test results depend on java version
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Key: MATH-186
URL: https://issues.apache.org/jira/browse/MATH-186
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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