| /* |
| * 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. |
| */ |
| package org.apache.hadoop.util; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * An implementation of the core algorithm of QuickSort. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Unstable |
| public final class QuickSort implements IndexedSorter { |
| |
| private static final IndexedSorter alt = new HeapSort(); |
| |
| public QuickSort() { } |
| |
| private static void fix(IndexedSortable s, int p, int r) { |
| if (s.compare(p, r) > 0) { |
| s.swap(p, r); |
| } |
| } |
| |
| /** |
| * Deepest recursion before giving up and doing a heapsort. |
| * Returns 2 * ceil(log(n)). |
| */ |
| protected static int getMaxDepth(int x) { |
| if (x <= 0) |
| throw new IllegalArgumentException("Undefined for " + x); |
| return (32 - Integer.numberOfLeadingZeros(x - 1)) << 2; |
| } |
| |
| /** |
| * Sort the given range of items using quick sort. |
| * {@inheritDoc} If the recursion depth falls below {@link #getMaxDepth}, |
| * then switch to {@link HeapSort}. |
| */ |
| @Override |
| public void sort(IndexedSortable s, int p, int r) { |
| sort(s, p, r, null); |
| } |
| |
| @Override |
| public void sort(final IndexedSortable s, int p, int r, |
| final Progressable rep) { |
| sortInternal(s, p, r, rep, getMaxDepth(r - p)); |
| } |
| |
| private static void sortInternal(final IndexedSortable s, int p, int r, |
| final Progressable rep, int depth) { |
| if (null != rep) { |
| rep.progress(); |
| } |
| while (true) { |
| if (r-p < 13) { |
| for (int i = p; i < r; ++i) { |
| for (int j = i; j > p && s.compare(j-1, j) > 0; --j) { |
| s.swap(j, j-1); |
| } |
| } |
| return; |
| } |
| if (--depth < 0) { |
| // give up |
| alt.sort(s, p, r, rep); |
| return; |
| } |
| |
| // select, move pivot into first position |
| fix(s, (p+r) >>> 1, p); |
| fix(s, (p+r) >>> 1, r - 1); |
| fix(s, p, r-1); |
| |
| // Divide |
| int i = p; |
| int j = r; |
| int ll = p; |
| int rr = r; |
| int cr; |
| while(true) { |
| while (++i < j) { |
| if ((cr = s.compare(i, p)) > 0) break; |
| if (0 == cr && ++ll != i) { |
| s.swap(ll, i); |
| } |
| } |
| while (--j > i) { |
| if ((cr = s.compare(p, j)) > 0) break; |
| if (0 == cr && --rr != j) { |
| s.swap(rr, j); |
| } |
| } |
| if (i < j) s.swap(i, j); |
| else break; |
| } |
| j = i; |
| // swap pivot- and all eq values- into position |
| while (ll >= p) { |
| s.swap(ll--, --i); |
| } |
| while (rr < r) { |
| s.swap(rr++, j++); |
| } |
| |
| // Conquer |
| // Recurse on smaller interval first to keep stack shallow |
| assert i != j; |
| if (i - p < r - j) { |
| sortInternal(s, p, i, rep, depth); |
| p = j; |
| } else { |
| sortInternal(s, j, r, rep, depth); |
| r = i; |
| } |
| } |
| } |
| |
| } |