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communicator A communicator is an opaque object with a number of attributes, together with simple rules that govern its creation, use and destruction. The communicator specifies a communication domain which can be used for point-to-point communications. communication domain An intracommunicator is used for communicating within a single group of processes; we call such communication intra-group communication. An intracommunicator has two fixed attributes. intracommunicator intra-group communication domain These are the process group and the topology describing the logical layout of the processes in the group. Process topologies are the subject of chapter gif. Intracommunicators are also used for collective operations within a group of processes.

An intercommunicator is used for point-to-point intercommunicator communication between two disjoint groups of processes. We call such communication inter-group communication. inter-group communication domain The fixed attributes of an intercommunicator are the two groups. No topology is associated with an intercommunicator. In addition to fixed attributes a communicator may also have user-defined attributes which are associated with the communicator using MPI's caching mechanism, as described in Section gif. The table below summarizes the differences cachingcommunicator, caching between intracommunicators and intercommunicators. communicator, intra vs inter

Intracommunicator operations are described in Section gif, and intercommunicator operations are discussed in Section gif.

Jack Dongarra
Fri Sep 1 06:16:55 EDT 1995