Can someone make a trac ticket for this please? On 25 Jul 2016 11:25, "Robin Houston" <robin.hous...@gmail.com> wrote:
> I ran into an unexpected error in EllipticCurve_from_cubic, with the > following cubic and rational point: > > R.<x,y,z> = QQ[] > cubic = -3*x^2*y + 3*x*y^2 + 4*x^2*z + 4*y^2*z - 3*x*z^2 + 3*y*z^2 - 8*z^3 > EllipticCurve_from_cubic(cubic, (-4/5, 4/5, 3/5)) > > Note that it works as expected using instead the different rational point > (1, 1, 0). > > On investigation, I found there is a case that isn’t handled correctly. > The code computes > > P2 = chord_and_tangent(F, P) > > and if P2 is projectively equivalent to P then it uses a different > algorithm. If they’re different, it then computes > > P3 = chord_and_tangent(F, P2) > > and uses an algorithm that fails if P3 is equivalent to P2. > > I think the attached patch fixes this problem. At least, with this patch > it now works for my examples. > > Best wishes, > Robin > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-devel+unsubscr...@googlegroups.com. > To post to this group, send email to sage-devel@googlegroups.com. > Visit this group at https://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
