[ET Trac] [Einstein Toolkit] #1222: Reduction weight for periodic domains.

[Einstein Toolkit]

#1222: Reduction weight for periodic domains.
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  Reporter:  bentivegna  |       Owner:  eschnett           
      Type:  defect      |      Status:  new                
  Priority:  minor       |   Milestone:                     
 Component:  Carpet      |     Version:  development version
Resolution:              |    Keywords:                     
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Comment (by eschnett):

 When vertex centering is used, then each of the boundary points
 contributes with weight 1/2 to the reduction, as explained above. If I
 interpret the patch correctly, then it essentially shifts the domain by
 1/2 grid point in the periodic directions, so that one boundary point
 contributes with weight 1 and the other with weight 0. Given that one
 boundary point has a shiftout of 0 and the other has a shiftout of 1, this
 will then use exactly the interior points and ignore all points set by the
 periodic boundary condition.

 I wonder what this domain-shifting does when several refinement levels are
 used, since each level would be shifted by a different amount, depending
 on the grid spacing. With many refinement levels, there can be many finest
 grid points in the region where the coarsest grid has been shifted.

 Another way of obtaining the same effect would be to use cell-centred
 refinement. In this case, there are no grid cells with weight 1/2; all
 cells have either weight 0 or weight 1.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1222#comment:1>
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