RE: [Bug-gnubg] Holding games

[Albert Silver]

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
> 
>