nchammas commented on code in PR #45036:
URL: https://github.com/apache/spark/pull/45036#discussion_r1491158277
##########
core/src/main/scala/org/apache/spark/util/collection/OpenHashSet.scala:
##########
@@ -110,6 +110,18 @@ class OpenHashSet[@specialized(Long, Int, Double, Float)
T: ClassTag](
this
}
+ /**
+ * Check if a key exists at the provided position using object equality
rather than
+ * cooperative equality. Otherwise, hash sets will mishandle values for
which `==`
+ * and `equals` return different results, like 0.0/-0.0 and NaN/NaN.
Review Comment:
Yes, the differences are subtle:
```scala
scala> 0.0 == -0.0
val res0: Boolean = true
scala> 0.0 equals -0.0
val res1: Boolean = false
scala> Double.NaN == Double.NaN
val res2: Boolean = false
scala> Double.NaN equals Double.NaN
val res3: Boolean = true
```
There is a long discussion on the Scala forums from 2017 about this
difference and some of the problems it causes:
[Can we get rid of cooperative
equality?](https://contributors.scala-lang.org/t/can-we-get-rid-of-cooperative-equality/1131)
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