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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-620) multiplication of infinity
Date Mon, 05 Sep 2011 14:22:10 GMT

    [ https://issues.apache.org/jira/browse/MATH-620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13097155#comment-13097155
] 

Gilles commented on MATH-620:
-----------------------------

Another bug (IMO) in CM:
{code}
Complex infInf = new Complex(Double.POSITIVE_INFINITY, Double.POSITIVE_INFINITY);
Assert.assertTrue(infInf.multiply(infInf).isInfinite());
{code}
succeeds, but the formula would have produced "NaN" in the real part.
Octave computes:
{noformat}
NaN + Infi
{noformat}
Added unit test (with alternative expectation) in revision 1165296.


> multiplication of infinity
> --------------------------
>
>                 Key: MATH-620
>                 URL: https://issues.apache.org/jira/browse/MATH-620
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.0
>            Reporter: Arne Plöse
>            Priority: Minor
>
> Take the following testcase 
> {code}
> Assert.assertEquals(neginf, inf* neginf, Double.MIN_VALUE);  // <--Passes ordinary
double
> Assert.assertEquals(new Complex(neginf, 0), new Complex(inf, 0).multiply(new Complex(neginf,
0)));// <-- Fail only real parts no imaginary parts 
> {code}
> The outcome of multiply is Complex.INF if one part is infinity.
> why not simply compute the multiplication and thats is?

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