#11521: Memleak when resolving the action of Integers on an Elliptic Curve
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Reporter: jpflori | Owner: robertwb
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.8
Component: coercion | Keywords: sd35
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #11900 #715
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Comment(by SimonKing):
Replying to [comment:100 jpflori]:
> Anyway, it does not make much sense to me that the _action_hash dict in
the Parent class uses "==" rather than "is", especially since the
TripleDict of the coercion model do.
The old `TripleDict` didn't - I changed that only in #715. Perhaps it is
debatable whether that change is fine. But:
> What do yo think? Have you any good reason to justify such a choice that
I might have missed?
See sage/structure/coerce.pyx:
{{{
if y_mor is not None:
all.append("Coercion on right operand via")
all.append(y_mor)
if res is not None and res is not y_mor.codomain():
raise RuntimeError, ("BUG in coercion model: codomains
not equal!", x_mor, y_mor)
}}}
That is why I think one should test for identity, not equality.
On the other hand, we also have
{{{
# Make sure the domains are correct
if R_map.domain() is not R:
if fix:
connecting = R_map.domain().coerce_map_from(R)
if connecting is not None:
R_map = R_map * connecting
if R_map.domain() is not R:
raise RuntimeError, ("BUG in coercion model, left domain
must be original parent", R, R_map)
if S_map is not None and S_map.domain() is not S:
if fix:
connecting = S_map.domain().coerce_map_from(S)
if connecting is not None:
S_map = S_map * connecting
if S_map.domain() is not S:
raise RuntimeError, ("BUG in coercion model, right domain
must be original parent", S, S_map)
}}}
in the same file. These lines apparently cope with the fact that there are
non-unique parents, and they suggest that `==` is the right thing to do in
the coerce caches.
But I think this is a discussion that belongs to #715.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11521#comment:101>
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