Norm Wiggins’s excellent book
*Boards, Blots, and Double Shots*
is based on Jellyfish rollouts.
Jellyfish was the strongest backgammon program available at the time,
but since then, stronger programs have emerged
(though still based on the same neural net paradigm).
In 2007, Torsten Schoop ran a head-to-head
competition among several bots.
The results
of this “Big Bot Shoot-out” were that Jellyfish
was decidedly weaker than BGBlitz, Snowie, and GNU Backgammon,
with GNU doing the best.
In 2010, Michael Depreli organized a bot
comparison project to compare BGBlitz, Snowie, GNU, and
eXtreme Gammon (version 1). The strongest bot according to this
project was eXtreme Gammon.

It is therefore interesting to see whether eXtreme Gammon
disagrees with Jellyfish on any of the positions in the book.
I manually entered all the positions,
as well as some variants mentioned by Wiggins in his analysis,
into eXtreme Gammon version 1.21.
Where XG Roller+ indicated that there might be an issue of some sort,
I asked my friend Miller Maley, who owns eXtreme Gammon version 2.00,
to perform a full rollout.
The most interesting results of this study are presented below.
All rollouts below were done with eXtreme Gammon version 2.00.

The most dramatic disagreements between the two bots
occur in positions 3, 14, and 89.
Other notable disagreements include
positions 60, 72, 80, 92, 100, 102, 118.
I have also included a number of other rollouts
for reasons explained in more detail below.

Except where otherwise specified,
the rollouts below assume that the Jacoby rule is in effect.
Wiggins is not entirely clear about whether the Jacoby rule
is supposed to apply in all the positions in the book.
His comments on Positions 80 and 93 suggest that Jacoby should
be assumed to apply.
However, in Problem 114, he talks about being too good to double
with the cube in the center.
The question is somewhat moot because I believe it is very unlikely
that the Jacoby rule will affect which play comes out on top
in any of the positions in the book
(unless two or more plays are almost tied for top).
For a general explanation of why the Jacoby rule rarely makes
a difference when it comes to checker plays,
see this
article that I posted to rec.games.backgammon.

I should mention that for many of the positions in the book,
the *absolute* equity figures of XG
differ substantially from Jellyfish’s;
however, if the overall qualitative verdict
(i.e., which play is best, and by a large or a small margin)
remains the same, then I have usually not bothered to
include the rollout here.

** NOTE:** I have included

1. | Rollout^{1} | 13/10 6/5* | eq: -0.070 | |||

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2. | Rollout^{1} | 6/5* 5/2 | eq: -0.194 (-0.124) | |||

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3. | Rollout^{1} | 13/10 11/10 | eq: -0.347 (-0.277) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

Below is a rollout with the Jacoby rule turned off. This is one of those rare positions where the Jacoby rule makes a detectable difference. With the Jacoby rule in force, 13/10 6/5* forces White to double from the bar in order to reap the full benefit of hitting back, whereas without Jacoby, White can leave the cube in the center and play on for a gammon when she hits back. Thus 13/10 6/5* is relatively less attractive without Jacoby, but it still rolls out way ahead of the alternatives.

1. | Rollout^{1} | 13/10 6/5* | eq: -0.132 | |||

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2. | Rollout^{1} | 6/5* 5/2 | eq: -0.215 (-0.083) | |||

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3. | Rollout^{1} | 13/10 11/10 | eq: -0.346 (-0.214) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

For reference, here is a rollout of White’s cube decision from the bar after 13/10 6/5* if the Jacoby rule is in force:

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 57.17% (G: 28.34% B: 3.05%) |

Opponent Winning Chances: | 42.83% (G: 27.04% B: 1.08%) |

Double/Take | |

Player Winning Chances: | 57.43% (G: 30.26% B: 3.70%) |

Opponent Winning Chances: | 42.57% (G: 27.53% B: 1.10%) |

Cubeless Equities | |

No Double: | +0.143 |

Double: | +0.404 |

Cubeful Equities | |

No Double: | -0.010 (-0.079) |

Double/Take: | +0.068 |

Double/Drop: | +1.000 (+0.932) |

Best Cube action: Double / Take | |

Rollout details | |

2592 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.004 (-0.014...-0.007) |

Confidence Double: | ± 0.008 (+0.060...+0.077) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 11 minutes 31 seconds |

And here is a rollout of White’s cube decision from the bar after 13/10 6/5* if the Jacoby rule is

