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/*
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* Copyright (c) 2009, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.java2d.marlin;
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/**
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* MergeSort adapted from (OpenJDK 8) java.util.Array.legacyMergeSort(Object[])
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* to swap two arrays at the same time (x & y)
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* and use external auxiliary storage for temporary arrays
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*/
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final class MergeSort {
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// insertion sort threshold
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public static final int INSERTION_SORT_THRESHOLD = 14;
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/**
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* Modified merge sort:
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* Input arrays are in both auxX/auxY (sorted: 0 to insertionSortIndex)
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* and x/y (unsorted: insertionSortIndex to toIndex)
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* Outputs are stored in x/y arrays
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*/
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static void mergeSortNoCopy(final int[] x, final int[] y,
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final int[] auxX, final int[] auxY,
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final int toIndex,
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final int insertionSortIndex)
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{
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if ((toIndex > x.length) || (toIndex > y.length)
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|| (toIndex > auxX.length) || (toIndex > auxY.length)) {
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// explicit check to avoid bound checks within hot loops (below):
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throw new ArrayIndexOutOfBoundsException("bad arguments: toIndex="
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+ toIndex);
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}
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// sort second part only using merge / insertion sort
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// in auxiliary storage (auxX/auxY)
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mergeSort(x, y, x, auxX, y, auxY, insertionSortIndex, toIndex);
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// final pass to merge both
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// Merge sorted parts (auxX/auxY) into x/y arrays
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if ((insertionSortIndex == 0)
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|| (auxX[insertionSortIndex - 1] <= auxX[insertionSortIndex])) {
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// System.out.println("mergeSortNoCopy: ordered");
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// 34 occurences
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// no initial left part or both sublists (auxX, auxY) are sorted:
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// copy back data into (x, y):
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System.arraycopy(auxX, 0, x, 0, toIndex);
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System.arraycopy(auxY, 0, y, 0, toIndex);
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return;
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}
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for (int i = 0, p = 0, q = insertionSortIndex; i < toIndex; i++) {
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if ((q >= toIndex) || ((p < insertionSortIndex)
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&& (auxX[p] <= auxX[q]))) {
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x[i] = auxX[p];
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y[i] = auxY[p];
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p++;
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} else {
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x[i] = auxX[q];
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y[i] = auxY[q];
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q++;
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}
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}
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}
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/**
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* Src is the source array that starts at index 0
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* Dest is the (possibly larger) array destination with a possible offset
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* low is the index in dest to start sorting
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* high is the end index in dest to end sorting
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*/
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private static void mergeSort(final int[] refX, final int[] refY,
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final int[] srcX, final int[] dstX,
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final int[] srcY, final int[] dstY,
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final int low, final int high)
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{
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final int length = high - low;
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/*
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* Tuning parameter: list size at or below which insertion sort
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* will be used in preference to mergesort.
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*/
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if (length <= INSERTION_SORT_THRESHOLD) {
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// Insertion sort on smallest arrays
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dstX[low] = refX[low];
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dstY[low] = refY[low];
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for (int i = low + 1, j = low, x, y; i < high; j = i++) {
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x = refX[i];
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y = refY[i];
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while (dstX[j] > x) {
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// swap element
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dstX[j + 1] = dstX[j];
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dstY[j + 1] = dstY[j];
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if (j-- == low) {
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break;
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}
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}
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dstX[j + 1] = x;
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dstY[j + 1] = y;
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}
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return;
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}
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// Recursively sort halves of dest into src
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// note: use signed shift (not >>>) for performance
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// as indices are small enough to exceed Integer.MAX_VALUE
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final int mid = (low + high) >> 1;
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mergeSort(refX, refY, dstX, srcX, dstY, srcY, low, mid);
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mergeSort(refX, refY, dstX, srcX, dstY, srcY, mid, high);
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// If arrays are inverted ie all(A) > all(B) do swap A and B to dst
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if (srcX[high - 1] <= srcX[low]) {
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// System.out.println("mergeSort: inverse ordered");
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// 1561 occurences
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final int left = mid - low;
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final int right = high - mid;
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final int off = (left != right) ? 1 : 0;
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// swap parts:
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System.arraycopy(srcX, low, dstX, mid + off, left);
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System.arraycopy(srcX, mid, dstX, low, right);
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System.arraycopy(srcY, low, dstY, mid + off, left);
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System.arraycopy(srcY, mid, dstY, low, right);
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return;
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}
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// If arrays are already sorted, just copy from src to dest. This is an
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// optimization that results in faster sorts for nearly ordered lists.
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if (srcX[mid - 1] <= srcX[mid]) {
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// System.out.println("mergeSort: ordered");
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// 14 occurences
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System.arraycopy(srcX, low, dstX, low, length);
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System.arraycopy(srcY, low, dstY, low, length);
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return;
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}
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// Merge sorted halves (now in src) into dest
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for (int i = low, p = low, q = mid; i < high; i++) {
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if ((q >= high) || ((p < mid) && (srcX[p] <= srcX[q]))) {
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dstX[i] = srcX[p];
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dstY[i] = srcY[p];
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p++;
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} else {
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dstX[i] = srcX[q];
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dstY[i] = srcY[q];
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q++;
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}
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}
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}
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private MergeSort() {
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}
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}
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