#13394: Write a WeakValueDictionary with safer key removal
-------------------------------------+-------------------------------------
Reporter: nbruin | Owner: rlm
Type: enhancement | Status: positive_review
Priority: major | Milestone: sage-6.0
Component: memleak | Resolution:
Keywords: | Merged in:
Authors: Simon King, Nils | Reviewers: Nils Bruin, Simon
Bruin | King
Report Upstream: None of the above | Work issues:
- read trac for reasoning. | Commit:
Branch: | 1a12ce6982bbe1f050e4ae627972023d5ddfa5ef
u/SimonKing/ticket/13394 | Stopgaps:
Dependencies: |
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Old description:
> On ticket #12313 we found that the use of `WeakValueDictionaries` as
> caches can cause `removal` callbacks in rather harsh environments. Normal
> `WeakValueDictionaries` remove keys with dead values by looking up the
> key. This involves Python equality testing on the key, which can cause
> any kind of operation in Sage. We need a dictionary where we can delete
> entries without key comparisons. See below for possible strategies.
>
> '''To the release manager:''' please fold this branch upon merging. There
> is quite a bit of back-and-forth in the history of this branch that is
> not very instructive to have in the global history of sage.
New description:
On ticket #12313 we found that the use of `WeakValueDictionaries` as
caches can cause `removal` callbacks in rather harsh environments. Normal
`WeakValueDictionaries` remove keys with dead values by looking up the
key. This involves Python equality testing on the key, which can cause any
kind of operation in Sage. We need a dictionary where we can delete
entries without key comparisons. See below for possible strategies.
'''To the release manager:'''
There is quite a bit of back-and-forth in the history of this branch that
is not very instructive to have in the global history of sage. Hence, we
have provided a single patch, if that seems to suite better. Moreover, it
is in the old folder layout, so that it should be possible to apply before
Apply [attachment:trac13394-weak_value_dictionary.patch]
--
Comment (by SimonKing):
I have removed the trailing whitespace from the patch, but not from the
branch yet (I can do so when requested).
This patch does apply to sage-5.12.beta5 (that's the latest non-git
version on my machine). Note that there was a mismatch in
`sage/structure/factory.pyx`, because someone appears to have removed
trailing whitespace. It must have happened somehow between sage-5.12.beta5
and the master branch on trac, but `git blame` does not show how the
whitespace has vanished.
Anyway. Nils, please verify that the attached patch applies to some non-
git Sage, and that the patch does what we do in the branch.
Apply trac13394-weak_value_dictionary.patch
--
Ticket URL: <http://trac.sagemath.org/ticket/13394#comment:97>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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