[ET Trac] [Einstein Toolkit] #1499: Error in synchronisation after restriction

[Einstein Toolkit]

#1499: Error in synchronisation after restriction
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  Reporter:  hinder  |       Owner:  eschnett           
      Type:  defect  |      Status:  reopened           
  Priority:  major   |   Milestone:  ET_2014_05         
 Component:  Carpet  |     Version:  development version
Resolution:          |    Keywords:                     
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Comment (by hinder):

 I have prepared two patches for the ET_2013_11 release of Carpet. The
 first adds a test case which fails on 2 processes due to the bug.  The
 second reverts the commit which removed the sync, causing the test to
 pass.  I believe that this fixes the regression, unless there was some
 other commit which causes some other problem.  Notes:
 * I have not addressed the application of boundary conditions for high
 order restriction operators since this was broken in the previous release
 as well.  If people think this is very important and safe, please
 implement and test the patch, but I don't really have more time to spend
 on this, and I think an announcement that cell-centering with boundaries
 near refinement boundaries is not yet working is sufficient.
 * I have not included the change to restrict into ghost zones, or the
 optimisation which avoids the sync for vertex-centered code.  As such, the
 performance should be the same as the last release.  The trunk will be
 faster, but this is a less trivial change.
 * The commit which removed the sync was from May 2014, not September as we
 thought in the telecon.  This means that anyone using the trunk since then
 could potentially have been affected by this.
 * All tests pass on Datura with the new code.

 OK to backport to the release?

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1499#comment:13>
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