Simple Decomp

This library utilises a pencil-like approach to decompose two- and three-dimensional structured meshes among multiple (MPI) processes:

Here, a two-dimensional domain depicted in the left image, with each grey cube representing an element of the array, undergoes decomposition into \(1 \times 6\) chunks. The right image illustrates the differently coloured chunks resulting from the decomposition. Each coloured chunk is assigned to a distinct process, enabling the distribution of the overall workload.

Likewise, a three-dimensional domain displayed in the left image is partitioned into \(1 \times 3 \times 4\) chunks. These instances are referred to as x1pencils since each chunk resembles a pencil pointing in the \(x\) direction.

It is possible to align the pencils differently, i.e.

for two-dimensional domains, or

for three-dimensional domains.

In these cases, each process encompasses all grid points in the \(y\) (or \(z\)) direction. This can be advantageous when conducting operations that require access to all information along a particular axis, such as multi-dimensional Fast Fourier Transforms.

The primary emphasis of this library revolves around these types of pencil rotations.