Group Types

Groups can be either scalars, grid functions (GFs), or grid arrays. Different attributes are relevant for the different group types.

SCALAR

This is just a single number, e.g. the total energy of some field. These variables aren't communicated between processors--what would be the result of such communication?

GF

This is the most common group type. A GF is an array with a specific size, set at run time in the parameter file, which is distributed across processors. All GFs have the same size, and the same number of ghostzones. Groups of GFs can also specify a dimension, number of timelevels, and stagger type.

ARRAY

This is a more general form of the GF. Each group of arrays can have a distinct size and number of ghostzones, in addition to dimension, number of timelevels and stagger type. The drawback of using an array over a GF is that a lot of data about the array can only be determined by function calls, rather than the quicker methods available for GFs.