#13447: Make libsingular multivariate polynomial rings collectable
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Reporter: nbruin |
Owner:
Type: defect |
Status: needs_work
Priority: major |
Milestone: sage-5.4
Component: memleak |
Resolution:
Keywords: | Work
issues: Understand why sometimes `new_RingWrap` needs an incref and sometimes
not
Report Upstream: None of the above - read trac for reasoning. |
Reviewers: Simon King
Authors: Nils Bruin, Simon King | Merged
in:
Dependencies: #11521 |
Stopgaps:
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Comment (by SimonKing):
I have posted a new patch
[attachment:trac_13447-attempted_improvement.patch]. According to Hans, it
may happen that Singular functions return NULL, which means that there has
been an error. Therefore, I suggest to actually ''raise'' a `RuntimeError`
if the return value is NULL. Apart from that, I postpone another `ggetid`
call to a location where `currRing` is guaranteed to exist; however,
according to Hans, that call to `ggetid` (namely in the case of a library
functions) should be fine also without `currRing`.
Here is the problem:
{{{
sage -t --verbose
devel/sage/sage/rings/polynomial/multi_polynomial_ideal.py
...
Trying:
R = QQ['a, b']; (a, b,) = R._first_ngens(2); I =
R.ideal(a**Integer(2)+b**Integer(2)-Integer(1))###line 3581:_sage_ >>>
R.<a,b> = QQ[]; I = R.ideal(a^2+b^2-1)
Expecting nothing
ok
Trying:
Q = QuotientRing(R,I); K = Frac(Q)###line 3582:_sage_ >>> Q =
QuotientRing(R,I); K = Frac(Q)
Expecting nothing
// ** char_series returns 0 x 0 matrix from 2 input polys (0)
I[1,1]=b2+a2-1*** *** Error: TIMED OUT! PROCESS KILLED! *** ***
[360.3 s]
}}}
I have absolutely no idea why that happens.
The error occurs in the Singular library function `primdecSY`. I did check
that `currRing` is definitely not NULL when calling the function,
`currRingHdl.data.uring==currRing`, and there are plenty of references to
`currRing`. Moreover, the error does not occur if one copies the whole
example (which is from the groebner_basis method) into an interactive
session.
`primdecSY` hangs, there is no return value (not even NULL).
Since there is no segfault, I guess gdb would not help here. Since
currRing is referenced several times, I guess that it has not been double-
freed - but who knows? Can it be that a ring was double-freed, then a new
ring was created in the same location, and then an error occurs when
working with that new ring?
For now:
Apply trac_13447-sanitise_ring_refcount.patch
trac_13447-attempted_improvement.patch
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13447#comment:80>
Sage <http://www.sagemath.org>
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