Scalable, Global, Optimal-bandwidth, Application-Specific Routing

High performance computing platforms can benefit from additional bandwidth from the interconnection network because there are many applications with significant communication demands. Further, many HPC applications expressed as MPI programs have stable communication patterns across runs. Ideally, one would like to exploit the stable communication patterns by using global routing of communication paths to minimize network contention. Unfortunately, existing optimal-bandwidth, global routing techniques use mixed integer linear programs which fundamentally do not scale to the sizes that HPC workloads and platforms demand. Consequently, HPC platforms use simple distributed routing techniques, possibly with local adaptive routing, at best. Our design - Scalable Global Routing (SGR) - addresses this gap. Simulations reveal that in a 4096-node, 4D-torus network, SGR achieves global route computation with a speedup of nearly two orders of magnitude over prior global routing techniques. SGR outperforms simpler (non-global) routing techniques such as minimal adaptive routing by a 3.1X margin and non-minimal adaptive routing by a 37% margin.