A Comparison of Fat Trees and Express Cubes

We compare two types of multiprocessor interconnection networks, fat trees and express cubes. Sample networks of each type were designed using realistic hardware constraints. We model different communication patterns on them and compute metrics such as average hop count, average latency, and bisection bandwidth, and show approximate costs for each network in terms of router and wire counts. Results show that two dimensional express cubes provide slightly lower hop counts across most communication patterns, andprovide much lower hop countswhen communicatingdirectlywith neighbors. Threedimensional express cubes have slightly higher hop counts, but have a larger bisection bandwidth than similar fat trees.