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501 Essential Backgammon Problems #33

Posted By: Igor
Date: Thursday, 22 August 2013, at 2:19 p.m.

In Response To: 501 Essential Backgammon Problems #33 (Igor)

The 3 is clear, for the 5 Robertie's choice is a thematic ace point hit "to break the connection between the opponent's back men." I always thought that the purpose of that hit is twofold:

• Deprive the opponent from good sixes
• Protect the split
It turns out that in this position unstacking the midpoint and reinforcing the stripped 8pt is a better plan.

 White is Player 2 score: 0 pip: 159 Unlimited GameJacoby pip: 159 score: 0 Blue is Player 1
XGID=-a-B--DaB---dEa--c-e----B-:0:0:1:53:0:0:1:0:10
Blue to play 53

1.Rollout124/21 13/8eq: +0.078
 Player:Opponent: 51.26% (G:14.84% B:0.54%)48.74% (G:10.98% B:0.44%) Conf.: ± 0.005 (+0.073...+0.083) - [100.0%]Duration: 1 hour 04 minutes
2.Rollout124/21 6/1* eq: +0.049 (-0.029)
 Player:Opponent: 50.16% (G:17.31% B:0.56%)49.84% (G:12.35% B:0.61%) Conf.: ± 0.006 (+0.043...+0.055) - [0.0%]Duration: 1 hour 06 minutes
1 10368 Games rolled with Variance Reduction.
Dice Seed: 25949992
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

So I thought to myself: let's give blue more incentive to protect the split by moving white spare from her 11pt to her 10pt.

 White is Player 2 score: 0 pip: 158 Unlimited GameJacoby pip: 159 score: 0 Blue is Player 1
XGID=-a-B--DaB---dE-a-c-e----B-:0:0:1:53:0:0:1:0:10
Blue to play 53

1.Rollout124/21 13/8eq: +0.038
 Player:Opponent: 50.21% (G:15.41% B:0.60%)49.79% (G:12.16% B:0.51%) Conf.: ± 0.007 (+0.031...+0.045) - [100.0%]Duration: 31 minutes 25 seconds
2.Rollout124/21 6/1* eq: +0.009 (-0.029)
 Player:Opponent: 49.19% (G:16.77% B:0.58%)50.81% (G:12.90% B:0.65%) Conf.: ± 0.008 (+0.001...+0.017) - [0.0%]Duration: 34 minutes 22 seconds
1 5184 Games rolled with Variance Reduction.
Dice Seed: 69445117
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

Nope, hitting on the ace didn't go up in value. I guess duplication of sixes could be a factor.

P.S. Mile, don't bother cherry picking some of these positions as candidates for your database. I'll later collect, nactate, and send them your way.

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