#7096: bug in dual isogeny computation
-----------------------------+----------------------------------------------
Reporter: cremona | Owner: davidloeffler
Type: defect | Status: new
Priority: major | Milestone: sage-4.1.3
Component: elliptic curves | Keywords: elliptic curve isogeny
Reviewer: | Author:
Merged: |
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{{{
sage: p = 1019
sage: F = GF(p)
sage: E = EllipticCurve(F,[1,-1,0,1,1])
sage: psi = E.division_polynomial(7).factor()[3][0]
sage: phi = E.isogeny(kernel=psi)
sage: assert phi.degree()==7
sage: phi.dual()
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
/home/jec/.sage/temp/selmer/14232/_home_jec__sage_init_sage_0.py in
<module>()
/home/jec/sage-4.1.2.rc0/local/lib/python2.6/site-
packages/sage/schemes/elliptic_curves/ell_curve_isogeny.pyc in dual(self)
2998
2999 phi_hat.set_pre_isomorphism(pre_isom)
-> 3000 phi_hat.set_post_isomorphism(post_isom)
3001
3002 self.__dual = phi_hat
/home/jec/sage-4.1.2.rc0/local/lib/python2.6/site-
packages/sage/schemes/elliptic_curves/ell_curve_isogeny.pyc in
set_post_isomorphism(self, postWI)
2627
2628 if (self.__E2 != WIdom):
-> 2629 raise ValueError, "Invalid parameter: isomorphism must
have domain curve equal to this isogenies'codomain."
2630
2631 if (None == self.__post_isomorphism):
ValueError: Invalid parameter: isomorphism must have domain curve equal to
this isogenies' codomain.
}}}
This looks like something which should be easy to fix.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7096>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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