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 57.44% (G: 30.13% B: 3.63%) |

Opponent Winning Chances: | 42.56% (G: 27.52% B: 1.10%) |

Double/Take | |

Player Winning Chances: | 57.43% (G: 30.27% B: 3.70%) |

Opponent Winning Chances: | 42.57% (G: 27.53% B: 1.10%) |

Cubeless Equities | |

No Double: | +0.200 |

Double: | +0.404 |

Cubeful Equities | |

No Double: | +0.137 |

Double/Take: | +0.068 (-0.069) |

Double/Drop: | +1.000 (+0.863) |

Best Cube action: No Double / Take | |

Rollout details | |

2592
Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.005 (+0.132...+0.142) |

Confidence Double: | ± 0.008 (+0.060...+0.077) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 16 minutes 24 seconds |

1. | Rollout^{1} | 24/22 6/5 | eq: -0.312 | |||

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2. | Rollout^{1} | 6/5 6/4 | eq: -0.328 (-0.017) | |||

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3. | Rollout^{1} | 24/23 6/4 | eq: -0.351 (-0.039) | |||

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4. | Rollout^{1} | 16/15 6/4 | eq: -0.358 (-0.047) | |||

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5. | Rollout^{1} | 16/13 | eq: -0.362 (-0.050) | |||

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6. | Rollout^{1} | 24/21 | eq: -0.376 (-0.064) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 13/7 9/8 | eq: +0.130 | |||

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2. | Rollout^{1} | 13/6 | eq: +0.091 (-0.039) | |||

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3. | Rollout^{1} | 24/18 10/9 | eq: +0.071 (-0.059) | |||

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4. | Rollout^{1} | 24/23 10/4 | eq: -0.007 (-0.136) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

The play 13/7 9/8 is volatile enough that I thought the Jacoby rule might be relevant. However, the rollout below with the Jacoby rule turned off indicates that the Jacoby rule makes no difference.

1. | Rollout^{1} | 13/7 9/8 | eq: +0.127 | |||

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2. | Rollout^{1} | 13/6 | eq: +0.091 (-0.037) | |||

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3. | Rollout^{1} | 24/18 10/9 | eq: +0.072 (-0.056) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 13/10 8/7* | eq: +0.271 | |||

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2. | Rollout^{1} | 21/18 8/7* | eq: +0.266 (-0.005) | |||

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3. | Rollout^{1} | 8/7* 7/4 | eq: +0.238 (-0.033) | |||

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4. | Rollout^{1} | 8/5 8/7* | eq: +0.218 (-0.053) | |||

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5. | Rollout^{1} | 21/18 5/4 | eq: +0.217 (-0.054) | |||

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6. | Rollout^{1} | 23/22 21/18 | eq: +0.200 (-0.071) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | Bar/24 6/3 | eq: -0.251 | |||

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2. | Rollout^{1} | Bar/24 13/10 | eq: -0.324 (-0.073) | |||

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3. | Rollout^{1} | Bar/21 | eq: -0.365 (-0.114) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 70.15% (G: 10.83% B: 0.39%) |

Opponent Winning Chances: | 29.85% (G: 3.31% B: 0.03%) |

Double/Take | |

Player Winning Chances: | 70.67% (G: 11.80% B: 0.39%) |

Opponent Winning Chances: | 29.33% (G: 3.81% B: 0.04%) |

Cubeless Equities | |

No Redouble: | +0.482 |

Redouble: | +0.993 |

Cubeful Equities | |

No Redouble: | +0.766 (-0.121) |

Redouble/Take: | +0.887 |

Redouble/Drop: | +1.000 (+0.113) |

Best Cube action: Redouble / Take | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Redouble: | ± 0.003 (+0.763...+0.769) |

Confidence Redouble: | ± 0.005 (+0.882...+0.892) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 30 minutes 12 seconds |

1. | Rollout^{1} | 11/10 6/4* | eq: +0.350 | |||

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2. | Rollout^{1} | 24/23 6/4* | eq: +0.328 (-0.022) | |||

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3. | Rollout^{1} | 6/4* 4/3 | eq: +0.306 (-0.043) | |||

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^{1} 5184 Games
rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller |

1. | Rollout^{1} | 24/16 | eq: -0.334 | |||

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2. | Rollout^{1} | 8/2* 4/2 | eq: -0.390 (-0.056) | |||

