#21092: Unhandled case in EllipticCurve_from_cubic
-------------------------------------+-------------------------------------
Reporter: jdemeyer | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-7.4
Component: elliptic curves | Resolution:
Keywords: | Merged in:
Authors: Robin Houston | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/slelievre/unhandled_case_in_ellipticcurve_from_cubic|
507d31230e79b0cc0bf849818fb9a99981333644
Dependencies: | Stopgaps:
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Comment (by slelievre):
Testing the patched src/sage/schemes/elliptic_curves/constructor.py fails
for me:
{{{
sage -t --long --warn-long 59.7
src/sage/schemes/elliptic_curves/constructor.py
**********************************************************************
File "src/sage/schemes/elliptic_curves/constructor.py", line 880, in
sage.schemes.elliptic_curves.constructor.EllipticCurve_from_cubic
Failed example:
EllipticCurve_from_cubic(cubic, (-4/5, 4/5, 3/5) )
Expected:
Scheme morphism:
From: Closed subscheme of Projective Space of dimension 2 over
Rational Field defined by:
-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
To: Elliptic Curve defined by y^2 + 10*x*y + 112*y = x^3 + 46*x^2
+ 336*x over Rational Field
Defn: Defined on coordinates by sending (x : y : z) to
(1/3*z : y - 1/3*z : 1/112*x - 1/112*y - 1/42*z)
Got:
Scheme morphism:
From: Closed subscheme of Projective Space of dimension 2 over
Rational Field defined by:
-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
To: Elliptic Curve defined by y^2 - 6*x*y - 112*y = x^3 + 62*x^2 +
560*x over Rational Field
Defn: Defined on coordinates by sending (x : y : z) to
(1/3*z : -y - 1/3*z : 1/112*x - 1/112*y - 1/42*z)
**********************************************************************
1 item had failures:
1 of 36 in
sage.schemes.elliptic_curves.constructor.EllipticCurve_from_cubic
[185 tests, 1 failure, 81.44 s]
}}}
Is there some randomness involved?
Also, when this works, it would be worth adding a reference to
":trac:`21902`"
--
Ticket URL: <https://trac.sagemath.org/ticket/21092#comment:6>
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