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Nacbracs -- explanation

Posted By: Nack Ballard
Date: Sunday, 31 January 2010, at 6:09 p.m.

In Response To: free drops (christian munk-christensen)

The 64 should off course be 14* - I am not too comfortable with the nacbracs.

How should that be written?

The Nactation for 24/14* is either H (Hit) or R (Run). To get comfortable with Nactation (I assume that's what you meant), here is an explanation.

In case you don't already know this, "21S-64" means that the opening roll is 21 played as "S" (Split, 24/23 13/11) and that 64 is now rolled in reply.

The term "nacbracs" is short for "Nactation brackets." This is a method of describing plays and their error sizes (for a given position) in condensed form.

For example,

21S-64 [H P120]

This means that for the position 21S-64, H (Hit, 24/14*) is the best play or money, and P (Point, 8/2* 6/2) is an error of .120 (according to truncated rollout, in this case). That is, error sizes are listed in thousandths of a point.

Here is a position where the two plays (S = Split 24/21 13/8, and P = 8/3 6/3) are a lot closer:

21S-53 [S P11] 31k

The above is a Snowie rollout that indicates S is better than P by a margin of .011. The number to the right of the brackets indicates the number of trials, in thousands (rounded down) -- usually though not always a multiple of 1296. Here, "31k" stands for 31104.

By contrast, Gnu's rollout shows P to be slightly better:

21S-53 [P S2.6] 46k

Here, I've introduced a decimal point. (GnuBG provides the option of displaying more than three decimal places.) I could have rounded the margin to the nearest thousandth as "[P S3]," meaning that P is .003 better (than S), but I chose instead to represent it to the nearest ten-thousandth: [P S2.6] means that P is .0026 better, according to a rollout of 46656 trials.

And, more recently, we have an XG (3-ply) rollout of

21S-53 [S P6] 15k

This result is in between that of Snowie and Gnu (a bit closer to the former's). S beats P by .006 (after 15552 trials).

Note that in the absence of some other indication, money is assumed. A good way to indicate that the rollout is at double match point (DMP), gammon go (GG) or gammon save (GS) is to add a "d," "s" or "g" just before the left bracket (or sometimes inside the brackets), like this:

21S-53 m[P S2.6] 46k
21S-53 d[S P1.9] 10k
21S-53 s[S P16] 5k

I repeated Gnu's money result on the first line. Normally, the "m" is omitted, though it is sometimes added in context for clarity, for example in a list like this or when one is flipping back and forth between scores.

The second line is Gnu's rollout at "d" (double match point), and the third line is its rollout at "s" (gammon save).

It is not necessary to repeat the "21S-53" on every line of a list. It can be written on a single line above the others (a common preference) or just mentioned somewhere close by in the text, or even in the title of the post.

I hope that helps you understand the nacbracs that you have been seeing in so many of the posts here. There is a wealth of information being offered in a small amount of space and I would hate for you not to reap the benefits.

I also recommend reading my post from a few weeks ago, entitled simply "Nacbracs."

Good luck,

Nack

• free drops
christian munk-christensen -- Saturday, 30 January 2010, at 9:38 p.m.
• free drops
Petter Bengtsson -- Saturday, 30 January 2010, at 10:05 p.m.
• free drops
Stick -- Saturday, 30 January 2010, at 10:17 p.m.
• free drops
David Rockwell -- Saturday, 30 January 2010, at 10:45 p.m.
• free drops
Petter Bengtsson -- Saturday, 30 January 2010, at 11:16 p.m.
• free drops
David Rockwell -- Saturday, 30 January 2010, at 11:43 p.m.
• free drops
Stick -- Sunday, 31 January 2010, at 8:45 a.m.
• free drops
Stick -- Sunday, 31 January 2010, at 8:44 a.m.
• free drops
christian munk-christensen -- Sunday, 31 January 2010, at 4:29 p.m.
• Nacbracs -- explanation
Nack Ballard -- Sunday, 31 January 2010, at 6:09 p.m.
• free drops
Timothy Chow -- Saturday, 30 January 2010, at 10:24 p.m.
• free drops
Mochy -- Sunday, 31 January 2010, at 12:34 a.m.
• free drops
Stick -- Sunday, 31 January 2010, at 8:49 a.m.
• free drops
Christian Plenz -- Sunday, 31 January 2010, at 2:50 a.m.
• free drops
christian munk-christensen -- Sunday, 31 January 2010, at 4:36 p.m.
• Rollouts
Stick -- Sunday, 31 January 2010, at 10:44 p.m.
• Rollouts
christian munk-christensen -- Monday, 1 February 2010, at 4:28 p.m.
• Rollouts
Stick -- Monday, 1 February 2010, at 4:39 p.m.

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