Cactus Code Thorn CarpetProlongateTest
Author(s)    : Erik Schnetter <schnetter@cct.lsu.edu>
Maintainer(s): Erik Schnetter <schnetter@cct.lsu.edu>
Licence      : GPL
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1. Purpose

Test prolongation in Carpet.

The basic idea is to set up a grid function containing a polynomial of
a certain order of the coordinates. Prolongation (interpolation) with
sufficiently high order must preserve these polynomials exactly (up to
floating-point round-off).

We test restriction as well, but the restriction operators are not
high-order accurate. Since restriction is first order accurate, and we
disable the restriction tests for the higher orders.