[jira] Commented: (MATH-314) New sparse vector implementation: int[] indices; double[] values;

["Luc Maisonobe (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MATH-314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12804223#action_12804223 ] 

Luc Maisonobe commented on MATH-314:
------------------------------------

I don't remember the status of this issue yet.
Jake, did you provide another patch that I again forgot to apply ?

> 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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