1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/utilities/quickSort.hpp Wed Apr 27 01:25:04 2016 +0800
1.3 @@ -0,0 +1,138 @@
1.4 +/*
1.5 + * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.23 + * or visit www.oracle.com if you need additional information or have any
1.24 + * questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#ifndef SHARE_VM_UTILITIES_QUICKSORT_HPP
1.29 +#define SHARE_VM_UTILITIES_QUICKSORT_HPP
1.30 +
1.31 +#include "memory/allocation.hpp"
1.32 +#include "runtime/globals.hpp"
1.33 +#include "utilities/debug.hpp"
1.34 +
1.35 +class QuickSort : AllStatic {
1.36 +
1.37 + private:
1.38 + template<class T>
1.39 + static void swap(T* array, int x, int y) {
1.40 + T tmp = array[x];
1.41 + array[x] = array[y];
1.42 + array[y] = tmp;
1.43 + }
1.44 +
1.45 + // As pivot we use the median of the first, last and middle elements.
1.46 + // We swap in these three values at the right place in the array. This
1.47 + // means that this method not only returns the index of the pivot
1.48 + // element. It also alters the array so that:
1.49 + // array[first] <= array[middle] <= array[last]
1.50 + // A side effect of this is that arrays of length <= 3 are sorted.
1.51 + template<class T, class C>
1.52 + static int find_pivot(T* array, int length, C comparator) {
1.53 + assert(length > 1, "length of array must be > 0");
1.54 +
1.55 + int middle_index = length / 2;
1.56 + int last_index = length - 1;
1.57 +
1.58 + if (comparator(array[0], array[middle_index]) == 1) {
1.59 + swap(array, 0, middle_index);
1.60 + }
1.61 + if (comparator(array[0], array[last_index]) == 1) {
1.62 + swap(array, 0, last_index);
1.63 + }
1.64 + if (comparator(array[middle_index], array[last_index]) == 1) {
1.65 + swap(array, middle_index, last_index);
1.66 + }
1.67 + // Now the value in the middle of the array is the median
1.68 + // of the fist, last and middle values. Use this as pivot.
1.69 + return middle_index;
1.70 + }
1.71 +
1.72 + template<class T, class C, bool idempotent>
1.73 + static int partition(T* array, int pivot, int length, C comparator) {
1.74 + int left_index = -1;
1.75 + int right_index = length;
1.76 + T pivot_val = array[pivot];
1.77 +
1.78 + while (true) {
1.79 + do {
1.80 + left_index++;
1.81 + } while (comparator(array[left_index], pivot_val) == -1);
1.82 + do {
1.83 + right_index--;
1.84 + } while (comparator(array[right_index], pivot_val) == 1);
1.85 +
1.86 + if (left_index < right_index) {
1.87 + if (!idempotent || comparator(array[left_index], array[right_index]) != 0) {
1.88 + swap(array, left_index, right_index);
1.89 + }
1.90 + } else {
1.91 + return right_index;
1.92 + }
1.93 + }
1.94 +
1.95 + ShouldNotReachHere();
1.96 + return 0;
1.97 + }
1.98 +
1.99 + template<class T, class C, bool idempotent>
1.100 + static void inner_sort(T* array, int length, C comparator) {
1.101 + if (length < 2) {
1.102 + return;
1.103 + }
1.104 + int pivot = find_pivot(array, length, comparator);
1.105 + if (length < 4) {
1.106 + // arrays up to length 3 will be sorted after finding the pivot
1.107 + return;
1.108 + }
1.109 + int split = partition<T, C, idempotent>(array, pivot, length, comparator);
1.110 + int first_part_length = split + 1;
1.111 + inner_sort<T, C, idempotent>(array, first_part_length, comparator);
1.112 + inner_sort<T, C, idempotent>(&array[first_part_length], length - first_part_length, comparator);
1.113 + }
1.114 +
1.115 + public:
1.116 + // The idempotent parameter prevents the sort from
1.117 + // reordering a previous valid sort by not swapping
1.118 + // fields that compare as equal. This requires extra
1.119 + // calls to the comparator, so the performance
1.120 + // impact depends on the comparator.
1.121 + template<class T, class C>
1.122 + static void sort(T* array, int length, C comparator, bool idempotent) {
1.123 + // Switch "idempotent" from function paramter to template parameter
1.124 + if (idempotent) {
1.125 + inner_sort<T, C, true>(array, length, comparator);
1.126 + } else {
1.127 + inner_sort<T, C, false>(array, length, comparator);
1.128 + }
1.129 + }
1.130 +
1.131 + // for unit testing
1.132 +#ifndef PRODUCT
1.133 + static void print_array(const char* prefix, int* array, int length);
1.134 + static bool compare_arrays(int* actual, int* expected, int length);
1.135 + template <class C> static bool sort_and_compare(int* arrayToSort, int* expectedResult, int length, C comparator, bool idempotent = false);
1.136 + static void test_quick_sort();
1.137 +#endif
1.138 +};
1.139 +
1.140 +
1.141 +#endif //SHARE_VM_UTILITIES_QUICKSORT_HPP
