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Help with XG Rollout of Advanced BG #56

Posted By: Albert Steg
Date: Monday, 4 January 2016, at 8:48 p.m.

I hate to waste people's time but I'm trying to build competence in using XG while also reviewing some of the old books in my BG collection, looking for useful positions.

I'm aware that many of the positions in Bill Robertie's 'Advanced Backgammon' books have proven to be mistaken, and I've got Jeremy Bagai's book at hand, and have also found many old posts on this forum with rollouts/discussions of various positions. I *haven't* found any complaints about Vol. I Position #56 in , and this also seems to be one of the most straightforwardly calculable positions in the books, so I'm puzzled as to why I'm getting a contrary Evaluation and Rollout from XG when I plug it in.

In the text, Robertie's point is that this is an initial Double/Take (raising Black's equity from .33 to .44), but not a Re-cube. It's hard to believe this isn't an initial cube with 24 hitters? But I am seeing that XG suggests White can take a cube even after getting hit and immediately entering, which Robertie assumes to be a pass. Can this possibly be enough to tip it all the way into No Double territory, or am I missing something else -- either in Robertie or in setting up XG properly?

Thanks for any help here and apologies if this is obvious to most.





White is Player 2

score: 0
pip: 63
Unlimited Game
Jacoby Beaver
pip: 115
score: 0

Blue is Player 1
XGID=--BBBBB-----aC----Bcbbbcb-:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 63.78% (G:2.79% B:0.04%) 64.64% (G:3.04% B:0.08%)
Opponent Winning Chances: 36.22% (G:2.97% B:0.06%) 35.36% (G:2.82% B:0.05%)
Cubeless Equities +0.274 +0.590
Cubeful Equities
No double:+0.336±0.003 (+0.333..+0.339)
Double/Take:+0.327 (-0.009)±0.005 (+0.322..+0.333)
Double/Pass:+1.000 (+0.664)
Best Cube action: No double / Take
Percentage of wrong pass needed to make the double decision right: 1.3%
Rollout details
2592 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:99.8%
Take Decision confidence:100.0%
Duration: 37.6 seconds

eXtreme Gammon Version: 2.10

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