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Subject: Re: hash table size - is a power of 2 still an advantage these days?

Author: Robert Hyatt

Date: 14:52:35 09/24/03

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On September 24, 2003 at 17:38:13, Dieter Buerssner wrote:

>On September 24, 2003 at 17:17:26, Ricardo Gibert wrote:
>
>>When did an old trivial technique become "Dieter's trick?"
>
>I agree, that it is a trivial trick. I did not know, that it is old. I have no
>doubt, that many people would have thought about it, and come up with it. When I
>told it to other chess programmers, none of them seemed to be aware of it,
>however. You might even see often the argument of "mod is too slow" in the
>history of CCC positings, without mentioning the possibility to avoid modulo and
>still to have an arbitrary number of hash entries.
>
>Regards,
>Dieter


This is common on older Cray programs.  The Cray has _no_ hardware divide
instruction at all.  It can compute 1/n (reciprocal approximation instruction)
but it requires more work to take that all the way to a remainder (modulus
result).




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