[stdlib] Use merge sort for sortWith

2018-08-21 16:08:18 +07:00
parent 314cd0993b
commit 04c0cd3dd4
3 changed files with 137 additions and 26 deletions
@@ -1468,6 +1468,10 @@ task sort1(type: RunKonanTest) {
    source = "runtime/collections/sort1.kt"
 }

+task sortWith(type: RunKonanTest) {
+    source = "runtime/collections/SortWith.kt"
+}
+
 task if_else(type: RunKonanTest) {
    source = "codegen/branching/if_else.kt"
 }
@@ -0,0 +1,83 @@
+package runtime.collections.SortWith
+
+import kotlin.test.*
+
+val correctIncreasing = Comparator<Int> { a, b ->  // correct one.
+    when {
+        a > b -> 1
+        a < b -> -1
+        else -> 0
+    }
+}
+
+val correctDecreasing = Comparator<Int> { a, b ->  // correct one.
+    when {
+        a < b -> 1
+        a > b -> -1
+        else -> 0
+    }
+}
+
+fun Array<Int>.assertSorted(cmp: Comparator<Int>, message: String = "") {
+    for (i in 1 until size) {
+        assertTrue(cmp.compare(this[i - 1], this[i]) <= 0, message)
+    }
+}
+
+data class ComparatorInfo(val name: String, val comparator: Comparator<Int>, val isCorrect: Boolean)
+
+// Assert that the array is sorted in terms of a comparator only for correct/partially correct cases
+val comparators = listOf<ComparatorInfo>(
+    ComparatorInfo("Correct increasing", correctIncreasing ,  true),
+    ComparatorInfo("Correct decreasing", correctDecreasing ,  true),
+    ComparatorInfo("Incorrect increasing", Comparator { a ,b -> if (a > b) 1 else -1 },  false),
+    ComparatorInfo("Incorrect decreasing", Comparator { a ,b -> if (a < b) 1 else -1 },  false),
+    ComparatorInfo("Always 1",  Comparator { a ,b ->  1  },  false),
+    ComparatorInfo("Always -1", Comparator { a ,b ->  -1 },  false),
+    ComparatorInfo("Alwasy 0",  Comparator { a ,b ->  0  },  false)
+)
+
+val arrays = listOf<Array<Int>>(
+    arrayOf(),
+    arrayOf(1),
+    arrayOf(Int.MIN_VALUE, 0, Int.MAX_VALUE),
+    arrayOf(Int.MAX_VALUE, 0, Int.MIN_VALUE),
+    arrayOf(1, 2, 3),
+    arrayOf(-2, -1, 99, 1, 2),
+    arrayOf(90, 91, 0, 98, 99),
+    arrayOf(2, 1, 99, -1, 2),
+    arrayOf(99, 98, 0, 91, 90),
+    arrayOf(42, 42, 42),
+    arrayOf(99, 42, 0, 42, 50),
+    arrayOf(
+        100000, 190001, 200002, 200003, 200004, 210005, 220006, 250007, 300008, 310009, 360010, 365011,
+        380012, 390013, 390014, 399015, 400016, 400017, 400018, 400019, 400020, 400021, 400022, 400023,
+        400024, 400025, 400026, 450027, 450028, 480029, 480030, 500031, 500032, 500033, 500034, 500035,
+        500036, 500037, 500038, 500039, 500040, 500041, 500042, 500043, 500044, 500045, 500046, 500047,
+        500048, 500049, 500050, 500051, 500052, 500053, 505054, 510055, 510056, 510057, 510058, 510059,
+        510060, 510061, 510062, 510063, 410064, 410065, 511066, 511067, 520068, 520069, 420070, 520071,
+        530072, 530073, 530074, 430075, 430076, 530077, 540078, 540079, 540080, 540081, 540082, 540083,
+        540084, 490085, 540086, 540087, 542088, 544089, 546090, 550091, 550092, 550093, 550094, 590095,
+        590096, 595097, 600098, 600099, 600100, 600101, 600102, 600103, 600104, 550105, 600106, 600107,
+        600108, 600109, 600110, 610111, 610112, 610113, 620114, 620115, 620116, 620117, 620118, 620119,
+        640120, 640121, 645122, 645123, 645124, 645125, 645126, 645127, 650128, 700129, 700130
+    )
+)
+
+
+@Test fun runTest() {
+    arrays.forEach { array ->
+        comparators.forEach {
+            val arrayUnderTest = array.copyOf()
+
+            arrayUnderTest.sortWith(it.comparator)
+            if (it.isCorrect) {
+                arrayUnderTest.assertSorted(it.comparator, """
+                    Assert sorted failed for comparator: "${it.name}"
+                    Array: ${array.joinToString()}
+                    Array after sorting: ${arrayUnderTest.joinToString()}
+                """.trimIndent())
+            }
+        }
+    }
+}
@@ -53,34 +53,58 @@ private fun <T> quickSort(array: Array<T>, left: Int, right: Int) {
        quickSort(array, index, right)
 }

