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From "Dmitriy Lyubimov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAHOUT-638) Stochastic svd's is not handling well all cases of sparse vectors
Date Sun, 17 Apr 2011 20:42:06 GMT

    [ https://issues.apache.org/jira/browse/MAHOUT-638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13020863#comment-13020863
] 

Dmitriy Lyubimov commented on MAHOUT-638:
-----------------------------------------

Github url for this issue: https://github.com/dlyubimov/mahout-commits/tree/MAHOUT-638 (pull
requests are welcome).

> 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-622-2.patch, MAHOUT-638-2.patch, MAHOUT-638-2.patch, 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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