[ET Trac] [Einstein Toolkit] #181: AEILocalInterp should not off-centre the interpolation stencil by default

[Einstein Toolkit]

#181: AEILocalInterp should not off-centre the interpolation stencil by default
----------------------------+-----------------------------------------------
 Reporter:  hinder          |       Owner:     
     Type:  defect          |      Status:  new
 Priority:  minor           |   Milestone:     
Component:  Cactus          |     Version:     
 Keywords:  AEILocalInterp  |  
----------------------------+-----------------------------------------------
 AEILocalInterp by default will off-centre the interpolation stencil if
 there are insufficient points to perform the interpolation.  In a parallel
 setting, this could happen due to there being insufficient ghost points
 for the interpolator chosen.  The off-centering leads to an interpolation
 error which is of the correct order but larger than for a centered
 stencil.  More importantly, it leads to different results on different
 numbers of processes.  This violates a basic design principle of Cactus,
 and the expectation of users, that changing the number of processors
 should not change the results of a simulation.

 I propose that instead of silently off-centering the stencil,
 AEILocalInterp should abort with an error indicating that there are
 insufficient ghost-zones.  The interpolator options corresponding to this
 are:

   boundary_off_centering_tolerance={0.0 0.0 0.0 0.0 0.0 0.0}
   boundary_extrapolation_tolerance={0.0 0.0 0.0 0.0 0.0 0.0}

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/181>
Einstein Toolkit <http://einsteintoolkit.org>
The Einstein Toolkit