[ET Trac] [Einstein Toolkit] #1238: implement buffer mask in CarpetEvolutionMask

[Einstein Toolkit]

#1238: implement buffer mask in CarpetEvolutionMask
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  Reporter:  rhaas        |       Owner:  eschnett           
      Type:  enhancement  |      Status:  review             
  Priority:  minor        |   Milestone:                     
 Component:  Carpet       |     Version:                     
Resolution:               |    Keywords:  CarpetEvolutionMask
--------------------------+-------------------------------------------------

Comment (by rhaas):

 I had not really though of it but yes there is a variable
 dd.local_boxes.at(mglevel).at(reflevel).at(local_component).buffers that
 holds an ibset of the local buffers. Patch 0002 uses it and would have the
 decided advantage of not copying the logic to create the buffer region
 description to several places in the code.

 However I found that using these buffers is not really what I want. They
 are computed using the owned points so that ghost zones that are also
 buffer zones are flagged as non-buffers which is not what I want. My
 intention is to use the buffer mask to find out where eg. con2prim does
 not have to run. Since con2prim runs everywhere (also in ghosts and
 buffers) since it runs after SYNC (since con2prim scales better than a
 SYNC of the primitives) I need to know if a point is both a buffer and a
 ghost zone. This seems due to dh::regrid constructing buffers using the
 "owned" region rather than the "exterior".

 buffers is used in dh::regrid in line 956
 {{{
           // Prolongation must fill what cannot be synchronised, and
           // also all buffer zones
           needrecv += box.buffers;
 }}}
 where I believe one *currently* could use buffers constructed using
 "exterior" instead of "owned". However this depends on needrecv being set
 up in the "#else" branch of line 936.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/1238#comment:7>
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