Path-based multicast communication in wormhole-routed unidirectional torus networks

This paper addresses the problem of one-to-many or multicast, communication in wormhole-routed, n-dimensional torus networks, The proposed methods are designed for systems that support intermediate reception, which permits multidestination messages to be pipelined through several nodes, depositing a copy at each node, A key issue in the design of such systems is the routing function, which must support both unicast and multifast traffic while preventing deadlock among messages, An efficient, deadlock-free routing function is developed and used as a basis for a family of multicast algorithms. The S-torus multicast algorithm uses a single multidestination message to perform an arbitrary multicast operation, The M-torus algorithm is a generalized multiphase multicast algorithm, in which a combination of multidestination messages is used to perform a multicast in one or more communication steps. Two specific instances of the M-torus algorithm, the M-d-torus and M-u-torus multicast algorithms, are presented, These algorithms product contention-free multicast operations and are deadlock-free under all combinations of network traffic. A simulation study compares the performance of the different multicast algorithms, and implementation issues are discussed. The results of this research are applicable to the design of architectures for both wormhole-routed massively parallel computers and high-speed local area networks with wormhole-routed switch fabrics. (C) 1997 Academic Press.