rdingankar commented on code in PR #5486:
URL: https://github.com/apache/hadoop/pull/5486#discussion_r1139490394
##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/util/SampleQuantiles.java:
##########
@@ -243,7 +245,12 @@ synchronized public Map<Quantile, Long> snapshot() {
Map<Quantile, Long> values = new TreeMap<Quantile, Long>();
for (int i = 0; i < quantiles.length; i++) {
- values.put(quantiles[i], query(quantiles[i].quantile));
+ /* eg : effectiveQuantile for 0.99 with inverseQuantiles will be 0.01.
+ For inverse quantiles higher numeric value is better and hence we want
+ to query from the opposite end of the sorted sample
+ */
+ double effectiveQuantile = inverseQuantiles ? 1 - quantiles[i].quantile
: quantiles[i].quantile;
+ values.put(quantiles[i], query(effectiveQuantile));
Review Comment:
Inversing the traversal does not give us the same thing. The iterator is a
variable for calculating the allowableError, which becomes high if the
traversal is inverted. It will require more math in the allowableError() method
based on [CKMS
paper.](http://dimacs.rutgers.edu/~graham/pubs/papers/bquant-icde.pdf)
Looking for the inverse quantile (1 - quantile) however works as expected
without changing the Math much as shown in the UT runs from the PR description.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: common-issues-unsubscr...@hadoop.apache.org
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
---------------------------------------------------------------------
To unsubscribe, e-mail: common-issues-unsubscr...@hadoop.apache.org
For additional commands, e-mail: common-issues-h...@hadoop.apache.org
