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xxP-64P-32

Posted By: Nack Ballard
Date: Saturday, 24 April 2010, at 8:04 p.m.

In Response To: xxP-64P-32 (mtuhtan)

Great set of positions, Miran, and terrific job on the nacbracs!

As you wrote:

61P-64P-32 [S U3 D18 Z22 T23 p52] 31k 10kD 2kp
31P-64P-32 [Z D13 S19 T34] 10k 5kT
42P-64P-32 [S D9 Z26 T41] 31k 2kZ
53P-64P-32 [D Z7 S8] 31k

S = 24/21 13/11, U = 24/22 24/21, D = 13/11 13/10, Z = 24/22 13/10, T = 13/8, p = 7/4 6/4

I have a couple of questions:

(1) Did you have a reason for excluding 64P-64P-32 from this set?

(2) Where is the T play for 53P-64P-32?

I see that U (Up, 24/22 24/21) is rolled out for only one of the positions. For completeness, I'll contribute the information that according to Snowie eval, U is 74, 59, and 61 (meaning -.074, -.059 and -.061 for the second, third and fourth positions, respectively); and for 53P-64P-32, T is 28.

I've added those U (and T) margins to the abbreviated summary below (the question marks mean they are evaluations only). I streamlined out the "k" info (thousands of trials), which can be consulted above, and omitted p (point, 7/4 6/4) as it is legal in only one of the positions.

61P-64P-32 [S U3 D18 Z22 T23]
31P-64P-32 [Z D13 S19 T34 U74?]
42P-64P-32 [S D9 Z26 T41 U59?]
53P-64P-32 [D Z7 S8 T21? U61?]

These four positions are diagrammed below, with the nacbracs encaptioned for easy reference. For anyone who wishes to you compare margins across positions, this will save hopping from rollout link to rollout link.


2O2X ' ' '4X '2X ' ' '4O

2X ' ' ' '5O2O2O ' ' '5X

61P-64P-32 ... [S U3 D18 Z22 T23]



2O2X ' ' '4X '2X ' ' '5O

2X ' ' '2O4O '2O ' ' '5X

31P-64P-32 ... [Z D13 S19 T34 U74?]



2O2X ' ' '4X '2X ' ' '5O

2X ' '2O '4O '2O ' ' '5X

42P-64P-32 ... [S D9 Z26 T41 U59?]



2O2X ' ' '4X '2X ' ' '5O

2X '2O ' '4O '2O ' ' '5X

53P-64P-32 ... [D Z7 S8 T21? U61?]


As you examine the positions and nacbracs above, note that it pays to position your builder(s) 6 pips away from vacant points (rather than already-made points). Hence, Z (reverse split, builder to 10pt) is best after making the 5pt (in large part, too, because 54 cannot hit the builder), S (Split, builder to 11pt) is optimal after making the 4pt, and D (Down, both 10pt and 11pt builders) edges out Z and S after making the out-of-6-range 3pt.

In the first (61P-64P-32) position, bringing builders down does poorly because the midpoint has already been reduced from five to four checkers; hence U (Up) goes all the way from being a blunder to being tied with S. The effect of distribution is huge.

I resonated with Casper's analysis, so I'll include it here as well:

In the case of a made home-board point, you bring builders down provided they bear on open points. So 2 down after 53; 11, 21 after 42; and 10, 22 after 31. This makes kind of sense, given the possibility to use the builders. The 61 result does not fit this pattern, possibly because having a home-point made is better for tactical exchanges and thus limit the risks of builder down plays.

Very instructive set of positions, Miran. Thanks!

Nack

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