Multiple Multicast with Minimized Node Contention on Wormhole k-ary n-cube Networks

This paper presents a new approach to minimize node contention while performing multiple multicast/broadcast on wormhole k-ary n-cube networks with overlapped destination sets. The existing multicast algorithms in the literature deliver poor performance under multiple multicast because these algorithms have been designed with only single multicast in mind. The new algorithms introduced in this paper do not use any global knowledge about the respective destination sets of the concurrent multicasts. Instead, only local information and source-speciic partitioning approach are used. For systems supporting unicast message-passing a new SPUmesh (Source-Partitioned Umesh) algorithm is proposed and shown to be superior than the conventional Umesh algorithm 14] for multiple multicast. Two diierent algorithms, SQHL (Source-Quadrant Hierarchical Leader) and SCHL (Source-Centered Hierarchical Leader), are proposed for systems with multidestination message-passing and shown to be superior than the HL scheme 18]. All these algorithms perform 1) 5-10 times faster than the existing algorithms under multiple multicast and 2) as fast as existing algorithms under single multicast. Furthermore, the SCHL scheme demonstrates that the latency of multiple multicast can, in fact, be reduced as the degree of multicast increases beyond a certain number. Such results related to multiple multicast are the rst of their kind in the wormhole literature. Thus, these algorithms demonstrate signiicant potential to be used for designing fast and scalable collective communication libraries on current and future generation wormhole systems.