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Rollout, OTB, and commentary

Posted By: John O'Hagan
Date: Monday, 13 January 2014, at 12:06 a.m.

In Response To: 4a-7a cube action? (John O'Hagan)

I had the dark checkers in this position yesterday in our local monthly tourney. Blonde doubled, I took and ended up with a well-timed ace point game but missed a couple of shots in the bearoff and lost a g and the match.

D/T is correct per the RO. What's interesting is that the calc I and others usually do to figure the true tp in gammonish positions doesn't work in this position. i.e. Starting with the dead cube gammonless tp then adjust for gammons then subtract for cube ownership. Here that gives you roughly 30% + .6(.23) = 43.8% - .09 for cube vig = 34.8%.

This is wrong however. It's wrong because the gammon-adjusted tp (43.8% in the above paragraph) can't be over what it would be if Black takes and auto recubes on his next shake. So what's the tp if Black auto recubes?

Pass: 0-4 with 23.79% MWC.

Take and lose: 0-7 with 0% MWC.

Take and win: 4-3 with 57.15% MWC.

Take and win a gammon: 7-3 with 100% MWC.

That makes the gammon-adjusted tp (assuming 7.5% g's for Black) of 36%.

The leader's 4-cube tp is 26% so the true tp assuming 80% efficiency is ~ 28.5%(36% x 26% x 80% = 7.5%. 36% - 7.5% = 28.5%). At least I think this is mathematically sound (I'm sure Stick, Neil, UBK, Chuck, Nigel, or someone else will correct me if it isn't).

is Player 2

score: 0
pip: 160
7 point match
pip: 139
score: 3

is Player 1
XGID=-aB-aBB-Ba--cE--Bcada-----:0:0:1:00:3:0:0:7:10
on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 67.55% (G:27.80% B:3.54%) 67.82% (G:29.54% B:4.48%)
Opponent Winning Chances: 32.45% (G:6.97% B:0.28%) 32.18% (G:7.48% B:0.31%)
Cubeless Equities +0.683 +1.497
Cubeful Equities
No double:+0.800 (-0.066)±0.017 (+0.784..+0.817)
Double/Take:+0.866±0.025 (+0.841..+0.891)
Double/Pass:+1.000 (+0.134)
Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence:100.0%
Take Decision confidence:100.0%
Duration: 41 minutes 48 seconds

eXtreme Gammon Version: 2.00, MET: Kazaross XG2

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