Instead of redirecting DescriptiveStatisticsHistogramStatistics calls to DescriptiveStatistics, it takes a point-in-time snapshot using an own
UnivariateStatistic implementation that
- calculates min, max, mean, and standard deviation in one go (as opposed to four iterations over the values array!)
- caches pivots for the percentile calculation to speed up retrieval of multiple percentiles/quartiles
This is also similar to the semantics of our implementation using codahale's DropWizard.