From daca24d8e7050eab9551b123cef010d7bf33f803 Mon Sep 17 00:00:00 2001
From: Aleksandar Prokopec <axel22@gmail.com>
Date: Wed, 6 Jun 2012 20:16:39 +0200
Subject: Fix SI-5880.

Add a ChiSquare test for the new hash code.
---
 test/files/run/t5880.scala | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 test/files/run/t5880.scala

(limited to 'test/files/run')

diff --git a/test/files/run/t5880.scala b/test/files/run/t5880.scala
new file mode 100644
index 0000000000..08cd0d6bf8
--- /dev/null
+++ b/test/files/run/t5880.scala
@@ -0,0 +1,41 @@
+
+
+import scala.collection.JavaConversions._
+
+
+
+object Test {
+  
+  def main(args:Array[String]) = {
+    val tests = 5000
+    val jm: java.util.Map[Int, Int] = scala.collection.mutable.Map((0 until tests) zip (0 until tests).reverse: _*)
+    val es = jm.entrySet()
+    val it = es.iterator
+    
+    // chi square test
+    val groups = 10
+    val hits = new Array[Int](groups)
+    def hit(hc: Int) {
+      val bucket = math.abs(hc) / (Int.MaxValue / groups)
+      hits(bucket) += 1
+    }
+    def expected = tests / groups
+    def Dstat = {
+      val diffs = for (i <- 0 until groups) yield math.abs(hits(i) - expected)
+      diffs.sum.toDouble / expected
+    }
+    def ChiSquare = {
+      val diffs = for (i <- 0 until groups) yield (hits(i) - expected) * (hits(i) - expected)
+      diffs.sum.toDouble / expected
+    }
+    
+    while (it.hasNext) {
+      val x = it.next()
+      hit(x.##)
+    }
+    // println(hits.toBuffer)
+    // println(ChiSquare)
+    assert(ChiSquare < 2.0)
+  }
+  
+}
-- 
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