[Pkg-openmpi-maintainers] Bug#850229: openmpi-bin: default for oversubscription changed

[Alastair McKinstry]

On 09/02/2017 09:51, Santiago Vila wrote:
> On Thu, Feb 09, 2017 at 09:28:45AM +0100, Ansgar Burchardt wrote:
>> On Thu, 2017-02-09 at 00:05 +0100, Santiago Vila wrote:
>>> In either case I'm setting this to serious again because it makes
>>> packages to fail on single-CPU systems, and having more than one CPU
>>> is
>>> definitely *not* part of the build-essential definition.
>>
> for example, so it is something definitely useful, not comparable
> with building in a path which includes spaces.
>
> (For the record, I am paying for some of my autobuilders directly from my pocket)
>
> Thanks.

Respectfully disagree here. I appreciate that you're paying for
autobuilders. While multi-cores
is not a requirement for build-essential (though dh, etc now default to
parallel builds), running
MPI on a single core is definitely an exception, and oversubscribing is
typically a user bug.

We have had users waste thousands of euro in compute attempting to run
10,000 core jobs
on 1000 cores by mistake, and they are the target audience for this
change in default behaviour.

For our particular case (building and testing on 1 core in Debian) I
recommend just setting

export OMPI_MCA_rmaps_base_oversubscribe=1


Regards
Alastair

-- 
Alastair McKinstry, <alastair at sceal.ie>, <mckinstry at debian.org>, https://diaspora.sceal.ie/u/amckinstry
Commander Vimes didn’t like the phrase “The innocent have nothing to fear,”
 believing the innocent had everything to fear, mostly from the guilty but in the longer term
 even more from those who say things like “The innocent have nothing to fear.”
 - Terry. Pratchett, Snuff

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