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From "Phil Steitz (JIRA)" <>
Subject [jira] Commented: (MATH-186) test results depend on java version
Date Sun, 03 Feb 2008 22:55:07 GMT


Phil Steitz commented on MATH-186:

For this to happen with other JVM impls with the change just made, the jvm would have to produce
different results for the exact same computations, which would be odd.  Equals is strictly
defined for this class, which I think is OK and the test is really supposed to just be testing
equals and hashcode.

> test results depend on java version
> -----------------------------------
>                 Key: MATH-186
>                 URL:
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 1.2
>         Environment: GNU/Linux (ubuntu Gutsy Gibbon),  java 1.3: eclipse compiler, java
1.4: Blackdown-1.4.2-02, java 1.6:  SUN 1.6.0_03-b05,  AMD athlon XP2000+
>            Reporter: Luc Maisonobe
>            Priority: Minor
>             Fix For: 1.2
> Running the tests with maven and changing the java version used by changing JAVA_HOME
in the ~/.mavenrc file, I get different results.
> With the Eclipse compiler set to 1.3 compatibility and with blackdown jvm (1.4), the
tests succed.
> With the Sun jvm (1.6), SummaryStatisticsAbstractTest.testEqualsAndHashCode (which is
used both by SummaryStatisticsTest and SynchronizedSummaryStatisticsTest) fails.
> The error is related to geometric mean computation, which lead to slightly different
results depending on the order of added elements. One instance returns 2.213363839400643 and
the other returns 2.2133638394006434. Both results are consistent with IEEE754 arithmetic
(they differ in the last two bits).
> Using Sun 1.6.0_03 jvm, the different values induce a test failure when SummaryStatistics.equals()
method is called (it checks for exact equality). If this part of the test is commented out,
another failure occurs when the SummaryStatistics.hashcode() method is called.
> Changing the equals method would be possible, but would be a change of semantics and
would imply choosing some threshold which would never suit everybody needs. Changing the hashcode
method simply does not seem realistic to me. So I would like to keep these methods as they
are now. So the main conclusion would be that the test is too sensitive to jvm implementation
(which are consistent with IEEE754 arithmetic in this case).
> I don't know what to do about this issue.

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