8080945: Improve the performance of primitive Arrays.sort for certain patterns of array elements
Reviewed-by: psandoz
Contributed-by: Sunny Chan <sunny.chan@gs.com>, Mohammad Rezaei <mohammad.rezaei@gs.com>
--- a/jdk/src/java.base/share/classes/java/util/DualPivotQuicksort.java Mon Jun 08 17:19:50 2015 -0700
+++ b/jdk/src/java.base/share/classes/java/util/DualPivotQuicksort.java Tue Jun 09 07:05:48 2015 +0100
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2009, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2015, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -61,11 +61,6 @@
private static final int MAX_RUN_COUNT = 67;
/**
- * The maximum length of run in merge sort.
- */
- private static final int MAX_RUN_LENGTH = 33;
-
- /**
* If the length of an array to be sorted is less than this
* constant, Quicksort is used in preference to merge sort.
*/
@@ -121,20 +116,24 @@
// Check if the array is nearly sorted
for (int k = left; k < right; run[count] = k) {
+ // Equal items in the beginning of the sequence
+ while (k < right && a[k] == a[k + 1])
+ k++;
+ if (k == right) break; // Sequence finishes with equal items
if (a[k] < a[k + 1]) { // ascending
while (++k <= right && a[k - 1] <= a[k]);
} else if (a[k] > a[k + 1]) { // descending
while (++k <= right && a[k - 1] >= a[k]);
+ // Transform into an ascending sequence
for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {
int t = a[lo]; a[lo] = a[hi]; a[hi] = t;
}
- } else { // equal
- for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) {
- if (--m == 0) {
- sort(a, left, right, true);
- return;
- }
- }
+ }
+
+ // Merge a transformed descending sequence followed by an
+ // ascending sequence
+ if (run[count] > left && a[run[count]] >= a[run[count] - 1]) {
+ count--;
}
/*
@@ -151,7 +150,7 @@
// Implementation note: variable "right" is increased by 1.
if (run[count] == right++) { // The last run contains one element
run[++count] = right;
- } else if (count == 1) { // The array is already sorted
+ } else if (count <= 1) { // The array is already sorted
return;
}
@@ -569,20 +568,24 @@
// Check if the array is nearly sorted
for (int k = left; k < right; run[count] = k) {
+ // Equal items in the beginning of the sequence
+ while (k < right && a[k] == a[k + 1])
+ k++;
+ if (k == right) break; // Sequence finishes with equal items
if (a[k] < a[k + 1]) { // ascending
while (++k <= right && a[k - 1] <= a[k]);
} else if (a[k] > a[k + 1]) { // descending
while (++k <= right && a[k - 1] >= a[k]);
+ // Transform into an ascending sequence
for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {
long t = a[lo]; a[lo] = a[hi]; a[hi] = t;
}
- } else { // equal
- for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) {
- if (--m == 0) {
- sort(a, left, right, true);
- return;
- }
- }
+ }
+
+ // Merge a transformed descending sequence followed by an
+ // ascending sequence
+ if (run[count] > left && a[run[count]] >= a[run[count] - 1]) {
+ count--;
}
/*
@@ -599,7 +602,7 @@
// Implementation note: variable "right" is increased by 1.
if (run[count] == right++) { // The last run contains one element
run[++count] = right;
- } else if (count == 1) { // The array is already sorted
+ } else if (count <= 1) { // The array is already sorted
return;
}
@@ -1053,20 +1056,24 @@
// Check if the array is nearly sorted
for (int k = left; k < right; run[count] = k) {
+ // Equal items in the beginning of the sequence
+ while (k < right && a[k] == a[k + 1])
+ k++;
+ if (k == right) break; // Sequence finishes with equal items
if (a[k] < a[k + 1]) { // ascending
while (++k <= right && a[k - 1] <= a[k]);
} else if (a[k] > a[k + 1]) { // descending
while (++k <= right && a[k - 1] >= a[k]);
+ // Transform into an ascending sequence
for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {
short t = a[lo]; a[lo] = a[hi]; a[hi] = t;
}
- } else { // equal
- for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) {
- if (--m == 0) {
- sort(a, left, right, true);
- return;
- }
- }
+ }
+
+ // Merge a transformed descending sequence followed by an
+ // ascending sequence
+ if (run[count] > left && a[run[count]] >= a[run[count] - 1]) {
+ count--;
}
/*
@@ -1083,7 +1090,7 @@
// Implementation note: variable "right" is increased by 1.
if (run[count] == right++) { // The last run contains one element
run[++count] = right;
- } else if (count == 1) { // The array is already sorted
+ } else if (count <= 1) { // The array is already sorted
return;
}
@@ -1537,20 +1544,24 @@
// Check if the array is nearly sorted
for (int k = left; k < right; run[count] = k) {
+ // Equal items in the beginning of the sequence
+ while (k < right && a[k] == a[k + 1])
+ k++;
+ if (k == right) break; // Sequence finishes with equal items
if (a[k] < a[k + 1]) { // ascending
while (++k <= right && a[k - 1] <= a[k]);
} else if (a[k] > a[k + 1]) { // descending
while (++k <= right && a[k - 1] >= a[k]);
+ // Transform into an ascending sequence
for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {
char t = a[lo]; a[lo] = a[hi]; a[hi] = t;
}
- } else { // equal
- for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) {
- if (--m == 0) {
- sort(a, left, right, true);
- return;
- }
- }
+ }
+
+ // Merge a transformed descending sequence followed by an
+ // ascending sequence
+ if (run[count] > left && a[run[count]] >= a[run[count] - 1]) {
+ count--;
}
/*
@@ -1567,7 +1578,7 @@
// Implementation note: variable "right" is increased by 1.
if (run[count] == right++) { // The last run contains one element
run[++count] = right;
- } else if (count == 1) { // The array is already sorted
+ } else if (count <= 1) { // The array is already sorted
return;
}
@@ -2117,20 +2128,24 @@
// Check if the array is nearly sorted
for (int k = left; k < right; run[count] = k) {
+ // Equal items in the beginning of the sequence
+ while (k < right && a[k] == a[k + 1])
+ k++;
+ if (k == right) break; // Sequence finishes with equal items
if (a[k] < a[k + 1]) { // ascending
while (++k <= right && a[k - 1] <= a[k]);
} else if (a[k] > a[k + 1]) { // descending
while (++k <= right && a[k - 1] >= a[k]);
+ // Transform into an ascending sequence
for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {
float t = a[lo]; a[lo] = a[hi]; a[hi] = t;
}
- } else { // equal
- for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) {
- if (--m == 0) {
- sort(a, left, right, true);
- return;
- }
- }
+ }
+
+ // Merge a transformed descending sequence followed by an
+ // ascending sequence
+ if (run[count] > left && a[run[count]] >= a[run[count] - 1]) {
+ count--;
}
/*
@@ -2147,7 +2162,7 @@
// Implementation note: variable "right" is increased by 1.
