#11521: Use weak references to cache homsets
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Reporter: jpflori | Owner: robertwb
Type: defect | Status: needs_work
Priority: major | Milestone: sage-5.3
Component: coercion | Resolution:
Keywords: sd35 | Work issues:
Report Upstream: N/A | Reviewers: Jean-Pierre
Flori
Authors: Simon King | Merged in:
Dependencies: #12969; to be merged with #715 | Stopgaps:
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Comment (by SimonKing):
Another comment: I use a weak reference to H (the homset) on the one hand,
and a weak reference to the category C as the third argument to the
`TripleDict`, on the other hand (see line 212). Since the keys of a
`TripleDict` are compared by identity and not by equality, I can not use a
callback function in the weak reference to C. Namely, weakref.ref(C) is
identical with weakref.ref(C), whereas two weak references with callback
are equal but not identical.
In conclusion, I will use a callback in the weak reference to H, so that
the dictionary item gets collected as soon as H gets collected. But I
think I can not use a callback in the weak reference to C. Anyway, a
callback for C is not needed: If H is alive, it has a reference to C and
keeps C alive. If H dies, then the callback for the weak reference to H
will remove the item, and thus C can be collected as well.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11521#comment:147>
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