If I create a covering_grid for a full domain that is not triply-periodic, the code will abort when I try to access the data in the covering grid with an error generated by selection_routines.pyx that is looking to make sure that the boundary conditions are supported. I understand that this support is not yet in place, but I don't think that it should be an issue for a covering_grid. The covering grid procedure itself should not ever need boundary conditions, if I understand what it intends to do. If you are just sampling the coarse data (or averaging the overlying fine data) into your zone, there is no need to do any interpolation that would require BCs. For the SmoothedCoveringGrid stuff, I understand that BCs should come into play. Am I missing something? or should this check on the BCs be considered a bug in this case? Mike -- Michael Zingale Associate Professor Dept. of Physics & Astronomy * Stony Brook University * Stony Brook, NY 11794-3800 *phone*: 631-632-8225 *e-mail*: Michael.Zingale@stonybrook.edu *web*: http://www.astro.sunysb.edu/mzingale