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3. | Rollout^{1} | 24/18 4/2* | eq: -0.413 (-0.080) | |||

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^{1} 5184 Games
rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller |

1. | Rollout^{1} | 24/21 6/4* | eq: +0.130 | |||

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2. | Rollout^{1} | 13/10 6/4* | eq: +0.118 (-0.012) | |||

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3. | Rollout^{2} | 6/4* 4/1* | eq: +0.051 (-0.079) | |||

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^{1} 20736 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller ^{2} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 5/2 3/2 | eq: -0.400 | |||

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2. | Rollout^{1} | 10/6* | eq: -0.424 (-0.024) | |||

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^{1} 5184 Games
rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller |

1. | Rollout^{1} | 11/5 4/3* | eq: +0.618 | |||

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2. | Rollout^{1} | 13/7 4/3* | eq: +0.582 (-0.036) | |||

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3. | Rollout^{1} | 10/3* | eq: +0.553 (-0.065) | |||

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4. | Rollout^{1} | 13/12 11/5 | eq: +0.513 (-0.105) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 14/4 | eq: +0.922 | |||

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2. | Rollout^{1} | 14/8 6/2* | eq: +0.917 (-0.005) | |||

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^{1} 5184 Games
rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller |

1. | Rollout^{1} | Bar/23 24/21 | eq: +0.238 | |||

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2. | Rollout^{1} | Bar/22 6/4 | eq: +0.220 (-0.018) | |||

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3. | Rollout^{1} | Bar/20 | eq: +0.210 (-0.027) | |||

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4. | Rollout^{1} | Bar/22 8/6 | eq: +0.192 (-0.046) | |||

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5. | Rollout^{1} | Bar/23 7/4 | eq: +0.189 (-0.049) | |||

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6. | Rollout^{1} | Bar/22 7/5 | eq: +0.173 (-0.065) | |||

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7. | Rollout^{1} | Bar/22 24/22 | eq: +0.171 (-0.067) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 68.13% (G: 34.84% B: 0.61%) |

Opponent Winning Chances: | 31.87% (G: 8.61% B: 0.33%) |

Double/Take | |

Player Winning Chances: | 68.21% (G: 37.68% B: 0.60%) |

Opponent Winning Chances: | 31.79% (G: 9.23% B: 0.43%) |

Cubeless Equities | |

No Double: | +0.363 |

Double: | +1.301 |

Cubeful Equities | |

No Double: | +0.678 (-0.322) |

Double/Take: | +1.061 (+0.061) |

Double/Drop: | +1.000 |

Best Cube action: Double / Drop | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.005 (+0.674...+0.683) |

Confidence Double: | ± 0.008 (+1.053...+1.069) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 26 minutes 52 seconds |

Similarly, Wiggins implies that if White rolls 5-3 and enters both checkers, then Black does not have a double. However, the XG rollout says that Black does have a double:

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 61.56% (G: 26.03% B: 0.53%) |

Opponent Winning Chances: | 38.44% (G: 10.85% B: 0.41%) |

Double/Take | |

Player Winning Chances: | 61.76% (G: 27.64% B: 0.53%) |

Opponent Winning Chances: | 38.24% (G: 11.46% B: 0.53%) |

Cubeless Equities | |

No Double: | +0.231 |

Double: | +0.794 |

Cubeful Equities | |

No Double: | +0.460 (-0.052) |

Double/Take: | +0.512 |

Double/Drop: | +1.000 (+0.488) |

Best Cube action: Double / Take | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.006 (+0.453...+0.466) |

Confidence Double: | ± 0.009 (+0.503...+0.521) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 1 hour 35 minutes |

1. | Rollout^{1} | Bar/20 24/23 | eq: -0.215 | |||

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2. | Rollout^{1} | Bar/20 6/5 | eq: -0.240 (-0.025) | |||

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3. | Rollout^{1} | Bar/20 11/10 | eq: -0.252 (-0.037) | |||

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4. | Rollout^{1} | Bar/24 13/8 | eq: -0.291 (-0.076) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 8/3* 5/1* | eq: +0.368 | |||

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2. | Rollout^{1} | 22/18 8/3* | eq: +0.339 (-0.029) | |||

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3. | Rollout^{1} | 22/13 | eq: +0.337 (-0.031) | |||

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4. | Rollout^{1} | 10/1* | eq: +0.335 (-0.033) | |||

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5. | Rollout^{1} | 10/6 8/3* | eq: +0.332 (-0.036) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 24/21 8/7* | eq: -0.077 | |||

