#11900: Serious regression caused by #9138
---------------------------+------------------------------------------------
Reporter: SimonKing | Owner: tbd
Type: defect | Status: needs_work
Priority: blocker | Milestone: sage-4.7.2
Component: performance | Keywords: categories regression
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #9138
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Comment(by nthiery):
Replying to [comment:33 SimonKing]:
> Replying to [comment:32 nthiery]:
> Which of the two work-arounds do you mean?
Actually both :-)
> The caching (so that the cache already happens when calling
> `Category.join(L)`, not only when creating the `JoinCategory`)? Or
> the attempt to directly create the `JoinCategory` during creation of
> a polynomial ring?
This might induce some quite big caching, since a given join may be
created in many different ways (order of arguments, ...). That being
said, maybe that's not so bad. Also, I need to check how this evolves
with the upcoming "more category constructions" patch. Anyway, I guess
we can wait until we actually meet the issue with that cache, if we
do, before removing it again.
> I think the latter is justified by having only few cases: It can be
`UniqueFactorisationDomain`, `IntegralDomain` or `EuclideanDomain`, and it
can be commutative or not. So, one can directly write down the result,
rather than calling the `Category.join(...)` mechanism. Of course, one
needs to verify that I wrote it down correctly.
The only potential issue is about the order of the categories in the join.
Having everything go through Category.join makes it easier to maintain
consistency, and make it evolve if needed. But if this remains a it is a
well documented and well motivated exception, that could be ok. It's not
worst than the order appearing in all the super_categories methods.
Cheers,
Nicolas
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11900#comment:34>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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