[Octave-bug-tracker] [bug #65424] svds(A) returns singular values in reversed order for complex A

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?65424>

                 Summary: svds(A) returns singular values in reversed order
for complex A
                   Group: GNU Octave
               Submitter: None
               Submitted: Wed 06 Mar 2024 07:17:42 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Angelika
        Originator Email: angies@cs.umu.se
             Open/Closed: Open
                 Release: 8.4.0
         Discussion Lock: Any
        Operating System: Any
           Fixed Release: None
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Wed 06 Mar 2024 07:17:42 PM UTC By: Anonymous
svds() returns the singular values in ascending order for complex matrices. By
definition, the singular values should appear in descending order. 

Reproducer:

n = 8;
A = rand(n,n) + 1i * rand(n,n);
[U, S, V] = svds(A);
diag(S)  % sorted from small to large, should be sorted from large to small


Notes:
(1) For a real input matrix A, the singular values are sorted as expected in
descending order.
(2) svds() in Matlab 2022 returns S in descending order for both real and
complex matrices.













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