PARI/GP Bug report logs - #1305
gp core() function: could do better?

Package: pari-stable; Maintainer for pari-stable is Aurel Page <aurel.page@normalesup.org>; Source for pari-stable is src:pari-stable.

Reported by: Kevin Buzzard <k.buzzard@imperial.ac.uk>

Date: Mon, 19 Mar 2012 11:18:16 UTC

Severity: normal

Done: Karim Belabas <Karim.Belabas@math.u-bordeaux1.fr>

Bug is archived. No further changes may be made.

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Subject: Bug#1305: gp core() function: could do better?
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Package: pari-stable
Version: 2.5.0

[Sorry -- I should upgrade to 2.5.1, but I didn't yet, and I don't see 
core mentioned in the changelog 2.5.0->2.5.1 so let me gamble that this 
is still an issue]

What do you think of this?

(11:00) gp > isprime(10^1000+1)
%1 = 0
(11:00) gp > core(5*(10^1000+1)^2)
[gp now goes into a very long loop, presumably because it's trying to 
factor (10^1000+1)^2?]

I am not C++-savvy enough to know what the "core" function was doing in 
2.5.0, but in this particular case I can see a relatively simple way of spotting the 
answer: if we use trial division or ECM or whatever to find a few small 
factors, then could it be worth checking to see if what we have left is a 
square?? If it is then we're done. Presumably core() is not currently 
doing this...

Kevin

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Bill Allombert <allomber@math.u-bordeaux.fr>. Last modified: Sat Aug 26 17:04:59 2023; Machine Name: pari

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