--- /dev/null
+package org.apache.lucene.util;
+
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * This class was inspired by CGLIB, but provides a better
+ * QuickSort algorithm without additional InsertionSort
+ * at the end.
+ * To use, subclass and override the four abstract methods
+ * which compare and modify your data.
+ * Allows custom swap so that two arrays can be sorted
+ * at the same time.
+ * @lucene.internal
+ */
+public abstract class SorterTemplate {
+
+ private static final int MERGESORT_THRESHOLD = 12;
+ private static final int QUICKSORT_THRESHOLD = 7;
+
+ /** Implement this method, that swaps slots {@code i} and {@code j} in your data */
+ protected abstract void swap(int i, int j);
+
+ /** Compares slots {@code i} and {@code j} of you data.
+ * Should be implemented like <code><em>valueOf(i)</em>.compareTo(<em>valueOf(j)</em>)</code> */
+ protected abstract int compare(int i, int j);
+
+ /** Implement this method, that stores the value of slot {@code i} as pivot value */
+ protected abstract void setPivot(int i);
+
+ /** Implements the compare function for the previously stored pivot value.
+ * Should be implemented like <code>pivot.compareTo(<em>valueOf(j)</em>)</code> */
+ protected abstract int comparePivot(int j);
+
+ /** Sorts via stable in-place InsertionSort algorithm
+ *(ideal for small collections which are mostly presorted). */
+ public final void insertionSort(int lo, int hi) {
+ for (int i = lo + 1 ; i <= hi; i++) {
+ for (int j = i; j > lo; j--) {
+ if (compare(j - 1, j) > 0) {
+ swap(j - 1, j);
+ } else {
+ break;
+ }
+ }
+ }
+ }
+
+ /** Sorts via in-place, but unstable, QuickSort algorithm.
+ * For small collections falls back to {@link #insertionSort(int,int)}. */
+ public final void quickSort(final int lo, final int hi) {
+ if (hi <= lo) return;
+ // from Integer's Javadocs: ceil(log2(x)) = 32 - numberOfLeadingZeros(x - 1)
+ quickSort(lo, hi, (Integer.SIZE - Integer.numberOfLeadingZeros(hi - lo)) << 1);
+ }
+
+ private void quickSort(int lo, int hi, int maxDepth) {
+ // fall back to insertion when array has short length
+ final int diff = hi - lo;
+ if (diff <= QUICKSORT_THRESHOLD) {
+ insertionSort(lo, hi);
+ return;
+ }
+
+ // fall back to merge sort when recursion depth gets too big
+ if (--maxDepth == 0) {
+ mergeSort(lo, hi);
+ return;
+ }
+
+ final int mid = lo + (diff >>> 1);
+
+ if (compare(lo, mid) > 0) {
+ swap(lo, mid);
+ }
+
+ if (compare(mid, hi) > 0) {
+ swap(mid, hi);
+ if (compare(lo, mid) > 0) {
+ swap(lo, mid);
+ }
+ }
+
+ int left = lo + 1;
+ int right = hi - 1;
+
+ setPivot(mid);
+ for (;;) {
+ while (comparePivot(right) < 0)
+ --right;
+
+ while (left < right && comparePivot(left) >= 0)
+ ++left;
+
+ if (left < right) {
+ swap(left, right);
+ --right;
+ } else {
+ break;
+ }
+ }
+
+ quickSort(lo, left, maxDepth);
+ quickSort(left + 1, hi, maxDepth);
+ }
+
+ /** Sorts via stable in-place MergeSort algorithm
+ * For small collections falls back to {@link #insertionSort(int,int)}. */
+ public final void mergeSort(int lo, int hi) {
+ final int diff = hi - lo;
+ if (diff <= MERGESORT_THRESHOLD) {
+ insertionSort(lo, hi);
+ return;
+ }
+
+ final int mid = lo + (diff >>> 1);
+
+ mergeSort(lo, mid);
+ mergeSort(mid, hi);
+ merge(lo, mid, hi, mid - lo, hi - mid);
+ }
+
+ private void merge(int lo, int pivot, int hi, int len1, int len2) {
+ if (len1 == 0 || len2 == 0) {
+ return;
+ }
+ if (len1 + len2 == 2) {
+ if (compare(pivot, lo) < 0) {
+ swap(pivot, lo);
+ }
+ return;
+ }
+ int first_cut, second_cut;
+ int len11, len22;
+ if (len1 > len2) {
+ len11 = len1 >>> 1;
+ first_cut = lo + len11;
+ second_cut = lower(pivot, hi, first_cut);
+ len22 = second_cut - pivot;
+ } else {
+ len22 = len2 >>> 1;
+ second_cut = pivot + len22;
+ first_cut = upper(lo, pivot, second_cut);
+ len11 = first_cut - lo;
+ }
+ rotate(first_cut, pivot, second_cut);
+ final int new_mid = first_cut + len22;
+ merge(lo, first_cut, new_mid, len11, len22);
+ merge(new_mid, second_cut, hi, len1 - len11, len2 - len22);
+ }
+
+ private void rotate(int lo, int mid, int hi) {
+ int lot = lo;
+ int hit = mid - 1;
+ while (lot < hit) {
+ swap(lot++, hit--);
+ }
+ lot = mid; hit = hi - 1;
+ while (lot < hit) {
+ swap(lot++, hit--);
+ }
+ lot = lo; hit = hi - 1;
+ while (lot < hit) {
+ swap(lot++, hit--);
+ }
+ }
+
+ private int lower(int lo, int hi, int val) {
+ int len = hi - lo;
+ while (len > 0) {
+ final int half = len >>> 1,
+ mid = lo + half;
+ if (compare(mid, val) < 0) {
+ lo = mid + 1;
+ len = len - half -1;
+ } else {
+ len = half;
+ }
+ }
+ return lo;
+ }
+
+ private int upper(int lo, int hi, int val) {
+ int len = hi - lo;
+ while (len > 0) {
+ final int half = len >>> 1,
+ mid = lo + half;
+ if (compare(val, mid) < 0) {
+ len = half;
+ } else {
+ lo = mid + 1;
+ len = len - half -1;
+ }
+ }
+ return lo;
+ }
+
+}
fnp / pylucene.git / blobdiff