#15996: Allow general base rings for WeierstrassForm
-------------------------------------+-------------------------------------
Reporter: jkeitel | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.2
Component: algebraic | Resolution:
geometry | Merged in:
Keywords: toric, | Reviewers:
weierstrass | Work issues:
Authors: Jan Keitel | Commit:
Report Upstream: N/A | 3c0999f8fe80473c74afb9b7500874cf21ece17b
Branch: | Stopgaps:
u/jkeitel/weierstrass_general_rings|
Dependencies: |
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Description changed by jkeitel:
Old description:
> Currently, one method in {{{sage.rings.invariant_theory}}} and another
> one in {{{sage.schemes.toric.weierstrass}}} make use of
> {{{__floordiv__}}}. More precisely, if p and m are elements in a ring R
> with base ring B, then one needs
> {{{p // m}}},
> where {{{m}}} always has a unit coefficient. However, {{{__floordiv__}}}
> is only implemented if B is a field and therefore doing something like
> {{{
> sage: P.<a> = QQ[]
> sage: R.<x,y,z> = P[]
> sage: cubic = x^3 + a*y^3 + a^2*z^3
> sage: WeierstrassForm(cubic)
> }}}
> does not work because
> {{{
> sage: cubic // x^3
> }}}
> fails. However, since the coefficients of {{{m}}} are always in {{{QQ}}},
> we can work around that and I've written a short patch that does so.
>
> It might not be very pretty (if someone has a nicer idea, that would be
> great), but it works and actually speeds up long calculations.
>
> Best,
> Jan
New description:
Currently, one method in {{{sage.rings.invariant_theory}}} and another one
in {{{sage.schemes.toric.weierstrass}}} make use of {{{__floordiv__}}}.
More precisely, if p and m are elements in a ring R with base ring B, then
one needs
{{{p // m}}},
where {{{m}}} always has a unit coefficient. However, {{{__floordiv__}}}
is only implemented if B is a field and therefore doing something like
{{{
sage: P.<a, b> = QQ[]
sage: R.<x,y,z> = P[]
sage: cubic = x^3 + a*y^3 + a^2*z^3
sage: WeierstrassForm(cubic)
}}}
does not work because
{{{
sage: cubic // x^3
}}}
fails. However, since the coefficients of {{{m}}} are always in {{{QQ}}},
we can work around that and I've written a short patch that does so.
It might not be very pretty (if someone has a nicer idea, that would be
great), but it works and actually speeds up long calculations.
Best,
Jan
--
--
Ticket URL: <http://trac.sagemath.org/ticket/15996#comment:5>
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