Author: Christophe Theron
Date: 12:20:17 06/22/00
Go up one level in this thread
On June 22, 2000 at 09:48:39, Ricardo Gibert wrote:
>On June 21, 2000 at 14:15:55, Christophe Theron wrote:
>
>>On June 20, 2000 at 21:22:38, Ricardo Gibert wrote:
>>
>>>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.
>>>
>>>I'm not sure I understand your analogy. It would seem to me to be much more
>>>difficult to kill a fly with a hammer, than with a much more appropriate tool
>>>like a fly swatter.
>>>
>>>I think your analogy would work better with a shotgun, though given the
>>>irritation factor of some flys, a shotgun does not seem like such a bad idea ;)
>>
>>
>>A shotgun, if you want. Anyway, for me that's the same.
>>
>>Tell me about the elegance of the bitboard concept, after that...
>
>Just for the record, I decided on the 16x16 scheme a long time ago after first
>hearing about 0x88 with its 16x8 board. 16x16 seemed like an obvious
>improvement. I never got into bitboards.
I think you picked the right design right from the start.
Christophe
>
>>
>>A 0x88 or 16x engine: 64Kb
>>A bitboard engine: 2MB
>>
>>They are of equal strength.
>>
>>But the bitboard design is so smart! And when we have 64 bits processors, the
>>bitboard program will not be stronger, but it will fit the processor's
>>architecture so nicely! Just thinking about it makes me wet everywhere!
>>
>>Cute piece of expensive art I would say.
>>
>>
>> Christophe
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