[Dmbu-l] talk this Friday 12/12 Natali Ruchansky 10:30 am MCS 148

Dora Erdos edori at bu.edu
Mon Dec 8 10:04:39 EST 2014

Hi All,

this Friday will be our last talk in 2014. Natali Ruchansky is going to 
talk about the Minimum Wiener Connector Problem.

We will continue our seminar in the next semester (same time and 


Title: Minimum Wiener Connector Problem

The Wiener index of a graph is the sum of all pairwise shortest-path 
distances between its vertices.
In a recently submitted paper we study the novel problem of finding a 
minimum Wiener connector: given a connected graph G=(V,E) and a set Q 
subset of V of query vertices, find a
subgraph of G that connects all query vertices and has minimum Wiener 
The problem falls naturally into the class of connectivity subgraphs, 
community search, and network design problems, and has potential 
in many scenarios, including visualization in online tools, finding 
community leaders, and finding bridges between communities.

In this talk I will give a historic introduction to the notion of Wiener 
index, how it differs from the more-known concept of Steiner tree, and 
give some simple heuristic algorithms for the Wiener Connector Problem. 
I'll also give a sample of experiments on real-world graphs, and cute toy 
examples on the Karate-Club network, and a 2014 KDD tweet graph.
Time permitting I will also give an (very) high-level taste of some 
theoretical results in the paper -- in particular of our main contribution 
is a constant-factor approximation algorithm running in
time O(|Q||E|), and of a comparison to a linear programming formulation.

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