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From "Thomas Neidhart (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-1070) Incorrect rounding of float
Date Thu, 09 Jan 2014 13:32:55 GMT

    [ https://issues.apache.org/jira/browse/MATH-1070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13866642#comment-13866642
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Thomas Neidhart commented on MATH-1070:
---------------------------------------

The problem you outline is quite interesting. In the case of Precision.round(double, scale),
the double value gets internally converted to a BigDecimal, but BigDecimal loses the sign
if the value is 0. This is even documented in the javadoc: http://docs.oracle.com/javase/7/docs/api/java/math/BigDecimal.html#BigDecimal%28java.lang.String%29

> Incorrect rounding of float
> ---------------------------
>
>                 Key: MATH-1070
>                 URL: https://issues.apache.org/jira/browse/MATH-1070
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.2
>         Environment: Windows 7, IntelliJ IDEA 10.5.4.
>            Reporter: Oleksandr Muliarevych
>            Priority: Critical
>             Fix For: 3.3
>
>
> package org.apache.commons.math3.util 
> example of usage of round functions of Precision class:
> Precision.round(0.0f, 2, BigDecimal.ROUND_UP) = 0.01
> Precision.round((float)0.0, 2, BigDecimal.ROUND_UP) = 0.01
> Precision.round((float) 0.0, 2) = 0.0
> Precision.round(0.0, 2, BigDecimal.ROUND_UP) = 0.0
> Seems the reason is usage of extending float to double inside round functions and getting
influence of memory trash as value.
> I think, same problem will be found at usage of other round modes.



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