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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-1414) Method reciprocal() in Complex for complex numbers with parts very close to 0.0
Date Thu, 20 Apr 2017 09:46:04 GMT

    [ https://issues.apache.org/jira/browse/MATH-1414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15976387#comment-15976387
] 

Gilles commented on MATH-1414:
------------------------------

Part of the refactoring that comes with moving the code to "Numbers" is to align with the
conventions of other languages. I think that Eric chose the C++ standard library.
Perhaps open a more general report (in "NUMBERS" JIRA) reminding that work is ongoing in that
regard (from which NUMBERS-22 could become a sub-task).


> Method reciprocal() in Complex for complex numbers with parts very close to 0.0
> -------------------------------------------------------------------------------
>
>                 Key: MATH-1414
>                 URL: https://issues.apache.org/jira/browse/MATH-1414
>             Project: Commons Math
>          Issue Type: Improvement
>            Reporter: Gunel Jahangirova
>            Priority: Minor
>
> In class Complex method reciprocal() returns INF only if the real and imaginary parts
are exactly equal to 0.0. In the cases when real and imaginary parts are double numbers very
close to 0.0, it does not hold. For example, if we run this code
> {code}
> Complex complex0 = new Complex((-2.44242319E-315));
> Complex complex1 = complex0.reciprocal();
> {code}
> the value of complex1.getReal() will be -Infinity and the value of complex1.getImaginary()
will be NaN, instead of complex1 being equal to INF.
> I think the code in the method 
> {code}
> if (real == 0.0 && imaginary == 0.0) {
>       return INF;
> }
> {code}
> should be replaced by the equality check with some tolerance (0.01 in this case):
> {code}
> if (equals(this, ZERO, 0.01)) {
>      return INF;
> }
> {code}



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