#12313: Fix yet another memory leak caused by caching of coercion data
-------------------------------------------------+--------------------------
Reporter: SimonKing | Owner: rlm
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.0
Component: memleak | Resolution:
Keywords: coercion weak dictionary | Work issues:
Report Upstream: N/A | Reviewers: Simon King
Authors: Simon King, Jean-Pierre Flori | Merged in:
Dependencies: #715, #11521, #11599 | Stopgaps:
-------------------------------------------------+--------------------------
Changes (by SimonKing):
* reviewer: => Simon King
Old description:
> The following could not be fixed in #715:
>
> {{{
> sage: K = GF(1<<55,'t')
> sage: for i in range(50):
> ....: a = K.random_element()
> ....: E = EllipticCurve(j=a)
> ....: b = K.has_coerce_map_from(E)
> ....:
> sage: import gc
> sage: gc.collect()
> 0
> }}}
> The problem is that any parent has a dictionary that stores any coerce
> map (and a different dictionary for conversion maps) ending at this
> parent. The keys are given by the domains of the maps. So, in the example
> above, the field `K` has an attribute that is a dictionary whose keys are
> the different elliptic curves.
>
> In coercion, it is usually best to compare parents not by equality but by
> identity. Therefore, I suggest to implement a container called `MonoDict`
> that works similar to the new weak `TripleDict` (see #715), but takes a
> single item as a key.
>
> First tests show that one can actually gain a lot of speed: `MonoDict`
> can access its items much faster than a usual dictionary.
>
> __Apply__
>
> * [attachment:trac_12313-mono_dict-take2.patch]
> * [attachment:trac_12313-rebase_11599-take2.patch]
> * [attachment:trac_12313-cparent-take2.patch]
> * [attachment:trac_12313-reviewer-take2.patch]
> * [attachment:trac_12313-size_t-take2.patch]
New description:
The following could not be fixed in #715:
{{{
sage: K = GF(1<<55,'t')
sage: for i in range(50):
....: a = K.random_element()
....: E = EllipticCurve(j=a)
....: b = K.has_coerce_map_from(E)
....:
sage: import gc
sage: gc.collect()
0
}}}
The problem is that any parent has a dictionary that stores any coerce map
(and a different dictionary for conversion maps) ending at this parent.
The keys are given by the domains of the maps. So, in the example above,
the field `K` has an attribute that is a dictionary whose keys are the
different elliptic curves.
In coercion, it is usually best to compare parents not by equality but by
identity. Therefore, I suggest to implement a container called `MonoDict`
that works similar to the new weak `TripleDict` (see #715), but takes a
single item as a key.
First tests show that one can actually gain a lot of speed: `MonoDict` can
access its items much faster than a usual dictionary.
__Apply__
* [attachment:trac_12313-mono_dict-combined.patch]
--
Comment:
I have attached a combined patch, that is obtained by folding all patches
that have previously to be applied. In particular, it contains the fix
"use size_t instead of Py_ssize_t".
For me (64 bit), all tests pass (thus, positive review from me for the
parts of code written by Jean-Pierre), but we should wait for Jean-
Pierre's results on 32 bit.
For the patchbot:
Apply trac_12313-mono_dict-combined.patch
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12313#comment:62>
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