if (run[count] == right++) { // The last run contains one element
run[++count] = right;
- } else if (count == 1) { // The array is already sorted
+ } else if (count <= 1) { // The array is already sorted
return;
}
@@ -2656,20 +2671,24 @@
// Check if the array is nearly sorted
for (int k = left; k < right; run[count] = k) {
+ // Equal items in the beginning of the sequence
+ while (k < right && a[k] == a[k + 1])
+ k++;
+ if (k == right) break; // Sequence finishes with equal items
if (a[k] < a[k + 1]) { // ascending
while (++k <= right && a[k - 1] <= a[k]);
} else if (a[k] > a[k + 1]) { // descending
while (++k <= right && a[k - 1] >= a[k]);
+ // Transform into an ascending sequence
for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {
double t = a[lo]; a[lo] = a[hi]; a[hi] = t;
}
- } else { // equal
- for (int m = MAX_RUN_LENGTH; ++k <= right && a[k - 1] == a[k]; ) {
- if (--m == 0) {
- sort(a, left, right, true);
- return;
- }
- }
+ }
+
+ // Merge a transformed descending sequence followed by an
+ // ascending sequence
+ if (run[count] > left && a[run[count]] >= a[run[count] - 1]) {
+ count--;
}
/*
@@ -2686,7 +2705,7 @@
// Implementation note: variable "right" is increased by 1.
if (run[count] == right++) { // The last run contains one element
run[++count] = right;
- } else if (count == 1) { // The array is already sorted
+ } else if (count <= 1) { // The array is already sorted
return;
}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/util/Arrays/SortingIntBenchmarkTestJMH.java Tue Jun 09 07:05:48 2015 +0100
@@ -0,0 +1,708 @@
+/*
+ * Copyright 2015 Goldman Sachs.
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Thread)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.SECONDS)
+public class SortingIntBenchmarkTestJMH {
+ private static final int QUICKSORT_THRESHOLD = 286;
+ private static final int MAX_RUN_COUNT = 67;
+ private static final int INSERTION_SORT_THRESHOLD = 47;
+ public static final int MAX_VALUE = 1_000_000;
+
+ @Param({"pairFlipZeroPairFlip", "pairFlipOneHundredPairFlip"
+ , "zeroHi", "hiZeroLow", "hiFlatLow", "identical",
+ "randomDups", "randomNoDups", "sortedReversedSorted", "pairFlip", "endLessThan"})
+
+ public String listType;
+
+ private int[] array;
+ private static final int LIST_SIZE = 10_000_000;
+ public static final int NUMBER_OF_ITERATIONS = 10;
+
+ @Setup
+ public void setUp() {
+ Random random = new Random(123456789012345L);
+ this.array = new int[LIST_SIZE];
+ int threeQuarters = (int) (LIST_SIZE * 0.75);
+ if ("zeroHi".equals(this.listType)) {
+ for (int i = 0; i < threeQuarters; i++) {
+ this.array[i] = 0;
+ }
+ int k = 1;
+ for (int i = threeQuarters; i < LIST_SIZE; i++) {
+ this.array[i] = k;
+ k++;
+ }
+ }
+ else if ("hiFlatLow".equals(this.listType)) {
+ int oneThird = LIST_SIZE / 3;
+ for (int i = 0; i < oneThird; i++) {
+ this.array[i] = i;
+ }
+ int twoThirds = oneThird * 2;
+ int constant = oneThird - 1;
+ for (int i = oneThird; i < twoThirds; i++) {
+ this.array[i] = constant;
+ }
+ for (int i = twoThirds; i < LIST_SIZE; i++) {
+ this.array[i] = constant - i + twoThirds;
+ }
+ }
+ else if ("hiZeroLow".equals(this.listType)) {
+ int oneThird = LIST_SIZE / 3;
+ for (int i = 0; i < oneThird; i++) {
+ this.array[i] = i;
+ }
+ int twoThirds = oneThird * 2;
+ for (int i = oneThird; i < twoThirds; i++) {
+ this.array[i] = 0;
+ }
+ for (int i = twoThirds; i < LIST_SIZE; i++) {
+ this.array[i] = oneThird - i + twoThirds;
+ }
+ }
+ else if ("identical".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE; i++) {
+ this.array[i] = 0;
+ }
+ }
+ else if ("randomDups".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE; i++) {
+ this.array[i] = random.nextInt(1000);
+ }
+ }
+ else if ("randomNoDups".equals(this.listType)) {
+ Set<Integer> set = new HashSet();
+ while (set.size() < LIST_SIZE + 1) {
+ set.add(random.nextInt());
+ }
+ List<Integer> list = new ArrayList<>(LIST_SIZE);
+ list.addAll(set);
+ for (int i = 0; i < LIST_SIZE; i++) {
+ this.array[i] = list.get(i);
+ }
+ }
+ else if ("sortedReversedSorted".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE / 2; i++) {
+ this.array[i] = i;
+ }
+ int num = 0;
+ for (int i = LIST_SIZE / 2; i < LIST_SIZE; i++) {
+ this.array[i] = LIST_SIZE - num;
+ num++;
+ }
+ }
+ else if ("pairFlip".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE; i++) {
+ this.array[i] = i;
+ }
+ for (int i = 0; i < LIST_SIZE; i += 2) {
+ int temp = this.array[i];
+ this.array[i] = this.array[i + 1];
+ this.array[i + 1] = temp;
+ }
+ }
+ else if ("endLessThan".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE - 1; i++) {
+ this.array[i] = 3;
+ }
+ this.array[LIST_SIZE - 1] = 1;
+ }
+ else if ("pairFlipZeroPairFlip".equals(this.listType)) {
+ //pairflip
+ for (int i = 0; i < 64; i++) {
+ this.array[i] = i;
+ }
+ for (int i = 0; i < 64; i += 2) {
+ int temp = this.array[i];
+ this.array[i] = this.array[i + 1];
+ this.array[i + 1] = temp;
+ }
+ //zero
+ for (int i = 64; i < this.array.length - 64; i++) {
+ this.array[i] = 0;
+ }
+ //pairflip
+ for (int i = this.array.length - 64; i < this.array.length; i++) {
+ this.array[i] = i;
+ }
+ for (int i = this.array.length - 64; i < this.array.length; i += 2) {
+ int temp = this.array[i];
+ this.array[i] = this.array[i + 1];
+ this.array[i + 1] = temp;
+ }
+ }
+ else if ("pairFlipOneHundredPairFlip".equals(this.listType)) {
+ //10, 5
+ for (int i = 0; i < 64; i++) {
+ if (i % 2 == 0) {
+ this.array[i] = 10;
+ }
+ else {
+ this.array[i] = 5;
+ }
+ }
+
+ //100
+ for (int i = 64; i < this.array.length - 64; i++) {
+ this.array[i] = 100;
+ }
+
+ //10, 5
+ for (int i = this.array.length - 64; i < this.array.length; i++) {
+ if (i % 2 == 0) {
+ this.array[i] = 10;
+ }
+ else {
+ this.array[i] = 5;
+ }
+ }
+ }
+ }
+
+ @Warmup(iterations = 20)
+ @Measurement(iterations = 10)
+ @Benchmark
+ public void sortNewWay() {
+ for (int i = 0; i < NUMBER_OF_ITERATIONS; i++) {
+ SortingIntTestJMH.sort(this.array, 0, this.array.length - 1, null, 0, 0);
+ }
+ }
+
+ @Warmup(iterations = 20)
+ @Measurement(iterations = 10)
+ @Benchmark
+ public void sortCurrentWay() {
+ for (int i = 0; i < NUMBER_OF_ITERATIONS; i++) {
+ Arrays.sort(this.array);
+ }
+ }
+
+ static void sort(int[] a, int left, int right,
+ int[] work, int workBase, int workLen) {
+ // Use Quicksort on small arrays
+ if (right - left < QUICKSORT_THRESHOLD) {
+ SortingIntTestJMH.sort(a, left, right, true);
+ return;
+ }
+
+ /*
+ * Index run[i] is the start of i-th run
+ * (ascending or descending sequence).
