to lose and not to win rating from this tournament. This should be the performance. It is not a problem for a computer program to calculate it and you only need the exact equation of the rating that can be based on the normal distribution or on some linear approximation. In Israel I remember that the formula was based on some linear approximation(at least this was the idea behind the formula in the past). If my opponent has the same rating I earn 12 points from winning If my opponent is 375 points weaker I earn 0.75 points from winning. If my opponent is at least 750 points weaker I earn 0 points from winning. If my opponent is between 0 and 375 points weaker than me the formula is linear and the same for difference between 375 and 750 points weaker than me Examples: I earn 12 points from winning a player with the same rating I earn 11.25 point from winning a player who is 25 point weaker than me because 11.25=12-25*3/100 I earn 10.5 points from winning a player who is 50 points weaker than me because 10.5=12-50*3/100 I earn 9 point from winning a player who is 100 points weaker than me because 9=12-100*3/100 I earn 0.75 points from winning a player who is 375 points weaker than me because 0.75=12-375*3/100 between 375 and 750 the formula is also linear but different when 750 elo difference say that I earn nothing and 375 difference say that I earn 0.75 It means for example that I earn: 0.7 points from winning if the difference is 400 0.6 points if the difference is 450 0.5 point if the difference is 500 There was another rule that players get 0.25 point from every game. This was the situation many years ago. There were some changes in the rules and I do not remember the exact rules today but I think that they are still based on a linear formula. Uri
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