bugGNU Octave - Bugs: bug #36104, determinant of a sparse zero matrix

 
 

bug #36104: determinant of a sparse zero matrix

Submitted by:  Marco Caliari <caliari>
Submitted on:  Thu 05 Apr 2012 07:39:42 PM UTC  
 
Category: NoneSeverity: 3 - Normal
Priority: 5 - NormalItem Group: Incorrect Result
Status: FixedAssigned to: David Bateman <dbateman>
Originator Name: Open/Closed: Closed
Release: 3.6.0Operating System: GNU/Linux

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Mon 21 May 2012 11:29:41 AM UTC, comment #3:

Link to changeset:

http://hg.savannah.gnu.org/hgweb/octave/rev/8d2ce821e38a

John W. Eaton <jwe>
Project Administrator
Sat 19 May 2012 12:01:37 AM UTC, comment #2:

This could be considered a bug in UMFPACK from my point of view, though it did point out another problem in the sparse constructor. The issue is that if the index vectors for empty then the sparse constrctor creates ridx and data indices that are 0 as they should be used. Apparently UMFPACK checks that these indices have valid values before doing any calculation even though they shouldn't be used.

However, if we define nzmax we should have valid ridx and data indicies and as the constructor stands we don't. So the easiest fix is just to ensure that ridx and data are valid in all cases.

See the changeset 8d2ce821e38a

D.

David Bateman <dbateman>
Project MemberIn charge of this item.
Thu 05 Apr 2012 08:52:10 PM UTC, comment #1:

Confirmed on a recent tip. There seems to be a problem in the sparse() call when some dimensions are null ([]) rather than explicitly zero.

Rik <rik5>
Project Administrator
Thu 05 Apr 2012 07:39:42 PM UTC, original submission:

Dear all,

I found the following:

So, A e B are equal, but it is not possible to compute the determinant of B. The definition of B is weird, I know, but it is precisely what you get from

This bug is present at least since 3.0.5. By the way, in Matlab A and B coincides and have the same zero determinant.

Marco

Marco Caliari <caliari>
Project Member

 

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    Follow 4 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Sat 19 May 2012 12:01:37 AM UTCdbatemanStatusConfirmed=>Fixed
      Assigned toNone=>dbateman
      Open/ClosedOpen=>Closed
    Thu 05 Apr 2012 08:52:10 PM UTCrik5StatusNone=>Confirmed

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