+ */
+ int[] run = new int[MAX_RUN_COUNT + 1];
+ int count = 0;
+ run[0] = left;
+
+ // Check if the array is nearly sorted
+ for (int k = left; k < right; run[count] = k) {
+ while (k < right && a[k] == a[k + 1])
+ k++;
+ if (k == right) break;
+ if (a[k] < a[k + 1]) { // ascending
+ while (++k <= right && a[k - 1] <= a[k]) ;
+ }
+ else if (a[k] > a[k + 1]) { // descending
+ while (++k <= right && a[k - 1] >= a[k]) ;
+ for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {
+ int t = a[lo];
+ a[lo] = a[hi];
+ a[hi] = t;
+ }
+ }
+ if (run[count] > left && a[run[count]] >= a[run[count] - 1]) {
+ count--;
+ }
+ /*
+ * The array is not highly structured,
+ * use Quicksort instead of merge sort.
+ */
+ if (++count == MAX_RUN_COUNT) {
+ sort(a, left, right, true);
+ return;
+ }
+ }
+
+ // Check special cases
+ // Implementation note: variable "right" is increased by 1.
+ if (run[count] == right++) {
+ run[++count] = right;
+ }
+ if (count <= 1) { // The array is already sorted
+ return;
+ }
+
+ // Determine alternation base for merge
+ byte odd = 0;
+ for (int n = 1; (n <<= 1) < count; odd ^= 1) {
+ }
+
+ // Use or create temporary array b for merging
+ int[] b; // temp array; alternates with a
+ int ao, bo; // array offsets from 'left'
+ int blen = right - left; // space needed for b
+ if (work == null || workLen < blen || workBase + blen > work.length) {
+ work = new int[blen];
+ workBase = 0;
+ }
+ if (odd == 0) {
+ System.arraycopy(a, left, work, workBase, blen);
+ b = a;
+ bo = 0;
+ a = work;
+ ao = workBase - left;
+ }
+ else {
+ b = work;
+ ao = 0;
+ bo = workBase - left;
+ }
+
+ // Merging
+ for (int last; count > 1; count = last) {
+ for (int k = (last = 0) + 2; k <= count; k += 2) {
+ int hi = run[k], mi = run[k - 1];
+ for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) {
+ if (q >= hi || p < mi && a[p + ao] <= a[q + ao]) {
+ b[i + bo] = a[p++ + ao];
+ }
+ else {
+ b[i + bo] = a[q++ + ao];
+ }
+ }
+ run[++last] = hi;
+ }
+ if ((count & 1) != 0) {
+ for (int i = right, lo = run[count - 1]; --i >= lo;
+ b[i + bo] = a[i + ao]
+ ) {
+ }
+ run[++last] = right;
+ }
+ int[] t = a;
+ a = b;
+ b = t;
+ int o = ao;
+ ao = bo;
+ bo = o;
+ }
+ }
+
+ private static void sort(int[] a, int left, int right, boolean leftmost) {
+ int length = right - left + 1;
+
+ // Use insertion sort on tiny arrays
+ if (length < INSERTION_SORT_THRESHOLD) {
+ if (leftmost) {
+ /*
+ * Traditional (without sentinel) insertion sort,
+ * optimized for server VM, is used in case of
+ * the leftmost part.
+ */
+ for (int i = left, j = i; i < right; j = ++i) {
+ int ai = a[i + 1];
+ while (ai < a[j]) {
+ a[j + 1] = a[j];
+ if (j-- == left) {
+ break;
+ }
+ }
+ a[j + 1] = ai;
+ }
+ }
+ else {
+ /*
+ * Skip the longest ascending sequence.
+ */
+ do {
+ if (left >= right) {
+ return;
+ }
+ }
+ while (a[++left] >= a[left - 1]);
+
+ /*
+ * Every element from adjoining part plays the role
+ * of sentinel, therefore this allows us to avoid the
+ * left range check on each iteration. Moreover, we use
+ * the more optimized algorithm, so called pair insertion
+ * sort, which is faster (in the context of Quicksort)
+ * than traditional implementation of insertion sort.
+ */
+ for (int k = left; ++left <= right; k = ++left) {
+ int a1 = a[k], a2 = a[left];
+
+ if (a1 < a2) {
+ a2 = a1;
+ a1 = a[left];
+ }
+ while (a1 < a[--k]) {
+ a[k + 2] = a[k];
+ }
+ a[++k + 1] = a1;
+
+ while (a2 < a[--k]) {
+ a[k + 1] = a[k];
+ }
+ a[k + 1] = a2;
+ }
+ int last = a[right];
+
+ while (last < a[--right]) {
+ a[right + 1] = a[right];
+ }
+ a[right + 1] = last;
+ }
+ return;
+ }
+
+ // Inexpensive approximation of length / 7
+ int seventh = (length >> 3) + (length >> 6) + 1;
+
+ /*
+ * Sort five evenly spaced elements around (and including) the
+ * center element in the range. These elements will be used for
+ * pivot selection as described below. The choice for spacing
+ * these elements was empirically determined to work well on
+ * a wide variety of inputs.
+ */
+ int e3 = (left + right) >>> 1; // The midpoint
+ int e2 = e3 - seventh;
+ int e1 = e2 - seventh;
+ int e4 = e3 + seventh;
+ int e5 = e4 + seventh;
+
+ // Sort these elements using insertion sort
+ if (a[e2] < a[e1]) {
+ int t = a[e2];
+ a[e2] = a[e1];
+ a[e1] = t;
+ }
+
+ if (a[e3] < a[e2]) {
+ int t = a[e3];
+ a[e3] = a[e2];
+ a[e2] = t;
+ if (t < a[e1]) {
+ a[e2] = a[e1];
+ a[e1] = t;
+ }
+ }
+ if (a[e4] < a[e3]) {
+ int t = a[e4];
+ a[e4] = a[e3];
+ a[e3] = t;
+ if (t < a[e2]) {
+ a[e3] = a[e2];
+ a[e2] = t;
+ if (t < a[e1]) {
+ a[e2] = a[e1];
+ a[e1] = t;
+ }
+ }
+ }
+ if (a[e5] < a[e4]) {
+ int t = a[e5];
+ a[e5] = a[e4];
+ a[e4] = t;
+ if (t < a[e3]) {
+ a[e4] = a[e3];
+ a[e3] = t;
+ if (t < a[e2]) {
+ a[e3] = a[e2];
+ a[e2] = t;
+ if (t < a[e1]) {
+ a[e2] = a[e1];
+ a[e1] = t;
+ }
+ }
+ }
+ }
+
+ // Pointers
+ int less = left; // The index of the first element of center part
+ int great = right; // The index before the first element of right part
+
+ if (a[e1] != a[e2] && a[e2] != a[e3] && a[e3] != a[e4] && a[e4] != a[e5]) {
+ /*
+ * Use the second and fourth of the five sorted elements as pivots.
+ * These values are inexpensive approximations of the first and
+ * second terciles of the array. Note that pivot1 <= pivot2.
