#11639: conductor of simple curve over Q(cube root 3) takes forever
-----------------------------------+----------------------------------------
Reporter: was | Owner: cremona
Type: defect | Status: closed
Priority: major | Milestone:
sage-duplicate/invalid/wontfix
Component: elliptic curves | Resolution: duplicate
Keywords: | Work issues:
Report Upstream: N/A | Reviewers: Jeroen Demeyer
Authors: | Merged in:
Dependencies: | Stopgaps:
-----------------------------------+----------------------------------------
Changes (by jdemeyer):
* status: positive_review => closed
* resolution: => duplicate
Old description:
> {{{
> sage: x=var('x'); K.<a> = NumberField(x^3 - 2);
> EllipticCurve([0,a]).conductor()
> [[ wait forever! ]]
> }}}
>
> The correct answer has norm 322486272, and should be instant:
> {{{
> sage: magma(E).Conductor()
> Ideal
> Basis:
> [864 0 0]
> [ 0 864 0]
> [ 0 0 432]
> sage: magma(E).Conductor().Norm()
> 322486272
> }}}
>
> Trying with {{{proof.all(False)}}} doesn't help, by the way, so I don't
> think it is just some complexity issue... and yet, I just tried control-c
> after letting "E.conductor()" sit there for a while, then typed "%debug",
> then "u", then saw that two ideals of the integers of the cubic field
> were being multiplied. I printed the gens of one ideal and got
> {{{
> ipdb> u
> > /Users/wstein/sage/install/current/local/lib/python2.6/site-
> packages/sage/rings/ideal.py(857)__mul__()
> 856 other = self.ring().ideal(other)
> --> 857 return self.ring().ideal([x*y for x in self.gens() for y
> in other.gens()])
> 858
>
> ipdb> print self.gens()
> (16384, 8192*a, 8192*a, 4096*a^2, 8192*a, 4096*a^2, ... goes on
> redundantly for many pages!)
> }}}
>
> So, maybe ideals aren't being properly reduced, which is causing huge
> trouble.
New description:
{{{
sage: x=var('x'); K.<a> = NumberField(x^3 - 2);
EllipticCurve([0,a]).conductor()
[[ wait forever! ]]
}}}
The correct answer has norm 322486272, and should be instant:
{{{
sage: magma(E).Conductor()
Ideal
Basis:
[864 0 0]
[ 0 864 0]
[ 0 0 432]
sage: magma(E).Conductor().Norm()
322486272
}}}
Trying with {{{proof.all(False)}}} doesn't help, by the way, so I don't
think it is just some complexity issue... and yet, I just tried control-c
after letting "E.conductor()" sit there for a while, then typed "%debug",
then "u", then saw that two ideals of the integers of the cubic field were
being multiplied. I printed the gens of one ideal and got
{{{
ipdb> u
> /Users/wstein/sage/install/current/local/lib/python2.6/site-
packages/sage/rings/ideal.py(857)__mul__()
856 other = self.ring().ideal(other)
--> 857 return self.ring().ideal([x*y for x in self.gens() for y
in other.gens()])
858
ipdb> print self.gens()
(16384, 8192*a, 8192*a, 4096*a^2, 8192*a, 4096*a^2, ... goes on
redundantly for many pages!)
}}}
Fixed by #13958.
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11639#comment:12>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.
