#8997: riemann_roch_basis is implemented incorrectly in sage
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Reporter: was | Owner: AlexGhitza
Type: defect | Status: positive_review
Priority: major | Milestone: sage-4.6.2
Component: algebraic geometry | Keywords:
Author: Moritz Minzlaff | Upstream: N/A
Reviewer: David Joyner, Oleksandr Motsak | Merged:
Work_issues: |
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Changes (by jdemeyer):
* status: needs_review => positive_review
Old description:
> See the file schemes/plane_curves/projective_curve.py, where it says
> {{{
>
> The following example illustrates that the Riemann-Roch space
> function in Singular doesn't *not* work correctly.
>
> ::
>
> sage: R.<x,y,z> = GF(5)[]
> sage: f = x^7 + y^7 + z^7
> sage: C = Curve(f); pts = C.rational_points()
> sage: D = C.divisor([ (3, pts[0]), (-1,pts[1]), (10, pts[5])
> ])
> sage: C.riemann_roch_basis(D) # output is random (!!!!)
> [x/(y + x), (z + y)/(y + x)]
>
> The answer has dimension 2 (confirmed via Magma). But it varies
> between 1 and quite large with Singular.
> }}}
>
> The problem can be solved by learning how the relevant code in Singular
> works then correctly wrapping it.
New description:
See the file schemes/plane_curves/projective_curve.py, where it says
{{{
The following example illustrates that the Riemann-Roch space
function in Singular doesn't *not* work correctly.
::
sage: R.<x,y,z> = GF(5)[]
sage: f = x^7 + y^7 + z^7
sage: C = Curve(f); pts = C.rational_points()
sage: D = C.divisor([ (3, pts[0]), (-1,pts[1]), (10, pts[5])
])
sage: C.riemann_roch_basis(D) # output is random (!!!!)
[x/(y + x), (z + y)/(y + x)]
The answer has dimension 2 (confirmed via Magma). But it varies
between 1 and quite large with Singular.
}}}
The problem can be solved by learning how the relevant code in Singular
works then correctly wrapping it.
'''Apply''': [attachment:trac_8997_fix_rr_basis_and_doc.patch]
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8997#comment:21>
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