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 A. Steger, D. Steurer and B. Sudakov)

Mittagsseminar Talk Information

Date and Time: Thursday, November 12, 2020, 12:15 pm

Duration: 30 minutes

Location: Zoom: conference room

Speaker: Goran Zuzic

Low-Congestion Shortcuts are Universally Optimal for Distributed Computing

The modern computation and information processing systems shaping our world have become massively distributed and a fundamental understanding of distributed algorithmics has never been more important. At the same time, despite 40 years of intense study, we do not have a satisfactory understanding of how a network topology influences the runtime of various distributed tasks.

I will present a new result that resolves the question in many interesting ways. Concretely, suppose we are solving a distributed optimization problem (e.g., minimum spanning tree problem, minimum cut, or shortest path) in the classic CONGEST model of distributed computing. The work shows, via an information-theoretic argument, that a fast distributed algorithm for any of the above problems induces a specific combinatorial structure in the graph called "low-congestion shortcuts". In other words, the non-existence of this structure represents the first non-trivial lower bound on the runtime of distributed optimization tasks that can be applied to any network topology. Moverover, the lower bound holds even when all the nodes know the entire network topology in advance.

Furthermore, in other work, we show that the bound is tight in the known-topology setting---the existence of low-congestion shortcuts implies the existence of fast distributed algorithms for the above problems. Together, these two results resolve a long-standing open problem posed in [Garay, Kutten, Peleg; 1998] about identifying the salient network topology parameters that characterize the runtime of various problems in distributed optimization, at least in the known-topology setting.

This talk presents joint work with Bernhard Haeupler and David Wajc.

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

Previous talks by year:   2023  2022  2021  2020  2019  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