yade-dev team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Good that you found this, guys. For me it is ok to unlink it in default
builds. Still unclear why I never saw the problem before.
Other options:
- link alternatives (lapack + atlas, for instance)
- put a good version of openblas in PPA

For someone doing PFV simulation, openblas is still a "must have". It is
much faster than all possible replacements (legacy blas being the worst
case).
So the last option would be the best maybe.

B

On 28/02/14 11:58, Anton Gladky wrote:
> Alexander has really found a source of problems.
> OpenBlas is really a problem here [1]. It was fixed in Debian package
> on 02 Mar 2013:
>   * Disable processor affinity. (Closes: #684338)
>
> It means, that Debian Wheezy as well as all Ubuntus 12.10 and older
> are affected by the bug. We can disable the linkage of openblas
> for these affected distros.
>
> [1] https://bugs.debian.org/684338
> [2] http://metadata.ftp-master.debian.org/changelogs/main/o/openblas/unstable_changelog
>
> Anton
>
>
> 2014-02-28 11:47 GMT+01:00 Eulitz, Alexander
> <Alexander.Eulitz@xxxxxxxxxxxxxxxx>:
>> yes, and it can be assumed that some modules that are imported in yade could be the reason fort he problem:[1]
>>
>> "After some more googling I found the answer here.
>> It turns out that certain Python modules (numpy, scipy, tables, pandas, skimage...) mess with core affinity on import. As far as I can tell, this problem seems to be specifically caused by them linking against multithreaded OpenBLAS libraries.
>> A workaround is to reset the task affinity using
>> os.system("taskset -p 0xff %d" % os.getpid())
>> With this line pasted in after the module imports, my example now runs on all cores.
>> There are also two ways to disable the CPU affinity-resetting behaviour of OpenBLAS itself. At run-time you can use the environment variable OPENBLAS_MAIN_FREE (or GOTOBLAS_MAIN_FREE), for example
>> OPENBLAS_MAIN_FREE=1 python myscript.py
>> Or alternatively, if you're compiling OpenBLAS from source you can permanently disable it at build-time by editing the Makefile.rule to contain the line
>> NO_AFFINITY=1
>> "
>>
>> Are we compiling OpenBLAS from source?
>> But even if we are, why does the cpu affinity problem appear even for a built from late 2013 which definitely worked well concerning multicore operation?
>> Maybe it was an update oft he openblas modul that was done by apt-get update?
>>
>>
>> [1] http://stackoverflow.com/questions/15639779/what-determines-whether-different-python-processes-are-assigned-to-the-same-or-d?lq=1 answer#25
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Bruno Chareyre
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