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https://issues.apache.org/jira/browse/MATH-578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13034068#comment-13034068
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Mikkel Meyer Andersen commented on MATH-578:
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Sorry for my (too) short first answer. Thanks for your proper introduction,
Phil.
I'll try a more detailed profiling to see what's causing the performance
problems.
> 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
> Assignee: Mikkel Meyer Andersen
> Priority: Minor
> Attachments: percentile.png
>
>
> 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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