Re: [Bug-gnubg] Odd rollout results of classic reference position

[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

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.

-Ned

----- Original Message ----- 
From: "ershaw" <address@hidden>
To: "GNUBackgammon bug reporting" <address@hidden>
Cc: "Ian Shaw" <address@hidden>
Sent: Sunday, May 18, 2003 8:22 AM
Subject: [Bug-gnubg] Odd rollout results of classic reference position


> Five off and one closed out is traditioanlly a take. A GnuBg rollout has
it
> as a pass. I've got no problem with that.
>
> What is odd is that the equit of No DOuble is greater than 1. How can this
> be? That would make it Too Good in a position where no gammons are
possible.
>
> This is yet another position where the doubler is seen to win more games
by
> doubling than by holding on to the cube. I would expect O to double X out
in
> some games if O has cube access. Therefore X ought to win less games if he
> gives up the cube. Something seems wrong. Is it me?
>
> --Ian
>
>     GNU Backgammon  Position ID: tw0AANp2dwAAAA
>                     Match ID   : UQkAAAAAAAAA
>     +24-23-22-21-20-19------18-17-16-15-14-13-+  O: gnubg
>   O | O  O  O  O       | O |                  |  0 points
>   O | O  O  O  O       |   |                  |
>   O | O                |   |                  |
>   O |                  |   |                  |
>   O |                  |   |                  |
>     |                  |BAR|                  |v
>     |                  |   |                  |
>     |                  |   |                  |
>     |          X  X  X |   |                  |
>     | X  X  X  X  X  X |   |                  |  On roll
>     | X  X  X  X  X  X |   |                  |  0 points
>     +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: user (Cube: 2)
>
> Cube analysis
> Rollout cubeless equity  +0.584
>
> Cubeful equities:
> 1. Double, pass         +1.000
> 2. Double, take         +1.061  ( +0.048)
> 3. No double            +1.013  ( +0.000)
> Proper cube action: Redouble, pass
> Rollout details:
> Player user owns 2-cube:
>   0.792 0.000 0.000 - 0.208 0.000 0.000 CL  +0.584 CF  +1.013
>  [0.000 0.000 0.000 - 0.000 0.000 0.000 CL   0.001 CF  +0.003]
> Player gnubg owns 4-cube:
>   0.795 0.000 0.000 - 0.205 0.000 0.000 CL  +1.181 CF  +1.061
>  [0.001 0.000 0.000 - 0.001 0.000 0.000 CL   0.002 CF  +0.003]
> Full cubeful rollout with var.redn.
> 1296 games, seed 1206724736 using quasi-random dice and Mersenne Twister
> Play and cube: 2-ply cubeful 100% speed [world class]
>
>
>
>
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