#18589: isogeny efficiency improvement
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Reporter: | Owner:
cremona | Status: needs_review
Type: | Milestone: sage-6.8
enhancement | Resolution:
Priority: major | Merged in:
Component: | Reviewers:
elliptic curves | Work issues:
Keywords: | Commit:
isogeny | 47ccfd587402b953c612fcd3cddaa541a6847bd3
Authors: John | Stopgaps:
Cremona |
Report Upstream: N/A |
Branch: |
u/cremona/18589 |
Dependencies: |
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Comment (by cremona):
Thanks for the comments, I noticed you over at pari-dev and wondered what
you were up to.
I don't know how general the pari code is -- here we can handle arbitrary
fields (but only separable isogenies). Over number fields the really hard
part is determining which prime degrees to test to get the whole class,
and I put a lot of work into this (including CM and "potential CM" cases).
Some checking is necessary: I have an example where the 13-division poly
factors as 14 degree 6 factors, but only 2 of them are kernel polys! For
the rest you need to make a quadratic extension which splits each into two
cubics, and then you have to match the factors. The Sage code does this!
--
Ticket URL: <http://trac.sagemath.org/ticket/18589#comment:5>
Sage <http://www.sagemath.org>
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