PolyChord: nested sampling for cosmology

PolyChord is a novel nested sampling algorithm tailored for high dimensional parameter spaces. In addition, it can fully exploit a hierarchy of parameter speeds such as is found in CosmoMC and CAMB. It utilises slice sampling at each iteration to sample within the hard likelihood constraint of nested sampling. It can identify and evolve separate modes of a posterior semi-independently and is parallelised using openMPI. PolyChord is available for download at: http://ccpforge.cse.rl.ac.uk/gf/project/polychord/Comment: Accepted by MNRAS 2015 March 20. Received 2015 March 20; in original form 2015 February 6, 5 pages, 5 figure

FUBAR: Flow utility based routing

We present FUBAR, a system that reduces congestion and maximizes the utility of the entire network by installing new routes and changing the traffic load on existing ones. FUBAR works offline to periodically adjust the distribution of traffic on paths. It requires neither changes to end hosts nor precise prior knowledge of the traffic matrix. We demonstrate that even in the presence of traffic from all network devices to all other devices, FUBAR can optimize a real-world core-level network in a matter of minutes

Low-Latency Routing on Mesh-Like Backbones

Early in in the Internet's history, routing within a single provider's WAN centered on placing traffic on the shortest path. More recent traffic engineering efforts aim to reduce congestion and/or increase utilization within the status quo of greedy shortest-path first routing on a sparse topology. In this paper, we argue that this status quo of routing and topology is fundamentally at odds with placing traffic so as to minimize latency for users while avoiding congestion. We advocate instead provider backbone topologies that are more mesh-like, and hence better at providing multiple low-latency paths, and a routing system that directly considers latency minimization and congestion avoidance while dynamically placing traffic on multiple unequal-cost paths. We offer a research agenda for achieving this new low-latency approach to WAN topology design and routing