Some time ago, someone (can't find the email right now) reported problems with CarpetRegrid2, where the grid structure may be inconsistent. I have restructured the code, but since this is a fairly invasive change I would like this to be thoroughly tested before committing it.

This change may lead to Carpet using a (slightly) different grid structure than before. The differences are not "important"; what potentially changes is the order in which consistency conditions are applied. I expect that, in most cases, there will be no differences. The list of consistency conditions is:

- ensure proper nesting (level must be larger than next finer level) - add buffer zones (only once, not really a consistency condition) - combine regions into a single box (if this is efficient) - apply rotating 90/180 symmetry (if requested) - clip at outer boundary (so that boxes that are too large or are outside are cut off)

I have uploaded the patch to the Einstein Toolkit TRAC at https://trac.einsteintoolkit.org/ticket/442.

-erik