[ET Trac] [Einstein Toolkit] #1850: Severe performance problem on Stampede

[Einstein Toolkit]

#1850: Severe performance problem on Stampede
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  Reporter:  hinder      |       Owner:                     
      Type:  defect      |      Status:  confirmed          
  Priority:  major       |   Milestone:                     
 Component:  SimFactory  |     Version:  development version
Resolution:              |    Keywords:                     
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Comment (by eschnett):

 The description of KMP_AFFINITY was clearly written by a professional
 documentation writer who knows how to write a lot of text while
 introducing sufficient ambiguity to not even be wrong.

 As I mentioned above, setting this variable (when not using
 SystemTopology) is probably wrong unless there is only one MPI process per
 node. Please read my description above, and say what it is unclear if you
 don't understand it; I won't repeat it here.

 Yes, we all agree that the default options should be better. There are two
 options:

 (1) Examine all possible "reasonable" configurations (MPI processes per
 node, OpenMP threads per process), and ensure that the new setting work
 fine in all cases
 (2) Examine only a subset of configurations, and ensure that things don't
 change except for these configurations, using appropriate if-statements in
 the submit script.

 I mentioned earlier that I am regularly running benchmarks on a variety of
 systems. Of course I am using SystemTopology, so I didn't notice this
 problem. I usually run multiple benchmarks for multiple configurations
 (MPI processes / OpenMP threads) to find the optimum configuration.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1850#comment:17>
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