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nactation middlegame pos.

Posted By: Nack Ballard
Date: Friday, 25 December 2009, at 7:08 a.m.

In Response To: nactation middlegame pos. (Andreas)

Andreas: We got the following position in our OLM at Hardy's forum:

180


1O ' ' '2X3X1O2X2X ' '2O

2O2O1O2X2O2O ' ' '2O '2X

Blue trails 4-5 to 7119

Position ID: sLNhgGFbNoxBIA Match ID: cIkQAAAAAAAA

The move chosen by the team was 10/6 10/9 -> how to nactate? (D with "6 convention"?)
Alternatives were 18/14 10/9 (no idea how to nactate)
and the (imho not total obvious)blunder 18/14 3/2. (possibly L?)

Experts please advice :-)

----------------------------------

Nack: I don't know. I'll have to kick this upstairs and ask a real expert.

Just kidding.

10/6 10/9: I like O (chosen by David and Matt). The strict definition states that half the move is played out of the Outer board (10/6) and the other half is played into the Outer board. That's not the same as within, but as there is no other possible O move and into/within is a small technicality. [Btw, when I refer to "the outer board" I always mean the one on the player's near side.]

I'd say that equally good is J (Jostle). The simple (listed) definition is sliding a blot within the outer board (usually a pip or two), but by broader definition since there is no blot you just move what you can (10/9), then apply the 6pt convention for the rest of the move. In short, O and J both qualify by default.

A fine alternative to O and J (and perhaps technically best) is 6. After moving the 4 to the 6pt, you play the ace to the destination closest to the 6pt which is the 9pt. [Note that you can't count the 5pt as a destination because it would violate the choice of 6 itself: 10/6/5 is the same as 10/5 and would become "5."]

There is even a fourth reasonable choice, which is "i." (Matt was close with his guess of I.) My current guideline for I is that it preferably moves one checker in (because that definition fills a better niche in the system); thus I is 10/5 and "i" is 10/6 10/9 (closest to 6pt with the other checker). However, I'm still contemplating the specifics of the I rules.

David and Matt are right that D is 13/8 (though I'd use 8 if that were the move). N was also mentioned in passing, but it is the ugly 13/9 6/5, not 10/6 3/2 (while n is 13/9 3/2).

For the other two moves, the main piece of information I think you all lack is that the entire far side minus the midpoint (25pt to 14pt) is actually considered the back quadrant for most purposes. If you think of 18/14 like a back checker move (with the exception of applying U/V to it), nactating middle game moves will be much easier.

Another piece of information (mentioned in a couple of posts a while back) is that S applies even when you are not breaking an anchor. Just imagine one of your back blots (or lone back checker) is splitting even though it is just "scooting," a substitution word suggested by Bob Koca. For such a case, if you like, S can be thought of as Scoot-and-down instead of Split-and-down. :)

Here, 24/23 13/9 is 41S (split), or 41Z (reverse split) if you prefer, but that is the only play that fits the definition of a split/scoot. You may be thinking, "Why can't 18/14 11/10 be S?" Answer: a splitting move includes coming down with a checker. If I were to expand the S definition to include playing aces within the outer board, the destination quadrant would be consistent, but then opening 21S would be 24/22 8/7 and 41S would be 24/20 8/7 and we wouldn't retain S for the standard 21 and 41 opening splits.

I did, however, broaden the definition of B (the simplistic one being "Both up and down") to include aces within the outer board. For a doublet example, consider 31P-63S-11: B is 24/23(2) 8/7*(2) and b is 24/22 8/7*(2). For a non-doublet example, consider 21$-62Z-425-41: B is 22/18 8/7. (Or for opening 41: B is the unorthodox 24/20 8/7, as mentioned.)

18/14 10/9: By now, you've probably figured out that B is a valid answer. (David was on the right track looking in the "BEACON for non-doublets" section; it's just that B doesn't appear there yet.)

It's slippery, but in the past (before modifying B) I used "s" for a move like 18/14 10/9. The only move that fits the S criteria is 24/23 13/9, so using "s" telegraphs a code violation, and the smallest breach is to allow a 1 to move within the outer board instead of down to it. [You can't use Z because it (as well as S) describes 24/23 13/9, as mentioned previously. You might manage to convey your intention with z, but the additional violation of splitting with the larger instead of smaller number puts the deductive interpretation further out of reach.]

Another correct answer for 18/14 10/9 is the italic R. The hierarchy for run characters is R, r, R, r. 18/13 is R, and 18/14 24/23 is r. Having exhausted the moves that run the back checkers 5 pips, you are allowed to move the lead back checker 4 pips and use the ace to move the next closest checker to the extended back quadrant (25pt through 14pt), and since the midpoint checkers cannot legally move an ace, it defaults to the 10pt. 18/14 10/9 is therefore allocated the third character in the hierarchy, R.

18/14 3/2: With the benefit of the background above, this move is now within your grasp. The letter E refers to Each inner board, but with the extended back quadrant the 18pt checker is eligible to move. Applying the 6pt convention, E is 18/14 6/5, e is 18/14 3/2, and (italic) E is 18/14 2/1 (lol). Yours is the one in the middle, "e."

You, David and Matt, perhaps with a bit of luck, all correctly supplied the alternative of L, which I like best here. L means Lift a blot to safety. My current priority rules are: Lift to the destination closest to the 6pt, with a leftover number don't break a point, and after that closest to 6pt (destination). Thus, L is 18/14 3/2, and "l" (lower case L) is 10/6 3/2. (Italic) L is 13/9 3/2.

[Note that none of the T hierarchy (T, t, T nor t) apply to a 3/2 move because a sTack/Tower is at least four checkers on a point. Indeed, T is 6/2 3/2, and t is 5/1 2/1!]

Answer summary:

10/6 10/9 is O, J, 6 or i.
18/14 10/9 is B or R (or possibly s).
18/14 3/2 is e or L.

Nack

180


1O ' ' '2X3X1O2X2X ' '2O

2O2O1O2X2O2O ' ' '2O '2X

Blue trails 4-5 to 7119

Position ID: sLNhgGFbNoxBIA Match ID: cIkQAAAAAAAA

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