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Subject: Re: 64 bits

Author: Keith Evans

Date: 11:32:43 06/20/02

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On June 20, 2002 at 13:30:28, Eugene Nalimov wrote:

>Such the experiment will answer the question: "On the 64-bit architecture, how
>much speedup is caused by the 64-bittness"? I.e. let's imagine 32-bit Alpha or
>Itanium2. How slower Crafty will be on such the animal?
>
>I suspect that the difference will be only ~10%. I.e. Alpha and Itanium2 run
>Crafty well not because it uses 64-bit data structures, but because they run
>everything well.
>
>Unfortunately, suggested experiment is flawed. Lot of compilers will generate
>much worse code for the operations with structures than for the operations with
>the builtin types.
>
>Eugene
>

But if the 32-bit datastructures perform _better_ than Bob predicts, despite the
"much worse code", then the experimental results could still be useful. I agree
that if the performance of the 32-bit datastructures is significantly lower
(matching Bob's prediction) then we won't be able to say whether it's due to the
compiler or just the 32-bit widths.

Of course this may not motivate Bob to perform the experiment, because it can
only show that his 64-bit bitboard performance claims are a bit exagerrated. If
it's in the other direction then the argument will continue.

We can only hope that a scientifically minded new chess engine author who is
considering the use of bitboards will do some experimentation on these new
processors and share the results.

-Keith



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