Github user kayousterhout commented on a diff in the pull request:
https://github.com/apache/spark/pull/16867#discussion_r107812807
--- Diff:
core/src/test/scala/org/apache/spark/util/collection/MedianHeapSuite.scala ---
@@ -0,0 +1,70 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.util.collection
+
+import java.util.Arrays
+import java.util.NoSuchElementException
+
+import scala.collection.mutable.ArrayBuffer
+import scala.util.Random
+
+import org.apache.spark.SparkFunSuite
+
+class MedianHeapSuite extends SparkFunSuite {
+
+ test("If no numbers in MedianHeap, NoSuchElementException is thrown.") {
+ val medianHeap = new MedianHeap()
+ intercept[NoSuchElementException] {
+ medianHeap.median
+ }
+ }
+
+ test("Median should be correct when size of MedianHeap is even") {
+ val array = Array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
+ val medianHeap = new MedianHeap()
+ array.foreach(medianHeap.insert(_))
+ assert(medianHeap.size() === 10)
+ assert(medianHeap.median === ((array(4) + array(5)) / 2.0))
+ }
+
+ test("Median should be correct when size of MedianHeap is odd") {
+ val array = Array(0, 1, 2, 3, 4, 5, 6, 7, 8)
+ val medianHeap = new MedianHeap()
+ array.foreach(medianHeap.insert(_))
+ assert(medianHeap.size() === 9)
+ assert(medianHeap.median === (array(4)))
+ }
+
+ test("Median should be correct though there are duplicated numbers
inside.") {
+ val array = Array(0, 0, 1, 1, 2, 2, 3, 3, 4, 4)
--- End diff --
Can you change this to something like:
Array(0, 0, 1, 1, 2, 3, 4)?
Otherwise the median heap could be handling the duplicates wrong (e.g., by
not actually inserting duplicates), and the assertion at the bottom would still
old. Then the check at the end can be `medianHeap.median === 1`.
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