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What and Who
Title:Median Filtering is Equivalent to Sorting
Speaker:Jukka Suomela
coming from:Aalto University
Speakers Bio:Jukka Suomela ( is an Assistant Professor in the Department of Computer Science at Aalto University. He received his PhD from the University of Helsinki in 2009, and the title of Docent in Computer Science in 2012. Suomela's research group ( conducts basic research related to the theoretical foundations of distributed computing, with particular emphasis on the concept of locality in the context of distributed graph algorithms.
Event Type:Talk
Visibility:D1, D2, D3, D4, D5, RG1, SWS, MMCI
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Level:MPI Audience
Date, Time and Location
Date:Wednesday, 11 March 2015
Duration:30 Minutes
Building:E1 4
In this talk I will show that the following problems are equivalent,

both in theory and in practice:

(1) median filtering: given an n-element vector, compute the sliding
window median with window size k,

(2) piecewise sorting: given an n-element vector, divide it in n/k
blocks of length k and sort each block.

By prior work, median filtering is known to be at least as hard as
piecewise sorting: with a single median filter operation we can sort
θ(n/k) blocks of length θ(k). Our recent work shows that median
filtering is also as easy as piecewise sorting: we can do median
filtering with one piecewise sorting operation and linear-time
postprocessing; moreover, the algorithm is very efficient in practice.

See for more information.

Name(s):Christoph Lenzen
Video Broadcast
Video Broadcast:NoTo Location:
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  • Christoph Lenzen, 02/26/2015 10:30 AM -- Created document.