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From "Luc Maisonobe (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (MATH-821) SparseRealVectorTest.testMap and testMapToSelf fail because zero entries lose their sign
Date Thu, 20 Feb 2014 16:17:25 GMT

     [ https://issues.apache.org/jira/browse/MATH-821?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Luc Maisonobe resolved MATH-821.
--------------------------------

       Resolution: Fixed
    Fix Version/s:     (was: 4.0)
                   3.3

Unit tests have been relaxed.

Comments have been added in the javadoc for SparseVector interface and OpenMapRealVector class.

> SparseRealVectorTest.testMap and testMapToSelf fail because zero entries lose their sign
> ----------------------------------------------------------------------------------------
>
>                 Key: MATH-821
>                 URL: https://issues.apache.org/jira/browse/MATH-821
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.0
>            Reporter: S├ębastien Brisard
>              Labels: linear, sparse
>             Fix For: 3.3
>
>
> Mapping {{Inverse}} to an {{OpenMapRealVector}} can lead to wrong answers, because {{1.0
/ 0.0}} should return {{+/-Infinity}} depending on the sign of the zero entry. Since the sign
is lost in {{OpenMapRealVector}}, the answer must be wrong if the entry is truly {{-0.0}}.
> This is a difficult bug, because it potentially affects any function passed to {{OpenMapRealVector.map()}}
or {{mapToSelf()}}. I would recommend we relax the requirements in the unit tests of this
class, and make people aware of the issue in the class documentation.



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