#11900: Serious regression caused by #9138
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Reporter: SimonKing |
Owner: tbd
Type: defect |
Status: needs_work
Priority: major |
Milestone: sage-4.7.3
Component: performance |
Keywords: categories regression
Work_issues: fiy doctests, fix categories for polynomial rings |
Upstream: N/A
Reviewer: |
Author: Simon King
Merged: |
Dependencies: #9138
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Comment(by SimonKing):
In order to keep patches small, my plan is to provide two patches. The
first will be an update of the "polynomial categories and coercion" patch.
The second shall deal with parent/element classes of categories, which is
a separate issue.
'''Concerning the "polynomial categories and coercion":'''
__Choice of category__
Replying to [comment:37 SimonKing]:
> I suggest to add a function somewhere (perhaps in
sage/rings/polynomial/multi_polynomial_ring.py) that takes the category of
the base ring and the number of generators as arguments, and returns the
appropriate category of the polynomial ring.
That seems to work fine. Since I directly construct a `JoinCategory`
rather than calling `Category.join`, it is a little faster, and it is
certainly easier to maintain than the current approach.
__Easier detection of ring structures__
Currently, if one wants to test whether a parent is a Euclidean domain,
one has to do `P in EuclideanDomains()`, which boils down to
`P.category().is_subcategory(EuclideanDomains())`. That implies the
construction of all super-categories of `P.category()` and is thus rather
slow.
I guess it would be ''much'' faster to add parent methods that tell
whether the ring has a certain structure, and to simply ask
`P.is_euclidean_domain()`.
Similar parent methods should exist for `Fields()`, `Rings()`,
`CommutativeRings()` and `IntegralDomains()`.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11900#comment:39>
Sage <http://www.sagemath.org>
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