[ET Trac] [Einstein Toolkit] #962: parallelize Multipole using OpenMP and MPI

[Einstein Toolkit]

#962: parallelize Multipole using OpenMP and MPI
------------------------------------+---------------------------------------
  Reporter:  rhaas                  |       Owner:           
      Type:  enhancement            |      Status:  closed   
  Priority:  minor                  |   Milestone:           
 Component:  EinsteinToolkit thorn  |     Version:           
Resolution:  wontfix                |    Keywords:  Multipole
------------------------------------+---------------------------------------
Changes (by rhaas):

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


Comment:

 I am not sure I buy into all arguments. Right now Multipole does one
 radius after the other so time there are nradii calls to the (global)
 interpolator. With the patch there are (given that we usually have more
 processors than extraction radii) 2 calls (one for the interpolator, one
 for MPI_Allgatherv which also transports to Root only). And even
 Allgatherv is only needed for HDF5 output where we use an inherently
 serial file layout with all data in a single file.

 The patch works fine with PUGH (just tried replacing Carpet with PUGH in
 the test_rads test), it  also works without MPI (since then NProcs==1 and
 the Allgatherv that will be skipped by the #ifdef would be a no-op, tested
 by manually #undef CCTK_MPI). I am not sure it would make sense to run
 without MPI since eg. Carpet requires it.

 However simplicity is certainly something good to have and premature
 optimization is to be avoided. I can live with the patch not being
 applied. I'll retract it.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/962#comment:6>
Einstein Toolkit <http://einsteintoolkit.org>
The Einstein Toolkit