+ */
+ int pivot1 = a[e2];
+ int pivot2 = a[e4];
+
+ /*
+ * The first and the last elements to be sorted are moved to the
+ * locations formerly occupied by the pivots. When partitioning
+ * is complete, the pivots are swapped back into their final
+ * positions, and excluded from subsequent sorting.
+ */
+ a[e2] = a[left];
+ a[e4] = a[right];
+
+ /*
+ * Skip elements, which are less or greater than pivot values.
+ */
+ while (a[++less] < pivot1) {
+ }
+ while (a[--great] > pivot2) {
+ }
+
+ /*
+ * Partitioning:
+ *
+ * left part center part right part
+ * +--------------------------------------------------------------+
+ * | < pivot1 | pivot1 <= && <= pivot2 | ? | > pivot2 |
+ * +--------------------------------------------------------------+
+ * ^ ^ ^
+ * | | |
+ * less k great
+ *
+ * Invariants:
+ *
+ * all in (left, less) < pivot1
+ * pivot1 <= all in [less, k) <= pivot2
+ * all in (great, right) > pivot2
+ *
+ * Pointer k is the first index of ?-part.
+ */
+ outer:
+ for (int k = less - 1; ++k <= great; ) {
+ int ak = a[k];
+ if (ak < pivot1) { // Move a[k] to left part
+ a[k] = a[less];
+ /*
+ * Here and below we use "a[i] = b; i++;" instead
+ * of "a[i++] = b;" due to performance issue.
+ */
+ a[less] = ak;
+ ++less;
+ }
+ else if (ak > pivot2) { // Move a[k] to right part
+ while (a[great] > pivot2) {
+ if (great-- == k) {
+ break outer;
+ }
+ }
+ if (a[great] < pivot1) { // a[great] <= pivot2
+ a[k] = a[less];
+ a[less] = a[great];
+ ++less;
+ }
+ else { // pivot1 <= a[great] <= pivot2
+ a[k] = a[great];
+ }
+ /*
+ * Here and below we use "a[i] = b; i--;" instead
+ * of "a[i--] = b;" due to performance issue.
+ */
+ a[great] = ak;
+ --great;
+ }
+ }
+
+ // Swap pivots into their final positions
+ a[left] = a[less - 1];
+ a[less - 1] = pivot1;
+ a[right] = a[great + 1];
+ a[great + 1] = pivot2;
+
+ // Sort left and right parts recursively, excluding known pivots
+ SortingIntTestJMH.sort(a, left, less - 2, leftmost);
+ SortingIntTestJMH.sort(a, great + 2, right, false);
+
+ /*
+ * If center part is too large (comprises > 4/7 of the array),
+ * swap internal pivot values to ends.
+ */
+ if (less < e1 && e5 < great) {
+ /*
+ * Skip elements, which are equal to pivot values.
+ */
+ while (a[less] == pivot1) {
+ ++less;
+ }
+
+ while (a[great] == pivot2) {
+ --great;
+ }
+
+ /*
+ * Partitioning:
+ *
+ * left part center part right part
+ * +----------------------------------------------------------+
+ * | == pivot1 | pivot1 < && < pivot2 | ? | == pivot2 |
+ * +----------------------------------------------------------+
+ * ^ ^ ^
+ * | | |
+ * less k great
+ *
+ * Invariants:
+ *
+ * all in (*, less) == pivot1
+ * pivot1 < all in [less, k) < pivot2
+ * all in (great, *) == pivot2
+ *
+ * Pointer k is the first index of ?-part.
+ */
+ outer:
+ for (int k = less - 1; ++k <= great; ) {
+ int ak = a[k];
+ if (ak == pivot1) { // Move a[k] to left part
+ a[k] = a[less];
+ a[less] = ak;
+ ++less;
+ }
+ else if (ak == pivot2) { // Move a[k] to right part
+ while (a[great] == pivot2) {
+ if (great-- == k) {
+ break outer;
+ }
+ }
+ if (a[great] == pivot1) { // a[great] < pivot2
+ a[k] = a[less];
+ /*
+ * Even though a[great] equals to pivot1, the
+ * assignment a[less] = pivot1 may be incorrect,
+ * if a[great] and pivot1 are floating-point zeros
+ * of different signs. Therefore in float and
+ * double sorting methods we have to use more
+ * accurate assignment a[less] = a[great].
+ */
+ a[less] = pivot1;
+ ++less;
+ }
+ else { // pivot1 < a[great] < pivot2
+ a[k] = a[great];
+ }
+ a[great] = ak;
+ --great;
+ }
+ }
+ }
+
+ // Sort center part recursively
+ SortingIntTestJMH.sort(a, less, great, false);
+ }
+ else { // Partitioning with one pivot
+ /*
+ * Use the third of the five sorted elements as pivot.
+ * This value is inexpensive approximation of the median.
+ */
+ int pivot = a[e3];
+
+ /*
+ * Partitioning degenerates to the traditional 3-way
+ * (or "Dutch National Flag") schema:
+ *
+ * left part center part right part
+ * +-------------------------------------------------+
+ * | < pivot | == pivot | ? | > pivot |
+ * +-------------------------------------------------+
+ * ^ ^ ^
+ * | | |
+ * less k great
+ *
+ * Invariants:
+ *
+ * all in (left, less) < pivot
+ * all in [less, k) == pivot
+ * all in (great, right) > pivot
+ *
+ * Pointer k is the first index of ?-part.
+ */
+ for (int k = less; k <= great; ++k) {
+ if (a[k] == pivot) {
+ continue;
+ }
+ int ak = a[k];
+ if (ak < pivot) { // Move a[k] to left part
+ a[k] = a[less];
+ a[less] = ak;
+ ++less;
+ }
+ else { // a[k] > pivot - Move a[k] to right part
+ while (a[great] > pivot) {
+ --great;
+ }
+ if (a[great] < pivot) { // a[great] <= pivot
+ a[k] = a[less];
+ a[less] = a[great];
+ ++less;
+ }
+ else { // a[great] == pivot
+ /*
+ * Even though a[great] equals to pivot, the
+ * assignment a[k] = pivot may be incorrect,
+ * if a[great] and pivot are floating-point
+ * zeros of different signs. Therefore in float
+ * and double sorting methods we have to use
+ * more accurate assignment a[k] = a[great].
+ */
+ a[k] = pivot;
+ }
+ a[great] = ak;
+ --great;
+ }
+ }
+
+ /*
+ * Sort left and right parts recursively.
+ * All elements from center part are equal
+ * and, therefore, already sorted.
+ */
+ SortingIntTestJMH.sort(a, left, less - 1, leftmost);
+ SortingIntTestJMH.sort(a, great + 1, right, false);
+ }
+ }
+
+ private static void swap(int[] arr, int i, int j) {
+ int tmp = arr[i];
+ arr[i] = arr[j];
+ arr[j] = tmp;
+ }
+}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/util/Arrays/SortingLongBenchmarkTestJMH.java Tue Jun 09 07:05:48 2015 +0100
@@ -0,0 +1,725 @@
+/*
+ * Copyright 2015 Goldman Sachs.
