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https://issues.apache.org/jira/browse/MAHOUT-843?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13150569#comment-13150569
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Jeff Eastman commented on MAHOUT-843:
-------------------------------------
You are correct. This is why the number of reducers needs to be >= the number
of clusters. Note the postprocessor then needs to move each part file into its
own directory for the bottom clustering to use. I think the bottom clusterer
can be given a single (likely huge) part file but we need to make sure this can
be split automatically by Hadoop or the large file needs to be broken up into
multiple smaller files (by another MR job).
> Top Down Clustering
> -------------------
>
> Key: MAHOUT-843
> URL: https://issues.apache.org/jira/browse/MAHOUT-843
> Project: Mahout
> Issue Type: New Feature
> Components: Clustering
> Affects Versions: 0.6
> Reporter: Paritosh Ranjan
> Labels: clustering, patch
> Fix For: 0.6
>
> Attachments: MAHOUT-843-patch, MAHOUT-843-patch-only-postprocessor,
> MAHOUT-843-patch-only-postprocessor-v1,
> MAHOUT-843-patch-only-postprocessor-v2, MAHOUT-843-patch-v1,
> Top-Down-Clustering-patch
>
>
> Top Down Clustering works in multiple steps. The first step is to find
> comparative bigger clusters. The second step is to cluster the bigger chunks
> into meaningful clusters. This can performance while clustering big amount of
> data. And, it also removes the dependency of providing input clusters/numbers
> to the clustering algorithm.
> The "big" is a relative term, as well as the smaller "meaningful" terms. So,
> the control of this "bigger" and "smaller/meaningful" clusters will be
> controlled by the user.
> Which clustering algorithm to be used in the top level and which to use in
> the bottom level can also be selected by the user. Initially, it can be done
> for only one/few clustering algorithms, and later, option can be provided to
> use all the algorithms ( which suits the case ).
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