Robust MPI Message Delivery with Guaranteed Resources

A mechanism for message delivery is at the core of any implementation of Message-Passing Interface (MPI) [1]. In a distributed memory computer, shared or not, it is most feasible to synchronize messages in the local memory of the destination process. Accordingly, the initial step in message delivery is for the source process to transmit a message envelope a small packet containing synchronization variables and possibly other information (p. 19) to the destination. Whether or not an MPI implementation provides buffer space (p. 27, ll. 26-32) (buffer space is for the message data, the application's data), it must store envelopes in the destination local memory when there is no matching posted receive. As local memory is a limited resource, so too is message envelope space.