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Playing X at gammon save

Posted By: Nack Ballard
Date: Tuesday, 12 October 2010, at 5:54 p.m.

This post is inspired by David's post and Tim's responses.

Below is all the data I seem to have so far for both money and gammon save for positions in which you have a reasonable option of X (hit-and-split), with the hit occurring on the 2pt or 1pt, on the second roll of the game.

I've emboldened the X play for emphasis. When splitting, simultaneously hitting (by virtue of "taking away half the roll") temporarily ameliorates the opponent's offensive threat, thereby increasing your chance of anchoring, the value of which is of especially great at gammon save.

The gammon save data is to the right of the money data.

21S-43
[Z X2 U20 D23 S23] ~31**20*
[X Z10 D19 S30 U32] /15**5* ... s[X S20] /5
[X Z2 S18 D19 U27] <62**31*
[Z=X D20] ^46 7

51S-43
[U D15 S17 Z20 X28] ~15
[U D3 S5 X6 Z14] /46***20 ...
[U D4 S9 Z10 X19] <62***52 ... s[X S4 U7 Z17 D25] <31**20 15
[U D6 S7 Z13 X17] ^46**7*

63S-52
[S X5] ~10
[X S7] /15 ... s[X S3] /15
[S X1] ^46

63S-53
[P X37] ~5
[P X25] /5 ... s[P X8] /15

41S-54
[S X4 R9] ~31
[X S6 R9] /31
[S X1 R10] <31 ... s[X S9 R24] <31

51S-54
[R S1 X40] ~31*5
[S R12] /15 ... s[S X12] /10
[S R4] <62

Key: X = hit and split, S = split (split and down), Z = reverse split (smaller split and down), U = Up, D = Down, R = Run. Error sizes are in thousandths.

"s" before the brackets means (gammon) save; else assume money. After the brackets is a bot symbol: ~ is Snowie, / is Gnu, < is XG 3-ply, and ^ is XG 4-ply. That symbol is followed by the number of trials (in thousands, rounded down) and an asterisk repeats a number.

For example, "s[X S4 U7 Z17 D25] <31**20 15" means that at (gammon) save, X is best, S is -.004, and U is -.007 after 31000+ trials, Z is -.017 after 20000+ trials, and D is -.025 after 15000+ trials (with < denoting an XG 3-ply rollout).

Nack