METHOD, SYSTEM, COMPUTE NODES AND COMPUTER PROGRAM FOR ALL-TO-ALL MESSAGE EXCHANGE IN PARALLEL PROCESSING SYSTEM (ALL-TO-ALL MESSAGE EXCHANGE IN PARALLEL COMPUTING SYSTEMS)

PROBLEM TO BE SOLVED: To provide a method and apparatus for all-to-all message exchange between program tasks.SOLUTION: The program tasks are connected by an interconnection network with a hierarchical network topology comprising N>1 hierarchy levels lwith n=1 to N. A first level lcomprises a plurality of groups of the tasks, and each higher level lcomprises at least one group of level lgroups. A unique hierarchical identifier is defined for each task, the hierarchical identifier being dependent on the groups to which that task belongs in respective hierarchy levels of the network topology. In each of successive phases of the exchange, each task sends a message via the network to a corresponding destination task whose hierarchical identifier is determined, on the basis of the hierarchical identifier of the sending task and the network topology, so that the resulting exchange pattern for the all-to-all message exchange exploits hierarchical distance in the network topology in a desired manner.