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From "Jake Mannix (JIRA)" <j...@apache.org>
Subject [jira] Created: (MATH-314) New sparse vector implementation: int[] indices; double[] values;
Date Thu, 29 Oct 2009 08:16:59 GMT
New sparse vector implementation: int[] indices; double[] values;
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                 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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