The Impact of Output Selection Function Choice on the Performance of Adaptive Wormhole Routing

Many adaptive routing algorithms have been proposed for wormhole-routed interconnection networks. Comparatively little work, however, has been done on determining how the output selection function (routing policy) affects the performance of an adaptive routing algorithm. In this paper, we present a detailed simulation study of various selection functions for a fully adaptive mesh routing algorithm. The simulation results show that the choice of selection function has a significant effect on the average message latency. Thus, a naive implementation of an adaptive routing algorithm may lead to poor performance. These selection functions are also compared with a theoretically optimal selection function [1]. We show that although theoretically optimal, the actual performance of the optimal selection function is not best. An explanation and interpretation of the results is provided.