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Interesting recube from the Seewald-S. Williams match – ** Rollout **

Posted By: Taper_Mike
Date: Tuesday, 3 February 2015, at 11:14 a.m.

In Response To: Interesting recube from the Seewald-S. Williams match (Taper_Mike)

Preliminaries

Blue has 27 hitting numbers. He also has a few second chances if he misses on this turn. His open board, however, is somewhat of a problem. He has one dead checker already, and filling the gap on the 3-point won’t be automatic. After entering, White will have to jump only a three-point block, so there are many in-and-out numbers for him. According to the pseudo-cubeless numbers below, Blue is winning 69% of the games, and netting about 15% gammons.

At the Original Score – No Redouble/Take

Leading 7-away/8-away it is a small technical error to cube this. When Blue redoubles and wins a gammon, there is some overage, so his gammon value is reduced compared to a money game. In practice, it is probably a good cube anyway, because Blue will get some passes. Indeed, Sean contemplated for a while before he correctly took.





White is Sean Williams

score: 1
pip: 50
9 point match
pip: 92
score: 2

Blue is Seewald
XGID=-BC-BBC-A-----a-a---Bccbe-:1:1:1:00:2:1:0:9:10
Blue on roll, cube action?

Analyzed in Rollout No redouble Redouble/Take
  Player Winning Chances: 68.795% (G:17.163% B:0.477%) 69.402% (G:16.611% B:0.670%)
  Opponent Winning Chances: 31.205% (G:1.569% B:0.029%) 30.598% (G:1.721% B:0.042%)
  Cubeless Equities +0.5438 +0.9991
Cubeful Equities
No redouble:+0.6497±0.0018 (+0.6480..+0.6515)
Redouble/Take:+0.6154 (-0.0344)±0.0031 (+0.6123..+0.6184)
Redouble/Pass:+1.0000 (+0.3503)
 
Best Cube action: No redouble / Take
Percentage of wrong pass needed to make the double decision right: 8.2%
Rollout details
5184 Games rolled with Variance Reduction.
Dice Seed: 48174001
Moves: 3-ply, cube decisions: XG Roller
 
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 3 minutes 49 seconds

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

When the Score Is Reversed – Redouble/Pass

When the scores are reversed, this becomes a massive double and a small pass. At 8-away, a gammon win on a 4-cube would cinch the victory.





White is Player 2

score: 2
pip: 50
9 point match
pip: 92
score: 1

Blue is Player 1
XGID=-BC-BBC-A-----a-a---Bccbe-:1:1:1:00:1:2:0:9:10
Blue on roll, cube action?

Analyzed in Rollout No redouble Redouble/Take
  Player Winning Chances: 68.557% (G:17.349% B:0.489%) 68.971% (G:17.415% B:0.751%)
  Opponent Winning Chances: 31.443% (G:1.504% B:0.007%) 31.029% (G:2.139% B:0.016%)
  Cubeless Equities +0.5582 +1.2368
Cubeful Equities
No redouble:+0.6810 (-0.3190)±0.0015 (+0.6795..+0.6825)
Redouble/Take:+1.0407 (+0.0407)±0.0034 (+1.0372..+1.0441)
Redouble/Pass:+1.0000
 
Best Cube action: Redouble / Pass
Rollout details
5184 Games rolled with Variance Reduction.
Dice Seed: 48174001
Moves: 3-ply, cube decisions: XG Roller
 
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 4 minutes 01 second

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

Unlimited Game – Redouble/Take

For money, the position is a solid double and an equally solid take. The open 3pt makes the take decision much easier than it would be otherwise.





White is Player 2

score: 0
pip: 50
Unlimited Game
pip: 92
score: 0

Blue is Player 1
XGID=-BC-BBC-A-----a-a---Bccbe-:1:1:1:00:0:0:0:0:10
Blue on roll, cube action?

Analyzed in Rollout No redouble Redouble/Take
  Player Winning Chances: 68.706% (G:17.207% B:0.474%) 69.058% (G:17.269% B:0.466%)
  Opponent Winning Chances: 31.294% (G:1.507% B:0.009%) 30.942% (G:1.578% B:0.012%)
  Cubeless Equities +0.5358 +1.0852
Cubeful Equities
No redouble:+0.6538 (-0.1949)±0.0015 (+0.6524..+0.6553)
Redouble/Take:+0.8488±0.0040 (+0.8447..+0.8528)
Redouble/Pass:+1.0000 (+0.1512)
 
Best Cube action: Redouble / Take
Rollout details
5184 Games rolled with Variance Reduction.
Dice Seed: 48174001
Moves: 3-ply, cube decisions: XG Roller
 
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 3 minutes 55 seconds

eXtreme Gammon Version: 2.10

Three different scores give three different cube actions. Backgammon is a difficult game!

Igor linked to a similar position from Robertie's Advanced Backgammon. The analysis Igor gives there is far better than my modest offering above.

Mike

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