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

Paul F. Dubois paul at pfdubois.com
Mon Oct 8 15:58:20 CDT 2001


No good deed goes unpunished. The contributor who put in these changes
wanted to improve Numeric, and I accepted the changes because they
seemed to work. I regret that I didn't investigate this in detail but
the truth is I have to depend on strangers. I have no idea what to do
about it.

-----Original Message-----
From: numpy-discussion-admin at lists.sourceforge.net
[mailto:numpy-discussion-admin at lists.sourceforge.net] On Behalf Of
Gerard Vermeulen
Sent: Monday, October 08, 2001 9:59 AM
To: numpy-discussion at lists.sourceforge.net
Subject: [Numpy-discussion] Warning: be carefull with the use of Fortran
Lapack/Blas libraries


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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