#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:31 SimonKing]:
> Last idea, before I go to sleep:
>
> We could
> - only have a ''weak'' reference to the values (here: a morphism, say,
phi) of the `MonoDict` in `_convert_from_hash` (here:
`CDF._convert_from_hash`),
> - keep a strong reference from the morphism to the domain (here: from Q
to phi)
> - add a ''strong'' reference from the domain (Q) to the morphism (phi).
>
> Would this save us?
>
> We want that a strong reference [edit: I mean an external strong
reference] to Q keeps phi alive. Well, it does, since we added a strong
reference Q->phi.
>
> We want that phi can be collected, if no external strong reference to Q
[edit: or to phi] exists. Well, there only are weak references from the
`MonoDict` to phi and to Q. Hence, the only strong reference to phi comes
from Q, and the only strong reference to Q comes from phi. This is a
circle, that Python's cyclic garbage collector can deal with. Both Q and
phi would be collected, and removed from the `MonoDict`.
>
> [edit:] And finally: An external strong reference to phi will keep Q
alive, since we have a strong reference from phi to its domain Q.
>
That would suit as well I guess and sounds kind of like the coerce_to
solution nils suggested.
If we go this way, I guess we should do the same for actions.
--
Ticket URL: <http://trac.sagemath.org/ticket/14711#comment:32>
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