Department of Computer Science | Institute of Theoretical Computer Science | CADMO

Theory of Combinatorial Algorithms

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar (in cooperation with M. Ghaffari, A. Steger and B. Sudakov)

Mittagsseminar Talk Information

Date and Time: Thursday, March 19, 2009, 12:15 pm

Duration: This information is not available in the database

Location: CAB G51

Speaker: Anna Huber (Max-Planck-Institut für Informatik, Saarbrücken)

Quasirandom Rumour Spreading

Randomized rumor spreading is a protocol for disseminating information in a network. Initially, one vertex of a finite, undirected connected graph has some piece of information (''rumor''). In each round, every vertex that knows the rumor tells it to a neighbor chosen uniformly at random. Results of Frieze and Grimmett show that in a complete graph on n vertices, this protocol spreads the rumor from one node to all others within (1 + o(1))(log2(n) + ln(n)) rounds with probability 1-o(1). This was improved to log2(n) + ln(n) + h(n) for every h \in ω(1) by Pittel.

Doerr, Friedrich and Sauerwald proposed a quasirandom analogue of this model. Here, each vertex has a cyclic permutation of its neighbors. When first passing the rumor, it chooses a neighbor uniformly at random. All subsequent gossiping is done to the successors of this vertex in the cyclic permutation. For complete graphs, hypercubes and a broader range of random graphs it was shown that this protocol also needs O(log n) rounds only to inform all other nodes.

We give a precise analysis of the evolution in the case of a complete graph on n vertices and show that this protocol also informs all nodes in (1 + o(1))(log2(n) + ln(n))rounds with probability 1-o(1).

Joint work with Benjamin Doerr and Nikolaos Fountoulakis.


Upcoming talks     |     All previous talks     |     Talks by speaker     |     Upcoming talks in iCal format (beta version!)

Previous talks by year:   2018  2017  2016  2015  2014  2013  2012  2011  2010  2009  2008  2007  2006  2005  2004  2003  2002  2001  2000  1999  1998  1997  1996  

Information for students and suggested topics for student talks


Automatic MiSe System Software Version 1.4803M   |   admin login