[torquedev] [Bug 93] Resource management semantics of Torque need to be well defined

bugzilla-daemon at supercluster.org bugzilla-daemon at supercluster.org
Mon Dec 6 12:31:57 MST 2010


--- Comment #13 from Glen <glen.beane at gmail.com> 2010-12-06 12:31:56 MST ---
(In reply to comment #5)

> Processes per node is often how it is explained,
> The fact of the matter is that ppn hasn't been clearly defined over time, and
> what it has become in practice is probably best described as processes per
> node.

Describing it as "processes per node" is very misleading and completely
inaccurate.  Take for example a multi-threaded program.  I routinely run
multi-threaded code on our cluster.  We have 32 cores per node, and if I run a
_single process_ that uses 32 threads, I request ppn=32.  If that meant
_processes_ I would request ppn=1 because, after all, my mult-threaded program
is still a single process. It is, however, using multiple-cores.

virtual processor per node is the correct definition of ppn - the number of
virtual processors will typically be set to the total number of cores on a
node. redefining it as processes per node will lead to problems.

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