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Advanced Backgammon #34 -- Rollouts

Posted By: Igor
Date: Wednesday, 5 February 2014, at 5:13 p.m.

In Response To: Advanced Backgammon #34 (Igor)

There isn't much left for me to discuss after Nack and Paul dissected the position. If this were a pure race white could take with no more than 14 pip deficit. The minimal contact left in the position favors blue. By how much? It depends on the strength of white's half of the board position. The weaker white's position the more aggressively blue can hit the white straggler. In the OP white has just enough for a thin take.





White is Player 2

score: 0
pip: 135
Unlimited Game
Jacoby Beaver
pip: 126
score: 0

Blue is Player 1
XGID=---B-aD-C-B-dD---baeb-----:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 74.02% (G:9.09% B:0.09%) 74.27% (G:9.88% B:0.10%)
Opponent Winning Chances: 25.98% (G:1.56% B:0.04%) 25.73% (G:1.68% B:0.04%)
Cubeless Equities +0.556 +1.136
Cubeful Equities
No double:+0.832 (-0.129)0.005 (+0.827..+0.837)
Double/Take:+0.9610.007 (+0.954..+0.969)
Double/Pass:+1.000 (+0.039)
Best Cube action: Double / Take
Rollout details
2592 Games rolled with Variance Reduction.
Dice Seed: 86477631
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 7 minutes 34 seconds

eXtreme Gammon Version: 2.10

Keep the same take point but reduce white's recube power and it becomes a drop.





White is Player 2

score: 2
pip: 135
7 point match
pip: 126
score: 0

Blue is Player 1
XGID=---B-aD-C-B-dD---baeb-----:0:0:1:00:0:2:0:7:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 73.72% (G:10.43% B:0.10%) 74.06% (G:10.62% B:0.10%)
Opponent Winning Chances: 26.28% (G:1.90% B:0.06%) 25.94% (G:1.88% B:0.07%)
Cubeless Equities +0.561 +1.173
Cubeful Equities
No double:+0.874 (-0.126)0.006 (+0.868..+0.881)
Double/Take:+1.046 (+0.046)0.010 (+1.036..+1.056)
Double/Pass:+1.000
Best Cube action: Double / Pass
Rollout details
1296 Games rolled with Variance Reduction.
Dice Seed: 27547115
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 4 minutes 29 seconds

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

The other way around -- more recube power to white -- is a clear take.





White is Player 2

score: 2
pip: 135
7 point match
pip: 126
score: 4

Blue is Player 1
XGID=---B-aD-C-B-dD---baeb-----:0:0:1:00:4:2:0:7:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 74.10% (G:9.92% B:0.13%) 74.45% (G:9.86% B:0.36%)
Opponent Winning Chances: 25.90% (G:1.70% B:0.04%) 25.55% (G:1.76% B:0.04%)
Cubeless Equities +0.583 +1.255
Cubeful Equities
No double:+0.845 (-0.088)0.008 (+0.837..+0.853)
Double/Take:+0.9330.012 (+0.921..+0.945)
Double/Pass:+1.000 (+0.067)
Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction.
Dice Seed: 27547115
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 6 minutes 39 seconds

eXtreme Gammon Version: 2.10, MET: Kazaross XG2

Adding just one more checker in the zone for blue is enough to force white to drop.





White is Player 2

score: 0
pip: 132
Unlimited Game
Jacoby Beaver
pip: 123
score: 0

Blue is Player 1
XGID=---B-aD-C-C-cC-a-baeb-----:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 75.46% (G:8.46% B:0.10%) 75.78% (G:9.98% B:0.13%)
Opponent Winning Chances: 24.54% (G:1.50% B:0.04%) 24.22% (G:1.68% B:0.05%)
Cubeless Equities +0.579 +1.198
Cubeful Equities
No double:+0.870 (-0.130)0.007 (+0.863..+0.877)
Double/Take:+1.037 (+0.037)0.011 (+1.025..+1.048)
Double/Pass:+1.000
Best Cube action: Double / Pass
Rollout details
1296 Games rolled with Variance Reduction.
Dice Seed: 62901579
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 3 minutes 08 seconds

eXtreme Gammon Version: 2.10

As for the other variants, let's see what changes if we start moving white straggler one pip back at a time.





