#13400: Use strong caches diligently
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Reporter: nbruin | Owner: robertwb
Type: enhancement | Status: new
Priority: major | Milestone: sage-wishlist
Component: coercion | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by SimonKing):
I think the ticket description is a bit too broad. I hope you don't mind
that I change the title? If you do, please change back.
The reason for the name change I'm suggesting is the observation that
quite some objects are created during startup of Sage, and are then
garbage collected before even the Sage prompt appears. I think that this
indicates potential trouble. I find the following with
sage-5.2.beta3+#12313 and its dependencies:
When Sage starts, 37 different objects appearing as ''values'' in a weak
value dictionary get removed. Some of the deleted values occur 4 or 8
times. In particular, the "Groupoid with underlying set Symbolic Ring" is
deleted 3 times, and the "Groupoid with underlying set Rational Field" is
deleted 8 times, before sage even starts. In addition, both CIF['x'] and
CC['x'] are created and deleted twice.
Perhaps one should emphasize that `UniqueRepresentation` and
`UniqueFactory` actually were supposed to have a weak cache, according to
the documentation. Nevertheless, some code relies on the fact (the bug)
that the documentation was misleading and the cache has been strong.
Would it be useful to have a switch for `TripleDict` and `MonoDict`, such
as `strong_cache_on()`, `strong_cache_off()`? The idea is that after
calling `strong_cache_on()`, every item put into a `TripleDict` or
`MonoDict` and every item created by `weak_cached_function` (such as
`UniqueRepresentation`) and every item created with `UniqueFactory` is
prevented from deletion by adding a strong reference, and
`strong_cache_off()` deletes the strong references created since last
calling `strong_cache_on()`, so that only the weak references remain and
stuff becomes collectable?
Perhaps that could even become a context, so that the computation of the
echelon form could be like
{{{
with strong_cache:
<the multimodular code>
}}}
Concerning startup, I think 37 objects are easy to take care of. Perhaps
one should add a strong reference to them in the modules creating them.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13400#comment:2>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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