Author: Vincent Diepeveen
Date: 10:21:21 01/28/02
Go up one level in this thread
On January 28, 2002 at 13:04:05, Sune Fischer wrote:
>On January 28, 2002 at 12:25:28, Vincent Diepeveen wrote:
>
>>>Bah, you guys are no fun, live a little, risk it all!;)
>>
>>In fact there has been more experimented here than you thought :)
>>
>>But the hard facts are that if you would go for every thought of a
>>18 year old kid who can't program, that you are busy for another 1000
>>years checking out all the crap.
>>
>>Note that in this case it is not entire crap. The idea to fiddle with a
>>bunch of MMX instructions in order to get something done in a bitboard
>>concept is pretty interesting. Nevertheless it depends heavily on your
>>evaluation.
>
>I don't understand his MMX idea, I think it's just to increase speed in 64-bit
>operations, I don't see why they should be needed here. We don't need to
>re-reverse the bitboards, they are incrementally constructed.
>
>I've made my little rook attack algorithm here on paper, it is about 20 64-bit
>operations in total - no table lookups and no if's or while's!
then your mobility concept sucks from chessknowledge quality viewpoint.
No mobility is better than stupid mobility say some programmers, though
i disagree here partly it sure has some truths in it.
>Think of the potential speed increase when we get 64-bit chips, the rotated
>bitboards will still be handicaped by the table lookups.
I still couldn't buy a 64 bits processor cheap that outguns a dual K7
system and right now i don't see how to make it either.
>Anyway, I'll write down the algorithm now and post it here, then you can tell me
>if it will stand a chance against rotated ;)
for generating moves from - to for bishops and rooks, that sure is
appreciated.
>I hope there are no mistakes, I haven't tested it.
>>IMHO bitboards are good for pawn structure but they suck further. Note
>>there are another zillion solutions to pawn structures and 32 bits
>>bitboards which are fast too.
>>
>>
>>>If it works it should be faster, I'll think it through and if I can't find any
>>>flaws I'll give it a try.
>>
>>>>Only the diagonals you need to take a look at at the design what is faster
>>>>for them. if that problem isn't solved in reversed bitboards, then obviously
>>>>rotated are going to be easier for you to take a look at.
>>>
>>>K, I will.
>>
>>the idea of rotated bitboards is pretty simple, it basically solves
>>the problem of the sliding pieces. So when someone mentions reversed
>>bitboards i don't care for knights for example, but *only* for
>>bishops, rooks.
>
>Yes we are talking about the sliding pieces only, the others are easy.
>I know the idea of rotated bitboards is simple, but the implementation is not ;)
>
>>I have missed the tricks how to do that with other solutions than rotated
>>bitboards in an efficient way.
>>
>>>
>>>>It seems there are however many methods at the K7 + intel processors to
>>>>use with rotated bitboards. In isichess it seems smaller tables are
>>>>getting used than in crafty for this.
>>>>
>>>>Others report they do it even different, but their speedresults are
>>>>not impressive.
>>>>
>>>>>I found this link (it was actually dead, but google had it cached so I put it up
>>>>>for a short while)
>>>>>http://www.fys.ku.dk/~fischer/Temp/New%20Technology.htm
>>>>>
>>>>>It is about reversed bitboards, the author claims it is faster than rotated:
>>>>>
>>>>>"When taking account of memory latencies, calculating the piece attacks using
>>>>>the forward and reverse bitboards can be done significantly faster due to total
>>>>>independence on lookup tables and complex calculations. There are a few slight
>>>>>snags with the diagonal calculations, but they are minor."
>>>>>
>>>>>
>>>>>His description ("significantly faster") entrigues me (hehe) but I can't find
>>>>>anything else on reversed bitboards and I've never heard of them before.
>>>>>
>>>>>What's the catch, is there something he is not telling?
>>>>>
>>>>>-S.
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