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Advanced Backgammon #8 -- Rollouts

Posted By: Igor
Date: Monday, 27 January 2014, at 5:27 p.m.

In Response To: Advanced Backgammon #8 (Igor)

This is a perfect example of structure and timing principle. In 8B we are well ahead in the race and can't prime or attack white's golden anchor, so the only viable game plan we have is racing. However, running all the way 24/15 walks into a double shot and in the presence of a solid "partial running" alternative 24/20 13/8 is not best.





White is Player 2

score: 0
pip: 162
Unlimited Game
Jacoby Beaver
pip: 148
score: 0

Blue is Player 1
XGID=---B-bD-B--adF---d-d----A-:0:0:1:54:0:0:3:0:10
Blue to play 54

1.Rollout124/20 13/8eq: +0.173
Player:
Opponent:
55.03% (G:9.18% B:0.32%)
44.97% (G:9.25% B:0.26%)
Conf.: 0.006 (+0.167...+0.179) - [100.0%]
Duration: 33 minutes 38 seconds
2.Rollout124/15eq: +0.152 (-0.021)
Player:
Opponent:
54.94% (G:6.42% B:0.22%)
45.06% (G:8.58% B:0.24%)
Conf.: 0.007 (+0.146...+0.159) - [0.0%]
Duration: 35 minutes 03 seconds
3.Rollout213/4eq: +0.123 (-0.050)
Player:
Opponent:
53.40% (G:9.48% B:0.29%)
46.60% (G:9.29% B:0.25%)
Conf.: 0.016 (+0.107...+0.139) - [0.0%]
Duration: 7 minutes 45 seconds
4.Rollout213/9 13/8eq: +0.102 (-0.071)
Player:
Opponent:
52.96% (G:9.88% B:0.29%)
47.04% (G:8.91% B:0.28%)
Conf.: 0.016 (+0.086...+0.117) - [0.0%]
Duration: 8 minutes 05 seconds
1 5184 Games rolled with Variance Reduction.
Dice Seed: 22956323
Moves: 3-ply, cube decisions: XG Roller

2 1296 Games rolled with Variance Reduction.
Dice Seed: 22956323
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

In contrast to this position, in 8A our structure points to a priming game plan and Robertie therefore recommends bringing two checkers down. However, this reasoning completely ignores the timing issue. We are 31 pips ahead in the race after the roll. So, timing considerations point to a racing game plan and not so much to a priming game plan. The pure racing move is 24/15, but then again it walks into a double shot. So, let's remain flexible and keep both game plans in mind. Additionally, white is probably going to bring one or two builders down on her move, so stepping up eyes the outfield and makes it more difficult for white to build up an attack -- the only game plan she has.





White is Player 2

score: 0
pip: 170
Unlimited Game
Jacoby Beaver
pip: 148
score: 0

Blue is Player 1
XGID=-b-B--D-B--adF---d-d----A-:0:0:1:54:0:0:3:0:10
Blue to play 54

1.Rollout124/20 13/8eq: +0.468
Player:
Opponent:
60.32% (G:18.34% B:1.44%)
39.68% (G:8.98% B:0.33%)
Conf.: 0.003 (+0.465...+0.470) - [99.5%]
Duration: 6 hours 22 minutes
2.Rollout113/9 13/8eq: +0.463 (-0.005)
Player:
Opponent:
59.91% (G:19.88% B:1.56%)
40.09% (G:8.77% B:0.35%)
Conf.: 0.003 (+0.460...+0.465) - [0.5%]
Duration: 6 hours 07 minutes
3.Rollout224/15eq: +0.454 (-0.014)
Player:
Opponent:
60.95% (G:15.92% B:1.03%)
39.05% (G:9.01% B:0.32%)
Conf.: 0.005 (+0.449...+0.459) - [0.0%]
Duration: 2 hours 02 minutes
1 46656 Games rolled with Variance Reduction.
Dice Seed: 25176799
Moves: 3-ply, cube decisions: XG Roller

2 15552 Games rolled with Variance Reduction.
Dice Seed: 25176799
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

If running all the way did not walk into a double shot, it would clearly be best.





White is Player 2

score: 0
pip: 169
Unlimited Game
Jacoby Beaver
pip: 148
score: 0

Blue is Player 1
XGID=-b-B--D-B---eF---d-d----A-:0:0:1:54:0:0:3:0:10
Blue to play 54

1.Rollout124/15eq: +0.539
Player:
Opponent:
63.67% (G:14.49% B:0.75%)
36.33% (G:7.54% B:0.30%)
Conf.: 0.014 (+0.526...+0.553) - [100.0%]
Duration: 6 minutes 12 seconds
2.Rollout113/9 13/8eq: +0.478 (-0.062)
Player:
Opponent:
60.44% (G:19.38% B:1.53%)
39.56% (G:8.31% B:0.31%)
Conf.: 0.016 (+0.462...+0.494) - [0.0%]
Duration: 6 minutes 21 seconds
3.Rollout124/20 13/8eq: +0.473 (-0.066)
Player:
Opponent:
60.43% (G:18.15% B:1.17%)
39.57% (G:8.89% B:0.28%)
Conf.: 0.016 (+0.458...+0.489) - [0.0%]
Duration: 6 minutes 33 seconds
1 1296 Games rolled with Variance Reduction.
Dice Seed: 75994980
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

I believe there is also another factor in play in 8A. White has only 8 checkers in the zone, so we are not afraid to step up to the 20pt. Add one more checker for white and it's best to stay out of harm's way for now and wait for a better chance to dart.





White is Player 2

score: 0
pip: 163
Unlimited Game
Jacoby Beaver
pip: 148
score: 0

Blue is Player 1
XGID=-b-B--D-B--acF---d-e----A-:0:0:1:54:0:0:3:0:10
Blue to play 54

1.Rollout113/9 13/8eq: +0.460
Player:
Opponent:
60.37% (G:18.82% B:1.33%)
39.63% (G:9.18% B:0.34%)
Conf.: 0.008 (+0.453...+0.468) - [100.0%]
Duration: 23 minutes 43 seconds
2.Rollout124/20 13/8eq: +0.440 (-0.021)
Player:
Opponent:
60.35% (G:17.00% B:1.33%)
39.65% (G:9.80% B:0.33%)
Conf.: 0.007 (+0.432...+0.447) - [0.0%]
Duration: 25 minutes 25 seconds
3.Rollout224/15eq: +0.424 (-0.036)
Player:
Opponent:
60.67% (G:14.85% B:0.86%)
39.33% (G:9.43% B:0.32%)
Conf.: 0.011 (+0.413...+0.435) - [0.0%]
Duration: 13 minutes 18 seconds
1 5184 Games rolled with Variance Reduction.
Dice Seed: 22956323
Moves: 3-ply, cube decisions: XG Roller

2 2592 Games rolled with Variance Reduction.
Dice Seed: 22956323
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

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