[
https://issues.apache.org/jira/browse/MATH-306?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12769675#action_12769675
]
Joerg Huber commented on MATH-306:
----------------------------------
Yes, it looks like a twofold check for an already solved problem. By splitting
the code up for the two cases
1. Math.abs(c) < Math.abs(d)
2. the other way around
the denominator of q is always non-zero, which would habe been a problem and
may have been the reason to apply those extra checks.
The special cases c = 0 and d = 0 lead always to q = 0, in the respective code
parts.
Which is no problem, because there is no division by q.
Effective code, if the extra checks are omitted.
Thank you Phil, I encourage the code cleanup you proposed.
> 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
> Environment: all
> Reporter: Joerg Huber
>
> 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.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
