MMLRU Selection Function: A Simple and Efficient Output Selection Function in Adaptive Routing

Adaptive routing algorithms, which dynamically select the route of a packet, have been widely studied for interconnection networks in massively parallel computers. An output selection function (OSF), which decides the output channel when some legal channels are free, is essential for an adaptive routing. In this paper, we propose a simple and efficient OSF called minimal multiplexed and least-recently-used (MMLRU). The MMLRU selection function has the following simple strategies for distributing the traffic: 1) each router locally grasps the congestion information by the utilization ratio of its own physical channels; 2) it is divided into the two selection steps, the choice from available physical channels and the choice from available virtual channels. The MMLRU selection function can be used on any type of network topology and adaptive routing algorithm. Simulation results show that the MMLRU selection function improves throughput and latency especially when the number of dimension becomes larger or the number of nodes per dimension become larger. key words: output selection function, adaptive routing, virtual channel, interconnection networks, massively parallel computers