#12357: Make groupoids garbage collectable
-------------------------+--------------------------------------------------
Reporter: SimonKing | Owner: rlm
Type: defect | Status: needs_review
Priority: major | Milestone: sage-5.0
Component: memleak | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #12313
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Comment(by SimonKing):
Concerning timings:
Without the patch, the groupoid of P is stored in a dictionary, indexed by
P. Hence, access to the cache is slow if `hash(P)` is slow.
Some data points:
{{{
sage: P = GF(151)['x','y']
sage: %timeit G = Groupoid(P) # slow hash
625 loops, best of 3: 20.9 µs per loop
sage: %timeit G = Groupoid(ZZ) # fast hash
625 loops, best of 3: 1.75 µs per loop
sage: class Bar(Parent): pass
....:
sage: P = Bar()
sage: %timeit G = Groupoid(P) # slow hash
625 loops, best of 3: 15.3 µs per loop
}}}
But with the patch, it is stored as an attribute of P. Hence, it is slow
if attribute access is slow. The point is that even slow attribute access
is faster than slow hash, and slow attribute access is only little slower
than fast hash:
{{{
sage: P = GF(151)['x','y']
sage: %timeit G = Groupoid(P) # slow attribute access
625 loops, best of 3: 3.11 µs per loop
sage: %timeit G = Groupoid(ZZ) # slow attribute access
625 loops, best of 3: 3.1 µs per loop
sage: class Bar(Parent): pass
....:
sage: P = Bar()
sage: %timeit G = Groupoid(P) # fast attribute access
625 loops, best of 3: 1.59 µs per loop
}}}
Hence, I believe that the patch is not only fixing a memory leak, but has
the potential to generate a speed-up.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12357#comment:3>
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