Author: James Robertson
Date: 20:56:11 06/20/00
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On June 20, 2000 at 21:09:58, Christophe Theron wrote: >On June 20, 2000 at 14:58:54, James Robertson wrote: > >>On June 20, 2000 at 12:18:06, Ralf Elvsén wrote: >> >>>I'm asking about things I don't have much personal experience from >>>so forgive me if this is a stupid question. With BB, as I understand >>>it, one usually have a lot of precomputed BB-arrays, like bishopsMoves[square], >>>maybe blocks[from][to] or the rotated BB-stuff. Is this causing problems >>>for the cache? How much precomputed stuff is needed in 0x88 compared to this? >>> >>>Ralf >> >>I'll answer your second question first. A tiny amount (guesstimate, maybe 1k) is >>needed for 0x88. Bitboards require much more... almost 600k for core arrays on >>my program. Crafty uses some funky thing called compact attacks which I guess >>compacts the attacks. I don't know how it works. (Dr. Hyatt, could you please >>explain how it works and what it's advantages are?) >> >>The precomputed arrays are usually in the form of attacks for ranks and files. >>To try to stuff all bishop or rook moves into one array is a bad idea. For >>instance, in my program, rook moves would require an array of dimensions >>8*64*256*256 bytes = 33MB! >> >>Taking two arrays, one for ranks and one files (each 8*64*256 = 131072 bytes) is >>a lot better. >> >>James > > >I thought bitboards were elegant? > >Sorry, but 128K arrays to do such simple things sounds really ugly! > >Like a hammer to kill a fly. Yes, but the hammer is used to kill elephants elsewhere. James > > > Christophe
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