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https://issues.apache.org/jira/browse/MAHOUT-208?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12789171#action_12789171
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Shashikant Kore commented on MAHOUT-208:
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It is important to have this caching to keep the work done on MAHOUT-121
intact.
Alternative to maintaining caching flag is to use the hashcode of underlying
constructs. For example, in case of SparseVector, we could use
OpenIntDoubleHashMap.hashCode() to see if the cached value is still valid. In
case of DenseVectors, hashcode of arrays can be used.
> Vector.getLengthSquared() is dangerously optimized
> --------------------------------------------------
>
> Key: MAHOUT-208
> URL: https://issues.apache.org/jira/browse/MAHOUT-208
> Project: Mahout
> Issue Type: Bug
> Components: Matrix
> 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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