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From Sébastien Brisard (JIRA) <j...@apache.org>
Subject [jira] [Updated] (MATH-821) SparseRealVectorTest.testMap and testMapToSelf fail because zero entries lose their sign
Date Thu, 12 Jul 2012 14:04:35 GMT

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

Sébastien Brisard updated MATH-821:
-----------------------------------

    Summary: SparseRealVectorTest.testMap and testMapToSelf fail because zero entries lose
their sign  (was: SparseRealVectorTest.testMap and testMapToSelf fail because lost sign of
zero entries)
    
> 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: Sébastien Brisard
>              Labels: linear, sparse
>
> 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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