Toward unprivileged, portable and generic network topology discovery

Abstract

International audienceWith the increase in size and complexity of supercomputers, it has become crucial to match applications and communication libraries to the underlying network topology. This matching may allow minimizing the time spent in waiting for high-latency communication and limiting contention on the network. While MPI implementations rely mostly on software such as hwloc to retrieve information about nodes topology, no tool currently gathers network topology information in a generic and portable fashion.In this paper, we propose an algorithm inspired by the Steiner Spanner problem that exploits end-to-end latency measurements to reconstruct a network topology. Our solution reconstructs the topology graph from a matrix of measured communication times. This is achieved by iteratively adding nodes to the graph while trying to match the shortest path length in the graph to the communication times. The total weight and the number of edges in the graph are also minimized