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 . 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 . The table below summarizes the differences cachingcommunicator, caching between intracommunicators and intercommunicators. communicator, intra vs inter
Intracommunicator operations are described in Section , and intercommunicator operations are discussed in Section .