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From Shashikant Kore <>
Subject Understanding Canopy/Map Reduce
Date Tue, 22 Sep 2009 13:59:48 GMT

I am unable to understand how the Canopy clustering works.

In Map stage, Canopy.addPointToCanopies() is called for every point
with list of canopies. This method adds to the existing canopy or
creates new one or both depending on the distance of the vector from
existing canopy centroids.  Map stage outputs all the canopy centroids
(with key "centroid").

In reduce phase,  these centroids will again undergo the same process
(so, possible merges) and finally centroids will be output'ed. But, I
see that in CanopyReducer the input values are the input vectors and
not the centroids received from the Map stage.

I think, I missing something here. Can you please let me know what it is?

Note: I am using CanopyDriver utility (and not CanopyClusteringJob).



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