LuciferYang commented on a change in pull request #32648:
URL: https://github.com/apache/spark/pull/32648#discussion_r638426438
##########
File path:
mllib/src/main/scala/org/apache/spark/mllib/evaluation/MultilabelMetrics.scala
##########
@@ -178,7 +178,11 @@ private[evaluation] class MultilabelSummarizer extends
Serializable {
* @return This MultilabelSummarizer object.
*/
def add(predictions: Array[Double], labels: Array[Double]): this.type = {
- val intersection = predictions.intersect(labels)
+ val intersection = if (predictions.isEmpty || labels.isEmpty) {
Review comment:
In Scala 2.13.5
```
Welcome to Scala 2.13.5 (OpenJDK 64-Bit Server VM, Java 1.8.0_232).
Type in expressions for evaluation. Or try :help.
scala> Array.empty[Double].intersect(Array(0.0))
val res0: Array[Double] = Array()
scala> Array(0.0).intersect(Array.empty[Double])
val res1: Array[Double] = Array()
```
but in Scala 2.13.6
```
Welcome to Scala 2.13.6 (OpenJDK 64-Bit Server VM, Java 1.8.0_232).
Type in expressions for evaluation. Or try :help.
scala> Array.empty[Double].intersect(Array(0.0))
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [D
... 32 elided
scala> Array(0.0).intersect(Array.empty[Double])
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [D
... 32 elided
```
`Array()` is replaced by throw `ClassCastException`, this change is
uncomfortable ... @dongjoon-hyun @maropu do you think this is a bug of Scala
2.13.6?
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