Re: CRC was: Re: beta testing version

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От Bruce Guenter
Тема Re: CRC was: Re: beta testing version
Дата
Msg-id 20001208121939.A10390@em.ca
обсуждение исходный текст
Ответ на Re: CRC was: Re: beta testing version  (ncm@zembu.com (Nathan Myers))
Ответы Re: CRC was: Re: beta testing version  (Ian Lance Taylor <ian@airs.com>)
Re: CRC  (ncm@zembu.com (Nathan Myers))
Re: CRC was: Re: beta testing version  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-hackers
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@em.ca>                       http://em.ca/~bruceg/

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