Author: Adrien Regimbald
Date: 17:15:08 06/23/00
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Hi, >It sounds like you have a bug, because my hashing apparently works just like >yours does, yet I don't see this often enough to give it any thought. IE in >the last couple of years, I can't remember a single game crafty drew because >of missing a repetition due to hashing... > >You might give your hash code a thorough look-see to see if anything seems >wrong. The problem seems to be entirely that I don't really handle cases where the score drops a lot on the PV at a new depth and Faile runs out of time to search. The way I deal with this case is rather crude - if Faile finished searching the PV branch before running out of time, it will return its result, otherwise it will say the search failed due to time and the result won't be trusted. If the score dropped significantly against the last depth's result, I just gamble and go with the move from the last depth. I imagine that the big difference here is that (if I recall correctly), Crafty does do something a bit less braindead here, and will try to search for a better move if its score drops. The problem is purely a result of running out of time after searching the PV but before having a chance to finish another branch. If I modify Faile to ensure that it finishes examining all root moves after it has begun a search at a particular depth, this problem does not occur. I suppose that the prudent thing to do would be to write a function to re-allocate some extra time when the score drops too much.. ;) I will certainly look into it! Adrien.
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