On 2013-09-24, at 10:00 , Ian Hinder <ian.hinder@aei.mpg.de> wrote:

Hi,

Suppose I want to set up a grid structure for a BBH evolution using CarpetRegrid2, but ensure that the outer levels never change.  What I usually do is set up two box hierarchies centred on the two BHs, but this doesn't guarantee that the outer levels don't change.  Instead, I would like to have three hierarchies, one for the outer levels, and two for the BHs, where the latter only contain boxes on the finest levels.  I would implement this by not setting the coarser radii for the BH hierarchies, and leaving them at -1.  

I was under the impression that this used to be possible, but there is a check in CarpetRegrid2 which prevents this:

-> The radius of refinement level 1 of region 2 is [-1,-1,-1], which is non-negative

I can't see anything in the code which would make this necessary.  Is it safe to disable this check?

Can you set them to zero instead? This should automatically extend them so that they are large enough for the next finer levels, which is the minimum possible size.