1 /* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.base; 18 19 import com.google.caliper.BeforeExperiment; 20 import com.google.caliper.Benchmark; 21 import com.google.caliper.Param; 22 import com.google.common.base.Strings; 23 24 /** 25 * Microbenchmark for {@link Strings#repeat} 26 * 27 * @author Mike Cripps 28 */ 29 public class StringsRepeatBenchmark { 30 @Param({"1", "5", "25", "125"}) int count; 31 @Param({"1", "10"}) int length; 32 33 private String originalString; 34 35 @BeforeExperiment void setUp() { 36 originalString = Strings.repeat("x", length); 37 } 38 39 @Benchmark void oldRepeat(int reps) { 40 for (int i = 0; i < reps; i++) { 41 String x = oldRepeat(originalString, count); 42 if (x.length() != (originalString.length() * count)) { 43 throw new RuntimeException("Wrong length: "+x); 44 } 45 } 46 } 47 @Benchmark void mikeRepeat(int reps) { 48 for (int i = 0; i < reps; i++) { 49 String x = mikeRepeat(originalString, count); 50 if (x.length() != (originalString.length() * count)) { 51 throw new RuntimeException("Wrong length: "+x); 52 } 53 } 54 } 55 @Benchmark void martinRepeat(int reps) { 56 for (int i = 0; i < reps; i++) { 57 String x = martinRepeat(originalString, count); 58 if (x.length() != (originalString.length() * count)) { 59 throw new RuntimeException("Wrong length: "+x); 60 } 61 } 62 } 63 64 private static String mikeRepeat(String string, int count) { 65 final int len = string.length(); 66 char[] strCopy = new char[len * Integer.highestOneBit(count)]; 67 string.getChars(0, len, strCopy, 0); 68 69 char[] array = new char[len * count]; 70 71 int strCopyLen = len; 72 int pos = 0; 73 while (count != 0) { 74 if ((count & 1) != 0) { 75 System.arraycopy(strCopy, 0, array, pos,strCopyLen); 76 pos += strCopyLen; 77 } 78 count >>= 1; 79 if (count != 0) { 80 System.arraycopy(strCopy, 0, strCopy, strCopyLen, strCopyLen); 81 strCopyLen <<= 1; 82 } 83 } 84 return new String(array); 85 } 86 87 private static String oldRepeat(String string, int count) { 88 // If this multiplication overflows, a NegativeArraySizeException or 89 // OutOfMemoryError is not far behind 90 final int len = string.length(); 91 final int size = len * count; 92 char[] array = new char[size]; 93 for (int i = 0; i < size; i+=len) { 94 string.getChars(0, len, array, i); 95 } 96 return new String(array); 97 } 98 99 private static String martinRepeat(String string, int count) { 100 final int len = string.length(); 101 final int size = len * count; 102 final char[] array = new char[size]; 103 string.getChars(0, len, array, 0); 104 int n; 105 for (n = len; n < size - n; n <<= 1) { 106 System.arraycopy(array, 0, array, n, n); 107 } 108 System.arraycopy(array, 0, array, n, size - n); 109 return new String(array); 110 } 111 } 112
