#715: Parents probably not reclaimed due to too much caching
-------------------------------------------------------------------+--------
Reporter: robertwb |
Owner: somebody
Type: defect |
Status: needs_work
Priority: major |
Milestone: sage-pending
Component: coercion |
Resolution:
Keywords: weak cache coercion Cernay2012 | Work
issues:
Report Upstream: N/A |
Reviewers: Jean-Pierre Flori, Simon King
Authors: Simon King, Jean-Pierre Flori | Merged
in:
Dependencies: #9138, #11900, #11599, to be merged with #11521 |
Stopgaps:
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Comment (by SimonKing):
Too bad. I tried to add the following to the old patch:
{{{
#!diff
diff --git a/sage/structure/coerce_dict.pxd
b/sage/structure/coerce_dict.pxd
--- a/sage/structure/coerce_dict.pxd
+++ b/sage/structure/coerce_dict.pxd
@@ -1,6 +1,7 @@
cdef class TripleDict:
cdef Py_ssize_t _size
cdef buckets
+ cdef dict _refcache
cdef double threshold
cdef TripleDictEraser eraser
cdef get(self, object k1, object k2, object k3)
diff --git a/sage/structure/coerce_dict.pyx
b/sage/structure/coerce_dict.pyx
--- a/sage/structure/coerce_dict.pyx
+++ b/sage/structure/coerce_dict.pyx
@@ -18,8 +18,6 @@
# removing dead references from the cache
############################################
-cdef dict _refcache = {}
-
cdef class TripleDictEraser:
"""
Erases items from a :class:`TripleDict` when a weak reference becomes
@@ -108,8 +106,10 @@
del bucket[i:i+4]
self.D._size -= 1
break
- cdef list L = _refcache[k1,k2,k3]
- del L[L.index(r)]
+ try:
+ self.D._refcache.__delitem__((k1,k2,k3))
+ except KeyError:
+ pass
cdef class TripleDict:
"""
@@ -432,22 +432,24 @@
PyList_Append(bucket, h3)
PyList_Append(bucket, value)
try:
- PyList_Append(_refcache.setdefault((h1 , h2, h3), []),
- KeyedRef(k1,self.eraser,(h1, h2, h3)))
+ ref1 = KeyedRef(k1,self.eraser,(h1, h2, h3)))
except TypeError:
- PyList_Append(_refcache.setdefault((h1, h2, h3), []), k1)
+ ref1 = k1
if k2 is not k1:
try:
- PyList_Append(_refcache.setdefault((h1 , h2, h3), []),
- KeyedRef(k2,self.eraser,(h1, h2, h3)))
+ ref2 = KeyedRef(k2,self.eraser,(h1, h2, h3)))
except TypeError:
- PyList_Append(_refcache.setdefault((h1, h2, h3), []), k2)
- if k3 is not k1 and k3 is not k2:
+ ref2 = k2
+ else:
+ ref2 = None
+ if k3 is not k2 or k3 is not k1:
try:
- PyList_Append(_refcache.setdefault((h1 , h2, h3), []),
- KeyedRef(k3,self.eraser,(h1, h2, h3)))
+ ref3 = KeyedRef(k3,self.eraser,(h1, h2, h3)))
except TypeError:
- PyList_Append(_refcache.setdefault((h1, h2, h3), []),k3)
+ ref3 = k3
+ else:
+ ref3 = None
+ self._refcache[h1,h2,h3] = (ref1,ref2,ref3)
self._size += 1
def __delitem__(self, k):
}}}
However, with the resulting code, the memory leak discussed here
reappears!
So far, I can only speculate why that has happened. It could be that
moving _refcache into the `TripleDict` created a reference cycle (namely,
`TripleDict` will occur as attribute to parents, and the parents occur as
references in _refcache). If a `__del__` method is involved, the items in
the reference cycle can't be collected.
If this holds true, then one has to have the necessary references in an
''external'' dictionary. But perhaps one can still ensure that the data
associated with one `TripleDict` will be removed, as soon as the
`TripleDict` gets garbage collected.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/715#comment:200>
Sage <http://www.sagemath.org>
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