Author: Matthias Gemuh
Date: 00:11:47 04/16/03
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On April 16, 2003 at 00:00:07, Mike Siler wrote: >Up until recently, my chess program generated all pseudo-legal moves, made each >move, checked to see if it's in check and unmakes the move if so. This annoyed >me a bit because my attack function that sees if the program is in check was not >too quick. So I came up with a method of avoiding calling the attack function as >often. Assuming the program is not in check at this particular node, we know >that there are only 2 ways the program can enter check: either the program moves >a piece and discovers a check on itself (it was pinned to the king by a sliding >piece) or the king moves into check. I wrote a function to determine which (if >any) of the program's pieces are pinned to its king. Then if a pseudo-legal move >involves the pinned piece, we know already that the movement will cause the king >to be in check, so we don't have to call the time-consuming make_move function, >attack function, or unmake_move function. > >Of course if the move involves the king, we can't skip the attack function. >Using this method, I experienced a very nice speed-up: from about 300knps to >about 375-400 knps. > >I've never seen another program that uses this. I'm just curious if there is >some down side I don't see or if programs do use this and I just didn't notice. > >Michael I do a partial MakeMake() and test for legality midway, then I partially unmake and abort if illegal. /Matthias.
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