GNU bug report logs - #12350
Composites identified as primes in factor.c (when HAVE_GMP)

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Package: coreutils;

Reported by: Torbjorn Granlund <tg <at> gmplib.org>

Date: Tue, 4 Sep 2012 13:29:02 UTC

Severity: normal

Done: Jim Meyering <meyering <at> hx.meyering.net>

Bug is archived. No further changes may be made.

Full log

Message #214 received at 12350 <at> debbugs.gnu.org (full text, mbox):

From: Torbjorn Granlund <tg <at> gmplib.org>
To: Pádraig Brady <P <at> draigBrady.com>
Cc: 12350 <at> debbugs.gnu.org, nisse <at> lysator.liu.se, jim <at> meyering.net
Subject: Re: bug#12350: Composites identified as primes in factor.c (when
	HAVE_GMP)
Date: Mon, 08 Oct 2012 14:59:11 +0200

Pádraig Brady <P <at> draigBrady.com> writes:

  Thanks for checking that.
  
  Torbjorn you seem to be interploating from your
  3.3 GHz Sandy bridge to my 2.1GHz i3-2310M Sandy Bridge,
  but it might not be linear due to cache, turbo boost,
  mem bandwidth, ...
  
It should be linear in clock frequency, yes.

The factor program's working set (code and data) is tiny.  Things should
fit in L1 caches.  We have a prime table, but it is smaller than L1D (at
about 10 kB).

All Sandy bridges in the world have the same L1 cache sizes.

Mem bandwidth is therefore irrelevamt, and so is higher-level caches.
"Turbo boost" is relevant, but I have that switched off since I am quite
fond of reproducible benchmarking results.

-- 
Torbjörn
This bug report was last modified 12 years and 277 days ago.

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