Backgammon Snowie

Snowie

Match equity table

From:   Harald Retter
Address:   harald.retter@okay.net
Date:   20 August 1998
Subject:   Snowie match equity chart
Forum:   rec.games.backgammon
Google:   6rhjv8$lfs$1@trader.ipf.de

Snowie uses its own match equity table, based on a gammon rate of 26%. I couldn't find those equities summarized in a diagram, so I spent some minutes to create one. As I am not willed to memorize more than that, I did it up to -9. Here is the result: Your opponent needs You need| 1* 1 2 3 4 5 6 7 8 9 ----+-------------------------------------------------- 1* | 50.0 -- 51.5 68.5 69.5 81.3 81.9 88.8 89.1 93.3 1 | -- 50.0 68.5 75.1 82.0 84.3 89.1 90.8 93.6 95.0 2 | 48.5 31.5 50.0 60.4 68.5 75.3 81.0 85.1 88.5 90.9 3 | 31.5 24.9 39.6 50.0 57.8 65.3 71.7 76.8 81.2 84.6 4 | 30.5 18.0 31.5 42.2 50.0 57.9 64.6 70.3 75.2 79.4 5 | 18.7 15.7 24.7 34.7 42.1 50.0 56.8 62.8 68.1 72.9 6 | 18.1 10.9 19.0 28.3 35.4 43.2 50.0 56.3 61.9 67.1 7 | 11.2 09.2 14.9 23.2 29.7 37.2 43.7 50.0 55.6 61.0 8 | 10.9 06.4 11.5 18.8 24.8 31.9 38.1 44.4 50.0 55.5 9 | 06.7 05.0 09.1 15.4 20.6 27.1 32.9 39.0 44.5 50.0 * = Post Crawford -- = Retter-Paradox ;-) While typing all those numbers, I was quite surprised how similar they seemed to be to the Woolsey-table, I used to work with (and actually still do). If my memory is right, Kits tables where computed assuming a gammon rate of 20%. Quite a difference, but the tables do not seem to reflect on it much. So I created a second diagramm to display the differences between the two versions. I took the numbers, which are printed in "Cubes and Gammons..." by Ortega and Kleinman and subtracted them from Snowie-values: YON YN | 1* 1 2 3 4 5 6 7 8 9 ----+-------------------------------------------------- 1*| # -- # # # # # # # # 1 | -- 0 -1.5 +0.1 -1.1 -0.9 -1.1 -0.5 -0.6 -0.1 2 | # +1.5 0 +0.6 +0.7 +0.5 +0.2 +0.3 +0.5 +0.1 3 | # -0.1 -0.6 0 -1.2 -0.5 +0.2 +0.4 +0.7 +0.2 4 | # +1.1 -0.7 +1.2 0 -0.1 +0.2 0 -0.2 0 5 | # +0.9 -0.5 +0.5 +0.1 0 -0.5 -0.5 -0.3 -0.4 6 | # +1.1 -0.2 -0.2 -0.2 +0.5 0 +0.1 -0.4 -0.2 7 | # +0.5 -0.3 -0.4 0 +0.5 -0.1 0 -0.6 -0.3 8 | # +0.6 -0.5 -0.7 +0.2 +0.3 +0.4 +0.6 0 +0.2 9 | # +0.1 -0.1 -0.2 0 +0.4 +0.2 +0.3 -0.2 0 # = only Snowie-data available Oh, how nice, only four matchscores (-1-2/-1-4/-1-6/-3-4) differ more than 1%point, the largest is 1.5%points. Once these figures should get "accepted", there is not as much to relearn as I feared. Most discrepancies appear at -1-T (T = points to go for Trailer). As expected the increased gammon rate favours the Trailer at these scores, with him only having usage of those extra-points. Regards, Harald Retter

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