#12408: Segfault on a simple piece of call using matrices that used to work with
4.7.2
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Reporter: nthiery | Owner: jason, was
Type: defect | Status: new
Priority: major | Milestone: sage-5.0
Component: linear algebra | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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The following piece of code, inserted in the matrix code, triggers a
segfault in Sage 4.8, whereas it used to work in 4.7.2:
{{{
def _travel_column( self, dict d, int k):
r"""
Triggers a seg fault in Sage 4.8 but not 4.7.2
sage: M = matrix(ZZ,3,[0,1,0,-1,0,-1,0,1,0]); M
[ 0 1 0]
[-1 0 -1]
[ 0 1 0]
sage: M._travel_column({0:1},0)
** BOOM, Segfault **
"""
cdef int i
for i from 0 <= i < self.ncols():
d[i] = 1
print any(self[i,j] != 1 for j in d)
}}}
To reproduce: apply the attached patch on vanilla Sage 4.8, and run
the example above. Platform: at least Ubuntu 11.10 on a Macbook pro.
Note: the code is meaningless by itself; it's the smallest reduction I
could make of a real piece of code that triggered the seg fault in the
first place (#10347). For example there is no segfault if `any` is
replaced by a list comprehension. I suspect this issue to be related
to the upgraded iterators in the new version of Cython included in
Sage.
Cython experts, please!
Also, please update the component once we know more precisely what the
issue is.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12408>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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