White is Player 2

score: 0
pip: 136
Unlimited Game
Jacoby Beaver
pip: 126
score: 0

Blue is Player 1
XGID=---Ba-D-C-B-dD---baeb-----:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 74.36% (G:10.84% B:0.11%) 74.31% (G:12.12% B:0.12%)
Opponent Winning Chances: 25.64% (G:2.26% B:0.06%) 25.69% (G:2.44% B:0.08%)
Cubeless Equities +0.573 +1.167
Cubeful Equities
No double:+0.882 (-0.118)0.001 (+0.881..+0.883)
Double/Take:+1.001 (+0.001)0.002 (+0.999..+1.003)
Double/Pass:+1.000
Best Cube action: Double / Pass
Rollout details
46656 Games rolled with Variance Reduction.
Dice Seed: 86477631
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:88.6%
Duration: 5 hours 19 minutes

eXtreme Gammon Version: 2.10

By moving white straggler one pip back we effectively made race deficit one pip more and it is now a borderline decision. Restoring the race deficit back to 9 pips gives a clear take.





White is Player 2

score: 0
pip: 135
Unlimited Game
Jacoby Beaver
pip: 126
score: 0

Blue is Player 1
XGID=---Ba-D-C-B-dD---abeb-----:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 73.81% (G:10.25% B:0.09%) 73.84% (G:11.50% B:0.10%)
Opponent Winning Chances: 26.19% (G:2.24% B:0.06%) 26.16% (G:2.42% B:0.07%)
Cubeless Equities +0.557 +1.136
Cubeful Equities
No double:+0.852 (-0.106)0.008 (+0.843..+0.860)
Double/Take:+0.9580.012 (+0.946..+0.969)
Double/Pass:+1.000 (+0.042)
Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction.
Dice Seed: 27547115
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 4 minutes 15 seconds

eXtreme Gammon Version: 2.10

Moving it further to 23 and 24 points still keeps white in the race take window, but allows a more flexible game plan -- stay back and harass blue or switch to a race if big numbers are rolled.





White is Player 2

score: 0
pip: 138
Unlimited Game
Jacoby Beaver
pip: 126
score: 0

Blue is Player 1
XGID=--aB--D-C-B-dD---baeb-----:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 73.76% (G:10.83% B:0.12%) 74.18% (G:11.90% B:0.13%)
Opponent Winning Chances: 26.24% (G:2.76% B:0.06%) 25.82% (G:2.93% B:0.08%)
Cubeless Equities +0.557 +1.148
Cubeful Equities
No double:+0.876 (-0.099)0.005 (+0.871..+0.881)
Double/Take:+0.9750.008 (+0.966..+0.983)
Double/Pass:+1.000 (+0.025)
Best Cube action: Double / Take
Rollout details
2592 Games rolled with Variance Reduction.
Dice Seed: 45820022
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 7 minutes 40 seconds

eXtreme Gammon Version: 2.10





White is Player 2

score: 0
pip: 139
Unlimited Game
Jacoby Beaver
pip: 126
score: 0

Blue is Player 1
XGID=-a-B--D-C-B-dD---baeb-----:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 73.26% (G:9.92% B:0.15%) 73.47% (G:10.40% B:0.16%)
Opponent Winning Chances: 26.74% (G:3.07% B:0.07%) 26.53% (G:3.27% B:0.09%)
Cubeless Equities +0.535 +1.083
Cubeful Equities
No double:+0.852 (-0.052)0.007 (+0.845..+0.859)
Double/Take:+0.9040.011 (+0.893..+0.915)
Double/Pass:+1.000 (+0.096)
Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction.
Dice Seed: 45820022
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 4 minutes 20 seconds

eXtreme Gammon Version: 2.10

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