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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:+0.2650.000 (+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:+0.5010.000 (+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:-0.6920.000 (-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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