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Initial Double Mystery -- SOLUTION

Posted By: Nack Ballard
Date: Tuesday, 7 May 2019, at 3:09 p.m.

In Response To: Initial Double Mystery (Nack Ballard)





White is Player 2

score: 0
pip: 167
Unlimited Game
Jacoby Beaver
pip: 167
score: 0

Blue is Player 1
XGID=-b----E-C---eE---c-e----B-:0:0:1:00:0:0:3:0:10

One checker play on each side, Initial Double

Blue wins the (non-doublet) opening roll and does not make a point. In reply, White does not leave a direct shot. Nevertheless, back on roll, Blue has a correct initial Double, according to XGR++ evaluation.

What is Blue's play, and what is White's play?

SOLUTION

Congratulations to Karol Eyechart Szczerek, Bob Koca, John O'Hagan, Brian Lonergan and Joe Russell, for solving the Initial Double mystery!

The diagram below encapsulates the solution.






White is Player 2

score: 0
pip: 159
Unlimited Game
Jacoby Beaver
pip: 160
score: 0

Blue is Player 1
XGID=-b---ADAC---dDa----h----B-:0:0:1:00:0:0:3:0:10

61N-22O̥-C


Analyzed in XG Roller++ No double Double/Take
Player Winning Chances: 67.39% (G:23.82% B:1.54%) 67.52% (G:24.03% B:1.53%)
Opponent Winning Chances: 32.61% (G:8.27% B:0.38%) 32.48% (G:8.07% B:0.38%)
Cubeless Equities +0.515 +1.043
Cubeful Equities
No double:+0.780 (-0.031)
Double/Take:+0.811
Double/Pass:+1.000 (+0.189)
Best Cube action: Double / Take

Bonus kudos to Brian for his correct Nactation of 61N-22O̥ (see Nactation tutorial, page 100). "Outer" means to move both in (13/11) and out of (8/6) the outer board. An underline or underdot is added when the ratio is 3:1 or 1:3 (respectively). Thus:

.....O = 13/11(2) 8/6(2) (doublet) or 13/11 8/6 (non-doublet),
.....O = 13/11(3) 8/6, and
.....O̥ = 13/11 8/6(3)

In typing, you may find it easier to add the underscore or dot at the end: O_ or O. -- and if it is part of a sequence, the hyphen can be replaced. For example, 61N-22O̥-C or 61N-22O.C or 61N-22O.-C are all fine.

Honorable mention to Casper, who submitted the correct opening play (61N), and had the right idea for the reply (11T (sTack, 8/6(2)), but who isn't capable of playing poorly enough to have found the play that actually gets doubled (22O̥).

Nack

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