#11521: Memleak when resolving the action of Integers on an Elliptic Curve
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Reporter: jpflori | Owner: robertwb
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.8
Component: coercion | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Changes (by SimonKing):
* status: needs_review => needs_work
Comment:
In the following example, there is no memory leak that would be caused by
the `sage.categories.homset` cache:
{{{
sage: len(sage.categories.homset._cache.keys())
100
sage: for p in prime_range(10^5):
....: K = GF(p)
....:
sage: len(sage.categories.homset._cache.keys())
100
}}}
However, when you do a conversion `K(...)` then a convert map is created,
and apparently is cached:
{{{
sage: for p in prime_range(10^5):
....: K = GF(p)
....: a = K(0)
....:
sage: len(sage.categories.homset._cache.keys())
9692
}}}
The homset cache does use weak references. Hence, it is surprising that
the unused stuff can not be garbage collected. Apparently there is some
direct reference involved at some point.
I am very stronglyagainst removing the cache of `sage.categories.homset`.
Namely, elliptic curve code uses finite fields and maps involving finite
fields ''a lot'', and killing the cache is likely to cause a massive
regression.
However, since we actually have coercion maps (not just any odd map), I
expect that the direct reference comes from the coercion model. I suggest
to look into the coercion code and use weak references there.
By the way, I don't know why the status is "needs review". I think it
clearly is "needs work".
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11521#comment:21>
Sage <http://www.sagemath.org>
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