[ET Trac] [Einstein Toolkit] #1256: scheduling MoL_PostStep in Post_Recover_Variables

[Einstein Toolkit]

#1256: scheduling MoL_PostStep in Post_Recover_Variables
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  Reporter:  rhaas   |       Owner:     
      Type:  task    |      Status:  new
  Priority:  major   |   Milestone:     
 Component:  Cactus  |     Version:     
Resolution:          |    Keywords:  MoL
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Comment (by Wolfgang Kastaun <wolfgang.kastaun@…>):

 I disagree with the previous comment. There is no version of con2prim
 which may not modify the conserved state. This would be a version which
 may leave primitives and conserved variables in an inconsistent state. The
 reason is that there are unphysical values of the conserved variables
 which cannot be represented by primitive variables. Those corner cases
 appear frequently at NS surfaces. Another example is with realistic EOSs
 at low temperatures and high densities, where the energy is basically the
 degeneracy energy. The smallest numerical error can lead to conserved
 energy densities becoming smaller than in the zero-temperature limit. For
 the thermal branch, we have a clear policy how to adjust such cases (and
 when to abort the run). Those adjustments are really a piece of the
 evolution that has to be taken seriously. Therefore it _has_ to change the
 conserved variables sometimes. In any case, I do not see any reason not to
 call C2P on all points after any modification of the conserved variables.
 We do not need two C2P, but another schedule group for recomputing
 dependent variables that are not checkpointed to save disk space or
 memory.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1256#comment:9>
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