Routing Algorithms for IBM SP1

. Scalable multicomputers are based upon interconnection networks that typically provide multiple communication routes between any given pair of processor nodes. Routes must be selected for communication so that the load is distributed evenly among the links and switches to prevent congestion in the network. We describe the route selection algorithm used in the IBM 9076 SP1 multicomputer. We then describe a new algorithm for reducing network congestion and compare the two algorithms. 1 Introduction Scalable multicomputers are based upon interconnection networks that typically provide multiple communication routes between any given pair of processor nodes. Multiple routes provide low latency, high bandwidth, and reliable interprocessor communication. In such networks, the selection of the routes is important because of its impact on the communication performance. Routes must be selected so that the communication load is distributed evenly among the links and switches to prevent congest..