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Subject: Re: Hash codes

Author: Gian-Carlo Pascutto

Date: 03:08:46 11/14/01

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On November 14, 2001 at 05:23:08, Dan Newman wrote:

>I think several of us here have done the experiment.  ISTR that Bob did
>this some time ago (perhaps with Cray Blitz) and I vaguely recall that
>Vincent (or was it Ed?) also has measured the (high) error rate that you
>get with too few bits.  I'm sure others have, too.
>
>When I measured it several years back I got about one collision (error)
>per second with a 32-bit hash code.  (I can't remember the probe rate,
>but it was probably about 100k/s at the time.)
>
>Anyway, 32 bits seems too small, but I don't really know if the errors
>would have any measurable effect on engine strength.  I've always just
>assumed that any such error is a bad thing, and 64 bits virtually
>eliminates them...

This is _exactly_ my point. Bob and others, and now you, have been
claiming for a long time that 32 bits is not enough because they
see a lot of collisions with it.

Why would this necessarily mean 32 bits hashing is not enough?

--
GCP



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