#13447: Make libsingular multivariate polynomial rings collectable
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Reporter: nbruin | Owner: rlm
Type: defect | Status:
needs_info
Priority: major | Milestone:
sage-5.4
Component: memleak | Resolution:
Keywords: | Work issues: Input
from libsingular experts
Report Upstream: Reported upstream. No feedback yet. | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
Replying to [comment:20 SimonKing]:
> {{{
> sage -t -force_lib devel/sage/sage/modular/modsym/ambient.py
> **********************************************************************
> File "/scratch/sking/sage-5.4.beta0/devel/sage-
main/sage/modular/modsym/ambient.py", line 1351:
> sage: ModularSymbols(20,2).boundary_space().dimension()
> Expected:
> 6
> Got:
> 0
> }}}
I have seen that error before, with other work-arounds (and I think also
with `singular-malloc`), so if it's indeed only a lower bound, then sage
has merely changed. It's not an error. If you're worried you can see where
that dimension is computed and put a hard ref in the creation of the
relevant object. If garbage collection is the cause of the observed
amnesia, a hard ref should "solve" it. In that case you can just change
the doctest answer.
> The second error is apparently ignored and only printed to stderr:
> {{{
> Exception AttributeError:
AttributeError('PolynomialRing_field_with_category' object has no
attribute '_modulus',) in ignored
> Exception AttributeError:
AttributeError('PolynomialRing_field_with_category' object has no
attribute '_modulus',) in ignored
> }}}
This is a worrisome error because it's fickle. One a linux x86_64 box, get
this reliably in `sage/rings/polynomial/multi_polynomial_libsingular.pyx`.
When I let it print the lines it's doctesting I get:
{{{
set_random_seed(0L)
change_warning_output(sys.stdout)
F = GF(Integer(7)**Integer(2), names=('a',)); (a,) =
F._first_ngens(1)###line 1913:_sage_ >>> F.<a> = GF(7^2)
R = F['x, y']; (x, y,) = R._first_ngens(2)###line 1914:_sage_ >>>
R.<x,y> = F[]
p = a*x**Integer(2) + y + a**Integer(3); p###line 1915:_sage_ >>> p =
a*x^2 + y + a^3; p
q = copy(p)###line 1917:_sage_ >>> q = copy(p)
p == q###line 1918:_sage_ >>> p == q
p is q###line 1920:_sage_ >>> p is q
lst = [p,q];###line 1922:_sage_ >>> lst = [p,q];
matrix(ZZ, Integer(2), Integer(2), lambda i,j:
bool(lst[i]==lst[j]))###line 1923:_sage_ >>> matrix(ZZ, 2, 2, lambda
i,j: bool(lst[i]==lst[j]))
Exception AttributeError:
AttributeError('PolynomialRing_field_with_category' object has no
attribute '_modulus',) in ignored
Exception AttributeError:
AttributeError('PolynomialRing_field_with_category' object has no
attribute '_modulus',) in ignored
matrix(ZZ, Integer(2), Integer(2), lambda i,j: bool(lst[i] is
lst[j]))###line 1926:_sage_ >>> matrix(ZZ, 2, 2, lambda i,j:
bool(lst[i] is lst[j]))
sig_on_count()
}}}
so it happens when doctesting line 1923. These are probably errors
encountered during a dealloc, so it might be happening in a garbage
collection. It could also be a `WeakValueDict` deletion callback that's
trying to do a comparison that fails. Googling shows that you've asked
about that exact error message on `cython-users` on 27 January, 2012, so
if you solved the bug that led to that question then, perhaps you can also
solve this one. It could also be a straight memory corruption.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13447#comment:22>
Sage <http://www.sagemath.org>
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