Department of Computer Science | Institute of Theoretical Computer Science | CADMO
Prof. Emo Welzl and Prof. Bernd Gärtner
|Mittagsseminar Talk Information|
Date and Time: Wednesday, August 05, 2015, 12:15 pm
Duration: 30 minutes
Location: CAB G51
Speaker: Dominik Scheder (Shanghai Jiaotong University)
Let G=(V,E) be a directed graph (digraph). A decycling set is a set of vertices X such that G-X has no directed cycles. In this talk we consider digraphs in which every vertex has two incoming and two outgoing edges. We call those graphs (2,2)-regular graphs.
It is easy to show that every (2,2)-regular digraph has a decycling set of size at most 2/3 |V|, and this is tight. Things become much more exciting if we consider (2,2)-regular digraphs of *large girth*.
For those one can show that a decycling set of roughly size 0.38 |V| exists. This follows from the analysis of the PPSZ k-SAT algorithm. We improve the bound significantly to (1-ln(2))|V| ~ 0.31 |V|.
The motivation for this work comes from the hope that better upper bounds on decycling sets translate into an improved analysis of the PPSZ k-SAT algorithm, which is currently the fastest algorithm for the important NP-complete problem k-SAT.
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