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

[Roland Haas]

#181: AEILocalInterp should not off-centre the interpolation stencil by default

 Reporter: Ian Hinder
   Status: open
Milestone: 
  Version: 
     Type: bug
 Priority: minor
Component: Cactus

Changes (by Roland Haas):

assignee: Roland Haas (was )
responsible: [] (was )

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}


**Keyword:** AEILocalInterp

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/181/aeilocalinterp-should-not-off-centre-the
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