#11372: nasty side effect of a failed simon_two_descent search
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Reporter: was | Owner: cremona
Type: defect | Status: new
Priority: critical | Milestone: sage-4.7.1
Component: elliptic curves | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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This could seriously confuse a person:
{{{
deep:sage-4.7.rc1 wstein$ ./sage
----------------------------------------------------------------------
| Sage Version 4.7.rc1, Release Date: 2011-04-29 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: E = EllipticCurve([1, 1, 0, -23611790086, 1396491910863060])
sage: E.simon_two_descent()
(1, 2, [(88716 : -44358 : 1)])
sage: E.gens()
[]
sage: E.rank()
0
sage: E = EllipticCurve([1, 1, 0, -23611790086, 1396491910863060])
sage: E.gens()
[(4311692542083/48594841 : -13035144436525227/338754636611 : 1)]
}}}
The point that simon_two_descent finds is a torsion point. But for some
reason E then thinks it has rank 0! Even though simon_two_descent's first
output was 1, and in fact E has rank 1. This is pretty scary.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11372>
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