-private fun <T> partition(
-        array: Array<T>, left: Int, right: Int, comparator: Comparator<T>): Int {
-    var i = left
-    var j = right
-    val pivot = array[(left + right) / 2]
-    while (i <= j) {
-        while (comparator.compare(array[i], pivot) < 0)
-            i++
-        while (comparator.compare(array[j], pivot) > 0)
-            j--
-        if (i <= j) {
-            val tmp = array[i]
-            array[i] = array[j]
-            array[j] = tmp
-            i++
-            j--
-        }
+// We use merge sort with comparators becuase the quick sort may cause segfaults if
+// the comparator is incorrect (e.g. if it never returns 0).
+private fun <T> mergeSort(array: Array<T>, start: Int, endInclusive: Int, comparator: Comparator<T>) {
+    @Suppress("UNCHECKED_CAST")
+    val buffer = arrayOfNulls<Any?>(array.size) as Array<T>
+    val result = mergeSort(array, buffer, start, endInclusive, comparator)
+    if (result !== array) {
+        result.forEachIndexed { i, v-> array[i] = v }
    }
-    return i
 }

-private fun <T> quickSort(
-        array: Array<T>, left: Int, right: Int, comparator: Comparator<T>) {
-    val index = partition(array, left, right, comparator)
-    if (left < index - 1)
-        quickSort(array, left, index - 1, comparator)
-    if (index < right)
-        quickSort(array, index, right, comparator)
+// Both start and end are inclusive indices.
+private fun <T> mergeSort(array: Array<T>, buffer: Array<T>, start: Int, end: Int, comparator: Comparator<T>): Array<T> {
+    if (start == end) {
+        return array
+    }
+
+    val median = (start + end) / 2
+    val left = mergeSort(array, buffer, start, median, comparator)
+    val right = mergeSort(array, buffer, median + 1, end, comparator)
+    
+    val target = if (left === buffer) array else buffer
+
+    // Merge
+    var leftIndex = start
+    var rightIndex = median + 1
+    for (i in start..end) {
+        when {
+            leftIndex <= median && rightIndex <= end -> {
+                val leftValue = left[leftIndex]
+                val rightValue = right[rightIndex]
+
+                if (comparator.compare(leftValue, rightValue) < 0) {
+                    target[i] = leftValue
+                    leftIndex++
+                } else {
+                    target[i] = rightValue
+                    rightIndex++
+                }
+            }
+            leftIndex <= median -> {
+                target[i] = left[leftIndex]
+                leftIndex++
+            }
+            else /* rightIndex <= end */ -> {
+                target[i] = right[rightIndex]
+                rightIndex++
+            }
+        }
+    }
+
+    return target
 }

 // ByteArray    =============================================================================
@@ -339,7 +363,7 @@ private fun quickSort(
 internal fun <T> sortArrayWith(
        array: Array<out T>, fromIndex: Int = 0, toIndex: Int = array.size, comparator: Comparator<T>) {
    @Suppress("UNCHECKED_CAST")
-    quickSort(array as Array<T>, fromIndex, toIndex - 1, comparator)
+    mergeSort(array as Array<T>, fromIndex, toIndex - 1, comparator)
 }

 /**