[ET Trac] [Einstein Toolkit] #2059: SimFactory should detect the number of cores automatically

Einstein Toolkit trac-noreply at einsteintoolkit.org
Thu Sep 7 07:51:44 CDT 2017

#2059: SimFactory should detect the number of cores automatically
  Reporter:  hinder       |       Owner:                     
      Type:  enhancement  |      Status:  review             
  Priority:  minor        |   Milestone:                     
 Component:  SimFactory   |     Version:  development version
Resolution:               |    Keywords:                     

Comment (by rhaas):

 True, a very point. I attach output files to back up the stated speed
 improvement for 12 MPI ranks and 1 threads vs. 2 MPI ranks and 6 threads
 on my workstation. Speed difference is (for static_tov.par) 200Msun/hr vs.
 250Msun/hr so ~25% speedup. I also tested 12 threads (hyperthreading)
 which (keeping the parfile unchanged) makes it much slower: 10M/hr.

 Question is then: do we want this? Ie having simfactory's auto-detect
 logic set up an "unusual" setting that differs from what is typically used
 on clusters? Mostly interesting if (which I assume will happen) to set up
 a new cluster, people will start from "sim setup" on the login node.
 Typically I am not concerned with speed on individual workstations,
 reproducibility and debug-ability are much more important to me on my
 workstation (since I used it to debug and test code but not to run

 Testsuites may be a issue (namely that we want both multiple MPI ranks and
 multiple threads in a testsuite run) but those always can be enforced by
 passing --num-threads and --procs options to simfactory.

 So MPI only gives more speed (very nice). It is less "common" on clusters
 which may be an issue if "sim setup" is used as a base for cluster
 installations (it will have to be modified anyway).

 I tended to prefer having something closer to a cluster setup, but really
 see the advantages of having faster evolutions so could certainly live
 with it. In particular for actual laptops/workstations only. Is there
 anyone who cannot live with either option?

Ticket URL: <https://trac.einsteintoolkit.org/ticket/2059#comment:20>
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