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From Arne Plöse (JIRA) <j...@apache.org>
Subject [jira] [Commented] (MATH-620) multiplication of infinity
Date Wed, 10 Aug 2011 08:09:27 GMT

    [ https://issues.apache.org/jira/browse/MATH-620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13082219#comment-13082219
] 

Arne Plöse commented on MATH-620:
---------------------------------

evaluate this testcase:
{code}
    @Test
    public void testMultiplyInf() {
        Complex z = new Complex(1, neginf);
        Complex w = z.multiply(z);
        Assert.assertEquals(w.getReal(), neginf, 0);
        Assert.assertEquals(w.getImaginary(), neginf, 0);
        Assert.assertEquals(w, z.divide(Complex.ONE.divide(z)));
    }
{code}
the result should be -inf -infi but actually is inf + infi ...
The division looks also broken...

> 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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