CRASHED attempts to capture the positions where one side has only a small number of "active pieces". The number of active pieces has been arbitrarily set at 6, and the definition requires that you have at most 6 checkers not on points 1 or 2, accounting for the possibility of one checker from 2 sent back after the rest piled on point 1.
The most important part in this celebration of arbitrary decisions was to use a definition which is non cyclic - positions resulting from a crashed positions should be crashed. When this is violated, performance deteriorates since each net is trained only on it's own kind of positions. That was my experience anyway. I will be happy to see someone coming up with a better definition and performance. GNUbg pathetic play in many backgame situations leaves it open to abuse from humans. -Joseph On 9 February 2012 00:23, Mark Higgins <[email protected]> wrote: > 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 > > > > _______________________________________________ > Bug-gnubg mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/bug-gnubg > _______________________________________________ Bug-gnubg mailing list [email protected] https://lists.gnu.org/mailman/listinfo/bug-gnubg
