/*

 * 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;

                        }

                    }