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Nackgammon: Opening doublets

Posted By: Nack Ballard
Date: Saturday, 17 June 2017, at 8:10 p.m.

In Response To: My Takeaway From This (Paul Weaver)

I appreciate you pointing out the practicalities of this endeavor. You always know how to keep us well grounded.

It is indeed possible to get back to the opening position (of BG or NG) after opening doublets (from BG or NG), even though offensive key point(s) have been made. We think of these as "permanent" assets, but they're not really. It's just a matter of steering the position into a forced break.

In order to get back to the opening position, I practiced setting up these forced breaks when I thought that for a FARE position, each side must own at least one inside point. (Ultimately, I discovered a FARE position with no inside points made.)

For example, if you want to break a player's 4pt, one way is to block all his aces elsewhere and make bar/20* 4/3 his best play. Repeat this technique for as many points as you need to break. The only point that is unbreakable (while still keeping all checkers on the board) is the 1pt.

Below are XGR++ evaluations of the six doublets from the opening position of Nackgammon. First, nacbracs:

...NG 11 .[E e7 E10 P46 N84] "&e
...NG 22 .[N E56] "&e
...NG 33 .[B D44 E60 C61 b70] "&e
...NG 44 .[P B36] "&e
...NG 55 .[B M57 S82 b84 R86 P88] "&e
...NG 66 .[B] "&e

Nactation Key: B = Both, C = Cross, D = Down, E = Each, M = Magnify, N = Near, P = Point, R = Run, S = Split 3:1.
explanation of nacbracs

Below, these results come with diagrams. I've got higher-priority positions on my queue, but I hope you will feel free to roll these out. :)

Nack






White is Player 2

score: 0
pip: 194
Unlimited Game
Jacoby Beaver
pip: 194
score: 0

Blue is Player 1
XGID=-bb---D-C---dD---c-d---BB-:0:0:1:11:0:0:3:0:10

Blue to play 11


1.XG Roller++23/22(2) 6/5(2)eq: +0.245
Player:
Opponent:		55.51% (G:16.68% B:0.93%)
44.49% (G:11.13% B:0.53%)
2.XG Roller++24/22 6/5(2)eq: +0.239 (-0.007)
Player:
Opponent:		55.55% (G:16.59% B:0.93%)
44.45% (G:11.32% B:0.54%)
3.XG Roller++23/21 6/5(2)eq: +0.236 (-0.010)
Player:
Opponent:		55.46% (G:16.43% B:0.89%)
44.54% (G:11.14% B:0.59%)
4.XG Roller++8/5 6/5eq: +0.199 (-0.046)
Player:
Opponent:		54.29% (G:16.95% B:1.00%)
45.71% (G:11.75% B:0.62%)
5.XG Roller++8/7(2) 6/5(2)eq: +0.161 (-0.084)
Player:
Opponent:		53.90% (G:15.72% B:0.87%)
46.10% (G:13.05% B:0.75%)
White is Player 2

score: 0
pip: 194
Unlimited Game
Jacoby Beaver
pip: 194
score: 0

Blue is Player 1
XGID=-bb---D-C---dD---c-d---BB-:0:0:1:22:0:0:3:0:10

Blue to play 22


1.XG Roller++13/11(2) 6/4(2)eq: +0.217
Player:
Opponent:		54.80% (G:17.15% B:1.08%)
45.20% (G:12.03% B:0.65%)
2.XG Roller++23/21(2) 6/4(2)eq: +0.161 (-0.056)
Player:
Opponent:		53.49% (G:15.03% B:0.76%)
46.51% (G:10.84% B:0.43%)
White is Player 2

score: 0
pip: 194
Unlimited Game
Jacoby Beaver
pip: 194
score: 0

Blue is Player 1
XGID=-bb---D-C---dD---c-d---BB-:0:0:1:33:0:0:3:0:10

Blue to play 33


1.XG Roller++23/20(2) 13/10(2)eq: +0.235
Player:
Opponent:		55.12% (G:16.01% B:0.76%)
44.88% (G:9.39% B:0.35%)
2.XG Roller++13/7(2)eq: +0.191 (-0.044)
Player:
Opponent:		54.22% (G:16.47% B:0.97%)
45.78% (G:11.99% B:0.61%)
3.XG Roller++23/20(2) 6/3(2)eq: +0.175 (-0.060)
Player:
Opponent:		53.56% (G:15.25% B:0.78%)
46.44% (G:9.92% B:0.34%)
4.XG Roller++23/20(2) 8/5(2)eq: +0.174 (-0.061)
Player:
Opponent:		53.31% (G:16.16% B:0.78%)
46.69% (G:10.34% B:0.41%)
5.XG Roller++24/21(2) 23/20(2)eq: +0.165 (-0.070)
Player:
Opponent:		53.64% (G:13.92% B:0.59%)
46.36% (G:9.68% B:0.30%)
White is Player 2

score: 0
pip: 194
Unlimited Game
Jacoby Beaver
pip: 194
score: 0

Blue is Player 1
XGID=-bb---D-C---dD---c-d---BB-:0:0:1:44:0:0:3:0:10

Blue to play 44


1.XG Roller++13/5(2)eq: +0.286
Player:
Opponent:		55.63% (G:19.90% B:1.27%)
44.37% (G:11.37% B:0.61%)
2.XG Roller++24/20(2) 13/9(2)eq: +0.250 (-0.036)
Player:
Opponent:		55.40% (G:16.38% B:0.85%)
44.60% (G:9.45% B:0.33%)
White is Player 2

score: 0
pip: 194
Unlimited Game
Jacoby Beaver
pip: 194
score: 0

Blue is Player 1
XGID=-bb---D-C---dD---c-d---BB-:0:0:1:55:0:0:3:0:10

Blue to play 55


1.XG Roller++23/18(2) 13/8(2)eq: +0.180
Player:
Opponent:		54.08% (G:15.78% B:0.73%)
45.92% (G:11.49% B:0.46%)
2.XG Roller++23/18 13/3 8/3eq: +0.123 (-0.057)
Player:
Opponent:		52.15% (G:17.15% B:1.10%)
47.85% (G:12.38% B:0.61%)
3.XG Roller++23/18 23/8eq: +0.098 (-0.082)
Player:
Opponent:		52.18% (G:14.83% B:0.75%)
47.82% (G:12.27% B:0.56%)
4.XG Roller++23/8 13/8eq: +0.096 (-0.084)
Player:
Opponent:		51.88% (G:15.30% B:0.76%)
48.12% (G:12.28% B:0.57%)
5.XG Roller++23/13(2)eq: +0.095 (-0.086)
Player:
Opponent:		52.14% (G:14.35% B:0.69%)
47.86% (G:12.28% B:0.51%)
6.XG Roller++13/3(2)eq: +0.092 (-0.088)
Player:
Opponent:		51.05% (G:17.56% B:1.09%)
48.95% (G:12.89% B:0.64%)
White is Player 2

score: 0
pip: 194
Unlimited Game
Jacoby Beaver
pip: 194
score: 0

Blue is Player 1
XGID=-bb---D-C---dD---c-d---BB-:0:0:1:66:0:0:3:0:10

Blue to play 66


1.XG Roller++24/18(2) 13/7(2)eq: +0.399
Player:
Opponent:		59.24% (G:18.13% B:1.05%)
40.76% (G:9.46% B:0.34%)

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