The support for virtual topologies as defined in this chapter is consistent with other parts of MPI, and, whenever possible, makes use of functions that are defined elsewhere. Topology information is associated with communicators. It is added to communicators using the caching mechanism described in Chapter Groups, Contexts, Communicators, and Caching.
Information representing a virtual topology may be added to a communicator at the time of its creation. If a communicator creation function adds information representing a virtual topology to the output communicator it creates, then it either propagates the topology representation from the input communicator to the output communicator, or adds a new topology representation generated from the input parameters that describe a virtual topology. The description of every MPI communicator creation function explicitly states how topology information is handled. Communicator creation functions that create new topology representations are described in Section Topology Constructors.