Neighbor Lists: Parallel Issues and Particles Off the Grid

If the 3-d head-of-cell grid is not large enough in a particular dimension to contain all the particles, it centers the grid in that direction about zero, and prints out a warning of the form ``Warning! NELIST: EXC true in ...'', listing the relevant dimension(s), as well as the number of grid cells which would have been required to fit all the particles and the current maximum.

In some cases, setting these grid dimensions to be symmetric around zero may be inappropriate for what you want to do, and you should change the algorithm accordingly.

The code can run perfectly well when particles fall outside the neighbor grids. If this happens, the code will produce a warning ``NELIST: WARNING !!! NPOUT='' listing the number of particles outside the grid. These particles will have no neighbors, and will not play a role in any hydrodynamic interactions. They will, however, be accounted for in gravitational interactions (see Sec. 3.3 for more on this).