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RE: [Bug-gnubg] Odd rollout results of classic reference position
From: |
Ian Shaw |
Subject: |
RE: [Bug-gnubg] Odd rollout results of classic reference position |
Date: |
Mon, 19 May 2003 15:06:56 +0100 |
> From: Ned Cross
>
> I think this would be a take if all of O's checkers were on
> the ace and 2
> pts, and even perhaps with 2 on the 3 pt. I think it's the
> distribution
> here that makes it a pass for O. Walter Trice had a good article on
> 1-checker closeouts in Gammon Village about a year or so ago.
> http://www.gammonvillage.com/backgammon/news/article_display.cfm?resourceid=1182
Thanks for the reference, Ned. I couldn't remember O's distribution offhand - 3
chequers on each of the 1, 2 & 3 points. The same situation applies. GnuBg
thinks it is a Take on evaluation, but the rollout has it as a pass. The No
double equity is less than 1.000 this time, even though O still makes bad
passes if X holds the cube.
Cube analysis
4-ply cubeless equity +0.552
0.776 0.000 0.000 - 0.224 0.000 0.000
Cubeful equities:
1. Double, take +0.959
2. Double, pass +1.000 ( +0.041)
3. No double +0.934 ( -0.025)
Proper cube action: Redouble, take
Cube analysis
Rollout cubeless equity +0.574
Cubeful equities:
1. Double, pass +1.000
2. Double, take +1.035 ( +0.035)
3. No double +0.998 ( -0.002)
Proper cube action: Redouble, pass
Rollout details:
Player Trailer owns 2-cube:
0.787 0.000 0.000 - 0.213 0.000 0.000 CL +0.574 CF +0.998
[0.000 0.000 0.000 - 0.000 0.000 0.000 CL 0.001 CF +0.002]
Player Leader owns 4-cube:
0.789 0.000 0.000 - 0.211 0.000 0.000 CL +1.157 CF +1.035
[0.000 0.000 0.000 - 0.000 0.000 0.000 CL 0.001 CF +0.002]
Full cubeful rollout with var.redn.
2592 games, seed 1206048640 using quasi-random dice and Mersenne Twister
Play and cube: 2-ply cubeful 100% speed [world class]
>
> I agree that it seems like X should be able to cash more
> games later by retaining cube access. I've seen this show up with GNUBg in
> other positions
> as well.
I'm concerned that there's a real problem here. Has anyone got a convincing
explanation as to how one can win more games by relinquishing the cube?
--Ian