[ET Trac] [Einstein Toolkit] #774: hack to unfix OpenMP threads from cores on Cray machines

[Einstein Toolkit]

#774: hack to unfix OpenMP threads from cores on Cray machines
-----------------------+----------------------------------------------------
  Reporter:  rhaas     |       Owner:  eschnett
      Type:  task      |      Status:  closed  
  Priority:  optional  |   Milestone:          
 Component:  Carpet    |     Version:          
Resolution:  fixed     |    Keywords:  hack    
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Changes (by eschnett):

  * status:  review => closed
  * resolution:  => fixed


Comment:

 I believe that the process affinity is inherited across exec. That means
 that one can write a wrapper that first sets the affinity, and then execs
 the Cactus executable.

 In fact, such a program already exists; it is called "numactl". I just
 tried on Hopper -- it does not run because it cannot find certain
 libraries. Maybe rebuilding numactl would already correct this problem?

 You would use it similar to "aprun -bla numactl -bla cactus_sim -bla
 my.par".

 I applied your patch with certain modifications. For example, instead of
 calling it "Cray hack" I view this as a generic feature that may also be
 useful elsewhere.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/774#comment:2>
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