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https://issues.apache.org/jira/browse/MAHOUT-208?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12805408#action_12805408
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Jake Mannix commented on MAHOUT-208:
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Hmm... I'm getting bitten by this again: setQuick() mutates, but only calls
"lengthSquared = -1.0" in DenseVector. The sparse vectors don't do this, and
nasty things happen. Will check in fix.
> Vector.getLengthSquared() is dangerously optimized
> --------------------------------------------------
>
> Key: MAHOUT-208
> URL: https://issues.apache.org/jira/browse/MAHOUT-208
> Project: Mahout
> Issue Type: Bug
> Components: Math
> Affects Versions: 0.1
> Environment: all
> Reporter: Jake Mannix
> Assignee: Sean Owen
> Fix For: 0.3
>
>
> SparseVector and DenseVector both cache the value of lengthSquared, so that
> subsequent calls to it get the cached value. Great, except the cache is
> never cleared - calls to set/setQuick or assign or anything, all leave the
> cached value unchanged.
> Mutating method calls should set lengthNorm to -1 so that the cache is
> cleared.
> This could be a really nasty bug if hit.
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