Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/897#discussion_r13357216
--- Diff: core/src/main/scala/org/apache/spark/api/java/JavaPairRDD.scala
---
@@ -672,40 +672,102 @@ class JavaPairRDD[K, V](val rdd: RDD[(K, V)])
/**
* Return approximate number of distinct values for each key in this RDD.
- * The accuracy of approximation can be controlled through the relative
standard deviation
- * (relativeSD) parameter, which also controls the amount of memory
used. Lower values result in
- * more accurate counts but increase the memory footprint and vise
versa. Uses the provided
- * Partitioner to partition the output RDD.
+ *
+ * The algorithm used is based on streamlib's implementation of
"HyperLogLog in Practice:
+ * Algorithmic Engineering of a State of The Art Cardinality Estimation
Algorithm", available
+ * <a href="http://research.google.com/pubs/pub40671.html";>here</a>.
--- End diff --
Better use the permanent link `http://dx.doi.org/10.1145/2452376.2452456`,
though Google's may live even longer...
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
