#9322: long time in simon_two_descent for elliptic curves
-------------------------------+--------------------------------------------
Reporter: cremona | Owner: AlexGhitza
Type: defect | Status: needs_info
Priority: major | Milestone: sage-4.7.2
Component: elliptic curves | Keywords: Simon
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Changes (by zimmerma):
* status: needs_work => needs_info
Old description:
> [NB This is a different bug from the one on #5153]
>
> Chris Wuthrich reports:
> {{{
> sage: K.<w> = NumberField(x^2-x-232)
> sage: E = EllipticCurve([2-w,18+3*w,209+9*w,2581+175*w,852-55*w])
> sage: E.local_data()
> []
> sage: E.simon_two_descent(verbose=2)
> booom.
> }}}
>
> The same example runs fine in gp using the same version of the script
> ell.gp that Sage has (in version 4.4.4) and the same version of gp.
New description:
[NB This is a different problem from the one on #5153]
Chris Wuthrich reports:
{{{
sage: K.<w> = NumberField(x^2-x-232)
sage: E = EllipticCurve([2-w,18+3*w,209+9*w,2581+175*w,852-55*w])
sage: E.local_data()
[]
sage: E.simon_two_descent(verbose=2)
}}}
This takes about 2.5 minutes with Sage 4.7.1 on a 1.6Ghz Core 2 Duo.
The same example runs fine in gp using the same version of the script
ell.gp that Sage has (in version 4.4.4) and the same version of gp.
--
Comment:
thank you John for your advice. After trying it, I figured out that with
Sage 4.7.1 on my laptop
in fact the example in the description actually works, but takes about 2.5
minutes, during which
top reports that the gp process takes 100% of the cpu time, while
evaluating the command
{{{
ans=bnfellrank(K, [-a + 2,3*a + 18,9*a + 209,175*a + 2581,-55*a + 852]);;
}}}
Can someone else confirm? Maybe a problem in the Sage-gp interface?
What should we do with that ticket?
Paul
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9322#comment:8>
Sage <http://www.sagemath.org>
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