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Thread)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.SECONDS)
+public class SortingLongBenchmarkTestJMH {
+ private static final int QUICKSORT_THRESHOLD = 286;
+ private static final int MAX_RUN_COUNT = 67;
+ private static final int INSERTION_SORT_THRESHOLD = 47;
+ public static final int MAX_VALUE = 1_000_000;
+
+ @Param({"pairFlipZeroPairFlip", "descendingAscending", "zeroHi", "hiZeroLow", "hiFlatLow", "identical",
+ "randomDups", "randomNoDups", "sortedReversedSorted", "pairFlip", "endLessThan"})
+ public String listType;
+
+ private long[] array;
+ private static final int LIST_SIZE = 10_000_000;
+ public static final int NUMBER_OF_ITERATIONS = 10;
+
+ @Setup
+ public void setUp() {
+ Random random = new Random(123456789012345L);
+ this.array = new long[LIST_SIZE];
+ int threeQuarters = (int) (LIST_SIZE * 0.75);
+ if ("zeroHi".equals(this.listType)) {
+ for (int i = 0; i < threeQuarters; i++) {
+ this.array[i] = 0;
+ }
+ int k = 1;
+ for (int i = threeQuarters; i < LIST_SIZE; i++) {
+ this.array[i] = k;
+ k++;
+ }
+ }
+ else if ("hiFlatLow".equals(this.listType)) {
+ int oneThird = LIST_SIZE / 3;
+ for (int i = 0; i < oneThird; i++) {
+ this.array[i] = i;
+ }
+ int twoThirds = oneThird * 2;
+ int constant = oneThird - 1;
+ for (int i = oneThird; i < twoThirds; i++) {
+ this.array[i] = constant;
+ }
+ for (int i = twoThirds; i < LIST_SIZE; i++) {
+ this.array[i] = constant - i + twoThirds;
+ }
+ }
+ else if ("hiZeroLow".equals(this.listType)) {
+ int oneThird = LIST_SIZE / 3;
+ for (int i = 0; i < oneThird; i++) {
+ this.array[i] = i;
+ }
+ int twoThirds = oneThird * 2;
+ for (int i = oneThird; i < twoThirds; i++) {
+ this.array[i] = 0;
+ }
+ for (int i = twoThirds; i < LIST_SIZE; i++) {
+ this.array[i] = oneThird - i + twoThirds;
+ }
+ }
+ else if ("identical".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE; i++) {
+ this.array[i] = 0;
+ }
+ }
+ else if ("randomDups".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE; i++) {
+ this.array[i] = random.nextInt(1000);
+ }
+ }
+ else if ("randomNoDups".equals(this.listType)) {
+ Set<Integer> set = new HashSet<>();
+ while (set.size() < LIST_SIZE + 1) {
+ set.add(random.nextInt());
+ }
+ List<Integer> list = new ArrayList<>(LIST_SIZE);
+ list.addAll(set);
+ for (int i = 0; i < LIST_SIZE; i++) {
+ this.array[i] = list.get(i);
+ }
+ }
+ else if ("sortedReversedSorted".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE / 2; i++) {
+ this.array[i] = i;
+ }
+ int num = 0;
+ for (int i = LIST_SIZE / 2; i < LIST_SIZE; i++) {
+ this.array[i] = LIST_SIZE - num;
+ num++;
+ }
+ }
+ else if ("pairFlip".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE; i++) {
+ this.array[i] = i;
+ }
+ for (int i = 0; i < LIST_SIZE; i += 2) {
+ long temp = this.array[i];
+ this.array[i] = this.array[i + 1];
+ this.array[i + 1] = temp;
+ }
+ }
+ else if ("endLessThan".equals(this.listType)) {
+ for (int i = 0; i < LIST_SIZE - 1; i++) {
+ this.array[i] = 3;
+ }
+ this.array[LIST_SIZE - 1] = 1;
+ }
+ else if ("pairFlipZeroPairFlip".equals(this.listType)) {
+ //pairflip
+ for (int i = 0; i < 64; i++) {
+ this.array[i] = i;
+ }
+ for (int i = 0; i < 64; i += 2) {
+ long temp = this.array[i];
+ this.array[i] = this.array[i + 1];
+ this.array[i + 1] = temp;
+ }
+ //zero
+ for (int i = 64; i < this.array.length - 64; i++) {
+ this.array[i] = 0;
+ }
+ //pairflip
+ for (int i = this.array.length - 64; i < this.array.length; i++) {
+ this.array[i] = i;
+ }
+ for (int i = this.array.length - 64; i < this.array.length; i += 2) {
+ long temp = this.array[i];
+ this.array[i] = this.array[i + 1];
+ this.array[i + 1] = temp;
+ }
+ }
+ else if ("pairFlipOneHundredPairFlip".equals(this.listType)) {
+ //10, 5
+ for (int i = 0; i < 64; i++) {
+ if (i % 2 == 0) {
+ this.array[i] = 10;
+ }
+ else {
+ this.array[i] = 5;
+ }
+ }
+
+ //100
+ for (int i = 64; i < this.array.length - 64; i++) {
+ this.array[i] = 100;
+ }
+
+ //10, 5
+ for (int i = this.array.length - 64; i < this.array.length; i++) {
+ if (i % 2 == 0) {
+ this.array[i] = 10;
+ }
+ else {
+ this.array[i] = 5;
+ }
+ }
+ }
+ }
+
+ @Warmup(iterations = 20)
+ @Measurement(iterations = 10)
+ @Benchmark
+ public void sortNewWay() {
+ for (int i = 0; i < NUMBER_OF_ITERATIONS; i++) {
+ SortingLongTestJMH.sort(this.array, 0, this.array.length - 1, null, 0, 0);
+ }
+ }
+
+ @Warmup(iterations = 20)
+ @Measurement(iterations = 10)
+ @Benchmark
+ public void sortOldWay() {
+ for (int i = 0; i < NUMBER_OF_ITERATIONS; i++) {
+ Arrays.sort(this.array);
+ }
+ }
+
+ /**
+ * Sorts the specified range of the array using the given
+ * workspace array slice if possible for merging
+ *
+ * @param a the array to be sorted
+ * @param left the index of the first element, inclusive, to be sorted
+ * @param right the index of the last element, inclusive, to be sorted
+ * @param work a workspace array (slice)
+ * @param workBase origin of usable space in work array
+ * @param workLen usable size of work array
+ */
+ static void sort(long[] a, int left, int right,
+ long[] work, int workBase, int workLen) {
+// Use Quicksort on small arrays
+ if (right - left < QUICKSORT_THRESHOLD) {
+ SortingLongTestJMH.sort(a, left, right, true);
+ return;
+ }
+
+ /*
+ * Index run[i] is the start of i-th run
+ * (ascending or descending sequence).
+ */
+ int[] run = new int[MAX_RUN_COUNT + 1];
+ int count = 0;
+ run[0] = left;
+
+ // Check if the array is nearly sorted
+ for (int k = left; k < right; run[count] = k) {
+ while (k < right && a[k] == a[k + 1])
+ k++;
+ if (k == right) break;
+ if (a[k] < a[k + 1]) { // ascending
+ while (++k <= right && a[k - 1] <= a[k]) ;
+ }
+ else if (a[k] > a[k + 1]) { // descending
+ while (++k <= right && a[k - 1] >= a[k]) ;
+ for (int lo = run[count] - 1, hi = k; ++lo < --hi; ) {
+ long t = a[lo];
+ a[lo] = a[hi];
+ a[hi] = t;
+ }
+ }
+ if (run[count] > left && a[run[count]] >= a[run[count] - 1]) {
+ count--;
+ }
+ /*
+ * The array is not highly structured,
+ * use Quicksort instead of merge sort.
