Author: Christophe Theron
Date: 18:09:58 06/20/00
Go up one level in this thread
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.
Christophe
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