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From Thomas Neidhart <thomas.neidh...@gmail.com>
Subject Re: [Math] Random tests sometimes fail (r1363105)
Date Mon, 23 Jul 2012 08:11:21 GMT
On Mon, Jul 23, 2012 at 12:44 AM, Gilles Sadowski <
gilles@harfang.homelinux.org> wrote:

> Hi Thomas.
>

Hi Gilles,


>
> I've encountered a failure of one the tests which you introduced in
> revision 1363105.  Here is an excerpt of the error:
> ---
>
> testNormalDistributionUnsymmetricMatrix(org.apache.commons.math3.linear.EigenDecompositionTest)
> Time elapsed: 0.044 sec  <<< FAILURE!
> java.lang.AssertionError: The norm of (X-Y) is too large
>         at org.junit.Assert.fail(Assert.java:93)
>         at org.junit.Assert.assertTrue(Assert.java:43)
>         at
> org.apache.commons.math3.linear.EigenDecompositionTest.checkUnsymmetricMatrix(EigenDecompositionTest.java:422)
>         at
> org.apache.commons.math3.linear.EigenDecompositionTest.testNormalDistributionUnsymmetricMatrix(EigenDecompositionTest.java:404)
> [... etc ...]
> ---
>
> For tests that uses a RNG, the conclusion was reached that it is better
> (for
> unit tests) to select a seed for which the test succeeds.
>

ok thanks for the hint. The random test principle is flawed but I wanted to
check with lots of different input data if the whole algorithm is stable.
Now there was not yet a way to quickly display the corresponding matrix,
but I added a RealMatrixFormat for that purpose. So I will update the test
and use also a fixed seed to make it predictable (and do more investigation
on failing cases).

Thomas

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