[This is preliminary documentation and is subject to change.]
The Communicator type exposes the following fields.
Special value for the source argument to Receivec> that indicates that the message can be received from any process in the communicator.
Special value for the tag argument to Receive that indices that the message with any tag can be received by the receive operation.
The "self" communicator is a simple communicator that contains only the currently-executing process.
The "world" communicator contains all of the processes that were originally created by MPI.