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2. | Rollout^{1} | 24/21 22/21 | eq: -0.092 (-0.014) | |||

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3. | Rollout^{1} | 8/7* 7/4 | eq: -0.144 (-0.067) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 9/5 8/5 | eq: -0.339 | |||

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2. | Rollout^{1} | 18/15* 15/11 | eq: -0.367 (-0.028) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 18/14 18/12* | eq: +0.598 | |||

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2. | Rollout^{1} | 24/18 10/6 | eq: +0.594 (-0.004) | |||

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3. | Rollout^{1} | 24/20 18/12* | eq: +0.560 (-0.038) | |||

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4. | Rollout^{2} | 18/12* 10/6 | eq: +0.468 (-0.130) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller ^{2} 1296 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 24/22 24/21 | eq: +0.179 | |||

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2. | Rollout^{1} | 24/22 8/5 | eq: +0.163 (-0.016) | |||

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3. | Rollout^{1} | 24/21 9/7 | eq: +0.162 (-0.016) | |||

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4. | Rollout^{1} | 24/22 9/6 | eq: +0.142 (-0.037) | |||

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5. | Rollout^{1} | 24/21 6/4 | eq: +0.139 (-0.040) | |||

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6. | Rollout^{1} | 24/21 8/6 | eq: +0.118 (-0.061) | |||

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7. | Rollout^{1} | 9/4 | eq: +0.095 (-0.084) | |||

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8. | Rollout^{1} | 24/22 13/10 | eq: +0.088 (-0.090) | |||

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^{1} 5184 Games
rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller |

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 71.68% (G: 18.63% B: 0.04%) |

Opponent Winning Chances: | 28.32% (G: 3.32% B: 0.12%) |

Double/Take | |

Player Winning Chances: | 71.92% (G: 19.79% B: 0.04%) |

Opponent Winning Chances: | 28.08% (G: 3.47% B: 0.12%) |

Cubeless Equities | |

No Redouble: | +0.586 |

Redouble: | +1.202 |

Cubeful Equities | |

No Redouble: | +0.819 (-0.174) |

Redouble/Take: | +0.993 |

Redouble/Drop: | +1.000 (+0.007) |

Best Cube action: Redouble / Take | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Redouble: | ± 0.002 (+0.817...+0.822) |

Confidence Redouble: | ± 0.005 (+0.987...+0.998) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 99.5% |

Duration: 15 minutes 23 seconds |

1. | Rollout^{1} | Bar/21 Bar/17* 13/9 | eq: +0.557 | |||

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2. | Rollout^{1} | Bar/17*(2) | eq: +0.549 (-0.008) | |||

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3. | Rollout^{1} | Bar/21 Bar/17* 17/13 | eq: +0.481 (-0.076) | |||

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^{1} 5184 Games
rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller |

1. | Rollout^{1} | 8/3 7/1 | eq: -0.286 | |||

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2. | Rollout^{1} | 14/3 | eq: -0.328 (-0.042) | |||

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3. | Rollout^{1} | 14/9 7/1 | eq: -0.346 (-0.060) | |||

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4. | Rollout^{1} | 7/1 6/1 | eq: -0.351 (-0.065) | |||

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5. | Rollout^{1} | 14/9 8/2 | eq: -0.360 (-0.075) | |||

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6. | Rollout^{1} | 22/16 8/3 | eq: -0.364 (-0.078) | |||

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7. | Rollout^{1} | 14/8 7/2 | eq: -0.370 (-0.084) | |||

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8. | Rollout^{1} | 22/16 14/9 | eq: -0.460 (-0.174) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 9/3 6/3 | eq: +0.459 | |||

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2. | Rollout^{1} | 24/18* 13/10 | eq: +0.420 (-0.039) | |||

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3. | Rollout^{2} | 24/18* 10/7 | eq: +0.384 (-0.075) | |||

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4. | Rollout^{2} | 24/18* 18/15 | eq: +0.366 (-0.093) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller ^{2} 1296 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

White’s cube decision after Black hits on the 18pt:

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 61.47% (G: 24.69% B: 0.89%) |

