bugGNU Octave - Bugs: bug #30035, The back division operator crashes...

 
 

bug #30035: The back division operator crashes Octave

Submitter:  None
Submitted:  Wed 02 Jun 2010 11:13:33 AM UTC
   
 
Category:  None Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Segfault, Bus Error, etc.
Status:  Works For Me Assigned to:  None
Originator Name:  ESP Originator Email:  -email is unavailable-
Open/Closed:  * Closed Release:  * 3.2.3
Operating System:  * GNU/Linux Fixed Release:  None
Planned Release:  None
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Thu 03 Jun 2010 04:08:31 PM UTC, comment #3: 

Thanks for doing the investigation.  From your reports, it sounds like it is not Octave, but rather whoever packaged Octave 3.2.3 for yum who introduced a bug.  I'm going to close bug on this site since we are dedicated only to bugs within Octave.

Incidentally, to build from source you need to have the development versions of the lapack and blas packages.  These are called lapack-devel and blas-devel on yum and can be installed next to the existing runtime libraries of lapack and blas.  You could try building from source again if you want to have a version that works on your Fedora 12 box.

Rik <rik5>
Group administrator
Thu 03 Jun 2010 03:48:35 PM UTC, comment #2: 

Hi, I have just created an account to be able to reply.

I have this bug in Fedora 12, using Octave 3.2.3 from the yum repository. I tried to remove and install Octave again (using yum), same bug.

I tried the same code on a Windows Seven machine running Octave 3.2.3 (Windows binaries) and it works. Also I tried it in Octave 3.0.5 running in Ubuntu in a VirtualBox and it works.

I tried to install the testing version of Octave (3.3.51) from the "bleeding-edge" directory on the octave ftp webpage (the links on the html page do not work), but I get some errors while running the ./configure script. It is written "You are required to have BLAS and LAPACK libraries", whereas I have installed these libraries from the yum repository. Therefore I could not test the code in the development version.

I think the back division problem comes from the Octave version present in the yum repository.

None <espk>
Wed 02 Jun 2010 07:01:17 PM UTC, comment #1: 

Your test code works correctly on the development version of Octave.  Could you try the development version from Mercurial sources and report whether your problem is solved?

Rik <rik5>
Group administrator
Wed 02 Jun 2010 11:13:33 AM UTC, original submission:  

A fatal error arises when using the back division operator to solve a linear system of equations with more equations than unknowns.
Such a system can be used to deconvolve a signal for example, where the (full) convolved data is typically larger than the original data, and using a circulant matrix made from the convolution filter as the equations coefficients.
The same code works correctly in Matlab (for the purpose of deconvolution, not tried for other systems of equations).

The simpler example below is used to illustrate a typical situation for the bug to occur. It does not use a circulant matrix but the same bug appears in Octave (and not in Matlab).
It seems that this bug is due to the use of inv and/or pinv (same bug appears when using inv and pinv on that matrix - even if the matrix is not invertible, at least it should not crash)


octave:1> mat1 = rand(200, 362);
octave:2> vect1 = rand(200, 1);
octave:3> mat1\vect1;
panic: Illegal instruction -- stopping myself...
attempting to save variables to `octave-core'...
save to `octave-core' complete
Illegal instruction (core dumped)

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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2010-06-03 rik5 Open/ClosedOpen Closed
    2010-06-02 rik5 StatusNone Works For Me

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