+ */
+ if (++count == MAX_RUN_COUNT) {
+ sort(a, left, right, true);
+ return;
+ }
+ }
+
+ // Check special cases
+ // Implementation note: variable "right" is increased by 1.
+ if (run[count] == right++) {
+ run[++count] = right;
+ }
+ if (count <= 1) { // The array is already sorted
+ return;
+ }
+
+ // Determine alternation base for merge
+ byte odd = 0;
+ for (int n = 1; (n <<= 1) < count; odd ^= 1) {
+ }
+
+ // Use or create temporary array b for merging
+ long[] b; // temp array; alternates with a
+ int ao, bo; // array offsets from 'left'
+ int blen = right - left; // space needed for b
+ if (work == null || workLen < blen || workBase + blen > work.length) {
+ work = new long[blen];
+ workBase = 0;
+ }
+ if (odd == 0) {
+ System.arraycopy(a, left, work, workBase, blen);
+ b = a;
+ bo = 0;
+ a = work;
+ ao = workBase - left;
+ }
+ else {
+ b = work;
+ ao = 0;
+ bo = workBase - left;
+ }
+
+ // Merging
+ for (int last; count > 1; count = last) {
+ for (int k = (last = 0) + 2; k <= count; k += 2) {
+ int hi = run[k], mi = run[k - 1];
+ for (int i = run[k - 2], p = i, q = mi; i < hi; ++i) {
+ if (q >= hi || p < mi && a[p + ao] <= a[q + ao]) {
+ b[i + bo] = a[p++ + ao];
+ }
+ else {
+ b[i + bo] = a[q++ + ao];
+ }
+ }
+ run[++last] = hi;
+ }
+ if ((count & 1) != 0) {
+ for (int i = right, lo = run[count - 1]; --i >= lo;
+ b[i + bo] = a[i + ao]
+ ) {
+ }
+ run[++last] = right;
+ }
+ long[] t = a;
+ a = b;
+ b = t;
+ int o = ao;
+ ao = bo;
+ bo = o;
+ }
+ }
+
+ /**
+ * Sorts the specified range of the array by Dual-Pivot Quicksort.
+ *
+ * @param a the array to be sorted
+ * @param left the index of the first element, inclusive, to be sorted
+ * @param right the index of the last element, inclusive, to be sorted
+ * @param leftmost indicates if this part is the leftmost in the range
+ */
+ private static void sort(long[] a, int left, int right, boolean leftmost) {
+ int length = right - left + 1;
+
+ // Use insertion sort on tiny arrays
+ if (length < INSERTION_SORT_THRESHOLD) {
+ if (leftmost) {
+ /*
+ * Traditional (without sentinel) insertion sort,
+ * optimized for server VM, is used in case of
+ * the leftmost part.
+ */
+ for (int i = left, j = i; i < right; j = ++i) {
+ long ai = a[i + 1];
+ while (ai < a[j]) {
+ a[j + 1] = a[j];
+ if (j-- == left) {
+ break;
+ }
+ }
+ a[j + 1] = ai;
+ }
+ }
+ else {
+ /*
+ * Skip the longest ascending sequence.
+ */
+ do {
+ if (left >= right) {
+ return;
+ }
+ }
+ while (a[++left] >= a[left - 1]);
+
+ /*
+ * Every element from adjoining part plays the role
+ * of sentinel, therefore this allows us to avoid the
+ * left range check on each iteration. Moreover, we use
+ * the more optimized algorithm, so called pair insertion
+ * sort, which is faster (in the context of Quicksort)
+ * than traditional implementation of insertion sort.
+ */
+ for (int k = left; ++left <= right; k = ++left) {
+ long a1 = a[k], a2 = a[left];
+
+ if (a1 < a2) {
+ a2 = a1;
+ a1 = a[left];
+ }
+ while (a1 < a[--k]) {
+ a[k + 2] = a[k];
+ }
+ a[++k + 1] = a1;
+
+ while (a2 < a[--k]) {
+ a[k + 1] = a[k];
+ }
+ a[k + 1] = a2;
+ }
+ long last = a[right];
+
+ while (last < a[--right]) {
+ a[right + 1] = a[right];
+ }
+ a[right + 1] = last;
+ }
+ return;
+ }
+
+ // Inexpensive approximation of length / 7
+ int seventh = (length >> 3) + (length >> 6) + 1;
+
+ /*
+ * Sort five evenly spaced elements around (and including) the
+ * center element in the range. These elements will be used for
+ * pivot selection as described below. The choice for spacing
+ * these elements was empirically determined to work well on
+ * a wide variety of inputs.
+ */
+ int e3 = (left + right) >>> 1; // The midpoint
+ int e2 = e3 - seventh;
+ int e1 = e2 - seventh;
+ int e4 = e3 + seventh;
+ int e5 = e4 + seventh;
+
+ // Sort these elements using insertion sort
+ if (a[e2] < a[e1]) {
+ long t = a[e2];
+ a[e2] = a[e1];
+ a[e1] = t;
+ }
+
+ if (a[e3] < a[e2]) {
+ long t = a[e3];
+ a[e3] = a[e2];
+ a[e2] = t;
+ if (t < a[e1]) {
+ a[e2] = a[e1];
+ a[e1] = t;
+ }
+ }
+ if (a[e4] < a[e3]) {
+ long t = a[e4];
+ a[e4] = a[e3];
+ a[e3] = t;
+ if (t < a[e2]) {
+ a[e3] = a[e2];
+ a[e2] = t;
+ if (t < a[e1]) {
+ a[e2] = a[e1];
+ a[e1] = t;
+ }
+ }
+ }
+ if (a[e5] < a[e4]) {
+ long t = a[e5];
+ a[e5] = a[e4];
+ a[e4] = t;
+ if (t < a[e3]) {
+ a[e4] = a[e3];
+ a[e3] = t;
+ if (t < a[e2]) {
+ a[e3] = a[e2];
+ a[e2] = t;
+ if (t < a[e1]) {
+ a[e2] = a[e1];
+ a[e1] = t;
+ }
+ }
+ }
+ }
+
+ // Pointers
+ int less = left; // The index of the first element of center part
+ int great = right; // The index before the first element of right part
+
+ if (a[e1] != a[e2] && a[e2] != a[e3] && a[e3] != a[e4] && a[e4] != a[e5]) {
+ /*
+ * Use the second and fourth of the five sorted elements as pivots.
+ * These values are inexpensive approximations of the first and
+ * second terciles of the array. Note that pivot1 <= pivot2.
+ */
+ long pivot1 = a[e2];
+ long pivot2 = a[e4];
+
+ /*
+ * The first and the last elements to be sorted are moved to the
+ * locations formerly occupied by the pivots. When partitioning
+ * is complete, the pivots are swapped back into their final
+ * positions, and excluded from subsequent sorting.
+ */
+ a[e2] = a[left];
+ a[e4] = a[right];
+
+ /*
+ * Skip elements, which are less or greater than pivot values.
