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62S-51H-55B-33B-63

Posted By: Nack Ballard
Date: Wednesday, 19 February 2014, at 7:49 a.m.

In Response To: Tricky DMP Play (Paul Weaver)

Need a bit of help nactating the doubles. 62S-51H-55-33-63

Sure thing, Paul. The short answer is that the 55 and 33 are both B. For a full answer, though, I address the 55, the 33, and also the 63 (each separately) below.






White is Player 2

score: 0
pip: 161
Unlimited Game
Jacoby Beaver
pip: 166
score: 0

Blue is Player 1
XGID=-b----E-C--AdD---cae----AA:0:0:1:55:0:0:3:0:10

62S-51H-55


To nactate a move (non-doublets or doublets) using an areal letter, identify the area (far, down, jump, or inside) where each move portion is played.

Blue's best move with his roll of 55, which is bar/20 20/15 15/10 13/8, has two fars (portions played on the far side) and two downs (portions played to or within the outer board). Any move with two fars and two downs is in the B family.

There is only one way to play two far side portions: bar/20/15. There are two ways to play two down portions: Either 15/10 13/8, or 13/8(2). By 6pt convention, capital B is awarded to the former, and the lower case "b" to the latter.

Familial ranking in Nactation is structured so that the best play earns the capital letter most of the time. In the outer board, blot/spare destinations farther from the 6pt rank higher. This has the effect of rescuing blots in the far outer board (e.g., the 15pt blot here) and putting blots or spares on higher quality points (farther from the 6pt tends to mean less likely to be hit or less stacky). If you don't remember the 6pt convention, you can just use the capital letter for the stronger-looking play and you'll be right most of the time! (A fringe benefit is that use of "assumption" is supported.)

In short, B = bar/10 13/8. Another example of this move (which happens to hit) can be seen here (White's fourth roll play, second diagram).

For bar/20 13/3 8/3, you can use P (Point) or M (Magnify).
For bar/10 11/6, you can use L (Lift) or F (Field).
For bar/5, you can use $ (Slot) or f (field) [or 5 (5pt).]

For the basics of the areal concept, review the end of section 5 (under #24) of the Nactation tutorial. For doublet examples of B, see #9, 39.3 and (especially) #77. For tri-areal doublets, read the entitled segment above #90, and for examples of F and M see #91. Style characters: For P, see #37 and #6566. For L, see 36.4 and #6970. For $, see #4, #2930 and #7273. For "assumption," see section 8 (page 35).






White is Player 2

score: 0
pip: 161
Unlimited Game
Jacoby Beaver
pip: 146
score: 0

Blue is Player 1
XGID=-b----E-D-AAdC---cae----A-:0:0:-1:33:0:0:3:0:10

62S-51H-55B-33


Here, White's standout move is 24/21(2) 13/7. This move has two "fars" and two "downs" (similar to Blue's 55B move just played) and is therefore in the B family. (For examples of B, see #9, 39.3 and #77 in the tutorial.)

This may be more than you ever need to know, but for reference there are four B-family plays:

........B = bar/21(2) 13/7
........b = bar/21(2) 13/10(2)
........B = bar/18 13/7
........b = bar/18 13/10(2)

The "more points" convention dictates that the first pair (which make an extra point, the 21pt) rank higher than the second pair of moves.

By (the first part of) the 6pt convention, the (owned) 7pt is closer to the 6pt than is the 10pt. That is the reason the first move trumps the second move, and the third move trumps the fourth move.

Alternatively, it is enough to see that bar/21(2) 13/7 is obviously the strongest move that fits B-family specifications (two fars and two downs). In Nactation (by design), the cream generally rises to the top, as evidenced by the use of capitals for the overwhelming majority of moves people play in backgammon. By the same token, it is no accident that the strength ranking of the four moves and the familial ranking of the four moves is the same.

Other moves aren't nearly as strong as B, but here they are anyway: A (Attack) = 8/5(2) 6/3(2); E (Each) = 24/21(2) 6/3(2); R (Run) = 24/21 24/15*; O (Outer) = 13/7 8/5(2); H (Hit) or S (Split 3:1) = 24/15* 13/10; C (Cross) = 24/21(2) 8/5(2). The XG evaluation is [B A86 E93 R113 O143 S148 C157 b164] "&e.






White is Player 2

score: 0
pip: 149
Unlimited Game
Jacoby Beaver
pip: 146
score: 0

Blue is Player 1
XGID=----b-E-D-AAcC---cbe----A-:0:0:1:36:0:0:3:0:10

62S-51H-55B-33B-63


Okay, so White played 33B. Here now are candidate moves for Blue's 63 in the final position:

........P (Point) = J (Jump) = 11/5 8/5
........p (point) = D (Down) = 13/7 10/7
........$ (Slot) = O (Outer) = 13/10 11/5
........% (alt slot) = o (outer) = 13/10 8/2

In nacbracs, use whatever characters you wish (style, areal, numerals, or a mixture). For your rollout results of 62S-51H-55B-33B-63 (diagrammed above), here are nacbracs with style characters:

..........[P $20 p40] "<=1
........d[$ P15 p19] "<=1
........s[P p17 $31] "<=1
........g[P $4 p43] "<=10*.6

A recent innovation is a best-play summary nacbracs for four scores. I haven't decided on exact formatting, but for 62S-51H-55B-33B-63 prototype possibilities are [P d$ sP gP], or simply [P$PP] or even [P d$].

In the introduction of the tutorial (second page), read the paragraph on "bookmarks." This is the fastest way to find diagrammed examples for all Nactation characters.

Explanation of nacbracs.

Nack

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