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Random failure in src/sage/schemes/elliptic_curves/ell_field.py #28383
Comments
comment:1
Ticket retargeted after milestone closed |
comment:2
Moving tickets to milestone sage-9.2 based on a review of last modification date, branch status, and severity. |
comment:5
I am not sure how to debug this at the Sage level. The test asks for all isogenies of the curve E of degree up to 3, and the error is raised when computing 2-isogenies, of which there are three. These are computed by constructing a EllipticCurveIsogeny object using EllipticCurveIsogeny(E, ker) where ker is a degree 1 polynomial of the form x-x0 over the base field. Since ker is a polynomial it should the 'kohel' algorithm, but the test in line 982 of ell_curve_isogeny tests whether ker is a point using "kernel in E", which attempts to construct a point via E(ker), and that is causing the error. There should be a better way to determine whether the caller has provided a point of E generating the kernel, and not a polynomial. The file ell_curve_isogeny is over 4000 lines long, mostly not written by me but I have spent many hours in it debugging (though not recently). I would have written it very differently. I can try replacing the test "kernel in E" with something like
but how to test whether the sporadic error has gone away? |
comment:6
Moving to 9.4, as 9.3 has been released. |
CC: @jdemeyer @slel
Component: elliptic curves
Keywords: random_fail
Issue created by migration from https://trac.sagemath.org/ticket/28383
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