#14471: Category refinement sometimes changes the hash of parents
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Reporter: vbraun | Owner: rlm
Type: defect | Status: needs_review
Priority: critical | Milestone: sage-5.11
Component: memleak | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Volker Braun | Merged in:
Dependencies: | Stopgaps:
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Changes (by vbraun):
* priority: major => critical
Old description:
> Old title: Exception KeyError: in WeakValueDictionary remove ignored
>
> Under some circumstances the !WeakValueDictionary remove callback is
> being called when the internal dictionary is in a bad state. The attached
> patch [attachment:trac_14471_demonstrate.patch] to demonstrate the issue
> just calls `hasattr` from the displayhook, which ends up generating weak
> references somewhere. The exact place for where the exception occurs
> depends on the garbage collector, but I always do get some unwanted
> exceptions with it.
> {{{
> sage -t devel/sage/sage/matrix/matrix0.pyx
> Exception KeyError: (((<class 'sage.matrix.matrix_space.MatrixSpace'>,
> Callable function ring with arguments (x, y), 2, 2, False), ()),) in
> <function remove at 0x18d8758> ignored
> **********************************************************************
> File "devel/sage/sage/matrix/matrix0.pyx", line 3370, in
> sage.matrix.matrix0.Matrix.is_hermitian
> Failed example:
> B.is_hermitian()
> Expected:
> True
> Got:
> Exception KeyError: (((<class 'sage.categories.algebras.Algebras'>,
> Callable function ring with arguments (x, y)), ()),) in <function remove
> at 0x18d8758> ignored
> True
> }}}
>
> Apply [attachment:trac_14471_dynamic_class_hash.patch]
New description:
Some objects with dynamical classes use `hash(self.__class__)`. Since this
is not an invariant of dynamical classes bad things will happen.
One such instance is that, under some circumstances, a
!WeakValueDictionary remove callback is being called but cannot find the
object in the dictionary since the hash changed.
Apply [attachment:trac_14471_dynamic_class_hash.patch]
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Comment:
I'm setting the priority to critical since it is a structural issue that
we must get right in order to trust computations.
Rediffed to sage-5.11.beta3
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14471#comment:27>
Sage <http://www.sagemath.org>
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