Bug#875618: openblas: please enable build on s390x

[Christian Borntraeger]

On 09/14/2017 09:58 AM, Sébastien Villemot wrote:
> On Wed, Sep 13, 2017 at 08:33:08PM +0000, PICCA Frederic-Emmanuel wrote:
>> Hello 
>>
>>> Unfortunately it does not look that simple. OpenBLAS is optimized for z13, but
>>> our s390x port is supposed to support all the z systems (see [1]).
>>
>> what about asking for a a z13-support package to the isa-support (source
>> package) maintainer. This way it could be possible to upload an optimise
>> vesion of openblas which can install on recent enought s390x machines.
> 
> I am not totally convinced by this solution. If we adopt it, somebody who
> installs e.g. octave on an old system-z machine will be hit by a failure in the
> dpkg installation process, which needs manual intervention. This is likely to
> generate problems in automated installers (and also confuse and annoy system
> admins).
> 
>> the question will be then : does the buildd support these instructions ?
> 
> I leave that to the s390 porters to answer.

FWIW, some years ago I did the atlas port for s390x. For dynamic linking the atlas
build/package process did support the exploitation of ELF HW_CAPS. So you could 
build a z900 (generic) and a z13 variant which is then picked by the linker at 
runtime. No idea if openblas allows the same. Of course the static variant (.a) 
must be the generic one.

Christian