#5970: Weak references in Polynomial Ring cache
--------------------------------------------+-------------------------------
Reporter: SimonKing | Owner: malb
Type: defect | Status: needs_info
Priority: critical | Milestone: sage-4.3.3
Component: commutative algebra | Keywords: polynomial ring
cache weak reference
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: regression for test_ec_leak? |
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Comment(by malb):
First, I can reproduce your results:
'''without patch'''
{{{
#!python
sage: %time test_poly_leak(10^5)
CPU times: user 11.11 s, sys: 0.31 s, total: 11.43 s
Wall time: 11.84 s
311.71875
sage: %time test_ec_leak(10^5)
CPU times: user 46.12 s, sys: 0.27 s, total: 46.39 s
Wall time: 47.27 s
206.26953125
sage: %time test_pc_leak(10^5)
CPU times: user 16.95 s, sys: 0.08 s, total: 17.03 s
Wall time: 17.64 s
54.1328125
}}}
'''with patch'''
{{{
#!python
sage: %time test_poly_leak(10^5)
CPU times: user 9.14 s, sys: 0.10 s, total: 9.25 s
Wall time: 9.58 s
70.53125
sage: %time test_ec_leak(10^5)
CPU times: user 57.96 s, sys: 0.50 s, total: 58.46 s
Wall time: 59.63 s
452.3671875
sage: %time test_pc_leak(10^5)
CPU times: user 17.03 s, sys: 0.07 s, total: 17.10 s
Wall time: 17.53 s
54.23046875
}}}
I would assume this is due to the fact that the elliptic curve constructor
does its own hashing somewhere (someone more familiar with this area might
want to comment on that) which prevents the GC from collecting the unused
polynomial rings. Also, since weak references need to keep track of more
information I find it plausible that each weak reference has some memory
overhead. Since we cannot free the unused polynomial rings this overhead
accumulates.
Maybe the elliptic curve constructor should use weak references as well?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5970#comment:17>
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