Scala implementation of fancier hashCode algori...

Scala implementation of fancier hashCode algorithm. At the moment it
isn't used unless you supply -Yjenkins-hashCodes to scalac. Without the
flag, the supplied test case generates 12559 unique hashCodes among
90000 case class instances; with the flag it generates 89999.

1 files changed, 17 insertions, 0 deletions

diff --git a/test/files/run/hashCodeDistribution.scala b/test/files/run/hashCodeDistribution.scala
new file mode 100644
index 0000000000..dbb6e833bd
--- /dev/null
+++ b/test/files/run/hashCodeDistribution.scala
@@ -0,0 +1,17 @@
+// See ticket #2537.
+object Test {
+  case class C(x: Int, y: Int) { }
+  val COUNT = 300
+  val totalCodes = COUNT * COUNT
+
+  def main (args: Array[String]) = {
+    val hashCodes =
+      for (x <- 0 until COUNT; y <- 0 until COUNT) yield C(x,y).hashCode
+
+    val uniques = hashCodes.removeDuplicates
+    val collisionRate = (totalCodes - uniques.size) * 1000 / totalCodes
+
+    assert(collisionRate < 5, "Collision rate too high: %d / 1000".format(collisionRate))
+    // println("collisionRate = %d / 1000".format(collisionRate))
+  }
+}
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