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Subject: [OMPI users] core binding confusion
From: Dave Love (d.love_at_[hidden])
Date: 2012-03-06 10:28:43


Could someone confirm whether this is a bug or misunderstanding the doc
(in which case it's not just me, and it needs clarifying!)? I haven't
looked at the current code in the hope of a quick authoritative answer.

This is with 1.5.5rc3, originally on Interlagos, but also checked on
Magny Cours. It's also seen on two Interlagos with different physical
numbering of the logical processors.

On a 48-core Magny Cours with

  mpirun --bysocket --bind-to-core --report-bindings -np 48

what I get is two processes per core, e.g.:

  [node247:09521] [[58099,0],0] odls:default:fork binding child [[58099,1],14] to socket 2 cpus 4000
  ...
  [node247:09521] [[58099,0],0] odls:default:fork binding child [[58099,1],38] to socket 2 cpus 4000

and hwloc-ps confirms the situation. However, I (and my boss, who did
it originally) expect one per core. With --bycore we do see one per
core, of course.

Is that actually expected?