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Re: [Bug-gnubg] Strange bearoff analysis
From: |
Joern Thyssen |
Subject: |
Re: [Bug-gnubg] Strange bearoff analysis |
Date: |
Thu, 12 Jun 2003 19:12:54 +0000 |
User-agent: |
Mutt/1.4.1i |
On Thu, Jun 12, 2003 at 08:21:40PM +0200, Jim Segrave wrote
>
> Using gnubg (development tree) from June 4th, still with 0.13b weights.
> I was analysing a match I played against it with 2 ply more or less
> Supremo settings when this came up:
>
> (jes) set matchid UQnrAFAAKAAA
> (jes) set board OwAAwCYAAAAAAA
> GNU Backgammon Position ID: OwAAwCYAAAAAAA
> Match ID : UQnrAFAAKAAA
> +24-23-22-21-20-19------18-17-16-15-14-13-+ O: gnubg
> OO | O O | | | 5 points
> OO | O O | | |
> OO | O | | |
> OO | | | |
> OO | | | |
> | |BAR| |v 7 point match
> XX | | | |
> XX | | | |
> XX | | | |
> XX | X X | | | Rolled 62
> XX | X X X | | | 5 points
> +-1--2--3--4--5--6-------7--8--9-10-11-12-+ X: jes (Cube: 2)
>
>
>
> Analysis and hints both say (this is the hint output, but the analysis
> is identical in it's values)
>
> 1. Cubeful 0-ply 4/off Eq.: +0.906
>
> 0.953 0.000 0.000 - 0.047 0.000 0.000
> 0-ply cubeful [expert]
> 2. Cubeful 0-ply 4/off 2/off Eq.: -0.925 ( -1.831)
> 0.037 0.000 0.000 - 0.963 0.000 0.000
> 0-ply cubeful [expert]
>
> Now I simply cannot see how taking two men off is a -1.831 blunder. In
> fact, there's one case where taking 2 men off matters - gnubg rolls
> doubles and I follow with double 1's. If I have two pieces on both the 1
> and 2 points, I will lose, if I have only 3 pieces, I will still win.
I can't reproduce your results. I get:
(jth) set evaluation chequerplay evaluation plies 0
`eval' and `hint' chequerplay will use 0 ply evaluation.
(jth) hint
1. Cubeful 0-ply 4/off 2/off Eq.: +0.516
0.758 0.000 0.000 - 0.242 0.000 0.000
0-ply cubeful [expert]
2. Cubeful 0-ply 4/off Eq.: +0.500 ( -0.016)
0.750 0.000 0.000 - 0.250 0.000 0.000
0-ply cubeful [expert]
In both cases O has roughly 1/6*5/6 + 5/6*5/6*1/6 = 25% (approx), so
this analysis looks right.
Can you try setting up the two resulting positions with gnubg on roll,
and post the output from "eval", please?
Jørn