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

Prof. Emo Welzl and Prof. Bernd Gärtner

Mittagsseminar Talk Information |

**Date and Time**: Tuesday, February 23, 2010, 12:15 pm

**Duration**: This information is not available in the database

**Location**: OAT S15/S16/S17

**Speaker**: Michael Hoffmann

A neat 1972 result of Pohl asserts that \lceil 3n/2 \rceil -2 comparisons are sufficient, and also necessary in the worst case, for finding both the minimum and the maximum of an n-element totally ordered set. The set is accessed via an oracle for pairwise comparisons. More recently, the problem has been studied in the context of the Rényi--Ulam liar games, where the oracle may give up to k false answers. For large k, an upper bound due to Aigner shows that (k+\O(\sqrt{k}))n comparisons suffice.

We improve on this by providing an algorithm with at most (k+1+C)n+\O(k^3) comparisons for some constant C. The known lower bounds are of the form (k+1+c_k)n-D, for some constant D, where c_0=0.5, c_1=23/32= 0.71875, and c_k=\Omega(2^{-5k/4}) as k\to\infty.

Joint work with Jirka Matousek, Yoshio Okamoto, and Philipp Zumstein

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

Previous talks by year: 2024 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