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Nactation Question 04

Posted By: Taper_Mike
Date: Tuesday, 29 November 2011, at 11:53 a.m.

In Response To: Nactation Question 04 (Mochy)

Nice work!

Your Nactations using the E (Each) and M (Mayfair split) families are perfect:

64S-51H-11 [E E23 m58 M92] &e




White is Player 2

score: 0
pip: 161
Unlimited Game
Jacoby Beaver
pip: 164
score: 0

Blue is Player 1
XGID=-b----E-CA--dD---cae----AA:0:0:1:11:0:0:3:0:10
Blue to play 11

I have appended a lower case "e" at the end of your nacbracs to emphasize that they are based on an eval. As Nack mentioned in another post, that may be redundant. As well, it is customary to include one space after the closing square bracket.

In an assumptive Nactation, two assumptions seem reasonable:

  1. Entry from the bar uses one die.
  2. Making the 5pt uses two more.
Thus, assumptive Nactation requires only that the last ace be nactated.

All of your choices are fine, except, perhaps, S (Split). In normal backgammon writing, "split" means to advance one of the rear checkers (usually by breaking the 24pt). When you chose S (Split), you were thinking about this meaning of "split."

In Nactation, "split" has a slightly different meaning. It denotes a move in which one die is played on the far side of the board, and the other die is used to bring a checker into the outer board from the opponent's outer board. More consisely, it means "split and down." There is always a down component to a play that is nactated in the S (Split) family.

The B, S and Z families were described in a recent post, the jist of which is summarized in the following table.

Family Non-doublets Doublets
B One die is played on the far side, and one die is played entirely within the outer board (on the near side). Two dice are played on the far side, and two dice are played down.
S The larger die is played on the far side, and the smaller die is played into the outer board from the opponent's outer board. When no such play exists, S can also be used as an alternative to Z. Three dice are played on the far side, and one die is played down. When no such play exists, S can also be used as an alternative to Z.
Z The smaller die is played on the far side, and the larger die is played into the outer board from the opponent's outer board. One die is played on the far side, and three dice are played down.

In all of these definitions, "down" refers to, "A move made to or within the outer board. The checker must land in the outer board on the near side, but can be moved from any point in either outer board."

A play on the far side of the board means, "The entire move is made on the far side of the board, including entering a checker from the bar. The checker can land anywhere on the far side, from the midpoint on up."

The following table shows the S (Split) family for the position above.

S (Split) Family
Traditional
Notation		 Far
3		 Down
1		 Jump
0		 Inside
0		 Hits on
These Points
(more is better)
(higher is better)		 Owned Points Not Held
by All Members in Family
(more is better)
(closer to 6pt is better)		 Blot and Spare
Destinations
(closer to 6pt is better)
(outer board: farther is better)		 Nactation
bar/23, 24/23, 9/8 bar/24
24/23
24/23		 9/8 23pt 8pt* S
bar/23, 24/23, 8/7 bar/24
24/23
24/23		 8/7 23pt 7pt* s
bar/22, 9/8 bar/24
24/23
23/22		 9/8 8pt* S
bar/22, 8/7 bar/24
24/23
23/22		 8/7 7pt* s

*This is the deciding criterion.

None of the these moves are remotely competitive, so perhaps you can get away with your choice of S (Split). Another possibility might be U (Up). The problem is that U = bar/21.

Mike

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