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package com.sun.marlin;

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
/** * 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 { // insertion sort threshold public static final int INSERTION_SORT_THRESHOLD = 14;
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
/** * 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) { 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); } // sort second part only using merge / insertion sort // in 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 if ((insertionSortIndex == 0) || (auxX[insertionSortIndex - 1] <= auxX[insertionSortIndex])) { // 34 occurences // no initial left part or both sublists (auxX, auxY) are sorted: // copy back data into (x, y): System.arraycopy(auxX, 0, x, 0, toIndex); System.arraycopy(auxY, 0, y, 0, toIndex); return; } 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++; } } }
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
/** * 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 occurences 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 occurences 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() { } }