Notes on building NumPy/SciPy with OpenBlas

This is a quick post to show how to build NumPy/SciPy with OpenBlas on Mac OS X. OpenBlas is a recently open-sourced version of Blas/Lapack that is competitive with the proprietary implementations, without being as hard to build as Atlas.

Note: this is experimental, largely untested, and I would not recommend using this for anything worthwhile at the moment.

Building OpenBlas

After checking out the sources from github, I had the most luck building openblas with a custom-build clang (I used llvm 3.1). With the apple-provided clang, I got some errors related to unsupported opcodes (fsubp).

With the correct version of clang, building is a simple matter of running make (CPU is automatically detected).

Building NumPy/SciPy

I have just added a initial support for customizable blas/lapack in the bento build of NumPy (and scipy). You will need a very recent clone of NumPy git repo,and a recent bento. The single file distribution of bento is the simplest way to make this work:

./bentomaker.py configure --with-blas-lapack-libdir=$OPENBLAS_DIRECTORY --blas-lapack-type=openblas ..
./bentomaker.py build -j4 # build with 4 processes in //

Same for SciPy. The code for bento’s blas/lapack detection is not very robust nor well tested, so it will likely not work on most platforms.