[vtkusers] vtkMath::Jacobi question

[David Gobbi]

My recommendation is that VTK4 should link to lapack, the same way
that VTK4-pre already links to zlib and libpng.  There is a
simplified version of lapack called 'lapack lite' that would be
suitable for inclusion in the VTK4 source tree.  This is what the
python Numeric package uses.

The matrix routines in vtkMath could just add a pretty interface to
the lapack routines.

 - David

--
  David Gobbi, MSc                       dgobbi at irus.rri.ca
  Advanced Imaging Research Group
  Robarts Research Institute, University of Western Ontario

On Thu, 9 Aug 2001, Miller, James V (CRD) wrote:

> 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
>
>
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