#11900: Serious regression caused by #9138
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Reporter: SimonKing
| Owner: tbd
Type: defect
| Status: needs_work
Priority: critical
| Milestone: sage-4.8
Component: performance
| Keywords: categories regression
Work_issues: Laurent series rings are fields. Add docs. Don't use is_ring and
friends | Upstream: N/A
Reviewer: Jeroen Demeyer, Nicolas M. Thiéry
| Author: Simon King
Merged:
| Dependencies: #9138 #11911
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Comment(by SimonKing):
Replying to [comment:122 nthiery]:
> I assume the wrong thing is that DeBruijnSequences subclasses
EnumeratedSets, where the intention probably was to be a subcategory.
Probably.
Another possibility: `Category_singleton.__classcall__` should be a usual
class method, but store the unique instance in an attribute (say, `_inst`)
of the class - or, to be precise, in the dictionary of the class. Then, we
could do something like
{{{
#!python
class Category_singleton(Category):
@staticmethod
def __classcall__(object cls):
try:
return (<dict>cls.__dict__)['_inst']
except KeyError:
inst = Category.__classcall__(cls)
cls._inst = inst
return inst
}}}
Then, I get
{{{
sage: from sage.categories.category_singleton import Category_singleton
sage: %timeit S=Category_singleton()
625 loops, best of 3: 2.13 µs per loop
sage: %timeit S=Singleton()
625 loops, best of 3: 2.07 µs per loop
}}}
So, the timing seems ok, and it is subclassable:
{{{
sage: class Test(Singleton): pass
....:
sage: Singleton()
Category of singleton
sage: Test()
Category of test
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11900#comment:123>
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