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, June 02, 2016, 12:15 pm

Duration: 30 minutes

Location: OAT S15/S16/S17

Speaker: Stephen Chestnut (IFOR)

Beating CountSketch for heavy hitters in insertion streams

The task of finding heavy hitters is one of the best known and well studied problems in the area of data streams. In a sense, the strongest guarantee available is the $\ell_2$ guarantee, which requires finding all items that occur at least $\epsilon \|f\|_2$ times in the stream, where the $i$th coordinate of the vector $f$ is the number of occurrences of $i$ in the stream. The first algorithm to achieve the $\ell_2$ guarantee was the CountSketch (Charikar, Chen, and Farach-Colton ICALP'02), which, for constant $\epsilon$, requires $O(\log n)$ words of memory and $O(\log n)$ update time. It is known to be space-optimal if the stream includes deletions. In this talk I will discuss recent improvements that allow us to find $\ell_2$ heavy hitters in $O(1)$ memory and $O(1)$ update time in insertion only streams. The improvements rely on a deeper understanding of the AMS sketch (Alon, Matias, and Szegedy STOC'96) and similar sketches and draw on the theory of Gaussian processes. This talk is based on joint work with Vladimir Braverman, Nikita Ivkin, Jelani Nelson, Zhengyu Wang, and David P. Woodruff in arxiv:1511.00661 and arxiv:1603.00759.


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