#10745: bug in elliptic curve gens()
-------------------------------+--------------------------------------------
Reporter: rlm | Owner: cremona
Type: defect | Status: new
Priority: major | Milestone:
Component: elliptic curves | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
-------------------------------+--------------------------------------------
{{{
sage: a = [1, 0, 1, -1751, -31352]
sage: F = EllipticCurve(a)
sage: K.<d> = QuadraticField(5)
sage: FK = EllipticCurve(K, a)
sage: F.gens()
[(52 : 111 : 1)]
sage: FK.gens()
[]
}}}
This isn't very good, because the default in Sage is proof=True, so one
would expect this to be a provable result (until reading the docs of
course. But if we try to look harder for the point, we run into a bug with
caching:
{{{
sage: FK.gens(lim1=6)
---------------------------------------------------------------------------
KeyError Traceback (most recent call
last)
/home/rlmill/<ipython console> in <module>()
/home/rlmill/sage-4.6.2.alpha2/local/lib/python2.6/site-
packages/sage/schemes/elliptic_curves/ell_number_field.pyc in gens(self,
verbose, lim1, lim3, limtriv, maxprob, limbigprime)
1772 """
1773
-> 1774 lower,upper,gens =
self.simon_two_descent(verbose=verbose,lim1=lim1,lim3=lim3,limtriv=limtriv,maxprob=maxprob,limbigprime=limbigprime)
1775 return gens
1776
/home/rlmill/sage-4.6.2.alpha2/local/lib/python2.6/site-
packages/sage/schemes/elliptic_curves/ell_number_field.pyc in
simon_two_descent(self, verbose, lim1, lim3, limtriv, maxprob,
limbigprime)
265
266 try:
--> 267 result =
self._simon_two_descent_data[lim1,lim3,limtriv,maxprob,limbigprime]
268 if verbose == 0:
269 return result
KeyError: (6, 50, 10, 20, 30)
}}}
So two problems: 1) Over Q, if the result is not provable a RuntimeError
is raised. This should be the same here. 2) One can't change parameters
due to the way the output is being cached.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10745>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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