#715: Parents probably not reclaimed due to too much caching
------------------------+---------------------------------------------------
Reporter: robertwb | Owner: somebody
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.0
Component: coercion | Keywords: weak cache coercion Cernay2012
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #9138, #11900
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Old description:
> Here is a small example illustrating the issue.
>
> The memory footprint of the following piece of code grows indefinitely.
>
> {{{
> sage: K = GF(1<<55,'t')
> sage: a = K.random_element()
> sage: while 1:
> ....: E = EllipticCurve(j=a); P = E.random_point(); 2*P; del E, P;
>
> }}}
> E and P get deleted, but when 2*P is computed, the action of integers on
> A, the abelian group of rational points of the ellitpic curve, gets
> cached in the corecion model.
>
> A key-value pair is left in coercion_model._action_maps dict:
>
> (ZZ,A,*) : IntegerMulAction
>
> Moreover there is at least also references to A in the IntegerMulAction
> and one in ZZ._action_hash.
>
> So weak refs should be used in all these places if it does not slow
> things too much.
>
> Apply [attachment:trac715_one_triple_dict.patch]
New description:
Here is a small example illustrating the issue.
The memory footprint of the following piece of code grows indefinitely.
{{{
sage: K = GF(1<<55,'t')
sage: a = K.random_element()
sage: while 1:
....: E = EllipticCurve(j=a); P = E.random_point(); 2*P; del E, P;
}}}
E and P get deleted, but when 2*P is computed, the action of integers on
A, the abelian group of rational points of the ellitpic curve, gets cached
in the corecion model.
A key-value pair is left in coercion_model._action_maps dict:
(ZZ,A,*) : IntegerMulAction
Moreover there is at least also references to A in the IntegerMulAction
and one in ZZ._action_hash.
So weak refs should be used in all these places if it does not slow things
too much.
Apply:
* [attachment:trac715_one_triple_dict.patch]
* [attachment:trac_715-reviewer.patch]
--
Comment(by jpflori):
I've added warning blocks at the top of files modified by Simon (and fixed
minor typos without introducing new ones I hope). The generated doc looks
ok.
All tests pass on my computer and the numerical evidence we've gathered so
far points that there is no speed regression.
If Simon or someone else could have a look at my "reviewer patch", this
can be put to positive review.
Personally, I'm happy with Simon patches.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/715#comment:152>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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