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From "Stavros Kontopoulos (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-2147) Approximate calculation of frequencies in data streams
Date Tue, 04 Apr 2017 12:59:41 GMT

    [ https://issues.apache.org/jira/browse/FLINK-2147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15955103#comment-15955103

Stavros Kontopoulos commented on FLINK-2147:

I think Count-min sketch can be implemented in way that each task keeps a local count-min
sketch as state, and as a next step it emits the frequencies after an aggregation of count-mi
sketches. This could be windows based and would involve to implement custom operators. This
is a high level description and may not fit exactly to the internals.

A distributed implementation here:

> Approximate calculation of frequencies in data streams
> ------------------------------------------------------
>                 Key: FLINK-2147
>                 URL: https://issues.apache.org/jira/browse/FLINK-2147
>             Project: Flink
>          Issue Type: New Feature
>          Components: DataStream API
>            Reporter: Gabor Gevay
>              Labels: approximate, statistics
> Count-Min sketch is a hashing-based algorithm for approximately keeping track of the
frequencies of elements in a data stream. It is described by Cormode et al. in the following
> http://dimacs.rutgers.edu/~graham/pubs/papers/cmsoft.pdf
> Note that this algorithm can be conveniently implemented in a distributed way, as described
in section 3.2 of the paper.
> The paper
> http://www.vldb.org/conf/2002/S10P03.pdf
> also describes algorithms for approximately keeping track of frequencies, but here the
user can specify a threshold below which she is not interested in the frequency of an element.
The error-bounds are also different than the Count-min sketch algorithm.

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