Re: OSR [Was: Re: [Bug-gnubg] call for cycles (unix/libux only for now)]

[Joern Thyssen]

On Thu, Aug 01, 2002 at 08:06:01AM +1200, Joseph Heled wrote
> Joern Thyssen wrote:
> > 
> > On Wed, Jul 31, 2002 at 01:18:09PM +1200, Joseph Heled wrote
> > >
> > > BTW, are you aware of the work I done about race doubling?
> > 
> > Not really. Can you elaborate?
> 
> When cube > 1, My cube code estimates the equity by  'a * live + (1-a) * dead'
> For contact positions, the best empirical value I found is a = 0.7

This is identical to gnubg (except that gnubg uses 0.68 for contact,
0.60 for BEAROFF1 and BEAROFF2, and some linear interpolation for
CLASS_RACE).

> For race, I developed another model
> 
>   a = M * P * I
> 
>   M = a magic scaler (0.0606)
>   P = average number of rolls to race end.
>       (Take the smaller value computed for the two players.)
>   I = redouble incentive

It was something like that I was looking for.

> P is obtained from a modified pip count. Wastage is accounted for by
> adding 2.5 points for every checker on the 1 point, 2 for checkers on
> the 2 point etc., and the total is divided by 8.16

If 'a' is to be used with a OSR, the average number of rolls from the
OSR or BEAROFF2 can be used.

> I is 'G/L', where G (gain) is (equity after redouble - equity at
> current cube) when he wins, and L is same when he loses. I tried to
> capture the "eagerness" of the cube holder to redouble.

So at -4, -5 with a centered cube:

G = MWC(-2,-5) - MWC(-3,-5) ~= 75% - 66% = 9%
L = MWC(-4,-4) - MWC(-4,-3) ~= 50% - 41% = 9%

So I = 1 in this case. Also, for money I = 1.

At -3, -4 the same calculation gives: I = 1.5

I think this should be easy to implememt in gnubg as well.

Jørn

-- 
Joern Thyssen, PhD
Vendsysselgade 3, 3., DK-9000 Aalborg, Denmark
+45 9813 2791 (private) / +45 2077 2689 (mobile) / +45 9633 7036 (work)