Here you can find the source of minRunLength(int n)
| Parameter | Description |
|---|---|
| n | the length of the array to be sorted |
private static int minRunLength(int n)
//package com.java2s; /*/* w ww. j a v a2s .co m*/ * Copyright (C) 2008 The Android Open Source Project * * Licensed 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. */ public class Main { /** * This is the minimum sized sequence that will be merged. Shorter * sequences will be lengthened by calling binarySort. If the entire * array is less than this length, no merges will be performed. * * This constant should be a power of two. It was 64 in Tim Peter's C * implementation, but 32 was empirically determined to work better in * this implementation. In the unlikely event that you set this constant * to be a number that's not a power of two, you'll need to change the * {@link #minRunLength} computation. * * If you decrease this constant, you must change the stackLen * computation in the TimSort constructor, or you risk an * ArrayOutOfBounds exception. See listsort.txt for a discussion * of the minimum stack length required as a function of the length * of the array being sorted and the minimum merge sequence length. */ private static final int MIN_MERGE = 32; /** * Asserts have been placed in if-statements for performance. To enable them, * set this field to true and enable them in VM with a command line flag. * If you modify this class, please do test the asserts! */ private static final boolean DEBUG = false; /** * Returns the minimum acceptable run length for an array of the specified * length. Natural runs shorter than this will be extended with * {@link #binarySort}. * * Roughly speaking, the computation is: * * If n < MIN_MERGE, return n (it's too small to bother with fancy stuff). * Else if n is an exact power of 2, return MIN_MERGE/2. * Else return an int k, MIN_MERGE/2 <= k <= MIN_MERGE, such that n/k * is close to, but strictly less than, an exact power of 2. * * For the rationale, see listsort.txt. * * @param n the length of the array to be sorted * @return the length of the minimum run to be merged */ private static int minRunLength(int n) { if (DEBUG) assert n >= 0; int r = 0; // Becomes 1 if any 1 bits are shifted off while (n >= MIN_MERGE) { r |= (n & 1); n >>= 1; } return n + r; } }