#14471: Exception KeyError: in WeakValueDictionary remove ignored
---------------------------+------------------------------------------------
Reporter: vbraun | Owner: rlm
Type: defect | Status: new
Priority: major | Milestone: sage-5.10
Component: memleak | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
Replying to [comment:5 vbraun]:
> {{{
> Exception KeyError: (((<class 'sage.categories.algebras.Algebras'>,
Callable function ring with arguments (x, y)), ()),) in <function remove
at 0x1acf758> ignored
> }}}
This entry is produced by the `__call__` doctest in `matrix0.pyx`:
{{{#!diff
sage: f(x,y) = x^2+y
sage: m = matrix([[f,f*f],[f^3,f^4]]); m
[ (x, y) |--> x^2 + y (x, y) |--> (x^2 + y)^2]
[(x, y) |--> (x^2 + y)^3 (x, y) |--> (x^2 + y)^4]
sage: m(1,2)
[ 3 9]
[27 81]
sage: m(y=2,x=1)
[ 3 9]
[27 81]
sage: m(2,1)
[ 5 25]
[125 625]
+ sage: D=UniqueRepresentation.__classcall__.get_cache()
+ sage: [k for k in D.data.keys() if k not in D.data]
+ []
}}}
With the added doctest, we get different behaviour depending on whether
attachment:trac_14471_demonstrate.patch is applied or not: Without the
patch, the test passes; with the patch the test fails. That means that the
line
{{{
hasattr(obj, '_foobar_')
}}}
changes the hash of one of the key components involved; probably the
"callable function ring", i.e., `parent(f)`. Indeed:
{{{
sage: f(x,y) = x^2+y
sage: H=hash(parent(f))
sage: m = matrix([[f,f*f],[f^3,f^4]]);
sage: hasattr(m,'a')
False
sage: H == hash(parent(f))
False
}}}
that last one's really bad! The `hasattr` on that matrix apparently
clobbers the hash of its base ring!
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14471#comment:12>
Sage <http://www.sagemath.org>
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