Re: [ublas] LAPACK using GEEV

Subject: Re: [ublas] LAPACK using GEEV
From: Thomas Klimpel (Thomas.Klimpel_at_[hidden])
Date: 2010-07-05 15:46:10

Kraus Philipp wrote:
> lapack::geev( 'U', 'L', l_matrix, l_eigval,  x,y,z, lapack::optimal_workspace() );

Well, 'U' and 'L' are not allowed parameter values in this case. Only 'N' and 'V' are allowed:
'N': left/right eigenvectors of A are not computed;
'V': left/right eigenvectors of A are computed.

"x" will be the imaginary part of the eigenvalues on output, "y" will be the left eigenvectors (subject to conventions for complex conjugated pairs) and "z" will be the right eigenvectors.

> Can anyone help me to solve the problem, so that I'll get the correct values?

It's probably easiest to directly read the documentation from the original fortran source code:

<http://www.netlib.org/lapack/double/dgeev.f>

The older numeric-bindings-v1 were written by hand and tried to hide much of these nasty details, but the current version of the bindings are automatically generated from the fortran sources and have not yet reached that level of comfort (but gees and geev are already on the TODO list for improved comfort similar to numeric-bindings-v1).

Regards,
Thomas