[Numpy-discussion] Warning: be carefull with the use of Fortran Lapack/Blas libraries

Gerard Vermeulen gvermeul at labs.polycnrs-gre.fr
Mon Oct 8 10:00:03 CDT 2001


When I build Numeric, I allways link the lapack_lite module to the Fortran
Lapack and Blas libraries on my system.
This time (Numeric-20.2.1), when calling the function eigenvalues(), I got a
message saying that parameter 13 of dgeev had a wrong value.

The reason is that the LinearAlgebra.py module assumes that you have
a very recent version of dgeev, that you can use to calculate the workspace
requirements for the real call.

On http://www.netlib.org/lapack/release_notes.html you'll find a table "The 
following bug fixes have NOT yet been incorporated in a release/update of
LAPACK."

I quote "LAPACK/SRC/dgeev.f -- Corrected error with LQUERY and setting
of WORK(1)".

LinearAlgebra.py assumes that this bug has been corrected.

So, if you want to use LinearAlgebra.py with Fortran Lapack/Blas, you'd
better apply all those patches listed on 
http://www.netlib.org/lapack/release_notes.html

Of course, it is not a bug in LinearAlgebra.py, but I don't know if it is
wise to program LinearAlgebra.py in such a way that you run into this
problem on probably more than 90 % of the Lapack installations.
(getting the latest lapack.tgz is not sufficient)
 
Gerard






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