#715: Parents probably not reclaimed due to too much caching
------------------------+---------------------------------------------------
Reporter: robertwb | Owner: somebody
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.8
Component: coercion | Keywords: weak cache coercion
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #9138, #11900
------------------------+---------------------------------------------------
Comment(by SimonKing):
I found another memory leak:
{{{
sage: K = GF(1<<55,'t')
sage: for i in range(50):
....: a = K.random_element()
....: E = EllipticCurve(j=a)
....: b = K.has_coerce_map_from(E)
....:
sage: import gc
sage: gc.collect()
0
}}}
Namely, `K.coerce_map_from(E)` stores the resulting map (or None) in a
strong dictionary.
Several questions: Would it suffice to change the dictionary into a
`WeakKeyDictionary`? If it would: Would it cause a regression? I guess the
answer to the second question is "yes", since getting an item out of a
weak key dictionary is quite slow and requesting a coerce map is a very
frequent operation.
So, I suppose one could introduce another type of dictionary, analogous to
`TripleDict`, which would not test for equality but for identity.
But should this be here or on a new ticket? I think the patch from here is
big enough, hence, do it on a different ticket, but you can try to
convince me to do it here.
Since the patchbot tried to use the wrong patches:
Apply trac715_one_tripledict.patch
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/715#comment:131>
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