# Wednesday, 29 November 2017: NODES Seminar, Durham

General meeting of all members of NODES and their PhD students.

## Location:

Room E240, Department of Computer Science, Durham University

## Timetable:

14.00-14.45 Iain Stewart (Durham, CS): On some mathematical aspects of data centre networks

14.45-15.30 Tea/Coffee break

15.30-16.15 Tom Nye (Newcastle, Maths): Geometric statistics in tree-space

Iain StewartÂ (Durham, CS): On some mathematical aspects of data centre networks

Abstract: Interconnection networks form the communication fabrics of distributed computer systems and are common-place in distributed-memory multiprocessor machines (supercomputers), systems on chips, and data centres. The massive number of processors involved in an interconnection networks means that it is simply not feasible to build prototypes and consequently interconnection network design is guided by appropriate graph-theoretical structural properties combined with simulation (in software). In this talk, I will illustrate a number of ways in which discrete mathematics impacts upon the design of interconnection networks for data centres.

Tom Nye (Newcastle, Maths): Geometric statistics in tree-space

Abstract: Phylogenetic trees represent evolutionary relationships between present-day species. Each tree can be considered as a combinatorial object, or when the tree is edge-weighted, as a point in a continuous metric space. Conventional statistical methods cannot be used to analyse data sets of trees since the space of all trees on a common set of species is not a vector space. Instead, tree-space has been shown to be a “non-positively curved” geodesic metric space and geodesics are computable in polynomial time. In this talk I will give an introduction to the geometry of phylogenetic tree-space, and describe a few ways to translate conventional statistical apparatus into this novel geometrical setting. This brings together ideas from metric geometry and analysis of stochastic processes.