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https://issues.apache.org/jira/browse/MAHOUT-1059?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13447442#comment-13447442
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Ted Dunning commented on MAHOUT-1059:
-------------------------------------
I have added a fix/enhancement to the basic matrix to make handling of size
caching more generic. The basic issue was that caching the squared length of a
vector makes distance calculations with L_2 faster for sparse vectors. This
should apply (or not) to all view-like vectors like DelegatingVector. So now
it does.
> New matrix extensions
> ---------------------
>
> Key: MAHOUT-1059
> URL: https://issues.apache.org/jira/browse/MAHOUT-1059
> Project: Mahout
> Issue Type: Improvement
> Components: Math
> Reporter: Ted Dunning
> Fix For: 0.8
>
> Attachments:
> 0001-MAHOUT-1059-Added-Centroid-WeightedVector-Delegating.patch,
> 0001-MAHOUT-1059-Added-Centroid-WeightedVector-Delegating.patch,
> 0001-MAHOUT-1059-Added-Centroid-WeightedVector-Delegating.patch,
> 0001-MAHOUT-1059-Added-Centroid-WeightedVector-Delegating.patch,
> 0002-MAHOUT-1059-Stylistic-cleanups.patch,
> 0002-MAHOUT-1059-Stylistic-cleanups.patch,
> 0002-MAHOUT-1059-Stylistic-cleanups.patch,
> 0003-MAHOUT-1059-Add-generic-vector-test.patch,
> 0003-MAHOUT-1059-Add-generic-vector-test.patch,
> 0004-MAHOUT-1059-Indentation.patch, 0004-MAHOUT-1059-Indentation.patch,
> 0005-MAHOUT-1059-Abstract-the-idea-of-a-cached-length.patch,
> 0006-MAHOUT-1059-Additional-test-for-weighted-vectors.patch,
> DelegatingVectorTest.java
>
>
> The upcoming clustering needs several capabilities to support different
> operations. These include some matrix extensions for adding behaviors to
> different kinds of matrices. Also there is a file based matrix that uses
> mmap to access a file as if it were a matrix in shared memory. Since this is
> off-heap and shared between processes, it can seriously help some programs.
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