#15483: Simon 2-descent gives RuntimeError for an elliptic curve over a
quadratic
field
-------------------------------------------------+-------------------------
Reporter: pbruin | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.2
Component: elliptic curves | Resolution:
Keywords: simon_two_descent | Merged in:
Authors: | Reviewers:
Report Upstream: Not yet reported upstream; | Work issues:
Will do shortly. | Commit:
Branch: | Stopgaps:
Dependencies: #11005 |
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Comment (by pbruin):
The basic problem seems to be that PARI is too optimistic about the
resulting precision when adding real numbers:
{{{
? b =
-1554544300737274875964190134520312870631312460283689944298138572669148295776039072867720281361776956435252620954745928376624817557704277432961924925312*y
+
23524523971732905757341977352314040726186200302188191824300117738073539522011689544444863977622786771332621915440577829842674416407299864303146477224320
? K = bnfinit(y^2 - 229);
? u=polcoeff(b,1)*K.roots[2]
%167 = -2.3524523971732905757341977352314040726 E151
? v=polcoeff(b,0)*1.
%168 = 2.3524523971732905757341977352314040726 E151
? u+v
%169 = -7.695704335233296721 E112
? precision(u)
%170 = 38
? precision(v)
%171 = 38
? precision(u+v)
%172 = 19
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/15483#comment:8>
Sage <http://www.sagemath.org>
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