[Pkg-scicomp-devel] Bug#572935: arpack: Bug in ARPACK handling unsymmetric matrices
Thomas Weber
thomas.weber.mail at gmail.com
Sun Mar 7 18:33:12 UTC 2010
Package: arpack
Severity: important
Tags: patch
Hi,
on the GNU Octave mailing list, the following issue was noted. It seems
that for some inputs, ARPACK causes a segfault in Octave.
The issue was first noted in 2006[1]. A patch was sent to ARPACK
upstream, but there never was an answer.
The issue came up again last year[2].
So, I'm asking you include the attached patch in ARPACK. A test program
(segtest.m) for Octave is included. It segfaults Octave with current
ARPACK, when called as segtest(100).
[1] http://www-old.cae.wisc.edu/pipermail/octave-maintainers/2006-November/001230.html
[2] http://www-old.cae.wisc.edu/pipermail/bug-octave/2009-November/009818.html
BTW, I think there's something wrong with the orig tarball. It seems to
duplicate all source files and directories in a directory ARPACK.
Thanks
Thomas
-- System Information:
Debian Release: 5.0.3
APT prefers stable
APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 2.6.26-2-amd64 (SMP w/2 CPU cores)
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Shell: /bin/sh linked to /bin/bash
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function aerr = segtest (iter)
%% This will seg-fault octave consistently, but not matlab.
n=20;
k=4;
A = sparse([3:n,1:n,1:(n-2)],[1:(n-2),1:n,3:n],[ones(1,n-2),4*ones(1,n),-ones(1,n-2)]);
opts.disp = 0; opts.p = 19;
aerr = 0;
for i=1:iter
[v1,d1] = eigs(A, k, 'sr', opts);
d1 = diag(d1);
merr = 0;
for i=1:k
newerr = max(abs((A - d1(i)*speye(n))*v1(:,i)));
if (newerr > merr)
merr = newerr;
end
end
fprintf('Max Err: %g\n', merr);
if (merr > aerr)
aerr = merr;
end
end
end
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