Re: [Bug-gnubg] Bug: Double/Beaver

[Christopher D. Yep]

At 12:51 PM 8/21/2003 +0000, Jørn Thyssen wrote:
> On Thu, Aug 21, 2003 at 08:35:25AM -0400, Christopher D. Yep wrote
>
> > Here is the output from Analyse - Evaluate:
> >
> >         Win     W(g)    W(bg)   L(g)    L(bg)   Equity    Cubeful
> > static:  42.0%   34.2%    7.7%   12.8%    0.1%   -0.159    +0.032
> >  1 ply:  42.6%   28.6%    6.2%   11.1%    0.1%   -0.148    -0.396
> >  2 ply:  38.3%   28.2%    6.2%   14.7%    0.0%   -0.235    -0.389
> >
> > Cube analysis
> > 2-ply cubeless equity  -0.038
> >    38.3%  28.2%   6.2% -  61.7%  14.7%   0.0%
> > Cubeful equities:
> > 1. Double, take         -0.236
> > 2. Double, pass         +1.000  ( +1.236)
> > 3. No double            -0.389  ( -0.153)
> > Proper cube action: Double, beaver
>
> This is _before_ the double. Try _after_ the double!

Oops, I wasn't thinking clearly.  My eyes were immediately drawn to the 
-0.235 without looking at the column headings!

> No, the equity-column is supposed to be the cubeless equity, but I can
> see there is a small bug in the calculation. The cubeful column is the
> interesting one.

Right, the cubeless equities reported don't seem to match up with the 
win/gammon/backgammon figures reported.  E.g. 2-ply cubeless equity should 
be .383 + .282 + .062 - (1 - .383) - .147 - .000 = -.037.

Here's Analyse - Evaluate after I move a 2-cube over to the other side:

        Win     W(g)    W(bg)   L(g)    L(bg)   Equity    Cubeful
static:  42.0%   34.2%    7.7%   12.8%    0.1%   +0.131    -0.066
 1 ply:  42.6%   29.0%    6.8%   11.2%    0.1%   +0.096    -0.083
 2 ply:  38.3%   28.6%    7.1%   14.9%    0.0%   -0.027    -0.107

Ok, so now I match your reported numbers exactly (you wrote: "0.383 0.286 
0.071 0.149 0.000 -0.027 -0.107").  But that means that there's another bug 
as -0.107 is quite different from -0.236.

Chris