#14711: Memleak when creating QuadraticField
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Reporter: jpflori | Owner:
Type: defect | davidloeffler
Priority: critical | Status: new
Component: number fields | Milestone: sage-5.12
Keywords: memleak, number field, | Resolution:
QuadraticField | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: u/SimonKing/ticket/14711 | Commit:
Dependencies: | Stopgaps:
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Comment (by jpflori):
Replying to [comment:23 SimonKing]:
> {{{
> sage:
objgraph.show_chain(objgraph.find_backref_chain(random.choice(objgraph.by_type('NumberField_quadratic_with_category')),inspect.ismodule),
filename='chain.png')
> }}}
> shows me the file chain.png in the attachment (of course, subject to
some random choice).
>
> What is happening there? If I am not mistaken, objgraph only shows
strong references. The quadratic field Q is used as key for the `MonoDict`
which stores conversions into `CDF`. This monodict has a weak reference to
the key Q, but a strong reference to the value, which is a morphism. The
morphism of course points to both domain and codomain, and there is your
problem.
>
> So, how can we break this chain?
Weakcaching the domain?
In such a situation it would make sense as in the monodict this domain is
already only weakcached, in contrast to the codomain which stays alive
anyway.
Didn't we do something similar for Action?
Not sure about the other uses of morphism though, a morphism could then
survive when its parent dies.
But whats the point of keeping a morphism alive if you don't use its
parent?
--
Ticket URL: <http://trac.sagemath.org/ticket/14711#comment:25>
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