#715: Parents probably not reclaimed due to too much caching
-------------------------------------------------------------------+--------
Reporter: robertwb |
Owner: somebody
Type: defect |
Status: needs_review
Priority: major |
Milestone: sage-5.4
Component: coercion |
Resolution:
Keywords: weak cache coercion Cernay2012 | Work
issues:
Report Upstream: N/A |
Reviewers: Jean-Pierre Flori, Simon King, Nils Bruin
Authors: Simon King, Jean-Pierre Flori | Merged
in:
Dependencies: #9138, #11900, #11599, to be merged with #11521 |
Stopgaps:
-------------------------------------------------------------------+--------
Comment (by nbruin):
Continuing on the bisection tour: While the argument above was sound (the
memory corruption must happen before the segfault), the following is a
heuristic: We observed that letting a doctest print/fail early in the file
prevents the segfault from happening. This could be because such a print
changes the memory layout (triggers a GC or something like that) and hence
the corruption that is still to come, happens in a different place and
doesn't lead to a segfault. This idea seems surprisingly robust in
practice: If you add failing doctests below a certain point, you have the
segfault in the place pointed out above. If you add failing doctests
before a certain point, no segfault happens. The hypothesis is now that
the crossover point is where the corruption happens. It's in example_21:
{{{
...
This class is a pickle. However, sometimes, pickles
need to be pickled another time.
TEST::
>>> PF = WeylGroup(['A',Integer(3)]).pieri_factors()###line
846:_sage_ >>> PF = WeylGroup(['A',3]).pieri_factors()
>>> a = PF.an_element()###line 847:_sage_ >>> a =
PF.an_element()
>>> 1
NOT THIS
>>> a.bruhat_lower_covers()###line 848:_sage_ >>>
a.bruhat_lower_covers()
...
}}}
With this in place, a segfault still happens. If I move the failing
doctest before `PF.an_element`, we don't get a segfault. So perhaps that
routine is to blame? Missing refcount increase perhaps?
Once again, this is only heuristic! I have no proof. It's just that around
this location, segfaulting seems to react to changes.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/715#comment:281>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en.
