Author: Bruce Moreland
Date: 22:45:32 07/11/01
Go up one level in this thread
On July 12, 2001 at 00:00:20, Robert Hyatt wrote: >On July 11, 2001 at 19:14:57, Bruce Moreland wrote: > >>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 > >I update this in MakeMove(). When I enter MakeMove() I copy EPTarget to ply+1. >If it is non-zero, this means that at this ply I could have made an EP capture, >and no matter whether I did or not, I need to clear this EP target, _and_ update >the hash signature by removing the EP[target] random number. > >This keeps my hash signature right for all cases, so that I can use it to hash, >to recognize repetitions, etc... > >And it costs essentially nothing in terms of performance... >. I decided that it's not worth messing with. The only time I check this is when I'm trying to determine if there has been a 3x repetition. So I actually took some code out -- I no longer bother with checking for a potential capturing pawn on either side. So not only am I not doing what Dann praises me for doing, I've removed the part that someone else praised me for. Now people can curse me for ignoring the entire problem. bruce
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