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Subject: Re: Speedups for BitBoard programs on 64-bit machines

Author: Robert Hyatt

Date: 17:35:03 06/06/02

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On June 06, 2002 at 19:47:14, Vincent Diepeveen wrote:

>On June 06, 2002 at 10:25:25, Robert Hyatt wrote:
>
>>On June 05, 2002 at 17:31:45, Gerd Isenberg wrote:
>>
>>>On June 05, 2002 at 13:22:30, Vincent Diepeveen wrote:
>>>
>>>>On June 05, 2002 at 04:14:41, Gerd Isenberg wrote:
>>>>
>>>>Gerd, a 33% speedup isn't much if you first slow down 2 times.
>>>>Right now the crafty datastructure is exactly 2 times slower doing
>>>>what i can do without bitboards.
>>>>
>>>
>>>Vincent, if, as you claim, bitboarders are two times slower per se on 32bit
>>>hardware, then i expect a speedup of >= 100% with bitboards on 64bit hardware.
>>>
>>>Gerd
>>
>>
>>This argument goes in circles, because he also claims they are not very
>>good on 64 bit machines either...
>
>Not really. the problem is the bitboarders have a different goal it seems.
>If all you want is a Sum(squaresattacked) as mobility function, then sure
>bitboards are an interesting thing to use at 64 bits processors. If you want
>more, then bad luck with bitboards. Factor 2 slower.

based on what?  Your lack of experience with them or proof that there are
some things that bitboards can't do?  I know the latter is not true...

Why do you want to waste so much time trying to explain why this approach
is bad, when you have not tried it yourself.  It takes time to get used to
it.  once you do, you discover that a lot of those "problems" are imaginary
only.



>
>At 64 bits processors 33% faster, still like 1.6 times slower.
>
>Best regards,
>Vincent


Again, what single cpu machine at 1ghz can run crafty at 1.5 M nodes per
second?  Absolutely none unless we go to a Cray.  Or a Mckinley 64 bit
processor...



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