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Date: Mon, 28 Mar 2011 20:29:05 +0000 (UTC)
From: "Ted Dunning (JIRA)" <jira@apache.org>
To: dev@mahout.apache.org
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Subject: [jira] [Commented] (MAHOUT-638) Stochastic svd's is not handling
 well all cases of sparse vectors
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    [ https://issues.apache.org/jira/browse/MAHOUT-638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13012205#comment-13012205 ] 

Ted Dunning commented on MAHOUT-638:
------------------------------------

I would drop most of the properties that specify versions.  Defining a symbol that is used in one place doesn't really even save much.

> Stochastic svd's is not handling well all cases of sparse vectors 
> ------------------------------------------------------------------
>
>                 Key: MAHOUT-638
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-638
>             Project: Mahout
>          Issue Type: Bug
>          Components: Math
>    Affects Versions: 0.5
>            Reporter: Dmitriy Lyubimov
>            Assignee: Dmitriy Lyubimov
>             Fix For: 0.5
>
>         Attachments: MAHOUT-638.patch
>
>
> The Mahout patch of the algorithm is not handling all types of sparse input efficiently. BtJob doesn't handle SequentialSparseVector in a way to pick only non-zero elements from initial input and QJob doesn't iterate over RandomAccessSparseVector correctly. With extremely sparse inputs (0.05% non-zero elements) that leads to a terrible inefficiency in the aforementioned jobs (QJob, BtJob).

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