Abstract: There is provided a computer-implemented method of communication between a plurality of processes, each process being responsible for a region of a space, and each process maintaining a routing tree, each node of the routing tree representing a respective one of the plurality of processes and containing an indication of the represented process and an indication of an associated region for which the represented process is responsible. The method comprises: receiving, by a first process, a message addressed to a target region of the space; determining, by the first process and using the routing tree of the first process, a set of subregions of the target region and associated processes; and for each of the determined subregions in the set, sending the message from the first process to the process associated with the determined subregion in the set.