I am using GNU Octave to diagonalize matrices. Installing openblas increases performance significantly.
I saw this news, installed blas-openblas and blas64-openblas, and updated.
After that, matrix diagonalization became much slower than before.
An workaround is to install https://aur.archlinux.org/packages/openblas-lapack, but it would be great if someone has some other suggestion. It takes a lot of time to compile openblas-lapack.
The following Octave code 12 seconds before the upgrade, and takes about 20 seconds afterwards. Installing openblas-lapack from AUR speeds it up once again.
ii = 1:2000;
a = sin(ii.^2 + ii');
a = (a + a')/2;
tic;[b,c]=eig(a);toc