T1 and T2 Values in Canopy (& MeanShift)
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Key: MAHOUT-626
URL: https://issues.apache.org/jira/browse/MAHOUT-626
Project: Mahout
Issue Type: Improvement
Components: Clustering
Affects Versions: 0.5
Reporter: Jeff Eastman
Assignee: Jeff Eastman
Fix For: 0.5
Users are reporting that the T1 and T2 threshold values which work in
sequential mode don't work as well in the mapreduce mode because both the
mapper and reducer are using the same values. The effect of coalescing a number
of points into a single centroid done by the mapper changes the distances
enough that independent threshold values are needed in the reducer.
Here is a patch which implements optional T3 and T4 threshold values which are
only used by the canopy reducer. Convenience methods have been added for API
compatibility and defaults included so that these values will default to T1 and
T2. A new unit test confirms the thresholds are being set correctly.
If this works out as a positive improvement, I will make the same changes to
MeanShift and commit them
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