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https://issues.apache.org/jira/browse/MAHOUT-1045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13414768#comment-13414768
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Sean Owen commented on MAHOUT-1045:
-----------------------------------
The fix may or may not be right to use POSITIVE_INFINITY; it may just be a part
of the puzzle. If switching from 0 to a really small positive value helps, then
I'd imagine that means NaN is creeping in somewhere as a divide by 0. And that
could happen if max never is different from 0 and ends up making a denominator
0? That might also explain why using POSITIVE_INFINITY does the same, as you
may end up with infinity/infinity somewhere. Sounds like some loop expects
there to be at least one iteration to make for valid max/min values, but there
isn't one loop. Is count 0?
> Cluster evaluators returning bad results
> ----------------------------------------
>
> Key: MAHOUT-1045
> URL: https://issues.apache.org/jira/browse/MAHOUT-1045
> Project: Mahout
> Issue Type: Bug
> Components: Clustering
> Affects Versions: 0.6, 0.7, 0.8
> Environment: Several environments and data sets
> Reporter: Pat Ferrel
> Fix For: 0.8
>
> Attachments: MAHOUT-1045.patch, first-time-density-nan.txt
>
>
> With real world crawl data the Intra-cluster density from ClusterEvaluator is
> almost always NaN. The CDbw inter-cluster density is almost always 0. I have
> also seen several cases where CDbw fails to return any results but have not
> tracked down why yet.
> I have sent a link to an 8G data set that reproduces these errors to Jeff
> Eastman.
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