Author: Stephen A. Boak
Date: 13:55:20 08/26/00
Go up one level in this thread
On August 26, 2000 at 15:52:39, Uri Blass wrote: >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 Here is a useful table, for linearly approximating USCF (ELO-based) rating changes. The USCF does not use linear approximations, so this table is close (approx 0-2 points from real rating changes) but not exact. Also, I believe the USCF rating system guarantees a minimum of 1 rating point change per win or loss (but I'd have to check to see if this is still true). Note that the k factor changes to 24 for players of 2100+ strength, and the k factor changes to 16 for players of 2400+ strength (if my memory is correct), so this table would look different for players in those stronger rating groups. To convert to a linear approximation table for players of 2100+ strength, multiply the shown rating changes by 2/3 (k factors ratio 24/32). To convert to a linear approximation table for players of 2400+, multiply the shown rating changes by 1/2 (k factors ratio 16/32). Here's the basic table: USCF Rating Changes--Linear Approximation for estimating, for k factor = 32 (max points won/lost per single game), for players under 2100 rating. Higher Rated Player Lower Rated Player Rtg Rating Change ----- Rating Change ----- Delta Win Draw Loss Win Draw Loss 0 16 0 -16 16 0 -16 25 15 -1 -17 17 1 -15 50 14 -2 -18 18 2 -14 75 13 -3 -19 19 3 -13 100 12 -4 -20 20 4 -12 125 11 -5 -21 21 5 -11 150 10 -6 -22 22 6 -10 175 9 -7 -23 23 7 -9 200 8 -8 -24 24 8 -8 225 7 -9 -25 25 9 -7 250 6 -10 -26 26 10 -6 275 5 -11 -27 27 11 -5 300 4 -12 -28 28 12 -4 325 3 -13 -29 29 13 -3 350 2 -14 -30 30 14 -2 375 1 -15 -31 31 15 -1 400 0 -16 -32 32 16 0
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