The index shape class provides access to the index bounds of a mesh block. The bounds are split into two domains which can be accessed using a class enum IndexDomain. The IndexDomain can either be entire or interior. Using the entire domain, allows one to access the starting indices of the full meshblock including ghost zones, The interior domain allows access to the interior of the meshblock excluding ghost cells.
The starting and ending indices of each dimension of the index shape can be accessed using the is, ie, js, je, ks, ke methods. Currently, access is limited to three dimensions, if needed it can be extended. In cases where the indices are called often it may be more conveneint to pull out the index bounds of a given domain. The IndexRange struct provides an easy way to group the indices together.
The IndexShape class also provides a means for accessing the number of cells in each dimension of each of the domains. This is provided with the ncellsi, ncellsj, and ncellsk methods.
Below is a diagram illustrating a 2d instance of an IndexShape which we will call cellbounds.
The index range struct simply contains the starting and ending indices as well as a method for returning the total number of cells within the range.
The primary use case of the IndexShape occurs when indexing over the different dimensions. Assuming we have a meshblock pointer given as pmb e.g.
const IndexRange ib = pmb->cellbounds.GetBoundsI(IndexDomain::interior);
const IndexRange jb = pmb->cellbounds.GetBoundsJ(IndexDomain::interior);
const IndexRange kb = pmb->cellbounds.GetBoundsK(IndexDomain::interior);
for( int k = kb.s; k <= kb.e; k++ ){
for( int j = jb.s; j <= jb.e; j++ ){
for( int i = ib.s; i <= ib.e; i++ ){
... code ..
}
}
}