[Octave-bug-tracker] [bug #45153] eigs returning an incorrrect number of eigenvalues

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?45153>

                 Summary: eigs returning an incorrrect number of eigenvalues
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Wed 20 May 2015 06:54:41 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: Renan
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.8.1
        Operating System: GNU/Linux

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Details:

When running the eigs function on a matrix (attached) while requesting a fixed
number of eigenvectors, eigs doesn't always return the requested number of
eigenvectors. 

In the following example, I requested the 16 smallest eigenvectors:


load('my_matrix')
[V, L] = eigs(my_matrix, 16, 'sm');
disp(size(L));


Running this code several times in succession sometimes returns 16 eigenvalues
and vectors, and sometimes 17:


>> [V, L] = eigs(my_matrix, 16, 'sm');
disp(size(L));
>>    16   16
>> [V, L] = eigs(my_matrix, 16, 'sm');
disp(size(L));
>>    17   17
>> 


In this example the matrix is sparse, but the same thing happens for the
equivalent full matrix. 



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File Attachments:


-------------------------------------------------------
Date: Wed 20 May 2015 06:54:41 PM UTC  Name: my_matrix  Size: 362kB   By: None

<http://savannah.gnu.org/bugs/download.php?file_id=34065>
-------------------------------------------------------
Date: Wed 20 May 2015 06:54:41 PM UTC  Name: example.m  Size: 69B   By: None

<http://savannah.gnu.org/bugs/download.php?file_id=34066>

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