Strangely, I was struggling hard to install numpy 1.8.0 (with pip in a virtualenv) on Debian 7.1 with OpenBLAS. I always got the following error message:

numpy.distutils.system_info.BlasNotFoundError:

    Blas (http://www.netlib.org/blas/) libraries not found.

    Directories to search for the libraries can be specified in the

    numpy/distutils/site.cfg file (section [blas]) or by setting

    the BLAS environment variable.

After googling (a lot), I stumbled on gromgull’s blog which mentioned at one point to install the header versions of the openblas lib for debian, aka

sudo apt-get install libopenblas-dev liblapack-dev

Though I did not follow the rest of the article. I just tried to install numpy through pip at this stage and everything worked! Actually, that’s because there was a Pull Request accepted in numpy to accept OpenBLAS transparently, since gromgull’s blog entry.

However, afterwards, I decided to remove all blas/atlas/etc lib from stock (all system libs), and compile openblas from source, to get a few performance improvement. To do this, I had to symlink libopenblas lib using update-alternatives (pip install numpy is looking for that specific path. If not there, one should add it or follow gromgull’s approach):

sudo update-alternatives --install /usr/lib/libblas.so.3 libblas.so.3 /usr/local/lib/libopenblas.so 90

And everything went great!