Author: Ian Osgood
Date: 10:05:35 04/05/03
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On April 04, 2003 at 22:14:02, Robert Hyatt wrote: >On April 04, 2003 at 15:06:37, Russell Reagan wrote: > >>On April 04, 2003 at 14:57:50, Keith Evans wrote: >> >>>What do you think you will gain by excluding certain elements? >> >>I have heard people discuss the drawbacks of including the fifty move counter in >>the past. I'm not sure of the details though. >> >>As far as an example, try this: >> >>[D] rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1 >> >>The en passant square is e3. > >You should not have an EP target there. There is _no_ EP possibility. >Setting e3 is bad, because if you move a knight out and back, then in your >scheme _that_ position won't have an ep square, and the hash won't match. > >You should only set an ep target if a pawn advances two squares _and_ there >is an enemy pawn on the right squares on either side of it, otherwise no >ep status should be kept. In the EPD standard, is that also the only time one should show the EP target square? That is, is the above EPD board description illegal? I also have a quick question about EP square hashing: I've seen implementations which devote an entire board of random values for the EP square to XOR into the Zobrist hash value. Isn't it sufficient to have a single rank of random values? EP squares can only be on ranks 3 or 6, and which rank is determined by the side to move, which is already XORed into the hash value. Ian
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