Re: CRC was: Re: beta testing version

From: Bruce Guenter <bruceg(at)em(dot)ca>
To: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: CRC was: Re: beta testing version
Date: 2000-12-08 18:19:39
Message-ID: 20001208121939.A10390@em.ca
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On Thu, Dec 07, 2000 at 04:01:23PM -0800, Nathan Myers wrote:
> 1. Computing a CRC-64 takes only about twice as long as a CRC-32, for
> 2^32 times the confidence. That's pretty cheap confidence.

Incidentally, I benchmarked the previously mentioned 64-bit fingerprint,
the standard 32-bit CRC, MD5 and SHA, and the fastest algorithm on my
Celeron and on a PIII was MD5. The 64-bit fingerprint was only a hair
slower, the CRC was (quite surprisingly) about 40% slower, and the
implementation of SHA that I had available was a real dog. Taking an
arbitrary 32 bits of a MD5 would likely be less collision prone than
using a 32-bit CRC, and it appears faster as well.
--
Bruce Guenter <bruceg(at)em(dot)ca> http://em.ca/~bruceg/

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