Introduced -Ymurmur with murmur hashcodes.

contributed by "archontophoenix", following in the grand tradition of
code by people whose actual names I don't know. References #2537, but it
doesn't close until some sensible hashcode is used by default. Review by
community.

2 files changed, 18 insertions, 0 deletions

diff --git a/test/files/run/hashCodeDistribution.flags b/test/files/run/hashCodeDistribution.flags
new file mode 100644
index 0000000000..5f7bd1a5be
--- /dev/null
+++ b/test/files/run/hashCodeDistribution.flags
@@ -0,0 +1 @@
+-Ymurmur
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diff --git a/test/files/run/hashCodeDistribution.scala b/test/files/run/hashCodeDistribution.scala
new file mode 100644
index 0000000000..5be9d1db6d
--- /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.distinct
+    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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