Author: Uri Blass
Date: 02:19:18 12/20/02
Go up one level in this thread
On December 20, 2002 at 04:33:13, Gerd Isenberg wrote: >On December 20, 2002 at 04:12:20, Uri Blass wrote: > >>On December 20, 2002 at 03:37:09, Gerd Isenberg wrote: >> >>>On December 19, 2002 at 18:49:56, Dann Corbit wrote: >>> >>>>On December 19, 2002 at 18:47:22, Joshua Haglund wrote: >>>> >>>>>Anyone know of a good site(s) for the programming of a (legal) move generator? >>>> >>>>You'll find a lot more help looking for a pseudo-legal move generator. I don't >>>>think anyone makes a strictly legal move generator (maybe Uri does...) >>> >>>I do it in IsiChess and i guess a lot of bitboarders too. >>> >>>Gerd >> >>I do not think that it is something special for bitboarders. >>I do it without bitboards. >> >>Uri > >Yes, sorry Uri. > >I thought detecting pinned pieces is a bitboard domain, but of course it's >independent of the data structure representing the board. > >Gerd detecting pinned pieces is something that I do without bitboard and it can be improved(also without bitboard) but maybe bitboard can help better. I will explain what I do in this post and explain my ideas of doing it better. today I have an array pin[64] that tells me for every square if the piece in it is pinned to the king. pin[i] is used only when there is a piece of the side to move in square i(in other cases pin[i] is not used so right for today I do not care if the value is wronf). pin[i]=-1 means that the piece is not pinned. pin[i]=0 means that the piece is pinned to the same file pin[i]=1 means that the piece is pinned to the same rank pin[i]=2 or pin[i]=3 means that the piece is pinned in diagnols. I also has a varaible pinnumber[ply] that tells me the number of piece that are pinned. Adding this varaible helped to do movei sligthly faster. when pinnumber[ply]=0 I can save the time of looking in pin[i] so when I undo moves and pinnumber[ply]=0 I do not care to update the pin array. the varaible pinnumber[ply] also help in the search algorithm but I still do not like my data structure because when a piece is pinned I have no easy way to find the square of the pinned piece or the value of the pinned piece and the only way for me is simply a loop on the piece list. I think it may be better if I replace the varaible pinnumber[ply] by pininfo[ply] because in 99% of the cases it may be possible to compress all the information about pins to one 32 bit integer. It is possible that in that case I do not need the array pin[64] because usually only one or 2 pieces are pinned and there is no problem to store the information in one 32 bit number. Maybe storing information about pins of both sides can be even faster but I decided not to do it in the near future and I think that checking not to have bugs in the move generator after doing it is not a simple task(I did things that may be even more complicated and my move generator have thousands of C lines but I decided that today it is fast enough and I do not like to work estimated time of some hundreds of hours to implement pins for both sides and check for bugs). Uri
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