Interpatch Interpolation

Erik Schnetter

September 2, 2018

Abstract

The Interpolate2 thorn provides interpatch interpolation.

1 Overview

The interpolator works in several steps.

In the first step, during startup, it decides which points need to be set via interpolation. This is usually a layer N grid points deep at the boundaries of the patches, excluding ghost zones, and also excluding the outer boundaries.

After each regridding, the Coordinates thorn iterates over these grid points, converts their locations to global coordinates, and finds out which patch “owns” each location. It then assumes that this location is sufficiently far in the interior of the patch that one can apply a full interpolation stencil there. That is, the interpolation source must be surrounded by sufficiently many ghost zones, outer boundary points, or additional overlap points that the stencil does not include any other inter-patch boundary points. This condition depends, among other things,