[Users] Simfactory: Machine definition variables

[Erik Schnetter]

On Aug 9, 2014, at 8:45 , Dumsani Ndzinisa <g14n8326 at campus.ru.ac.za> wrote:

> Hi everyone,
> 
> I am trying to configure and  add a new machine (cluster) into my 
> Simfactory machine database. (.../simfactory/mdb/machinses/).
> 
> However, I do not know what exactly what the following variables or 
> abbreviations are in the .ini file: spn, mpn. I have looked up values 
> given to these in different machine files and found that they are not 
> the same for all machines. Which brings me to the question of what 
> they are so I can give to them the correct values relevant to/for the 
> new machine that I want to add.
> 
> I understand ppn represents the number processors per node or 
> number of cores per node (SimfactoryAdvancedTutorial) . On this 
> one, what exactly should determine the value for min-ppn as far 
> as the machine being defined is concerned? Or the min-ppn's 
> value doesn't depend on the machine? 
> 
> Thank you in advance fr your help.

The MDB entries are defined in simfactory/etc/syntax/mdb-syntax.ini.

spn is "sockets per node"; this value was introduced, but is currently unused. Manufacturer abused the term "socket", so that this number is useless in practice.

mpn is "memory systems per node"; this should probably be called "NUMA nodes per node". If you are using OpenMP, the you likely either want 1 MPI process per node, or 1 MPI process per NUMA node. If you do not know this number, it is pretty safe to set it to 1. Tools such as hwloc can determine this number.

ppn is the number of cores per node, a hardware property. min-ppn is the minimum ppn you can request for a job; this is a software property enforced by the queuing system. Simfactory will automatically (excluding bugs) round up your request to the next multiple of min-ppn. In practice, most HPC systems either have min-ppn=1 or min-ppn=ppn.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>
http://www.perimeterinstitute.ca/personal/eschnetter/

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