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Re: Bug#875618: openblas: please enable build on s390x

Control: tags -1 upstream
Control: forwarded -1 https://github.com/xianyi/OpenBLAS/issues/1307

On Thu, Sep 14, 2017 at 12:34:34PM +0200, Christian Borntraeger wrote:
> On 09/14/2017 09:58 AM, Sébastien Villemot wrote:
> > On Wed, Sep 13, 2017 at 08:33:08PM +0000, PICCA Frederic-Emmanuel wrote:
> >>> 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.

Thanks for your feedback. I have opened a request upstream about the need for a
z900 kernel, and for a dynamic selection between the z900 and z13 kernels
(as OpenBLAS currently does on x86).

⢀⣴⠾⠻⢶⣦⠀  Sébastien Villemot
⣾⠁⢠⠒⠀⣿⡁  Debian Developer
⢿⡄⠘⠷⠚⠋⠀  http://sebastien.villemot.name
⠈⠳⣄⠀⠀⠀⠀  http://www.debian.org

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