+ */
+ while (a[++less] < pivot1) {
+ }
+ while (a[--great] > pivot2) {
+ }
+
+ /*
+ * Partitioning:
+ *
+ * left part center part right part
+ * +--------------------------------------------------------------+
+ * | < pivot1 | pivot1 <= && <= pivot2 | ? | > pivot2 |
+ * +--------------------------------------------------------------+
+ * ^ ^ ^
+ * | | |
+ * less k great
+ *
+ * Invariants:
+ *
+ * all in (left, less) < pivot1
+ * pivot1 <= all in [less, k) <= pivot2
+ * all in (great, right) > pivot2
+ *
+ * Pointer k is the first index of ?-part.
+ */
+ outer:
+ for (int k = less - 1; ++k <= great; ) {
+ long ak = a[k];
+ if (ak < pivot1) { // Move a[k] to left part
+ a[k] = a[less];
+ /*
+ * Here and below we use "a[i] = b; i++;" instead
+ * of "a[i++] = b;" due to performance issue.
+ */
+ a[less] = ak;
+ ++less;
+ }
+ else if (ak > pivot2) { // Move a[k] to right part
+ while (a[great] > pivot2) {
+ if (great-- == k) {
+ break outer;
+ }
+ }
+ if (a[great] < pivot1) { // a[great] <= pivot2
+ a[k] = a[less];
+ a[less] = a[great];
+ ++less;
+ }
+ else { // pivot1 <= a[great] <= pivot2
+ a[k] = a[great];
+ }
+ /*
+ * Here and below we use "a[i] = b; i--;" instead
+ * of "a[i--] = b;" due to performance issue.
+ */
+ a[great] = ak;
+ --great;
+ }
+ }
+
+ // Swap pivots into their final positions
+ a[left] = a[less - 1];
+ a[less - 1] = pivot1;
+ a[right] = a[great + 1];
+ a[great + 1] = pivot2;
+
+ // Sort left and right parts recursively, excluding known pivots
+ SortingLongTestJMH.sort(a, left, less - 2, leftmost);
+ SortingLongTestJMH.sort(a, great + 2, right, false);
+
+ /*
+ * If center part is too large (comprises > 4/7 of the array),
+ * swap internal pivot values to ends.
+ */
+ if (less < e1 && e5 < great) {
+ /*
+ * Skip elements, which are equal to pivot values.
+ */
+ while (a[less] == pivot1) {
+ ++less;
+ }
+
+ while (a[great] == pivot2) {
+ --great;
+ }
+
+ /*
+ * Partitioning:
+ *
+ * left part center part right part
+ * +----------------------------------------------------------+
+ * | == pivot1 | pivot1 < && < pivot2 | ? | == pivot2 |
+ * +----------------------------------------------------------+
+ * ^ ^ ^
+ * | | |
+ * less k great
+ *
+ * Invariants:
+ *
+ * all in (*, less) == pivot1
+ * pivot1 < all in [less, k) < pivot2
+ * all in (great, *) == pivot2
+ *
+ * Pointer k is the first index of ?-part.
+ */
+ outer:
+ for (int k = less - 1; ++k <= great; ) {
+ long ak = a[k];
+ if (ak == pivot1) { // Move a[k] to left part
+ a[k] = a[less];
+ a[less] = ak;
+ ++less;
+ }
+ else if (ak == pivot2) { // Move a[k] to right part
+ while (a[great] == pivot2) {
+ if (great-- == k) {
+ break outer;
+ }
+ }
+ if (a[great] == pivot1) { // a[great] < pivot2
+ a[k] = a[less];
+ /*
+ * Even though a[great] equals to pivot1, the
+ * assignment a[less] = pivot1 may be incorrect,
+ * if a[great] and pivot1 are floating-point zeros
+ * of different signs. Therefore in float and
+ * double sorting methods we have to use more
+ * accurate assignment a[less] = a[great].
+ */
+ a[less] = pivot1;
+ ++less;
+ }
+ else { // pivot1 < a[great] < pivot2
+ a[k] = a[great];
+ }
+ a[great] = ak;
+ --great;
+ }
+ }
+ }
+
+ // Sort center part recursively
+ SortingLongTestJMH.sort(a, less, great, false);
+ }
+ else { // Partitioning with one pivot
+ /*
+ * Use the third of the five sorted elements as pivot.
+ * This value is inexpensive approximation of the median.
+ */
+ long pivot = a[e3];
+
+ /*
+ * Partitioning degenerates to the traditional 3-way
+ * (or "Dutch National Flag") schema:
+ *
+ * left part center part right part
+ * +-------------------------------------------------+
+ * | < pivot | == pivot | ? | > pivot |
+ * +-------------------------------------------------+
+ * ^ ^ ^
+ * | | |
+ * less k great
+ *
+ * Invariants:
+ *
+ * all in (left, less) < pivot
+ * all in [less, k) == pivot
+ * all in (great, right) > pivot
+ *
+ * Pointer k is the first index of ?-part.
+ */
+ for (int k = less; k <= great; ++k) {
+ if (a[k] == pivot) {
+ continue;
+ }
+ long ak = a[k];
+ if (ak < pivot) { // Move a[k] to left part
+ a[k] = a[less];
+ a[less] = ak;
+ ++less;
+ }
+ else { // a[k] > pivot - Move a[k] to right part
+ while (a[great] > pivot) {
+ --great;
+ }
+ if (a[great] < pivot) { // a[great] <= pivot
+ a[k] = a[less];
+ a[less] = a[great];
+ ++less;
+ }
+ else { // a[great] == pivot
+ /*
+ * Even though a[great] equals to pivot, the
+ * assignment a[k] = pivot may be incorrect,
+ * if a[great] and pivot are floating-point
+ * zeros of different signs. Therefore in float
+ * and double sorting methods we have to use
+ * more accurate assignment a[k] = a[great].
+ */
+ a[k] = pivot;
+ }
+ a[great] = ak;
+ --great;
+ }
+ }
+
+ /*
+ * Sort left and right parts recursively.
+ * All elements from center part are equal
+ * and, therefore, already sorted.
+ */
+ SortingLongTestJMH.sort(a, left, less - 1, leftmost);
+ SortingLongTestJMH.sort(a, great + 1, right, false);
+ }
+ }
+
+ private static void swap(long[] arr, int i, int j) {
+ long tmp = arr[i];
+ arr[i] = arr[j];
+ arr[j] = tmp;
+ }
+}
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/java/util/Arrays/SortingNearlySortedPrimitive.java Tue Jun 09 07:05:48 2015 +0100
@@ -0,0 +1,274 @@
+/*
+ * Copyright 2015 Goldman Sachs.
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+/*
+ * @test
+ * @summary Tests the sorting of a large array of sorted primitive values,
+ * predominently for cases where the array is nearly sorted. This tests
+ * code that detects patterns in the array to determine if it is nearly
+ * sorted and if so employs and optimizes merge sort rather than a
+ * Dual-Pivot QuickSort.
