Numpy/Scipy with OpenBLAS for Ubuntu 12.04 - Second try

Attention conservation notice: Improved (?) writings to self about some mundane configuration process I somehow can't get right completely, filled up with fluffy words.

I recently set up an Arch Linux computer and found out that my original description for numpy/scipy with OpenBLAS here is way too convoluted: OpenBLAS fixed the missing symbols issue that resulted in the unnecessary workaround in my original post. It turns out, however, that getting everything running on Ubuntu 12.04 is still more work than on Arch Linux. Update June 3rd, 2013: deleted some non-sense paragraphs.

apt-get preparations for 12.04

sudo apt-get install git python-dev gfortran

You probably have these installed anyway.


git clone git://

Change into the new directory, then

make FC=gfortran
sudo make PREFIX=/usr/local/ install

The latest lapack release is downloaded, compiled and integreated into OpenBLAS automatically. Ready for the python part!


git clone

Usually one is interested in OpenBLAS because of its fast matrix-matrix multiplication. Whether numpy has a fast dot function is indicated by the presence of core/ However, currently (June 2013) this file is only build, if site.cfg has an [atlas] section (also see here and here). There is an interesting thread here with a link to this fix in order to add support for using OpenBLAS for the _dotblas function. However, right now do vi site.cfg and:

library_dirs = /usr/local/lib

atlas_libs = openblas
library_dirs = /usr/local/lib

lapack_libs = openblas
library_dirs = /usr/local/lib

Without the [lapack] section there were problems with installing scipy later on. Additionally:

export BLAS=/usr/local/lib/libopenblas.a
export LAPACK=/usr/local/lib/libopenblas.a
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib/

Check the detected configuration with python config. You should see several ATLAS_INFO paired with None. If there is something like 3.8.2 instead of None then you have an ATLAS install somewhere on your system and numpy won't use OpenBLAS. Get rid of this install (e.g. via apt-get purge) and rerun the config command. If ATLAS_INFO is completely missing then numpy couldn't find your libopenblas* libraries — you need to check all previous steps again. Now:

python build

If you look into build/numpy/core, the file should be available.

sudo python install

installs a system wide numpy that uses OpenBLAS for dot products. This test produces

maxint: 9223372036854775807

dot: 0.162246799469

You can change the number of cores OpenBLAS utilizes via OPENBLAS_NUM_THREADS, e.g. export OPENBLAS_NUM_THREADS=2 results in

maxint: 9223372036854775807

dot: 0.0949754238129 sec


git clone

Scipy can be installed without any workaround:

python build
sudo python install

Make sure that in your sudo command the variables BLAS, LAPACK and LD_LIBRARY_PATH are correctly set, as shown above! This test script (it has some room for improvement, though ...) works on my machine after the system wide install:

cholesky: 0.080588388443 sec
svd: 1.13443040848 sec

Finally, if you feel good enough (and do a pip install nose), you can run nose tests via

python -c "import numpy; numpy.test(verbose=2)"
python -c "import scipy; scipy.test(verbose=2)"

(Note: I didn't!). Comments, corrections, pointers, etc. are more than welcome.