I was suprised the the other day by a [SciPy][]-linking issue:

    $ python -c 'import scipy.linalg'
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/usr/lib/python2.7/site-packages/scipy/linalg/__init__.py", line 9, in <module>
        from basic import *
      File "/usr/lib/python2.7/site-packages/scipy/linalg/basic.py", line 14, in <module>
        from lapack import get_lapack_funcs
      File "/usr/lib/python2.7/site-packages/scipy/linalg/lapack.py", line 15, in <module>
        from scipy.linalg import clapack
    ImportError: /usr/lib/python2.7/site-packages/scipy/linalg/clapack.so: undefined symbol: clapack_sgesv

Searching around, it turns out there have been [problems like
this][129524] for a while, and it's flared up [again][vinyals]
recently.  There's a [new Gentoo bug][371099] tracking the most recent
issues.  In general, [NumPy][]/[SciPy][] seems to be picky about the
particular [BLAS][] implementation you're using, and you'll get
problems like the above if you're using the reference implementations
of BLAS and [LAPACK][].

    $ for x in blas cblas lapack; do eselect $x list; done
    Installed BLAS for library directory lib
      [1]   reference *
    Installed CBLAS for library directory lib
      [1]   gsl
      [2]   reference *
    Installed LAPACK for library directory lib
      [1]   reference *

You can fix the problem by installing and selecting the [ATLAS][]
libraries

    $ sudo emerge -av blas-atlas lapack-atlas
    $ for x in blas cblas lapack; do sudo eselect $x set atlas; done

after which you should re-install any packages that may need to be relinked.

    $ sudo emerge -av numpy scipy

Now you can import the linear algebra module without crashing:

    $ python -c 'import scipy.linalg'


[SciPy]: http://www.scipy.org/
[129524]: https://bugs.gentoo.org/show_bug.cgi?id=129524
[vinyals]: http://archives.gentoo.org/gentoo-science/msg_83c0a72f758099201944bdccd401603a.xml
[371099]: https://bugs.gentoo.org/show_bug.cgi?id=371099
[NumPy]: http://numpy.scipy.org/
[BLAS]: http://www.netlib.org/blas/
[LAPACK]: http://www.netlib.org/lapack/
[ATLAS]: http://math-atlas.sourceforge.net/


[[!tag tags/linux]]