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Blue's bearoff choice with 11, Rollout

Posted By: Nack Ballard
Date: Saturday, 14 June 2014, at 12:49 a.m.

In Response To: MCG vs Mochy: Nactated Match (Nack Ballard)





White is Player 2

score: 0
pip: 122
Unlimited Game
Jacoby Beaver
pip: 8
score: 0

Blue is Player 1
XGID=bDBa---------------cbcbb--:1:-1:1:11:0:0:3:0:10

Blue to play 11


1.Rollout12/Off(2)eq: +2.858
Player:
Opponent:
100.00% (G:100.00% B:85.79%)
0.00% (G:0.00% B:0.00%)
Conf.: ± 0.000 (+2.858...+2.858) - [99.9%]
Duration: 0.2 second
2.Rollout11/Off(4)eq: +2.857 (-0.001)
Player:
Opponent:
99.65% (G:95.64% B:90.86%)
0.35% (G:0.00% B:0.00%)
Conf.: ± 0.000 (+2.857...+2.858) - [0.1%]
Duration: 1 minute 29 seconds
1 5184 Games rolled with Variance Reduction.
Dice Seed: 57611092
Moves and cube decisions: 4-ply
Search interval: Large




White is Player 2

score: 0
pip: 120
Unlimited Game
Jacoby Beaver
pip: 8
score: 0

Blue is Player 1
XGID=bDBa---------------cbbbc--:1:-1:1:11:0:0:3:0:10

Blue to play 11


1.Rollout11/Off(4)eq: +2.8580
Player:
Opponent:
99.67% (G:95.67% B:90.87%)
0.33% (G:0.00% B:0.00%)
Conf.: ±0.0001 (+2.8579...+2.8581) - [97.7%]
Duration: 26 minutes 09 seconds
2.Rollout12/Off(2)eq: +2.8579 (-0.0001)
Player:
Opponent:
100.00% (G:100.00% B:85.79%)
0.00% (G:0.00% B:0.00%)
Conf.: ±0.0000 (+2.8579...+2.8579) - [2.3%]
Duration: 1.0 second
1 103680 Games rolled with Variance Reduction.
Dice Seed: 57611092
Moves and cube decisions: 4-ply
Search interval: Large

In the original position, shown in the first (or left-hand) rollout diagram above, Bob correctly chose 2/off(2), though it's only right by a hair.

In the second (or right-hand) position above, White's 4pt spare has been moved to her 2pt. This slight change is enough (according to the rollout) to barely alter Blue's best play, which is now 1/off(4).

A different way to alter the original position is shown in the first (or left-hand) position below. White's 22pt checker has been advanced 1 pip to her 21pt. This gives her a better chance to get off the backgammon (due to double 3s), and more clearly switches Blue's best play to 1/off(4).

In the second (right-hand) position below (a) White's 22pt checker is again advanced to her 21pt. On the other hand, (b) her board is now closed. Factor (a) has a bigger impact than factor (b), so the switch to 1/off(4) still holds.

Nack





White is Player 2

score: 0
pip: 121
Unlimited Game
Jacoby Beaver
pip: 8
score: 0

Blue is Player 1
XGID=bDB-a--------------cbcbb--:1:-1:1:11:0:0:3:0:10

Blue to play 11


1.Rollout11/Off(4)eq: +2.852
Player:
Opponent:
99.66% (G:95.65% B:90.35%)
0.34% (G:0.00% B:0.00%)
Conf.: ± 0.000 (+2.852...+2.853) - [100.0%]
Duration: 1 minute 16 seconds
2.Rollout12/Off(2)eq: +2.839 (-0.014)
Player:
Opponent:
100.00% (G:100.00% B:83.86%)
0.00% (G:0.00% B:0.00%)
Conf.: ± 0.000 (+2.839...+2.839) - [0.0%]
Duration: 0.2 second
1 5184 Games rolled with Variance Reduction.
Dice Seed: 57611092
Moves and cube decisions: 4-ply
Search interval: Large




White is Player 2

score: 0
pip: 113
Unlimited Game
Jacoby Beaver
pip: 8
score: 0

Blue is Player 1
XGID=bDB-a--------------bbbbbb-:1:-1:1:11:0:0:3:0:10

Blue to play 11


1.Rollout11/Off(4)eq: +2.846
Player:
Opponent:
99.61% (G:95.27% B:90.21%)
0.39% (G:0.00% B:0.00%)
Conf.: ± 0.000 (+2.846...+2.847) - [100.0%]
Duration: 28.3 seconds
2.Rollout12/Off(2)eq: +2.839 (-0.008)
Player:
Opponent:
100.00% (G:100.00% B:83.86%)
0.00% (G:0.00% B:0.00%)
Conf.: ± 0.000 (+2.839...+2.839) - [0.0%]
Duration: 0.2 second
1 5184 Games rolled with Variance Reduction.
Dice Seed: 57611092
Moves and cube decisions: 4-ply
Search interval: Large

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