Bounds on the Efficiency of Message-Passing Protocols for Parallel Computers

This paper considers the problem of creating message-passing protocols for parallel computers. It is assumed that the processors are connected by a network that provides guaranteed delivery of every message, provided that each message delivered by the network is removed by the receiving processor unconditionally and in finite time. Two models of message-passing are considered, namely a selective model in which the receiver specifies the source of the message, and a nonselective model in which the receiver accepts messages from all sources. We consider only space-efficient protocols in which each processor has storage for a constant number of messages and message headers. We present three main results. First, we give a protocol for the selective model that performs a constant amount of communication per send or receive posted by the application. Second, we prove that no such efficient protocol exists for the nonselective model. Third, we present a protocol for the nonselective model tha..