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Four Score -- R4 found

Posted By: Nack Ballard
Date: Sunday, 8 March 2015, at 11:17 p.m.

In Response To: Possible four-score position (Nack Ballard)





White is Player 2

score: 0
pip: 117
Unlimited Game
Jacoby Beaver
pip: 121
score: 0

Blue is Player 1
XGID=---CBBBbB---bB----beBb-aa-:0:0:1:53:0:0:3:0:10

Blue to play 53


After posting yesterday, I discovered the new position above, which adjusts my first position a compensatory 2 pips (which happens to give us the same pipcount as that of Tim's original position). Represented by nacbracs, the XGR++ evaluations for m, d, s and g (i.e., money, DMP, gammon save and gammon go), respectively, are

.....m.[J C23 R25 D34 O59]e
.....d..[R J1 C4 D18 O36]e
.....s...[D O37 R65 J77]e
.....g...[C J19 c59 Z73]e

C = Cross (20/15 8/5), c = cross (20/17 8/3), D = Down (13/10 13/8), J = Jump (8/5 8/3), O = Outer (13/5), R = Run (20/17 20/15), Z = reverse split (20/17 13/8).

Happily, according to 3-ply rollouts, for money J is able to (barely) fend off the typically understated R by at least .010, the apparent three-way DMP-tie is broken (R beats all rivals by at least .0045), and at gammon go C is able to stay ahead of J by at least .007. If and when I am able to verify these margins with 4-ply rollouts, I'll declare this to be an official R4 ("real" four-score position) and post all rollouts.

Nack

Nactation tutorial • explanation of nacbracs

P.S. It's inconsequential, but I listed a move incorrectly in my previous post. At the gammon go score, the fourth best play is c (cross, 20/17 8/3), not E (Each, 20/15 6/3).

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