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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MATH-821) SparseRealVectorTest.testMap and testMapToSelf fail because zero entries lose their sign
Date Mon, 22 Oct 2012 13:52:12 GMT

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

Gilles updated MATH-821:
------------------------

    Fix Version/s: 4.0

I guess that this will be automatically fixed when the sparse vector implementation is deleted.
:)

                
> 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: 4.0
>
>
> 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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