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From "Paolo Repele (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MATH-578) Decrease DescriptiveStatistics performance from 2.0 to 2.2
Date Mon, 16 May 2011 14:35:49 GMT
Decrease DescriptiveStatistics performance from 2.0 to 2.2
----------------------------------------------------------

                 Key: MATH-578
                 URL: https://issues.apache.org/jira/browse/MATH-578
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: 2.2
         Environment: Linux
            Reporter: Paolo Repele
            Priority: Minor


Switching between commons-math 2.0 to 2.2 we note how the
DescriptiveStatistics.addValue(double) has decrease the performance.

I tested with 2 million values.

DescriptiveStatistics ds = new DescriptiveStatistics();
for(int i = 0; i<1000*1000*2; i++) { //2 million values
    ds.addValue(v);
}

ds.getPercentile(50);


Seems that depending by the values inserted in the DescriptiveStatistics it takes different
time:

* with a single value (0)
** 2.0 -> take ~500 ms
** 2.2 -> take more than 10 minutes
* with 50% fixed value (0) and 50% Math.random()
** 2.0 -> take ~500 ms
** 2.2 -> take ~250000 ms -> ~250 second
* with 100% Math.random()
** 2.0 -> take ~500 ms
** 2.2 -> take ~70 ms



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