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Posted to issues@spark.apache.org by "Xiao Li (JIRA)" <ji...@apache.org> on 2018/01/20 17:07:00 UTC

[jira] [Resolved] (SPARK-23091) Incorrect unit test for approxQuantile

     [ https://issues.apache.org/jira/browse/SPARK-23091?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xiao Li resolved SPARK-23091.
-----------------------------
       Resolution: Fixed
         Assignee: Sean Owen
    Fix Version/s: 2.3.0

> Incorrect unit test for approxQuantile
> --------------------------------------
>
>                 Key: SPARK-23091
>                 URL: https://issues.apache.org/jira/browse/SPARK-23091
>             Project: Spark
>          Issue Type: Improvement
>          Components: ML, SQL, Tests
>    Affects Versions: 2.2.1
>            Reporter: Kuang Chen
>            Assignee: Sean Owen
>            Priority: Minor
>             Fix For: 2.3.0
>
>
> Currently, test for `approxQuantile` (quantile estimation algorithm) checks whether estimated quantile is within +- 2*`relativeError` from the true quantile. See the code below:
> [https://github.com/apache/spark/blob/master/sql/core/src/test/scala/org/apache/spark/sql/DataFrameStatSuite.scala#L157]
> However, based on the original paper by Greenwald and Khanna, the estimated quantile is guaranteed to be within +- `relativeError` from the true quantile. Using the double "tolerance" is misleading and incorrect, and we should fix it.
>  



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