by Steve Sax
20 August 2008

In March of this year we looked at two expert level players and how they fared against me in two different matches. This time we will look at how expert level players fare against each other.
As in the previous article we will take a look at 2007 Gammon Associates "Player of the Year", Justin Nunez, but this time we will also take a look at another player Frank Ley, Justin's opponent in this seven point match. Frank who has been playing at the Gammon Associate's club for five years was the 2005 G/A "Player of the Year".
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Maybe Snowie figures winning is MORE important than normal and gammons are less damaging than normal... They do lose the match, but losing the game gets Frank to Crawford, so he only loses an extra 15% match equity? Could this be a gammon price evaluation of some sort?
Steve, I have often suspected that Snowie messes up on match equity calculations. I reported the following cube action problem on the Snowie Forum, where I was equally baffled with Snowie's calculations. In nearly two years, nobody has ever responded with an explanation of why Snowie and I get very different conclusions. Perhaps you can figure it out! See: http://bgsnowie.com/forum/mostra.dhtml? f=bgsnowie/23&threadid=7292
Regarding the checker play problem, it may be that Snowie is calculating wrong, or not; it is more complicated. Snowie's evaluation is not just a crunching of the wins and gammons, but also factors in the value of cube access with the different plays. Even with the high doubling point at the score, there is still value in being able to offer an efficient double. It seems to me that running the back checker out creates maximum volatility. White's attack will either succeed or fail but it seems unlikely that white will ever get an efficient cube out of the resulting positions. With green maintaining the ace point anchor, white obtains scenarios where he escapes the back men and still stands to lose a fair share of games against green's ace point anchor, but in such positions, white will be able to turn the cube somewhat efficiently. The cube value may in Snowie's opinion offset the cubeless match equity difference.
"Position 8 .... I'm not sure I understand why Snowie gets it wrong so if anyone out there has an answer, please make a comment at the bottom of the article."
Hi, even if the winning chance is most important, I also have hard to see why those 15% extra gammons should be virtually worthless. I think your doubt about the Snowie rollout result here makes sense.
A GNU 2-ply evaluation agrees with your Snowie rollout: 24/16: -0,761 13/7 6/4: -0,787 (-0,026)
While a GNU 0-ply full rollout agrees with you and disagrees with your Snowie rollout:
24/16: -0,849 13/7 6/4: -0,767 (+0,082 ! ) +/- ~0,016
GNU by default does the rollouts with checker play accoring to score as well as live cube according to score, I believe that is what makes the difference. I don't have access to Snowie but maybe the live cube rollout result from Snowie in the hidden rollout tab makes more sense.
Sven-Olav Norén
Thanks for all the answers guys. Lots of new information although I might be more confused than before.
Just for the record, in case anyone is sceptical to 0-ply rollouts, I did a 2-ply rollout as well which gives a similar result to the 0-ply rollout. Now -0.878 vs -0.797 and still about 0.080 between the two moves.
Sven-Olav
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