Opponent Winning Chances: | 38.53% (G: 8.85% B: 0.54%) |

Double/Take | |

Player Winning Chances: | 61.40% (G: 26.60% B: 0.94%) |

Opponent Winning Chances: | 38.60% (G: 9.40% B: 0.60%) |

Cubeless Equities | |

No Double: | +0.229 |

Double: | +0.807 |

Cubeful Equities | |

No Double: | +0.509 (-0.004) |

Double/Take: | +0.513 |

Double/Drop: | +1.000 (+0.487) |

Best Cube action: Double / Take | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.007 (+0.503...+0.516) |

Confidence Double: | ± 0.010 (+0.504...+0.523) |

Double Decision confidence: | 75.7% |

Take Decision confidence: | 100.0% |

Duration: 1 hour 25 minutes |

White’s cube decision after Black anchors:

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 70.02% (G: 11.52% B: 0.27%) |

Opponent Winning Chances: | 29.98% (G: 3.98% B: 0.15%) |

Double/Take | |

Player Winning Chances: | 70.06% (G: 11.55% B: 0.28%) |

Opponent Winning Chances: | 29.94% (G: 4.07% B: 0.16%) |

Cubeless Equities | |

No Double: | +0.400 |

Double: | +0.954 |

Cubeful Equities | |

No Double: | +0.766 |

Double/Take: | +0.753 (-0.013) |

Double/Drop: | +1.000 (+0.234) |

Best Cube action: No Double / Take | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.007 (+0.759...+0.773) |

Confidence Double: | ± 0.007 (+0.745...+0.760) |

Double Decision confidence: | 99.6% |

Take Decision confidence: | 100.0% |

Duration: 1 hour 34 minutes |

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 65.28% (G: 48.46% B: 0.44%) |

Opponent Winning Chances: | 34.72% (G: 7.71% B: 0.43%) |

Double/Take | |

Player Winning Chances: | 66.63% (G: 50.77% B: 0.40%) |

Opponent Winning Chances: | 33.37% (G: 8.35% B: 0.58%) |

Cubeless Equities | |

No Double: | +0.306 |

Double: | +1.510 |

Cubeful Equities | |

No Double: | +0.712 (-0.288) |

Double/Take: | +1.234 (+0.234) |

Double/Drop: | +1.000 |

Best Cube action: Double / Drop | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.006 (+0.706...+0.718) |

Confidence Double: | ± 0.010 (+1.224...+1.245) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 47 minutes 07 seconds |

1. | Rollout^{1} | Bar/21 8/7* | eq: -0.629 | |||

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2. | Rollout^{1} | Bar/21 6/5 | eq: -0.675 (-0.046) | |||

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3. | Rollout^{1} | Bar/21 24/23 | eq: -0.789 (-0.160) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

Wiggins says that 6/5 “staves off White’s double” but the XG rollout says that it may be a marginal double:

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 64.60% (G: 24.44% B: 2.19%) |

Opponent Winning Chances: | 35.40% (G: 7.85% B: 0.34%) |

Double/Take | |

Player Winning Chances: | 64.67% (G: 24.60% B: 2.31%) |

Opponent Winning Chances: | 35.33% (G: 7.96% B: 0.36%) |

Cubeless Equities | |

No Double: | +0.292 |

Double: | +0.959 |

Cubeful Equities | |

No Double: | +0.667 (-0.007) |

Double/Take: | +0.674 |

Double/Drop: | +1.000 (+0.326) |

Best Cube action: Double / Take | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.008 (+0.659...+0.674) |

Confidence Double: | ± 0.010 (+0.663...+0.684) |

Double Decision confidence: | 85.7% |

Take Decision confidence: | 100.0% |

Duration: 1 hour 43 minutes |

For comparison, here is the rollout for White’s cube action after 8/7*:

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 61.40% (G: 29.44% B: 3.95%) |

Opponent Winning Chances: | 38.60% (G: 8.85% B: 0.41%) |

Double/Take | |

Player Winning Chances: | 61.36% (G: 29.69% B: 4.29%) |

Opponent Winning Chances: | 38.64% (G: 8.91% B: 0.45%) |

Cubeless Equities | |

No Double: | +0.228 |

Double: | +0.947 |

Cubeful Equities | |

No Double: | +0.598 (-0.026) |

Double/Take: | +0.624 |

Double/Drop: | +1.000 (+0.376) |

Best Cube action: Double / Take | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.009 (+0.589...+0.606) |

Confidence Double: | ± 0.012 (+0.611...+0.636) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 1 hour 58 minutes |

1. | Rollout^{1} | 18/9 | eq: +0.368 | |||

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2. | Rollout^{1} | 18/15 13/7 | eq: +0.339 (-0.029) | |||

