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/*
* Copyright (c) 2009, 2024, 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* 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
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*/
package com.sun.marlin;
import java.util.Arrays;
import static com.sun.marlin.DualPivotQuicksort20191112Ext.sort;
/**
* MergeSort adapted from (OpenJDK 8) java.util.Array.legacyMergeSort(Object[])
* to swap two arrays at the same time (x & y)
* and use external auxiliary storage for temporary arrays
*/
final class MergeSort {
static final boolean USE_DPQS = MarlinProperties.isUseDPQS();
static final String SORT_TYPE = USE_DPQS ? "DPQS_20191112" : "MERGE";
static final int DPQS_THRESHOLD = 256;
static final int DISABLE_ISORT_THRESHOLD = 1000;
private static final boolean CHECK_SORTED = false;
static {
MarlinUtils.logInfo("MergeSort: DPQS_THRESHOLD: " + DPQS_THRESHOLD);
MarlinUtils.logInfo("MergeSort: DISABLE_ISORT_THRESHOLD: " + DISABLE_ISORT_THRESHOLD);
if (CHECK_SORTED) {
MarlinUtils.logInfo("MergeSort: CHECK_SORTED: " + CHECK_SORTED);
}
}
/**
* Modified merge sort:
* Input arrays are in both auxX/auxY (sorted: 0 to insertionSortIndex)
* and x/y (unsorted: insertionSortIndex to toIndex)
* Outputs are stored in x/y arrays
*/
static void mergeSortNoCopy(final int[] x, final int[] y,
final int[] auxX, final int[] auxY,
final int toIndex,
final int insertionSortIndex,
final boolean skipISort,
final DPQSSorterContext sorter,
final boolean useDPQS)
{
if ((toIndex > x.length) || (toIndex > y.length)
|| (toIndex > auxX.length) || (toIndex > auxY.length)) {
// explicit check to avoid bound checks within hot loops (below):
throw new ArrayIndexOutOfBoundsException("bad arguments: toIndex="
+ toIndex);
}
if (skipISort) {
if (useDPQS) {
// sort full x/y in-place
sort(sorter, x, auxX, y, auxY, 0, toIndex);
} else {
// sort full auxX/auxY into x/y
mergeSort(auxX, auxY, auxX, x, auxY, y, 0, toIndex);
}
if (CHECK_SORTED) {
checkRange(x, 0, toIndex);
}
return;
} else {
if (useDPQS) {
// sort auxX/auxY in-place
sort(sorter, auxX, x, auxY, y, insertionSortIndex, toIndex);
} else {
// sort second part only using merge sort
// x/y into auxiliary storage (auxX/auxY)
mergeSort(x, y, x, auxX, y, auxY, insertionSortIndex, toIndex);
}
}
// final pass to merge both
// Merge sorted parts (auxX/auxY) into x/y arrays
for (int i = 0, p = 0, q = insertionSortIndex; i < toIndex; i++) {
if ((q >= toIndex) || ((p < insertionSortIndex)
&& (auxX[p] <= auxX[q]))) {
x[i] = auxX[p];
y[i] = auxY[p];
p++;
} else {
x[i] = auxX[q];
y[i] = auxY[q];
q++;
}
}
if (CHECK_SORTED) {
checkRange(x, 0, toIndex);
}
}
// insertion sort threshold for MergeSort()
static final int INSERTION_SORT_THRESHOLD = 14;
/**
* Src is the source array that starts at index 0
* Dest is the (possibly larger) array destination with a possible offset
* low is the index in dest to start sorting
* high is the end index in dest to end sorting
*/
private static void mergeSort(final int[] refX, final int[] refY,
final int[] srcX, final int[] dstX,
final int[] srcY, final int[] dstY,
final int low, final int high)
{
final int length = high - low;
/*
* Tuning parameter: list size at or below which insertion sort
* will be used in preference to mergesort.
*/
if (length <= INSERTION_SORT_THRESHOLD) {
// Insertion sort on smallest arrays
dstX[low] = refX[low];
dstY[low] = refY[low];
for (int i = low + 1, j = low, x, y; i < high; j = i++) {
x = refX[i];
y = refY[i];
while (dstX[j] > x) {
// swap element
dstX[j + 1] = dstX[j];
dstY[j + 1] = dstY[j];
if (j-- == low) {
break;
}
}
dstX[j + 1] = x;
dstY[j + 1] = y;
}
return;
}
// Recursively sort halves of dest into src
// note: use signed shift (not >>>) for performance
// as indices are small enough to exceed Integer.MAX_VALUE
final int mid = (low + high) >> 1;
mergeSort(refX, refY, dstX, srcX, dstY, srcY, low, mid);
mergeSort(refX, refY, dstX, srcX, dstY, srcY, mid, high);
// If arrays are inverted ie all(A) > all(B) do swap A and B to dst
if (srcX[high - 1] <= srcX[low]) {
// 1561 occurrences
final int left = mid - low;
final int right = high - mid;
final int off = (left != right) ? 1 : 0;
// swap parts:
System.arraycopy(srcX, low, dstX, mid + off, left);
System.arraycopy(srcX, mid, dstX, low, right);
System.arraycopy(srcY, low, dstY, mid + off, left);
System.arraycopy(srcY, mid, dstY, low, right);
return;
}
// If arrays are already sorted, just copy from src to dest. This is an
// optimization that results in faster sorts for nearly ordered lists.
if (srcX[mid - 1] <= srcX[mid]) {
// 14 occurrences
System.arraycopy(srcX, low, dstX, low, length);
System.arraycopy(srcY, low, dstY, low, length);
return;
}
// Merge sorted halves (now in src) into dest
for (int i = low, p = low, q = mid; i < high; i++) {
if ((q >= high) || ((p < mid) && (srcX[p] <= srcX[q]))) {
dstX[i] = srcX[p];
dstY[i] = srcY[p];
p++;
} else {
dstX[i] = srcX[q];
dstY[i] = srcY[q];
q++;
}
}
}
private MergeSort() {
}
private static void checkRange(int[] x, int lo, int hi) {
for (int i = lo + 1; i < hi; i++) {
if (x[i - 1] > x[i]) {
MarlinUtils.logInfo("Bad sorted x [" + (i - 1) + "]" + Arrays.toString(Arrays.copyOf(x, hi)));
return;
}
}
}
}
