Re: [Bug-gnubg] Re: more on bearoff databases

[Joern Thyssen]

On Sun, Oct 27, 2002 at 11:46:09AM -0600, Neil Kaz wrote
> Embedded comments inside prefaced by (NK)
> ----- Original Message -----
> From: "Joern Thyssen" <address@hidden>
> To: "GNU Backgammon Bugs" <address@hidden>
> Cc: "Neil Kaz" <address@hidden>
> Sent: Sunday, October 27, 2002 4:06 AM
> Subject: more on bearoff databases
> >
> > #pts #positions size(unc) estimated size comp
> > 11    7,726,160       988,948,480 250 MB
> > 12 17,383,860 2,225,134,080 550 MB
> > 13 37,442,160 4,792,596,480   1200 MB
> > 14 77,558,760 9,927,521,280 2500 MB
> >
> > So the practiacal limit appears to be the 12-pt or perhaps the 13-pt
> > databases. So if we want to go further we have to do something else:
> >
> (NK) I'd stop at the 13 point since this is where so many BG position become
> straight races. Even most midpoint to midpoint contact is essentially a
> straight race, but we may wish to ignore the database for playing with any
> midpoint contact. However, if there are a couple other checkers for both
> sides in the outboard, the database evaluation of racing chances with
> midpoint contact should be fine for cube evaluation purposes.
> 
> I'd stop the database at the 13 point (mid point) and add only the following
> expansion which would continue the database further out with 1 or 2 checkers
> only on points higher than the midpoint. This will be used only in non
> contact and will not require that many more positions (or will it) 

Unfortunately there are 10M positions with 13 chequers on 13 points, and
15 positions with 2 chequers on five points, hence a total of 150M
positions.

> (NK) I don't see how a normal distribution can pick up on wastage effects
> or tell GNU how to properly play during the bear in.

I keep the mean and the variance for the roll distribution, so I think
wastage effects are accounted for. 

If you have some bear-in examples that any bots misplay, I can check with
my bearoff databases?! So far I just have the 10 pt databases.

Jørn

-- 
Joern Thyssen, PhD
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