#11115: Rewrite cached_method in Cython
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Reporter: SimonKing | Owner: jason
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.7
Component: misc | Keywords: category cython cache
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies:
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Comment(by SimonKing):
Hi Andrey,
Replying to [comment:28 novoselt]:
> And as I understand, things don't break if you forget to do it, they
just work slower than they should.
What scenario does your statement refer to? (1) The status quo, (2) the
patch as it is, or (3) the patch without
`sage.structure.element.Element.__cached_methods`?
Here is my view on these three:
(1) Cached methods have been improved in #8611, but they are still not
fast enough, for my taste. Time and memory is wasted by assigning a
`__doc__` string to each instance of a cached method (that is noticeable
in the startup time). It can only be used in Python code. If a parent or
an element does not accept attribute assignment then it can inherit a
cached_method from the category -- but the cache breaks ''and'' there is a
huge overhead. cached_in_parent_method can not be inherited from the
category at all.
(2) cached_method can compete with a hand-written cache in Python, speed-
wise, provided that attribute assignment is possible. `__doc__` is now
replaced by `_sage_doc_`, which is used by sage's introspection anyway and
computes the docstring only when requested. It can, to some extent, be
used in Cython code. If a parent or an element does not accept attribute
assignment then it can inherit a cached_method from the category: The
return values ''are'' cached ("things don't break), but there is an
overhead (though much less than in (1)). The price to pay is 0.24% more
memory consumption at startup. cached_in_parent_method can be inherited
from the category.
(3) (Hypothetical) Cached methods are supported for elements only if
either the element allows attribute assignment, or the user did not forget
to provide it with a public attribute `__cached_methods`. If neither of
these conditions hold then things behave as in (1), for elements. In
particular, for an element that does not satisfy the conditions, the cache
of cached_method will break and will have a huge overhead. However,
cached_in_parent_method is fully supported (that is since the cache is in
the parent, and parents ''have'' `__cached_methods` in scenario (3)).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11115#comment:29>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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