Author: Bruce Moreland
Date: 16:14:57 07/11/01
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On July 11, 2001 at 18:57:02, Dann Corbit wrote: >On July 11, 2001 at 18:52:10, Bruce Moreland wrote: > >>On July 11, 2001 at 16:56:49, Artem Pyatakov wrote: >> >>>Thanks for the reply. Wow, that does sound like a really good solution to the >>>problem... One last question, even with your explanation of what Gerbil is >>>doing, I am still not good enough to find where he is actually hashing the >>>"useful" en passant squares. >>> >>>Could you or Bruce point me to where this hashing of EP squares is actually >>>done? >>> >>>Artem Pyatakov >> >>It's not. I completely ignored the problem. >> >>The next version hashes in en-passant and castling for purposes of detecting 3x >>repetition, but other than that it doesn't do anything with castling or >>en-passant yet. > >I must misunderstand your code then, because in makemove, I can see you dealing >with the e.p. status flag. There are two things I have to deal with. One is executing the en-passant capture, and the other is setting up the next ply if someone just played e2-e4. The current code just checks to see if there is a black pawn on d4 or f4 before setting the en-passant square to e3. The reason I do it like that is that's what I do in Ferret. Actually it's probably okay to dummy-check it in makemove (like I do). If I dummy check it in hash table probe/store, that's twice I have to deal with it. But perhaps that's the right place to XOR in the en-passant and castling hash crap. Maybe I'm on drugs. But Gerbil doesn't change the hash key based upon en-passant square or castling flags now (and neither does Ferret). Ferret handles it when it's doing opening book stuff (which uses the hash key) and 3x repetition checking, and Gerbil will in the next release. bruce
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