[Octave-bug-tracker] [bug #58297] severe lin algebra errors presumably only on my machine

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?58297>

                 Summary: severe lin algebra errors presumably only on my
machine
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Sun 03 May 2020 04:43:12 PM UTC
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: address@hidden
             Open/Closed: Open
                 Release: 5.2.0
         Discussion Lock: Any
        Operating System: GNU/Linux

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Details:

SVD gets non orthonormal V and can get totally wrong matrix products.

Using Octave 5.2.0. (re-installed latest and tried flatpack)
Octave was configured for "x86_64-pc-linux-gnu".
Running Ubuntu 19.10 on Intel Core I9-9820X with Gnome34.2 64 bit, regularly
updated.

TEST:

load data.mat % provided below

%size(B) 295    36, B cols are orthonormal, and real:

B(:,1:7)'*B(:,1:7) == eye(7) == B(:,2:8)'*B(:,2:8), but
B(:,1:8)'*B(:,1:8) = random looking numbers

%also size(MLD)=36   295, real matrix

[U,S,V]=svd(MLD,'econ');
U(:,1:4)'*U(:,1:4)==eye(4) but
V(:,1:4)'*V(:,1:4) =
   1.9966201  -0.0022979   0.0052995   0.0075676
  -0.0022979   1.9862628   0.0194220   0.0103522
   0.0052995   0.0194220   1.9644382  -0.0056048
   0.0075676   0.0103522  -0.0056048   1.9275569
 



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File Attachments:


-------------------------------------------------------
Date: Sun 03 May 2020 04:43:12 PM UTC  Name: data.mat  Size: 166KiB   By: None
see summary for use
<http://savannah.gnu.org/bugs/download.php?file_id=48994>

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