#7907: Bug in characteristic 2 isogenies of degree >3
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Reporter: cremona | Owner: cremona
Type: defect | Status: new
Priority: major | Milestone: sage-4.3.1
Component: elliptic curves | Keywords: isogeny
Work_issues: | Author:
Upstream: N/A | Reviewer:
Merged: |
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The method __compute_omega_general() in ell_curve_isogeny.py contains
{{{
for j in xrange(0,n-1):
psi_prpr = psi_prpr + \
binomial(j+2,2)*psi_coeffs[(j+2)]*cur_x_pow
cur_x_pow = x*cur_x_pow
}}}
where the degree of the isogeny is 2*n+1. In degree 3 (the only case
doctested) n=1 and the loop is empty. Otherwise there is a run-time error
since the name "binomial" has not been imported.
This will be simple to patch, but of course as this indicated that higher
degree isogenies in char.2 have not been tested, other issues might arise.
Patch up soon.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7907>
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