|
3779
|
1 /*
|
|
|
2 * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
|
|
|
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
|
|
|
4 *
|
|
|
5 * This code is free software; you can redistribute it and/or modify it
|
|
|
6 * under the terms of the GNU General Public License version 2 only, as
|
|
|
7 * published by the Free Software Foundation.
|
|
|
8 *
|
|
|
9 * This code is distributed in the hope that it will be useful, but WITHOUT
|
|
|
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
|
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
|
|
12 * version 2 for more details (a copy is included in the LICENSE file that
|
|
|
13 * accompanied this code).
|
|
|
14 *
|
|
|
15 * You should have received a copy of the GNU General Public License version
|
|
|
16 * 2 along with this work; if not, write to the Free Software Foundation,
|
|
|
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
|
|
|
18 *
|
|
|
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
|
|
|
20 * or visit www.oracle.com if you need additional information or have any
|
|
|
21 * questions.
|
|
|
22 *
|
|
|
23 */
|
|
|
24
|
|
|
25 #ifndef SHARE_VM_UTILITIES_QUICKSORT_HPP
|
|
|
26 #define SHARE_VM_UTILITIES_QUICKSORT_HPP
|
|
|
27
|
|
|
28 #include "memory/allocation.hpp"
|
|
|
29 #include "runtime/globals.hpp"
|
|
|
30 #include "utilities/debug.hpp"
|
|
|
31
|
|
|
32 class QuickSort : AllStatic {
|
|
|
33
|
|
|
34 private:
|
|
|
35 template<class T>
|
|
|
36 static void swap(T* array, int x, int y) {
|
|
|
37 T tmp = array[x];
|
|
|
38 array[x] = array[y];
|
|
|
39 array[y] = tmp;
|
|
|
40 }
|
|
|
41
|
|
|
42 // As pivot we use the median of the first, last and middle elements.
|
|
|
43 // We swap in these three values at the right place in the array. This
|
|
|
44 // means that this method not only returns the index of the pivot
|
|
|
45 // element. It also alters the array so that:
|
|
|
46 // array[first] <= array[middle] <= array[last]
|
|
|
47 // A side effect of this is that arrays of length <= 3 are sorted.
|
|
|
48 template<class T, class C>
|
|
|
49 static int find_pivot(T* array, int length, C comparator) {
|
|
|
50 assert(length > 1, "length of array must be > 0");
|
|
|
51
|
|
|
52 int middle_index = length / 2;
|
|
|
53 int last_index = length - 1;
|
|
|
54
|
|
|
55 if (comparator(array[0], array[middle_index]) == 1) {
|
|
|
56 swap(array, 0, middle_index);
|
|
|
57 }
|
|
|
58 if (comparator(array[0], array[last_index]) == 1) {
|
|
|
59 swap(array, 0, last_index);
|
|
|
60 }
|
|
|
61 if (comparator(array[middle_index], array[last_index]) == 1) {
|
|
|
62 swap(array, middle_index, last_index);
|
|
|
63 }
|
|
|
64 // Now the value in the middle of the array is the median
|
|
|
65 // of the fist, last and middle values. Use this as pivot.
|
|
|
66 return middle_index;
|
|
|
67 }
|
|
|
68
|
|
|
69 template<class T, class C, bool idempotent>
|
|
|
70 static int partition(T* array, int pivot, int length, C comparator) {
|
|
|
71 int left_index = -1;
|
|
|
72 int right_index = length;
|
|
|
73 T pivot_val = array[pivot];
|
|
|
74
|
|
|
75 while (true) {
|
|
|
76 do {
|
|
|
77 left_index++;
|
|
|
78 } while (comparator(array[left_index], pivot_val) == -1);
|
|
|
79 do {
|
|
|
80 right_index--;
|
|
|
81 } while (comparator(array[right_index], pivot_val) == 1);
|
|
|
82
|
|
|
83 if (left_index < right_index) {
|
|
|
84 if (!idempotent || comparator(array[left_index], array[right_index]) != 0) {
|
|
|
85 swap(array, left_index, right_index);
|
|
|
86 }
|
|
|
87 } else {
|
|
|
88 return right_index;
|
|
|
89 }
|
|
|
90 }
|
|
|
91
|
|
|
92 ShouldNotReachHere();
|
|
|
93 return 0;
|
|
|
94 }
|
|
|
95
|
|
|
96 template<class T, class C, bool idempotent>
|
|
|
97 static void inner_sort(T* array, int length, C comparator) {
|
|
|
98 if (length < 2) {
|
|
|
99 return;
|
|
|
100 }
|
|
|
101 int pivot = find_pivot(array, length, comparator);
|
|
|
102 if (length < 4) {
|
|
|
103 // arrays up to length 3 will be sorted after finding the pivot
|
|
|
104 return;
|
|
|
105 }
|
|
|
106 int split = partition<T, C, idempotent>(array, pivot, length, comparator);
|
|
|
107 int first_part_length = split + 1;
|
|
|
108 inner_sort<T, C, idempotent>(array, first_part_length, comparator);
|
|
|
109 inner_sort<T, C, idempotent>(&array[first_part_length], length - first_part_length, comparator);
|
|
|
110 }
|
|
|
111
|
|
|
112 public:
|
|
|
113 // The idempotent parameter prevents the sort from
|
|
|
114 // reordering a previous valid sort by not swapping
|
|
|
115 // fields that compare as equal. This requires extra
|
|
|
116 // calls to the comparator, so the performance
|
|
|
117 // impact depends on the comparator.
|
|
|
118 template<class T, class C>
|
|
|
119 static void sort(T* array, int length, C comparator, bool idempotent) {
|
|
|
120 // Switch "idempotent" from function paramter to template parameter
|
|
|
121 if (idempotent) {
|
|
|
122 inner_sort<T, C, true>(array, length, comparator);
|
|
|
123 } else {
|
|
|
124 inner_sort<T, C, false>(array, length, comparator);
|
|
|
125 }
|
|
|
126 }
|
|
|
127
|
|
|
128 // for unit testing
|
|
|
129 #ifndef PRODUCT
|
|
|
130 static void print_array(const char* prefix, int* array, int length);
|
|
|
131 static bool compare_arrays(int* actual, int* expected, int length);
|
|
|
132 template <class C> static bool sort_and_compare(int* arrayToSort, int* expectedResult, int length, C comparator, bool idempotent = false);
|
|
|
133 static bool test_quick_sort();
|
|
|
134 #endif
|
|
|
135 };
|
|
|
136
|
|
|
137
|
|
|
138 #endif //SHARE_VM_UTILITIES_QUICKSORT_HPP
|
