Load-Balanced Slim Fly Networks

The Slim Fly topology has recently been proposed for the future generation supercomputers. It has small diameter and relies on the Universal Globally Adaptive Load-balanced (UGAL) routing, which adapts the routes between minimal (MIN) routing and Valiant Load-Balancing (VLB) routing to exploit the network capacity. In this work, we show that the current Slim Fly is not load-balanced for both MIN routing and VLB routing, in that certain links in the network have a significantly higher probability to carry traffic than others. As such, hot spots are more likely to form on such links. We propose two approaches to address this problem and to make Slim Fly load-balanced: (1) modifying the topology by selectively increasing the bandwidth of the potential hot-spot links so that the original routing becomes load-balanced, and (2) modifying the routing scheme by using a weighted VLB routing to distribute the traffic in a more load balanced fashion than the original VLB routing on the original Slim Fly. The results of our performance analysis and simulation demonstrate that both approaches result in more effective Slim Fly than its current form.