Re: [Bug-gnubg] Holding games

[Joseph Heled]

I suspect that just holding an anchor would mark too many positions. 
Probably many you would not consider as a "holding game".

My benchmark shows that 46.5% of the positions are classified as holding 
by your definition. The error rate definitely supports the claim that 
GNUbg errs more in those positions.

nonholding (57431 53.43%) 0.009573
   holding (50054 46.56%) 0.011446

-Joseph

Albert Silver wrote:
> I was gone this weekend so couldn't respond earlier.
>
>
> > > I don't think we need that many to make the case, but if you can
> > > generate some positions I'll put them through sagnubg.
> >
> > I agree. Still waiting for a clear cut definition of a holding game
>
> from
>
> > you guys. How about "No checkers on points lower than 18, decent
>
> contact
>
> > (say at least 3 points separate the back checkers), and no blots in
>
> the
>
> > area of contact?
>
>
> I'm not sure I understand your desription. As I see it, you have a
> holding game if you have an anchor on my 3-pt, 4-pt, 5-pt, or 7-pt (my
> bar point). For example:
>
> GNU Backgammon  Position ID: 4HPDAQbg2+DBAA
>                  Match ID   : cAkAAAAAAAAA
>  +13-14-15-16-17-18------19-20-21-22-23-24-+     O: GNU
>  | X        O  O  X |   | O                |     0 points
>  | X        O  O  X |   | O                |     
>  | X           O    |   | O                |     
>  | X                |   | O                |     
>  |                  |   | O                |    
> v|                  |BAR|                  |     (Cube: 1)
>  |                  |   | X                |    
>  |                  |   | X                |     
>  | O                |   | X                |     
>  | O           X  X |   | X     O          |     On roll
>  | O           X  X |   | X     O          |     0 points
>  +12-11-10--9--8--7-------6--5--4--3--2--1-+     X: Albert
>
> Here the Os have a 3-point holding game, and the Xs have a bar-point
> holding game. Of course, one of the big issues (highlighted by Neil) is
> that the bots tend to overestimate positions where the holder has a 3rd
> rear checker such as:
>
> GNU Backgammon  Position ID: 4LnhACPgbfBgIA
>                  Match ID   : cAkAAAAAAAAA
>  +13-14-15-16-17-18------19-20-21-22-23-24-+     O: GNU
>  | X        O  O  X |   | O              X |     0 points
>  | X        O  O  X |   | O                |     
>  | X           O    |   | O                |     
>  | X                |   | O                |     
>  |                  |   |                  |    
> v|                  |BAR|                  |     (Cube: 1)
>  |                  |   |                  |    
>  |                  |   | X                |     
>  | O                |   | X                |     
>  | O           X  X |   | X     O          |     On roll
>  | O           X  X |   | X     O        O |     0 points
>  +12-11-10--9--8--7-------6--5--4--3--2--1-+     X: Albert
>
> I wasn't too sure about what was meant with " no blots in the area of
> contact". Do you mean if the blot on 1 was on the 5 point instead? If
> so, it would still be a 4-point holding game, even if it could change.
>
>                                         Albert
>
>
>
> > > Neil Kazaross has made the observation that "most bots tend to cube
> > > holding games a bit late". If an expert of Neil's calibre has noted
>
> this
>
> > > feature then I'm inclined to take it seriously. One of the best ways
>
> to
>
> > > improve gnubg must be to identify classes of position where it is
>
> weak.
>
> > > Expert opinion will be very valuable for this.
> >
> > Agreed.
> >
> > -Joseph
>
>
>
>
>
>
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