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2a-2a Very late double Rollout and more

Posted By: Trunky
Date: Sunday, 22 March 2015, at 2:26 p.m.

In Response To: 2a-2a Very late double (Trunky)

We got to this position where my less experienced opponent lead all the way in the game until getting here without doubling.

XG says blue is 53% favourite. I have read that when ever you're better than 50% at 2a-2a you should double. Well that's not the case here and I didn't understand why. Dmitriy has done the maths http://www.bgonline.org/forums/webbbs_config.pl?read=176277

 White is Player 2 score: 3 pip: 7 5 point match pip: 8 score: 3 Blue is Player 1
XGID=--D-------------------ab--:0:0:1:00:3:3:0:5:10
Blue on roll, cube action?

 Analyzed in Rollout No double Double/Take Player Winning Chances: 53.61% (G:0.00% B:0.00%) 53.61% (G:0.00% B:0.00%) Opponent Winning Chances: 46.39% (G:0.00% B:0.00%) 46.39% (G:0.00% B:0.00%) Cubeless Equities +0.072 +0.204 Cubeful Equities No double: +0.265 ±0.000 (+0.265..+0.265) Double/Take: +0.204 (-0.061) ±0.000 (+0.204..+0.204) Double/Pass: +1.000 (+0.735) Best Cube action: No double / Take Percentage of wrong pass needed to make the double decision right: 7.1% Rollout details 2592 Games rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller Double Decision confidence: 100.0% Take Decision confidence: 100.0% Duration: 0.3 second

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

This is the closest possition for a D/T that I found

 White is Player 2 score: 3 pip: 9 5 point match pip: 8 score: 3 Blue is Player 1
XGID=--D-----------------a--b--:0:0:1:00:3:3:0:5:10
Blue on roll, cube action?

 Analyzed in Rollout No double Double/Take Player Winning Chances: 58.88% (G:0.00% B:0.00%) 58.88% (G:0.00% B:0.00%) Opponent Winning Chances: 41.12% (G:0.00% B:0.00%) 41.12% (G:0.00% B:0.00%) Cubeless Equities +0.178 +0.501 Cubeful Equities No double: +0.315 (-0.186) ±0.000 (+0.315..+0.315) Double/Take: +0.501 ±0.000 (+0.501..+0.501) Double/Pass: +1.000 (+0.499) Best Cube action: Double / Take Rollout details 1296 Games rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller Double Decision confidence: 100.0% Take Decision confidence: 100.0% Duration: 0.1 second

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

And here is the possition after blue has taken 2 men off. It is a double for white despite being only 36% to win, which also goes against the double when 50% ahead (which AP points out).

 White is Player 1 score: 3 pip: 4 5 point match pip: 7 score: 3 Blue is Player 2
XGID=--B-------------------ab--:0:0:-1:00:3:3:0:5:10
Blue on roll, cube action?

 Analyzed in Rollout No double Double/Take Player Winning Chances: 37.72% (G:0.00% B:0.00%) 37.72% (G:0.00% B:0.00%) Opponent Winning Chances: 62.28% (G:0.00% B:0.00%) 62.28% (G:0.00% B:0.00%) Cubeless Equities -0.246 -0.692 Cubeful Equities No double: -0.722 (-0.030) ±0.000 (-0.722..-0.722) Double/Take: -0.692 ±0.000 (-0.692..-0.692) Double/Pass: +1.000 (+1.692) Best Cube action: Double / Take Rollout details 1296 Games rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller Double Decision confidence: 100.0% Take Decision confidence: 100.0% Duration: 8.1 seconds

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

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