1 /* 2 * Copyright (C) 2012 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 23 import java.util.Arrays; 24 import java.util.Iterator; 25 26 /** 27 * Benchmarks {@link Joiner} against some common implementations of delimiter-based 28 * string joining. 29 * 30 * @author Adomas Paltanavicius 31 */ 32 public class JoinerBenchmark { 33 34 private static final String DELIMITER_STRING = ","; 35 private static final char DELIMITER_CHARACTER = ','; 36 37 private static final Joiner JOINER_ON_STRING = Joiner.on(DELIMITER_STRING); 38 private static final Joiner JOINER_ON_CHARACTER = Joiner.on(DELIMITER_CHARACTER); 39 40 @Param({"3", "30", "300"}) int count; 41 @Param({"0", "1", "16", "32", "100"}) int componentLength; 42 43 private Iterable<String> components; 44 45 @BeforeExperiment 46 void setUp() { 47 String component = Strings.repeat("a", componentLength); 48 String[] raw = new String[count]; 49 Arrays.fill(raw, component); 50 components = Arrays.asList(raw); 51 } 52 53 /** 54 * {@link Joiner} with a string delimiter. 55 */ 56 @Benchmark int joinerWithStringDelimiter(int reps) { 57 int dummy = 0; 58 for (int i = 0; i < reps; i++) { 59 dummy ^= JOINER_ON_STRING.join(components).length(); 60 } 61 return dummy; 62 } 63 64 /** 65 * {@link Joiner} with a character delimiter. 66 */ 67 @Benchmark int joinerWithCharacterDelimiter(int reps) { 68 int dummy = 0; 69 for (int i = 0; i < reps; i++) { 70 dummy ^= JOINER_ON_CHARACTER.join(components).length(); 71 } 72 return dummy; 73 } 74 75 /** 76 * Mimics what the {@link Joiner} class does internally when no extra options like 77 * ignoring {@code null} values are used. 78 */ 79 @Benchmark int joinerInlined(int reps) { 80 int dummy = 0; 81 for (int i = 0; i < reps; i++) { 82 StringBuilder sb = new StringBuilder(); 83 Iterator<String> iterator = components.iterator(); 84 if (iterator.hasNext()) { 85 sb.append(iterator.next().toString()); 86 while (iterator.hasNext()) { 87 sb.append(DELIMITER_STRING); 88 sb.append(iterator.next()); 89 } 90 } 91 dummy ^= sb.toString().length(); 92 } 93 return dummy; 94 } 95 96 /** 97 * Only appends delimiter if the accumulated string is non-empty. 98 * Note: this isn't a candidate implementation for Joiner since it fails on leading 99 * empty components. 100 */ 101 @Benchmark int stringBuilderIsEmpty(int reps) { 102 int dummy = 0; 103 for (int i = 0; i < reps; i++) { 104 StringBuilder sb = new StringBuilder(); 105 for (String comp : components) { 106 if (sb.length() > 0) { 107 sb.append(DELIMITER_STRING); 108 } 109 sb.append(comp); 110 } 111 dummy ^= sb.toString().length(); 112 } 113 return dummy; 114 } 115 116 /** 117 * Similar to the above, but keeps a boolean flag rather than checking for the string 118 * accumulated so far being empty. As a result, it does not have the above-mentioned bug. 119 */ 120 @Benchmark int booleanIfFirst(int reps) { 121 int dummy = 0; 122 for (int i = 0; i < reps; i++) { 123 StringBuilder sb = new StringBuilder(); 124 boolean append = false; 125 for (String comp : components) { 126 if (append) { 127 sb.append(DELIMITER_STRING); 128 } 129 sb.append(comp); 130 append = true; 131 } 132 dummy ^= sb.toString().length(); 133 } 134 return dummy; 135 } 136 137 /** 138 * Starts with an empty delimiter and changes to the desired value at the end of the 139 * iteration. 140 */ 141 @Benchmark int assignDelimiter(int reps) { 142 int dummy = 0; 143 for (int i = 0; i < reps; i++) { 144 StringBuilder sb = new StringBuilder(); 145 String delim = ""; 146 for (String comp : components) { 147 sb.append(delim); 148 sb.append(comp); 149 delim = DELIMITER_STRING; 150 } 151 dummy ^= sb.toString().length(); 152 } 153 return dummy; 154 } 155 156 /** 157 * Always append the delimiter after the component, and in the very end shortens the buffer 158 * to get rid of the extra trailing delimiter. 159 */ 160 @Benchmark int alwaysAppendThenBackUp(int reps) { 161 int dummy = 0; 162 for (int i = 0; i < reps; i++) { 163 StringBuilder sb = new StringBuilder(); 164 for (String comp : components) { 165 sb.append(comp); 166 sb.append(DELIMITER_STRING); 167 } 168 if (sb.length() > 0) { 169 sb.setLength(sb.length() - DELIMITER_STRING.length()); 170 } 171 dummy ^= sb.toString().length(); 172 } 173 return dummy; 174 } 175 } 176
