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https://issues.apache.org/jira/browse/MATH-821?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13413659#comment-13413659
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Gilles commented on MATH-821:
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In revision 1361164, I disabled the two unit tests that demonstrate this bug.
When the bug is fixed, the tests should be made active again.
> 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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