[ET Trac] [Einstein Toolkit] #2030: Multi-block boundaries leave uninitialized boundary points

[Einstein Toolkit]

#2030: Multi-block boundaries leave uninitialized boundary points
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  Reporter:  eschnett               |       Owner:                     
      Type:  defect                 |      Status:  new                
  Priority:  major                  |   Milestone:                     
 Component:  EinsteinToolkit thorn  |     Version:  development version
Resolution:                         |    Keywords:                     
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Comment (by hinder):

 The first bug mentioned is one that we have discussed before, many years
 ago.  One solution was to apply the BCs twice, which would probably need
 to be handled in Kranc.  (I just looked, and cannot find a Kranc issue
 about this, unfortunately.)  This was the reason that for a long time, my
 McLachlan Llama BBH parameter files used poison = 0, because setting the
 uninitialised points to zero was better than having them as NaN,
 especially when the boundary was causally disconnected.  However,
 recently, I was not able to reproduce the problem.  I thought that maybe
 something had been fixed/changed, though this was perhaps optimistic.  Do
 you have a parameter file and a method for identifying that this problem
 has occurred?

 Presumably the long-term solution is for Cactus to keep track of variables
 read and written in different parts of the grid.  Is there a short-term
 solution that doesn't involve "clever" scheduling, and applying the BCs
 twice?

 As I understand it, this problem occurs only on initial data, not during
 evolution.  Is that your understanding as well?

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/2030#comment:1>
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