[jira] [Resolved] (SPARK-25289) ChiSqSelector max on empty collection

["Sean Owen (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-25289?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sean Owen resolved SPARK-25289.
-------------------------------
       Resolution: Fixed
    Fix Version/s: 2.4.0

Issue resolved by pull request 22303
[https://github.com/apache/spark/pull/22303]

> ChiSqSelector max on empty collection
> -------------------------------------
>
>                 Key: SPARK-25289
>                 URL: https://issues.apache.org/jira/browse/SPARK-25289
>             Project: Spark
>          Issue Type: Bug
>          Components: MLlib
>    Affects Versions: 2.3.1
>            Reporter: Marie Beaulieu
>            Assignee: Marco Gaido
>            Priority: Major
>             Fix For: 2.4.0
>
>
> In org.apache.spark.mllib.feature.ChiSqSelector.fit, there is a max taken on a possibly empty collection.
> I am using Spark 2.3.1.
> Here is an example to reproduce.
> {code:java}
> import org.apache.spark.mllib.feature.ChiSqSelector
> import org.apache.spark.mllib.linalg.Vectors
> import org.apache.spark.mllib.regression.LabeledPoint
> import org.apache.spark.sql.SQLContext
> val sqlContext = new SQLContext(sc)
> implicit val spark = sqlContext.sparkSession
> val labeledPoints = (0 to 1).map(n => {
>   val v = Vectors.dense((1 to 3).map(_ => n * 1.0).toArray)
>   LabeledPoint(n.toDouble, v)
> })
> val rdd = sc.parallelize(labeledPoints)
> val selector = new ChiSqSelector().setSelectorType("fdr").setFdr(0.05)
> selector.fit(rdd){code}
> Here is the stack trace:
> {code:java}
> java.lang.UnsupportedOperationException: empty.max
> at scala.collection.TraversableOnce$class.max(TraversableOnce.scala:229)
> at scala.collection.mutable.ArrayOps$ofInt.max(ArrayOps.scala:234)
> at org.apache.spark.mllib.feature.ChiSqSelector.fit(ChiSqSelector.scala:280)
> {code}
> Looking at line 280 in ChiSqSelector, it's pretty obvious how the collection can be empty. A simple non empty validation should do the trick.



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