+ *
+ * @run testng SortingNearlySortedPrimitive
+ */
+
+import org.testng.Assert;
+import org.testng.annotations.DataProvider;
+import org.testng.annotations.Test;
+
+import java.util.Arrays;
+import java.util.function.Supplier;
+
+public class SortingNearlySortedPrimitive {
+ private static final int ARRAY_SIZE = 1_000_000;
+
+ @DataProvider(name = "arrays")
+ public Object[][] createData() {
+ return new Object[][]{
+ {"hiZeroLowTest", (Supplier<int[]>) this::hiZeroLowData},
+ {"endLessThanTest", (Supplier<int[]>) this::endLessThanData},
+ {"highFlatLowTest", (Supplier<int[]>) this::highFlatLowData},
+ {"identicalTest", (Supplier<int[]>) this::identicalData},
+ {"sortedReversedSortedTest", (Supplier<int[]>) this::sortedReversedSortedData},
+ {"pairFlipTest", (Supplier<int[]>) this::pairFlipData},
+ {"zeroHiTest", (Supplier<int[]>) this::zeroHiData},
+ };
+ }
+
+ @Test(dataProvider = "arrays")
+ public void runTests(String testName, Supplier<int[]> dataMethod) throws Exception {
+ int[] intSourceArray = dataMethod.get();
+
+ // Clone source array to ensure it is not modified
+ this.sortAndAssert(intSourceArray.clone());
+ this.sortAndAssert(floatCopyFromInt(intSourceArray));
+ this.sortAndAssert(doubleCopyFromInt(intSourceArray));
+ this.sortAndAssert(longCopyFromInt(intSourceArray));
+ this.sortAndAssert(shortCopyFromInt(intSourceArray));
+ this.sortAndAssert(charCopyFromInt(intSourceArray));
+ }
+
+ private float[] floatCopyFromInt(int[] src) {
+ float[] result = new float[src.length];
+ for (int i = 0; i < result.length; i++) {
+ result[i] = src[i];
+ }
+ return result;
+ }
+
+ private double[] doubleCopyFromInt(int[] src) {
+ double[] result = new double[src.length];
+ for (int i = 0; i < result.length; i++) {
+ result[i] = src[i];
+ }
+ return result;
+ }
+
+ private long[] longCopyFromInt(int[] src) {
+ long[] result = new long[src.length];
+ for (int i = 0; i < result.length; i++) {
+ result[i] = src[i];
+ }
+ return result;
+ }
+
+ private short[] shortCopyFromInt(int[] src) {
+ short[] result = new short[src.length];
+ for (int i = 0; i < result.length; i++) {
+ result[i] = (short) src[i];
+ }
+ return result;
+ }
+
+ private char[] charCopyFromInt(int[] src) {
+ char[] result = new char[src.length];
+ for (int i = 0; i < result.length; i++) {
+ result[i] = (char) src[i];
+ }
+ return result;
+ }
+
+ private void sortAndAssert(int[] array) {
+ Arrays.sort(array);
+ for (int i = 1; i < ARRAY_SIZE; i++) {
+ if (array[i] < array[i - 1]) {
+ throw new AssertionError("not sorted");
+ }
+ }
+ Assert.assertEquals(ARRAY_SIZE, array.length);
+ }
+
+ private void sortAndAssert(char[] array) {
+ Arrays.sort(array);
+ for (int i = 1; i < ARRAY_SIZE; i++) {
+ if (array[i] < array[i - 1]) {
+ throw new AssertionError("not sorted");
+ }
+ }
+ Assert.assertEquals(ARRAY_SIZE, array.length);
+ }
+
+ private void sortAndAssert(short[] array) {
+ Arrays.sort(array);
+ for (int i = 1; i < ARRAY_SIZE; i++) {
+ if (array[i] < array[i - 1]) {
+ throw new AssertionError("not sorted");
+ }
+ }
+ Assert.assertEquals(ARRAY_SIZE, array.length);
+ }
+
+ private void sortAndAssert(double[] array) {
+ Arrays.sort(array);
+ for (int i = 1; i < ARRAY_SIZE; i++) {
+ if (array[i] < array[i - 1]) {
+ throw new AssertionError("not sorted");
+ }
+ }
+ Assert.assertEquals(ARRAY_SIZE, array.length);
+ }
+
+ private void sortAndAssert(float[] array) {
+ Arrays.sort(array);
+ for (int i = 1; i < ARRAY_SIZE; i++) {
+ if (array[i] < array[i - 1]) {
+ throw new AssertionError("not sorted");
+ }
+ }
+ Assert.assertEquals(ARRAY_SIZE, array.length);
+ }
+
+ private void sortAndAssert(long[] array) {
+ Arrays.sort(array);
+ for (int i = 1; i < ARRAY_SIZE; i++) {
+ if (array[i] < array[i - 1]) {
+ throw new AssertionError("not sorted");
+ }
+ }
+ Assert.assertEquals(ARRAY_SIZE, array.length);
+ }
+
+ private int[] zeroHiData() {
+ int[] array = new int[ARRAY_SIZE];
+
+ int threeQuarters = (int) (ARRAY_SIZE * 0.75);
+ for (int i = 0; i < threeQuarters; i++) {
+ array[i] = 0;
+ }
+ int k = 1;
+ for (int i = threeQuarters; i < ARRAY_SIZE; i++) {
+ array[i] = k;
+ k++;
+ }
+
+ return array;
+ }
+
+ private int[] hiZeroLowData() {
+ int[] array = new int[ARRAY_SIZE];
+
+ int oneThird = ARRAY_SIZE / 3;
+ for (int i = 0; i < oneThird; i++) {
+ array[i] = i;
+ }
+ int twoThirds = oneThird * 2;
+ for (int i = oneThird; i < twoThirds; i++) {
+ array[i] = 0;
+ }
+ for (int i = twoThirds; i < ARRAY_SIZE; i++) {
+ array[i] = oneThird - i + twoThirds;
+ }
+ return array;
+ }
+
+ private int[] highFlatLowData() {
+ int[] array = new int[ARRAY_SIZE];
+
+ int oneThird = ARRAY_SIZE / 3;
+ for (int i = 0; i < oneThird; i++) {
+ array[i] = i;
+ }
+ int twoThirds = oneThird * 2;
+ int constant = oneThird - 1;
+ for (int i = oneThird; i < twoThirds; i++) {
+ array[i] = constant;
+ }
+ for (int i = twoThirds; i < ARRAY_SIZE; i++) {
+ array[i] = constant - i + twoThirds;
+ }
+
+ return array;
+ }
+
+ private int[] identicalData() {
+ int[] array = new int[ARRAY_SIZE];
+ int listNumber = 24;
+
+ for (int i = 0; i < ARRAY_SIZE; i++) {
+ array[i] = listNumber;
+ }
+
+ return array;
+ }
+
+ private int[] endLessThanData() {
+ int[] array = new int[ARRAY_SIZE];
+
+ for (int i = 0; i < ARRAY_SIZE - 1; i++) {
+ array[i] = 3;
+ }
+ array[ARRAY_SIZE - 1] = 1;
+
+ return array;
+ }
+
+ private int[] sortedReversedSortedData() {
+ int[] array = new int[ARRAY_SIZE];
+
+ for (int i = 0; i < ARRAY_SIZE / 2; i++) {
+ array[i] = i;
+ }
+ int num = 0;
+ for (int i = ARRAY_SIZE / 2; i < ARRAY_SIZE; i++) {
+ array[i] = ARRAY_SIZE - num;
+ num++;
+ }
+
+ return array;
+ }
+
+ private int[] pairFlipData() {
+ int[] array = new int[ARRAY_SIZE];
+
+ for (int i = 0; i < ARRAY_SIZE; i++) {
+ array[i] = i;
+ }
+ for (int i = 0; i < ARRAY_SIZE; i += 2) {
+ int temp = array[i];
+ array[i] = array[i + 1];
+ array[i + 1] = temp;
+ }
+
+ return array;
+ }
+}