[Octave-bug-tracker] [bug #42097] 64bit Slackware, eig returning incorrect results

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?42097>

                 Summary: 64bit Slackware,eig returning incorrect results
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Fri 11 Apr 2014 02:25:36 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Russell Carden
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.6.4
        Operating System: GNU/Linux

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Details:

I am running Slackware 14.1 64bit.
I compiled octave using the scripts at slackbuilds.org.
I found that eig returns incorrect results for matrices with n>=3.
I found eig(A) and eig(A') as well as eig(Q'*A*Q'), where Q is unitary all
return different results.  If I compute the eigenvectors as well
[V D]=eig(A)
then if I compute
A*V-V*D, I get a matrix with
zeros in the first row and O(1) entries in the remaining rows.
I noticed that eig code for make check only tests matrices of size 2, which is
why this problem wasn't detected at comiple time.

Has anyone else encountered this problem?  If not I would be interested in
helping to figure out what is wrong.

Thank you




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