[ET Trac] [Einstein Toolkit] #1865: Automatically start SystemTopology

[Einstein Toolkit]

#1865: Automatically start SystemTopology
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  Reporter:  dradice@…            |       Owner:  eschnett           
      Type:  enhancement          |      Status:  review             
  Priority:  major                |   Milestone:                     
 Component:  Carpet               |     Version:  development version
Resolution:                       |    Keywords:                     
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Changes (by hinder):

  * status:  new => review


Comment:

 Aside: I think we shouldn't use the word "depends" in this case; OPTIONAL
 means "use this capability if it is present", so maybe we should say "MPI
 optionally uses hwloc".

 I don't understand what I wrote above.  Let me try again.  Looking at the
 configuration.ccl files mentioning hwloc, we have:

 {{{
 CactusUtils/SystemTopology/configuration.ccl:REQUIRES hwloc MPI

 Carpet/LoopControl/configuration.ccl:OPTIONAL CycleClock hwloc Vectors

 ExternalLibraries/MPI/configuration.ccl:OPTIONAL hwloc

 }}}

 SystemTopology requires both hwloc and MPI.

 MPI optionally uses hwloc, because it might be building MPI, and the MPI
 library might make use of hwloc.

 LoopControl optionally uses hwloc.  There doesn't seem to be anything in
 LoopControl that directly references hwloc.  Is this because LoopControl
 uses threads, and it is good to pin those threads?

 Assuming all the above is right, I think the right thing is to change the
 LoopControl OPTIONAL from hwloc to SystemTopology.  This would have the
 effect of automatically activating SystemTopology whenever anyone uses the
 ET thornlist, and allowing it to manage thread pinning.

 Agreed?

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/1865#comment:5>
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