Partialhalo

Partialhalo is a concept in distributed computing and numerical simulations that generalizes the traditional halo or ghost layer between partitions. It refers to a defined subset of boundary data associated with a subdomain, chosen according to criteria such as proximity, relevance to the current computation, or available bandwidth. Each boundary surface may have its own partialhalo composition, and the set can change between iterations or time steps to reflect evolving workloads or data dependencies.

A partialhalo consists of a collection of boundary elements and accompanying metadata indicating their source neighbors and the conditions under which they should be exchanged or updated. The width and composition of a partialhalo may vary across the computational domain, enabling adaptive communication patterns. This flexibility supports irregular grids, adaptive mesh refinement, and dynamic load balancing, where maintaining a full halo would be unnecessarily expensive.

Characteristics include potential reductions in communication volume, compatibility with asynchronous computation models, and the need for explicit dependency tracking to ensure data consistency. Implementations may represent partialhalos as per-face or per-edge data lists, with lightweight protocols that push only the necessary data when required by the computation.

Relation to related concepts: a partialhalo reduces to a full halo if all neighboring data are included, and it reduces to no halo if no boundary data is exchanged. It is related to halo exchange, ghost cells, and boundary data management in parallelized simulations and graph processing.

See also: halo, ghost cell, halo exchange, boundary data, asynchronous computation.