Revisiting this one - I read the eval.c ClassifyPosition code, so have a decent 
idea of how gnubg defines "crashed" (it's not what I described below).

What I don't get is why it uses this particular definition.

ie I'd imagine a crashed position is one where you're bearing in against an 
opponent anchor and have to start dismantling your beautiful barricade as the 
checkers come in.

So why isn't crashed something simple like "contact, and at least one player 
has all their checkers at their nine point or closer"? Seems like that's 
roughly when you'd start caring about how to bear off against an anchor. 

Or maybe you'd replace "nine point" with "six point" if you want to get closer 
to the end of the game. But I don't really see why how many checkers are on the 
1 or 2 point specifically matter than much (vs the 3 point, or why >1 checker 
is the threshold vs >0 checkers).

Anyone remember the motivation for the current definition? 



On Dec 17, 2011, at 12:22 PM, Øystein Schønning-Johansen wrote:

> 
> 
> On Sat, Dec 17, 2011 at 4:05 PM, Mark Higgins <[email protected]> wrote:
> I'm trying to find the exact definition gnubg uses for a "crashed" position.
> 
> The one reference I've found (Thomas Haug's thesis) says it's contact, plus 
> the restrictions that the player has fewer than 7 pieces remaining with none 
> in the opponent's 1 or 2 position. Is that correct? 
> 
> If so, can someone give a little color on why those particular restrictions? 
> eg why is it contact if the player has a piece on the opponent's 2 position, 
> but crashed if it's on their 3 position?
> 
> 
> The source is the documentation!
> http://cvs.savannah.gnu.org/viewvc/gnubg/gnubg/eval.c?revision=HEAD&view=markup
> 
> Search for the function called ClassifyPositon()
> 
> -Øystein

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