#12215: Memleak in UniqueRepresentation, @cached_method
-----------------------+----------------------------------------------------
Reporter: vbraun | Owner: rlm
Type: defect | Status: new
Priority: major | Milestone: sage-4.8
Component: memleak | Keywords: UniqueRepresentation cached_method
caching
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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The documentation says that UniqueRepresentation uses weak refs, but this
was switched over to the @cached_method decorator. The latter does
currently use strong references, so unused unique parents stay in memory
forever:
{{{
import sage.structure.unique_representation
len(sage.structure.unique_representation.UniqueRepresentation.__classcall__.cache)
for i in range(2,1000):
ring = ZZ.quotient(ZZ(i))
vectorspace = ring^2
import gc
gc.collect()
len(sage.structure.unique_representation.UniqueRepresentation.__classcall__.cache)
}}}
Related tickets:
* #11521 (needs review, introducing weak references for caching
homsets), and
* #715 (needs a lot of work, eventually aiming at using weak references
for caching coerce maps).
Further notes:
* not everything in Python can be weakref'ed, for example ``None``
cannot.
* some results that are expensive to compute should not just be cached
by a weak reference. Perhaps there is place for a permanent cache, or
maybe some minimal age before garbage collecting it.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12215>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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