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Simborg

Joined: 17 Aug 2006
Posts: 408
Location: Chicago

 Post subject: Snowie is not always right This came up in a match in Florida. Black to play 3-4. Snowie's 3 ply evaluation was entirely wrong, but after the rollout, we were able to determine the right play. There are obviously two choices: play safe and make your opponent's 4 point and make your 8 point, or hit and continue. Pick and pass turns out to be the best play. It is interesting that two of the top players in the world were watching and agreed that pick and past was best. When they were told that Snowie greatly preferred the other play, they both said, "roll it out and we'll see." And of course, they were right. the point is, you can't trust a 3 ply evaluation of any position...you really have to roll it out, and sometimes, the computer still doesn't get it right! Phil Simborg psimborg@sbcglobal.net
Mon Jan 14, 2008 2:11 am
giannisp

Joined: 27 Apr 2007
Posts: 101
Location: greece

 Post subject: So it is better to hit? May i ask what 3-ply evaluation is? Has it anything to do with the way Snowie evaluates the odds each time?
Mon Jan 14, 2008 7:14 am
Simborg

Joined: 17 Aug 2006
Posts: 408
Location: Chicago

 Post subject: 3 ply means that Snowie looks at the position and rolls the dice 3 times for each side and makes the 3 plays for each side and then looks to see what the board looks like at that point and estimates winning and losing and gammon odds from that point. In a rollout, it plays out the game to the very end and is much more likely to give a correct answer. The reason we ususally use 3 ply is a rollout takes a long time.
Mon Jan 14, 2008 1:36 pm
puzzle_t0rico

Joined: 20 Apr 2007
Posts: 72

 Post subject: I am glad I guessed it right this time. I would have played it so on the board. What made me think the best is to hit&pass is that it would probably make me much more gammons and therefore the match. I was right Hit&pass gives 11.4 instead of 3 percent. Ok, ok, it gives also much more gammons to the opponent but I am ready to take the risk because he will dance 2 rolls in the bar and I shall get a 6 or a 3 in the meanwhile. More, playing safe is not that safe. We are probably going to break in the next roll and white is ready to hit. Please tell me if I am wrong _________________If the brain were simple enough to be understood, we would be too stupid to understand it.
Mon Jan 14, 2008 1:52 pm
Simborg

Joined: 17 Aug 2006
Posts: 408
Location: Chicago

 Post subject: You are right, but I must add that if you make the "safe" play you could still get gammoned that way, so why not take a risk that is more likely to give you the win?
Mon Jan 14, 2008 1:57 pm
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