A Comparison of Adaptive Wormhole Routing

Improvement of message latency and network utilization in torus interconnection networks by increasing adaptivity in wormhole routing algorithms is studied. A recently proposed partially adaptive algorithm and four new fully-adaptive routing algorithms are compared with the well-known e-cube algorithm for uniform, hotspot, and local traac patterns. Our simulations indicate that the partially adaptive north-last algorithm, which causes unbalanced traac in the network, performs worse than the nonadaptive e-cube routing algorithm for all three traac patterns. Another result of our study is that the performance does not necessarily improve with full-adaptivity. In particular , a commonly discussed fully-adaptive routing algorithm, which uses 2 n virtual channels per physical channel of a k-ary n-cube, performs worse than e-cube for uniform and hotspot traac patterns. The other three fully-adaptive algorithms, which give priority to messages based on distances traveled, perform much better than the e-cube and partially-adaptive algorithms for all three traac patterns. One of the conclusions of this study is that adaptivity, full or partial, is not necessarily a beneet in wormhole routing.