[Buildroot] [PATCH v2] package/python-numpy: fix occasional build failure with lapack

[Giulio Benetti]

Hello Thomas, All,

Il 18/05/2019 22:13, Thomas Petazzoni ha scritto:
> Hello,
> 
> On Wed, 15 May 2019 23:03:42 +0200
> Giulio Benetti <giulio.benetti at micronovasrl.com> wrote:
> 
>> python-numpy build fails only if lapack is built before python-numpy
>> itself, and this doesn't always happen because lapack dependency is
>> missing in BR2_PYTHON_NUMPY_DEPENDENCIES. clapack is present
>> instead, but it's wrong since we're checking $(BR2_PACKAGE_LAPACK) not
>> $(BR2_PACKAGE_CLAPACK).
> 
> I don't follow here: in the current code, we're checking
> BR2_PACKAGE_CLAPACK and adding clapack to PYTHON_NUMPY_DEPENDENCIES,
> which is consistent.

You're right, I've done a mistake, I've substituted clapack with lapack.
So need to send a v3 with this corrected.

The problem was due to cohexistence of lapack and clapack, but they are 
both(like openblas) accelerators that can exist once(I mean or lapack, 
or clapack).
Here I was asking about inserting a menu to choose which accelerator to use:
http://lists.busybox.net/pipermail/buildroot/2019-May/250273.html

Can you take a look and answer with your opinion?

> In order to better understand the problem. Without this patch:
> 
>   - Does python-numpy builds fine when neither clapack nor lapack are
>     enabled ?

Yes it does(it works without accelerators).

>   - Does python-numpy builds fine when clapack is enabled, but not
>     lapack ?

Yes

>   - What happens when both clapack and lapack are enabled ?

Python-numpy will choose the accelerator according to this list:
https://www.numpy.org/devdocs/user/building.html#accelerated-blas-lapack-libraries

> Also, perhaps we need:
> 
> 	select BR2_PACKAGE_LAPACK_COMPLEX if BR2_PACKAGE_LAPACK
> 
> in the Config.in file, so that it's a bit easier for users: they don't
> have to know they need that specific sub-option of lapack.

If lapack selected yes, but that should come after adding a choice menu 
IMHO.

Kind regards
-- 
Giulio Benetti
CTO

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