#8301: segfault in m4ri
------------------------------+---------------------------------------------
Reporter: was | Owner: was
Type: defect | Status: new
Priority: major | Milestone: sage-4.3.3
Component: linear algebra | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Type in
{{{
sage: b = random_matrix(GF(2),4,200); b[3] = b[0]; b.rank()
}}}
and get an absolutely stupendous segfault!
For the first time ever I finally get to use GF(2) matrix algebra for some
actually interesting number theory research. So I wrote a program that
creates some fairly simple GF(2) matrices (using modular symbols), and
tried the first somewhat nontrivial thing (computing the rank of a 4xn
matrix) and got segfaults. This is on 64-bit Ubuntu Linux. Yikes. So:
1. These need to get fixed, obviously.
2. Is there an easy way to completely turn off m4ri? Seeing how easily
it fell over, I don't trust it, and though it is fast I definitely want to
rerun all my calculations m4ri free once I have everything setup. These
are calculations for a published paper that will play a key role in a
"proof by computer" of a potentially important result in number theory.
Regarding 2, here is a way that I seem to be able to get a matrix mod n
dense, and I can then compute the rank, which in this case uses linbox,
and is probably fast enough for my application:
{{{
sage: c =
sage.matrix.matrix_modn_dense.Matrix_modn_dense(b.parent(),b.list(),False,True)
sage: c.rank()
3
sage: timeit('c.rank()')
625 loops, best of 3: 534 ns per loop
sage: timeit('c._clear_cache(); c.rank()')
625 loops, best of 3: 161 µs per loop
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8301>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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