Limited Multi-path Routing on Extended Generalized Fat-trees

We consider a general form of routing, called limited multi-path routing, on extended generalized fat-trees where the number of paths between each pair of processing nodes is a parameter. Existing single-path routing and multi-path routing for such topologies are special cases of limited multi- path routing. We propose path calculation heuristics, including shift-1, disjoint, and random for limited multi-path routing on extended generalized fat-trees. All of these heuristics are based on existing single-path routing schemes, work for limited multi-path routing with any given number of paths between processing nodes, gracefully increase routing performance as the number increases, and reach optimal when all shortest paths between processing nodes are allowed for carrying traffics. Flow-level and flit-level simulation experiments are carried out to study the performance. The results show that the disjoint heuristic significantly out-performs the other methods.