Analytic performance comparison of hypercubes and star graphs with implementation constraints

Many theoretical-based comparison studies, relying on graph structural and algorithmic properties, have been conducted for the hypercube and the star graph. None of these studies, however, have considered real working conditions and implementation limits. We have compared the performance of the star and hypercube networks for different message lengths and number of virtual channels, and considered two implementation constraints, namely the constant bisection bandwidth and constant node pin-out. We use two accurate analytical models, already proposed for the star graph and hypercube, and implement the parameter changes imposed by technological implementation constraints. When no constraint is used, the comparison results reveal that the hypercube has a better performance compared to the equivalent star graph. The hypercube with more channels compared to its equivalent star graph saturates later showing that it can bear heavier traffic loads. However, when implementation constraints are considered, the star graph exhibits a superior performance over its equivalent hypercube in most cases.