Terminology

This page is an attempt to try to agree on a standard lexicon for the DGSWEM/LGD/HPX code. Every project ends up developing its own lexicon, and this project is the convergence of three totally separate projects. This has led to some terms being ambiguous due to having multiple definitions. On the other hand, other things are described by multiple terms.

The first goal will be just to catalog all of the different terms in use now, their origins, and exact definitions. Later, we may decide to try to standardize the lexicon in order to facilitate communication.

• submesh: AKA subdomain, partition, rank. A portion of the spatially-decomposed compute mesh, generated by ADCPREP. In the MPI version of DGSWEM, the number of submeshes was always equal to the number of MPI ranks, leading to the two terms being used interchangeably.

• subdomain (deprecated): See submesh.

• node: Depending on context, refers either to a "compute node" or a vertex of the mesh.

• cell: In LibGeoDecomp, the smallest unit of computation in the unstructured mesh. In DGSWEM/LGD/HPX, it is equivalent to a submesh.

• locality: An HPX term. Typically, one locality is one compute node, or one NUMA domain (one locality per socket). The number of localities is specified in the same way the number of MPI ranks is specified, for example, srun -N 4 -n 4 will ask for 4 localities on 4 compute nodes. srun -N 4 -n 8 will ask for 8 localities on 4 compute nodes, which may lead to better performance if the compute node has two sockets (and two NUMA domains).

• dataflow: An HPX feature. It is utilized by LibGeoDecomp's HPX unstructured grid backend.