#715: Parents probably not reclaimed due to too much caching
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Reporter: robertwb | Owner: somebody
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.8
Component: coercion | Keywords: weak cache coercion
Work_issues: Get some timings | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #9138, #11900
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Changes (by SimonKing):
* status: needs_info => needs_review
Comment:
It is always possible that there is a regression on some hardware, but not
on all.
I made an excessive log, i.e., I logged all Python commands. It turns out
that there are only little differences with or without patch. Hence, I am
sure that the regression does not come from an excessive garbage
collection (otherwise, I would have seen that some objects are created
repeatedly). So, I guess the regression comes from the C-level.
There is one thing that could make my code too slow: I use weak references
in my version of `TripleDict` and `TripleDictById`; however, when getting
dictionary items, I am calling the weak reference, in order to get the
object that it is pointing to, and compare then. That is slow.
I was thinking: Perhaps I could manage to use `id(X)` as key of
`TripleDictById`, rather than a weak reference to `X`. The weak reference
to `X` could be stored elsewhere.
Anyway, here is a data point:
Unpatched (there is only `TripleDict`, no `TripleDictById`):
{{{
sage: from sage.structure.coerce_dict import TripleDict
sage: D = TripleDict(113)
sage: L = []
sage: for p in prime_range(10^3):
....: K = GF(p)
....: P = K['x','y']
....: L.append((K,P))
....:
sage: for i,(K,P) in enumerate(L):
....: D[K,P,True] = i
....:
sage: cython("""
....: def testD(D, list L):
....: for K,P in L:
....: n = D[K,P,True]
....: """)
sage: %timeit testD(D,L)
625 loops, best of 3: 30.6 µs per loop
}}}
Patched (comparing `TripleDict` and `TripleDictById`):
{{{
sage: from sage.structure.coerce_dict import TripleDict, TripleDictById
sage: D = TripleDict(113)
sage: E = TripleDictById(113)
sage: L = []
sage: for p in prime_range(10^3):
....: K = GF(p)
....: P = K['x','y']
....: L.append((K,P))
....:
sage: for i,(K,P) in enumerate(L):
....: D[K,P,True] = i
....: E[K,P,True] = i
....:
sage: cython("""
....: def testD(D, list L):
....: for K,P in L:
....: n = D[K,P,True]
....: """)
sage: %timeit testD(D,L)
25 loops, best of 3: 21 ms per loop
sage: %timeit testD(E,L)
625 loops, best of 3: 61.9 µs per loop
}}}
In the applications, I am mainly using `TripleDictById`. Nevertheless, it
is only half as fast as the old `TripleDict`. So, this is what I have to
work at!
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/715#comment:111>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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