#11936: image_type of galois_representation of EllipticCurve hangs on first call
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Reporter: dkrenn | Owner: cremona
Type: defect | Status: new
Priority: minor | Milestone: sage-4.8
Component: elliptic curves | Keywords: ellipitc curve,
galois_representation, image_type, kash
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by johanbosman):
Let us look at the source code:
{{{
1158 try:
1159 G = K.galois_group()
1160 except:
1161 self.__image_type[p] = "The image is a group of
order %s."%d
1162 return self.__image_type[p]
1163
1164 else:
1165 if G.is_abelian():
1166 ab = ""
1167 else:
1168 ab = "non-"
1169 self.__image_type[p] = "The image is a " + ab +
"abelian group of order %s."%G.order()
1170 return self.__image_type[p]
}}}
The only thing that the Galois group computation using Kash adds is
checking whether the group is Abelian or not. I've tried this example
with Kash installed. It seems that the Kash process runs very briefly and
then crashes or so (?); in any case, Sage keeps waiting for a result that
it will never get. Magma supports Galois group computation for
irreducible polynomials of any degree over Q using an implementation of
Claus Fieker and Juergen Klueners; I guess Kash only goes up to a certain
degree. In any case, there's something wrong with Sage's interface to
Kash.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11936#comment:6>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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