1 /*
2 * Copyright (c) 2009, 2015, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package sun.java2d.marlin;
27
28 /**
29 * MergeSort adapted from (OpenJDK 8) java.util.Array.legacyMergeSort(Object[])
30 * to swap two arrays at the same time (x & y)
31 * and use external auxiliary storage for temporary arrays
32 */
33 final class MergeSort {
34
35 // insertion sort threshold
36 public static final int INSERTION_SORT_THRESHOLD = 14;
37
38 /**
39 * Modified merge sort:
40 * Input arrays are in both auxX/auxY (sorted: 0 to insertionSortIndex)
41 * and x/y (unsorted: insertionSortIndex to toIndex)
42 * Outputs are stored in x/y arrays
43 */
44 static void mergeSortNoCopy(final int[] x, final int[] y,
45 final int[] auxX, final int[] auxY,
46 final int toIndex,
47 final int insertionSortIndex)
48 {
49 if ((toIndex > x.length) || (toIndex > y.length)
50 || (toIndex > auxX.length) || (toIndex > auxY.length)) {
51 // explicit check to avoid bound checks within hot loops (below):
52 throw new ArrayIndexOutOfBoundsException("bad arguments: toIndex="
53 + toIndex);
54 }
55
56 // sort second part only using merge / insertion sort
57 // in auxiliary storage (auxX/auxY)
58 mergeSort(x, y, x, auxX, y, auxY, insertionSortIndex, toIndex);
59
60 // final pass to merge both
61 // Merge sorted parts (auxX/auxY) into x/y arrays
62 if ((insertionSortIndex == 0)
63 || (auxX[insertionSortIndex - 1] <= auxX[insertionSortIndex])) {
64 // System.out.println("mergeSortNoCopy: ordered");
65 // 34 occurences
66 // no initial left part or both sublists (auxX, auxY) are sorted:
67 // copy back data into (x, y):
68 System.arraycopy(auxX, 0, x, 0, toIndex);
69 System.arraycopy(auxY, 0, y, 0, toIndex);
70 return;
71 }
72
73 for (int i = 0, p = 0, q = insertionSortIndex; i < toIndex; i++) {
74 if ((q >= toIndex) || ((p < insertionSortIndex)
75 && (auxX[p] <= auxX[q]))) {
76 x[i] = auxX[p];
77 y[i] = auxY[p];
78 p++;
79 } else {
80 x[i] = auxX[q];
81 y[i] = auxY[q];
82 q++;
83 }
84 }
85 }
86
87 /**
88 * Src is the source array that starts at index 0
89 * Dest is the (possibly larger) array destination with a possible offset
90 * low is the index in dest to start sorting
91 * high is the end index in dest to end sorting
92 */
93 private static void mergeSort(final int[] refX, final int[] refY,
94 final int[] srcX, final int[] dstX,
95 final int[] srcY, final int[] dstY,
96 final int low, final int high)
97 {
98 final int length = high - low;
99
100 /*
101 * Tuning parameter: list size at or below which insertion sort
102 * will be used in preference to mergesort.
103 */
104 if (length <= INSERTION_SORT_THRESHOLD) {
105 // Insertion sort on smallest arrays
106 dstX[low] = refX[low];
107 dstY[low] = refY[low];
108
109 for (int i = low + 1, j = low, x, y; i < high; j = i++) {
110 x = refX[i];
111 y = refY[i];
112
113 while (dstX[j] > x) {
114 // swap element
115 dstX[j + 1] = dstX[j];
116 dstY[j + 1] = dstY[j];
117 if (j-- == low) {
118 break;
119 }
120 }
121 dstX[j + 1] = x;
122 dstY[j + 1] = y;
123 }
124 return;
125 }
126
127 // Recursively sort halves of dest into src
128
129 // note: use signed shift (not >>>) for performance
130 // as indices are small enough to exceed Integer.MAX_VALUE
131 final int mid = (low + high) >> 1;
132
133 mergeSort(refX, refY, dstX, srcX, dstY, srcY, low, mid);
134 mergeSort(refX, refY, dstX, srcX, dstY, srcY, mid, high);
135
136 // If arrays are inverted ie all(A) > all(B) do swap A and B to dst
137 if (srcX[high - 1] <= srcX[low]) {
138 // System.out.println("mergeSort: inverse ordered");
139 // 1561 occurences
140 final int left = mid - low;
141 final int right = high - mid;
142 final int off = (left != right) ? 1 : 0;
143 // swap parts:
144 System.arraycopy(srcX, low, dstX, mid + off, left);
145 System.arraycopy(srcX, mid, dstX, low, right);
146 System.arraycopy(srcY, low, dstY, mid + off, left);
147 System.arraycopy(srcY, mid, dstY, low, right);
148 return;
149 }
150
151 // If arrays are already sorted, just copy from src to dest. This is an
152 // optimization that results in faster sorts for nearly ordered lists.
153 if (srcX[mid - 1] <= srcX[mid]) {
154 // System.out.println("mergeSort: ordered");
155 // 14 occurences
156 System.arraycopy(srcX, low, dstX, low, length);
157 System.arraycopy(srcY, low, dstY, low, length);
158 return;
159 }
160
161 // Merge sorted halves (now in src) into dest
162 for (int i = low, p = low, q = mid; i < high; i++) {
163 if ((q >= high) || ((p < mid) && (srcX[p] <= srcX[q]))) {
164 dstX[i] = srcX[p];
165 dstY[i] = srcY[p];
166 p++;
167 } else {
168 dstX[i] = srcX[q];
169 dstY[i] = srcY[q];
170 q++;
171 }
172 }
173 }
174
175 private MergeSort() {
176 }
177 }