Author: Robert Hyatt
Date: 19:54:01 03/01/00
Go up one level in this thread
On March 01, 2000 at 17:19:38, Dann Corbit wrote: >On March 01, 2000 at 17:05:13, Dave Gomboc wrote: > >>On March 01, 2000 at 13:53:57, Dann Corbit wrote: >> >>>On March 01, 2000 at 10:28:56, Dave Gomboc wrote: >>>[snip] >>> >>>>Well, my computer resolved the fail high in twenty seconds or so. Odd. >>> >>>You have a multiple CPU machine (I think Bernhard does as well). I believe that >>>sometimes you will get different move orderings because of this and solve early >>>(or late). >> >>Yes. >> >>Occasionally Crafty does go on a "forever think", even on 1 cpu. I don't recall >>versions from say a year ago doing this. I'm sure Bob would do something about >>it if he knew of a good solution for it. Something somewhere must be blowing up >>somehow (as if that description helps. ;-) > >On the other hand, I am not sure it needs fixing. Look at the recent CCC >tournament where Crafty pounded the ether-bits out of all the competition, >including the best commercial programs in the world on top-notch hardware. > >The check extension explosions almost never cause crafty to make the wrong move >(that I have seen). If the timer fired and said "it's time to move now" it >seems like usually, it would make the right choice. It's just a bit puzzled >about exactly how good the choice is. > >Since "the proof of the pudding is in the eating" I'm not so sure it is a good >idea to 'fix' anything. These "hangs" are rarely extension problems. They are more commonly alpha/beta window problems. IE it is easy to search a position where most moves lead to mate, but the mates are not forced, so that the best score is just +.02... all the mates get pruned instantly. But on a fail high, where beta is relaxed to +inf, these mates can't be pruned, and now you have to search thru the forest of checks, mates, and shorter mates, to find the shortest mate. Often that can't be resolved inside the time limit. But who cares?
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