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Posted to issues@commons.apache.org by "Phil Steitz (JIRA)" <ji...@apache.org> on 2010/04/14 02:05:59 UTC
[jira] Updated: (MATH-306) Method 'divide' in class 'Complex' uses
a false formula for a special case resulting in erroneous division by zero.
[ https://issues.apache.org/jira/browse/MATH-306?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Phil Steitz updated MATH-306:
-----------------------------
Fix Version/s: 2.1
Affects Version/s: 2.0
1.2
1.1
> Method 'divide' in class 'Complex' uses a false formula for a special case resulting in erroneous division by zero.
> -------------------------------------------------------------------------------------------------------------------
>
> Key: MATH-306
> URL: https://issues.apache.org/jira/browse/MATH-306
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 1.1, 1.2, 2.0
> Environment: all
> Reporter: Joerg Huber
> Fix For: 2.1
>
>
> The formula that 'divide' wants to implement is
> ( a + bi ) / ( c + di ) = ( ac + bd + ( bc - ad ) i ) / ( c^2 + d^2 )
> as correctly written in the description.
> When c == 0.0 this leads to the special case
> ( a + bi ) / di = ( b / d ) - ( a / d ) i
> But the corresponding code is:
> if (c == 0.0) {
> return createComplex(imaginary/d, -real/c);
> }
> The bug is the last division -real/c, which should obviously be -real/d.
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