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From "Ted Dunning (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MATH-314) New sparse vector implementation: int[] indices; double[] values;
Date Mon, 25 Jan 2010 19:40:35 GMT

    [ https://issues.apache.org/jira/browse/MATH-314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12804667#action_12804667
] 

Ted Dunning commented on MATH-314:
----------------------------------


I just asked Jake about this off-list and his reply was that this functionality has been incorporated
in the Mahout math package.  This decreased his level of urgency below the critical level
required to get a patch into good shape and he is reluctant to give you guys an 80% done patch
since it would just increase the work for you.




> New sparse vector implementation: int[] indices; double[] values;
> -----------------------------------------------------------------
>
>                 Key: MATH-314
>                 URL: https://issues.apache.org/jira/browse/MATH-314
>             Project: Commons Math
>          Issue Type: New Feature
>    Affects Versions: 2.0
>         Environment: all
>            Reporter: Jake Mannix
>            Priority: Minor
>             Fix For: 2.1
>
>
> OpenMapRealVector is nice for fast random access, but if all you do with your sparse
vectors is dot them together, add them onto dense vectors, and so forth, the representation
as just an array of indices and an array of values is more compact, and faster (for these
operations).  
> It becomes prohibitive to do modification, however, so the usual thing is to have them
be immutable - use an OpenMapRealVector while modifing, then seal them up into the constructor
for an IntDoubleArrayVector form for fast iteration and so forth.

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