[Numpy-discussion] Correct way to query NumPy for linktime BLAS and LAPACK

Aron Ahmadia aron@ahmadia....
Thu Aug 8 09:42:52 CDT 2013

Hi Fred,

Thanks for the feedback.  We'll try this out in Clawpack moving forward.


On Tue, Aug 6, 2013 at 7:57 AM, Frédéric Bastien <nouiz@nouiz.org> wrote:

> Hi,
> In Theano, we use the information in this
> dictionnary: numpy.distutils.__config__.blas_opt_info. We do this for a few
> years already, so I don't know how much future proof it is, but I would
> expect that they aren't going to change this shortly.
> We use this dict for the default configuration, but still we allow the
> user to provide its own library and it work well. In case you don't know
> Theano, it is a compiler that generate dynamically c code, compile them as
> python module and load them in the python interpreter. So it happen that
> numpy and Theano module use different version of BLAS. Up to now, I never
> heard a problem about this.
> Don't forget that many different BLAS version use different internal
> symbol for the BLAS function and just provide an official function for the
> interface. So if we mix different BLAS, it work. But I'm not sure if what
> will happen if we link with different version of the same BLAS project,
> like different MKL version. Maybe just on the them will get imported if the
> library name is the same.
> Fred
> On Mon, Aug 5, 2013 at 5:06 PM, Aron Ahmadia <aron@ahmadia.net> wrote:
>> Dear NumPy Developers,
>> In the Clawpack/* repositories [1], we use a mixture of Fortran and
>> Python source, currently glued together using f2py.
>> Occasionally, we'll need to link the Fortran code directly against
>> LAPACK.  In particular, we're using dgeev and dgesv to solve several
>> different Riemann problems [2,3].
>> In the past, we've relied on either the operating system or the user to
>> provide these link commands for us, but it would be ideal in the future if
>> we could query NumPy for how it is linked.  Currently, the only information
>> I can find is in the hidden __config__ module of NumPy's distutils module:
>>     numpy.distutils.__config__.blas_opt_info['extra_link_args']
>>     numpy.distutils.__config__.lapack_opt_info['extra_link_args']
>> This seems to suggest that we shouldn't be relying on this information
>> being available in future versions of NumPy (or at least, not in this
>> location).  That said, we'd still probably like to use this to avoid the
>> possibility of multiple BLAS/LAPACK libraries being linked in to our builds.
>> Any comments?
>> Thanks,
>> Aron
>> [1] https://github.com/clawpack/clawpack
>> [2]
>> https://github.com/clawpack/riemann/blob/master/src/rp1_layered_shallow_water.f90#L687
>> [3]
>> https://github.com/clawpack/riemann/blob/master/src/rpn2_layered_shallow_water.f90#L478
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