Author: Robert Hyatt
Date: 09:30:34 12/11/03
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On December 11, 2003 at 09:35:27, Sune Fischer wrote: >On December 11, 2003 at 09:08:50, Robert Hyatt wrote: > >>On December 11, 2003 at 04:43:32, Andreas Guettinger wrote: >> >>>On December 10, 2003 at 22:42:05, Robert Hyatt wrote: >>> >>> >>>>>Could you point me to where is this going on? I can't seem to find it when >>>>>looking over the move generation functions or the search function. >>>> >>>> >>>>Hmmm. Neither can I. I don't remember where/when I stopped doing that. > >You might have changed it recently, but in the qsearch of Crafty 19.01, line 72, >it says: >if (Captured(*movep) == king) return(beta); That is the q-search. I used to do it in the normal part of the search also. That was the part that was changed a long while back... > >I think you also do it for perft, except at the leaf. >I guess it might be a good trick if the illegal move percentage is low enough. > >>>Maybe at the time you realized it's faster to make an incheck() test than >>>updating the extension counters, initailizing the next search and generating all >>>the moves for the next ply? >> >>Actually, I looked back at all my old notes. It had to do with null-move >>search. It was possible for a null-move to fail high even after making >>a move at the previous ply that was illegal, and that caused problems. I >>don't remember exactly what was happening, but apparently it was enough for >>me to start "checking". > >How did you do check extensions without knowledge of being in check? I extend when I check the opponent. That is a different test than asking "am I in check after making that move?" > >I can see how you can have the search return this knowledge if it finds an >illegal move (actually it could just have been a pinned piece), but suppose you >get lucky and fail high one on of the legal check evaders as the first move. >How do you discover that you were in check, do you force a nullmove first to >test it? Why would I care that I am in check if a legal move fails high getting me out? I've already extended at the previous ply for giving the check in the first place. > >-S.
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