pub fn decompose_2d(
global_nz: usize,
global_nr: usize,
pz: usize,
pr: usize,
halo: usize,
) -> FusionResult<Vec<CartesianTile>>Expand description
Decompose a 2D grid of shape (global_nz × global_nr) into a (pz × pr) Cartesian process topology.
Returns tiles in row-major order: tile[iz * pr + ir].