bugGNU Octave - Bugs: bug #36728, erroneous 'QZ' results

 
 

bug #36728: erroneous 'QZ' results

Submitted by:  None
Submitted on:  Mon 25 Jun 2012 04:39:33 PM UTC  
 
Category: NoneSeverity: 3 - Normal
Priority: 5 - NormalItem Group: Incorrect Result
Status: FixedAssigned to: Jordi Gutiérrez Hermoso <jordigh>
Originator Name: IdoOriginator Email: -unavailable-
Open/Closed: ClosedRelease: 3.6.2
Operating System: GNU/Linux

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Wed 18 Jul 2012 07:39:35 PM UTC, comment #4:

I checked in the following change:

http://hg.savannah.gnu.org/hgweb/octave/rev/54a386f2ac4e

John W. Eaton <jwe>
Project Administrator
Wed 18 Jul 2012 03:37:24 PM UTC, comment #3:

It turns out that for whatever reason

gives you the result in Octave.

The person who wrote this code has died. Can you help us work on it, and implement ordqz?

http://inversethought.com/hg/octave-max/file/tip/src/DLD-FUNCTIONS/qz.cc

None of us are very familiar with the QZ factorisation. I would be very happy to help you with the C++ and Octave API part, but I'm reading Golub & Van Loan to understand the QZ factorisation, and I could use your help.

Jordi Gutiérrez Hermoso <jordigh>
Project AdministratorIn charge of this item.
Tue 17 Jul 2012 08:58:06 PM UTC, comment #2:

What is "the equivalent Matlab code"? Matlab doesn't accept a "-" option.

Jordi Gutiérrez Hermoso <jordigh>
Project AdministratorIn charge of this item.
Tue 26 Jun 2012 02:30:15 PM UTC, comment #1:

I recognise those bit patterns. That's uninitialised memory. valgrind confirms it. This is indeed a bug. I'll attack it within the next few days.

Jordi Gutiérrez Hermoso <jordigh>
Project AdministratorIn charge of this item.
Mon 25 Jun 2012 04:39:33 PM UTC, original submission:

I am trying to compute ordered QZ decomposition but the results are erroneous. the code is:

and the results are:

where equivalent MATLAB code yields:

I am using debian, kernel 3.2.0-2-amd64.
I compiled octave by myself.
The output of octave_config_info is:

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  • -unavailable- added by jwe (Posted a comment)
  • -unavailable- added by jordigh (Posted a comment)
  • -unavailable- added by None (Submitted the item)
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    Follow 4 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Wed 18 Jul 2012 07:39:35 PM UTCjweStatusConfirmed=>Fixed
      Open/ClosedOpen=>Closed
    Tue 26 Jun 2012 02:30:15 PM UTCjordighStatusNone=>Confirmed
      Assigned toNone=>jordigh

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