Author: Andrew Williams
Date: 03:16:09 04/29/01
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On April 27, 2001 at 21:28:14, Dann Corbit wrote: Hi Dann, >Precomputing attack tables is a snap, of course. The burning question is, how >are they best utilized? > >I notice that nobody makes pawn attack tables. Is that because pawn attacks are >too trivial to compute on the fly? I have an array called attacks. Each element is a 32-bit unsigned int. Each bit of an element represents one piece (or pawn) on the board (16 white, 16 black). A bit is set if that piece or pawn attacks that square. This array is kept up to date in the makemove function. > >What is the typical savings of attack tables compared to performing the >computations on the fly? > >Is there any advantage to trying to compress the attack tables? > Never considered this. >Do you use attack tables against an entire side at once, or only against pieces >by set or even individual chess men? > In my evaluation they are mostly used in assessing attacks around the king, and for control of the centre. >Are they used in MVV/LVA primarily, or during all phases of evaluation? > I use them for move capture generation and for SEE calculations. >Obviously, knight attack tables can be performed with a single & operation, but >what do you do with bishops, queens, etc, where your own man or an intervening >piece can get in the way? Are they used only as a pre-test to see if the rest >is worth calculating? > Mine are actual attacks, not pseudo attacks. After I'd implemented my attacks stuff, I wished I'd done pseudo attacks first so that I could have had something to compare. >I thought of using all your own men, &'ed together as a mask, and then clearing >everything past a "pierce" mark, but that would probably be as expensive as >computation of the attack. Cheers Andrew
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