[MATH-578] Decrease DescriptiveStatistics performance from 2.0 to 2.2

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.2
• Fix Version/s: 3.1

Environment

Linux

• Assignee: Mikkel Meyer Andersen
• Reporter: Paolo Repele
• Created: 16/May/11 14:34
• Updated: 04/Mar/13 18:53
• Resolved: 22/Jul/12 15:01

Description

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

Issue Links

• is duplicated by: MATH-805 Percentile calculation is very slow when input data are constants