[
https://issues.apache.org/jira/browse/SLING-2361?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13185516#comment-13185516
]
Felix Meschberger edited comment on SLING-2361 at 1/16/12 3:28 PM:
-------------------------------------------------------------------
We could inline but the dependencies are tremendous (kind of) and the
replacement code is dead simple:
Assume three helper variables
n -- number of samples (request durations)
sumX -- sum of all samples
sumX2 -- sum of all samples squared
Then the following formula apply:
mean = sumX / n
stddev = sqrt( (sumX2 - sumX * sumX / n) / (n - 1) );
The formula for the stddev is taken from (german)
http://de.wikipedia.org/wiki/Standardabweichung section "Berechnung für
auflaufende Messwerte"
was (Author: fmeschbe):
We could inline but the dependencies are tremendous (kind of) and the
replacement code is dead simple:
double delta = value - this.mean;
this.mean = this.mean + delta / this.n;
if (n > 1) {
this.m2 += delta * (value - this.mean);
}
this.sigma = this.m2 / this.n;
Where this.m2 is a helper variable, this.mean is the cumulated mean value and
this.sigma is the cumulated variance.
> Drop commons.math dependency
> ----------------------------
>
> Key: SLING-2361
> URL: https://issues.apache.org/jira/browse/SLING-2361
> Project: Sling
> Issue Type: Improvement
> Components: Engine
> Reporter: Felix Meschberger
> Assignee: Felix Meschberger
> Fix For: Engine 2.2.6
>
>
> As of Rev. 1138159 (SLING-1476) the RequestProcessorMBeanImpl exists to
> convey Sling request processing statistics. For the mean and variance values
> the Commons Math SynchronizedSummaryStatistics class is used.
> IMHO this is quite a heavy dependency for such a simple computation (well,
> the mathematics behind this are not simple, at least not to me ;-) ). So I
> suggest we in lie a simple continuously updating algorithm into the
> addRequestDuration method, which is modified to be synchronized.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
