On Mon, Mar 12, 2018 at 10:58 AM, Jeroen Demeyer <j.deme...@ugent.be> wrote:
> There is some very bad behaviour related to CachedRepresentation caching
> that I'm observing on #24742 (but this is otherwise unrelated to that
> ticket):
>
> sage: timeit('MatrixSpace(ZZ,3,3)')
> 625 loops, best of 3: 117 µs per loop
>
> Now, we try again but we first create a strong reference:
>
> sage: S = MatrixSpace(ZZ,3,3)
> sage: timeit('MatrixSpace(ZZ,3,3)')
> 625 loops, best of 3: 4.13 µs per loop
>
> This is much faster the second time! In the first example, the caching of
> CachedRepresentation.__classcall__ is pointless since there is no strong
> reference to the entry in the cache, so it gets deleted immediately whenever
> the "MatrixSpace(ZZ,3,3)" is deleted.
>
> This is just the usual Py_DECREF of Python objects, it has nothing to do
> with the cyclic garbage collector: the behaviour remains the same even with
> gc.disable().
>
> This makes me think that we might need a version of CachedRepresentation
> which keeps semi-strong references: these would only be deleted by the
> cyclic garbage collector but not by a simple Py_DECREF().I'm not exactly sure what you have in mind here, but you might be interested in PEP-442 regardless: https://www.python.org/dev/peps/pep-0442/ -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
