#7262: Have multiplcation_by_m() return an EllipticCurveIsogeny object
-------------------------------+--------------------------------------------
Reporter: wuthrich | Owner: davidloeffler
Type: defect | Status: positive_review
Priority: minor | Milestone: sage-4.3.1
Component: elliptic curves | Keywords: elliptic curves, isogeny,
Author: Craig Citro | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
-------------------------------+--------------------------------------------
Comment(by wuthrich):
Looking at the code, I see that this is not doing exactly what my original
idea was when I opened this trac. The reason this is so slow is that a lot
of computations will be done several times. I thought that one should
create the isogeny without running through the current init of the object.
I think all data is known easily once the division polynomial is computed.
Of course, we can leave it like that by now, but I would suggest to open a
further ticket to improve this.
Another ugly thing is
{{{
sage: phi.codomain() == phi.domain()
False
}}}
One should set the post_isomorphism correctly.
As to the 4-isogeny, this is indeed not implemented since it is a bit more
complicated. The best would be to have the composition of morphisms
defined and then to defined by iterating [2]. We can leave it like that by
now. It is a shame though.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7262#comment:17>
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 post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en.
