Several routines exist, to extract the staggering in a specific direction, called directional staggerindex . The points are distributed across three processors. How to treat this case in a easy way is explained below. When a thorn programmer uses staggered gridpoints, he has to be aware of this gridpoint anomaly. For a given staggertype and direction, this 2d array returns the local number of gridpoints, including ghostzones and the necessary change for the staggering on the outermost processor.
Several functions exist to derive the staggertype for a given group and for a certain direction.