#7575: mwrank interface improvements
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Reporter: rlm | Owner: cremona
Type: defect | Status: positive_review
Priority: major | Milestone: sage-4.3.3
Component: elliptic curves | Keywords:
Author: Robert Miller | Upstream: N/A
Reviewer: John Cremona | Merged:
Work_issues: |
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Changes (by cremona):
* status: needs_review => positive_review
* reviewer: => John Cremona
Comment:
I applied trac_7575.patch successfully to 4.3.2 after first applying
everything from
#8184, #8155 and #8124 in that order.
The code looks good. It's great now that we do not have to make
embarrassing excuses for mwrank's incomplete output!
I only spotted one thing: in a couple of places the docstring says that
the default search bound is 16, whereas it is in fact 12. (Certainly 12
is more sensible!) That needs changing (trivial). It might be a good
idea to alert the user to how expensive (in time) adding one to the bound
is, so that (for example) a bound of 20 could lead to the program never
ending.
One other comment (to rlm): when doing descent by 2-isogeny, when the
second descent is used and the coefficients are large, it is a good idea
to increase the decimal precision a lot (to 100 or 200 digits) because
then the reduction of the second descent quartics is done much better.
Now, mwrank will not do that for you (though perhaps it should). I
suggest that when mwrank is used on curves with 2-torsion, we first call
mwrank_set_precision(200). This will not slow anything down (in fact the
opposite) -- but that is not the case for 2-descent in general (no
2-torsion). Perhaps we could do that on another ticket.
I tested the whole library with -long after applying this patch and the
earlier ones on which it depends (as well as the new eclib spkg at #8184):
all pass!
I really hope that this sequence of 4 tickets can all be merged quickly
into 4.3.3.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7575#comment:11>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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