[vtkusers] vtkMath::Jacobi question

[Miller, James V (CRD)]

Are you giving vtkMath::Jacobi a symmetric matrix?  The Jacobi algorithm only works on a symmetric
matrix.  If you are using Jacobi to do a general eigen analysis, that could explain why you are
seeing this message.

We have been looking at adding more general eigen analysis capabilities into vtk.  The trick is
finding an eigensystem implementation that is self contained so that it can be easily included and
maintained.



-----Original Message-----
From: Gerald Dalley [mailto:dalleyg at dma.org]
Sent: Wednesday, August 08, 2001 11:00 AM
To: VTK Users
Subject: [vtkusers] vtkMath::Jacobi question


I am using vtkMath::Jacobi to do some eigen analysis for me.  Whenever I
call that method, I get an "Error extracting eigenfunctions" error message.
I've looked in the source and the message is generated by a conditional
whose comment says "//// this is NEVER called".

Without digging into the source to understand the intricacies of the
algorithm, it looks like this condition will "often" happen rather than
"never": the outer loop preceeding the conditional terminates when
i=VTK_MAX_ROTATIONS and the conditional check is for i>=VTK_MAX_ROTATIONS,
so unless the loop exits early through one of its break statements, that
test will fail.

Is this error message a real one, and if so, what does it really mean?

--Gerald Dalley
  dalleyg at dma.org


_______________________________________________
This is the private VTK discussion list. 
Please keep messages on-topic. Check the FAQ at: <http://public.kitware.com/cgi-bin/vtkfaq>
Follow this link to subscribe/unsubscribe:
http://public.kitware.com/mailman/listinfo/vtkusers