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3. | Rollout^{1} | 13/4 | eq: +0.324 (-0.044) | |||

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^{1} 1296 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

Rollout of original position:

1. | Rollout^{1} | 6/4 6/3 | eq: +0.914 | |||

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2. | Rollout^{1} | 3/0ff 2/0ff | eq: +0.900 (-0.014) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

Rollout of variant in which White’s 10pt checker is moved to her 8pt:

1. | Rollout^{1} | 6/4 6/3 | eq: +0.920 | |||

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2. | Rollout^{1} | 3/0ff 2/0ff | eq: +0.919 (-0.001) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 15/9 8/4* | eq: -0.474 | |||

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2. | Rollout^{1} | 13/7 8/4* | eq: -0.474 | |||

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3. | Rollout^{1} | 15/9 13/9 | eq: -0.578 (-0.103) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | Bar/22 24/23 | eq: -0.445 | |||

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2. | Rollout^{1} | Bar/22 8/7 | eq: -0.497 (-0.052) | |||

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3. | Rollout^{1} | Bar/21 | eq: -0.512 (-0.067) | |||

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4. | Rollout^{1} | Bar/22 6/5 | eq: -0.541 (-0.096) | |||

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^{1} 5184 Games
rolled with Variance Reduction.Moves: 3-ply, cube decisions: XG Roller |

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 60.78% (G: 30.68% B: 1.82%) |

Opponent Winning Chances: | 39.22% (G: 10.09% B: 0.54%) |

Double/Take | |

Player Winning Chances: | 61.09% (G: 31.63% B: 2.30%) |

Opponent Winning Chances: | 38.91% (G: 10.28% B: 0.54%) |

Cubeless Equities | |

No Double: | +0.216 |

Double: | +0.906 |

Cubeful Equities | |

No Double: | +0.520 (-0.073) |

Double/Take: | +0.593 |

Double/Drop: | +1.000 (+0.407) |

Best Cube action: Double / Take | |

Rollout details | |

5184 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.008 (+0.512...+0.527) |

Confidence Double: | ± 0.011 (+0.582...+0.604) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 1 hour 45 minutes |

Analyzed in Rollout | |

No Double | |

Player Winning Chances: | 61.22% (G: 34.54% B: 1.78%) |

Opponent Winning Chances: | 38.78% (G: 9.63% B: 0.59%) |

Double/Take | |

Player Winning Chances: | 61.58% (G: 36.80% B: 1.72%) |

Opponent Winning Chances: | 38.42% (G: 10.16% B: 0.64%) |

Cubeless Equities | |

No Double: | +0.224 |

Double: | +1.017 |

Cubeful Equities | |

No Double: | +0.605 (-0.103) |

Double/Take: | +0.708 |

Double/Drop: | +1.000 (+0.292) |

Best Cube action: Double / Take | |

Rollout details | |

1296 Games rolled with Variance Reduction. Moves: 3 ply, cube decisions: XG Roller | |

Confidence No Double: | ± 0.010 (+0.594...+0.615) |

Confidence Double: | ± 0.017 (+0.691...+0.725) |

Double Decision confidence: | 100.0% |

Take Decision confidence: | 100.0% |

Duration: 16 minutes 10 seconds |

1. | Rollout^{1} | 6/2* | eq: -0.251 | |||

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2. | Rollout^{1} | 8/5 6/5 | eq: -0.255 (-0.005) | |||

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3. | Rollout^{1} | 23/22 8/5 | eq: -0.272 (-0.021) | |||

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4. | Rollout^{1} | 13/10 6/5 | eq: -0.290 (-0.039) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 24/15 | eq: -0.802 | |||

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2. | Rollout^{1} | 24/20 10/5 | eq: -0.824 (-0.021) | |||

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3. | Rollout^{1} | 10/1 | eq: -0.862 (-0.060) | |||

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4. | Rollout^{1} | 10/6 7/2 | eq: -0.870 (-0.068) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |

1. | Rollout^{1} | 24/14 | eq: -0.026 | |||

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2. | Rollout^{1} | 24/20 13/7 | eq: -0.066 (-0.040) | |||

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3. | Rollout^{1} | 8/2* 6/2 | eq: -0.071 (-0.045) | |||

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^{1} 5184 Games rolled with Variance Reduction.Moves: 3 ply, cube decisions: XG Roller |