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Subject: Re: Questions about hash table implementation?

Author: David Rasmussen

Date: 14:54:11 05/22/01

Go up one level in this thread


On May 22, 2001 at 16:26:10, David Rasmussen wrote:

>On May 22, 2001 at 09:52:11, Gian-Carlo Pascutto wrote:
>
>>On May 22, 2001 at 09:43:49, Robert Hyatt wrote:
>>
>>>>2) How to generate a 64 bit random number? (I use ran()*ran(). Is it OK?).
>>>
>
>Ran*Ran is not OK, as it will favor the higher bits.
>
>>>I would use ran()<<32 + ran myself.
>>
>>Just make sure you package your own ran(). The quality of C
>>libraries one will vary greatly.
>>
>>I did a test with 32 bit hashes and MSVC: average hamming distance
>>of 9.30, whereas my own (which I stole from Crafty, which stole it from...)
>>got 15.99, which is theoretically optimal I suppose.
>>
>

I measured my numbers. My minimum distance is 16, and my average distance is
31.9997 .

Are we talking about different things here?



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