120 lines
3.3 KiB
Java
120 lines
3.3 KiB
Java
/*
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* Copyright (C) 2011 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.base;
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import com.google.caliper.BeforeExperiment;
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import com.google.caliper.Benchmark;
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import com.google.caliper.Param;
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/**
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* Microbenchmark for {@link com.google.common.base.Strings#repeat}
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*
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* @author Mike Cripps
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*/
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public class StringsRepeatBenchmark {
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@Param({"1", "5", "25", "125"})
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int count;
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@Param({"1", "10"})
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int length;
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private String originalString;
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@BeforeExperiment
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void setUp() {
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originalString = Strings.repeat("x", length);
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}
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@Benchmark
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void oldRepeat(long reps) {
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for (int i = 0; i < reps; i++) {
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String x = oldRepeat(originalString, count);
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if (x.length() != (originalString.length() * count)) {
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throw new RuntimeException("Wrong length: " + x);
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}
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}
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}
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private static String oldRepeat(String string, int count) {
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// If this multiplication overflows, a NegativeArraySizeException or
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// OutOfMemoryError is not far behind
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final int len = string.length();
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final int size = len * count;
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char[] array = new char[size];
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for (int i = 0; i < size; i += len) {
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string.getChars(0, len, array, i);
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}
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return new String(array);
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}
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@Benchmark
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void mikeRepeat(long reps) {
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for (int i = 0; i < reps; i++) {
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String x = mikeRepeat(originalString, count);
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if (x.length() != (originalString.length() * count)) {
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throw new RuntimeException("Wrong length: " + x);
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}
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}
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}
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private static String mikeRepeat(String string, int count) {
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final int len = string.length();
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char[] strCopy = new char[len * Integer.highestOneBit(count)];
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string.getChars(0, len, strCopy, 0);
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char[] array = new char[len * count];
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int strCopyLen = len;
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int pos = 0;
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while (count != 0) {
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if ((count & 1) != 0) {
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System.arraycopy(strCopy, 0, array, pos, strCopyLen);
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pos += strCopyLen;
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}
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count >>= 1;
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if (count != 0) {
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System.arraycopy(strCopy, 0, strCopy, strCopyLen, strCopyLen);
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strCopyLen <<= 1;
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}
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}
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return new String(array);
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}
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@Benchmark
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void martinRepeat(long reps) {
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for (int i = 0; i < reps; i++) {
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String x = martinRepeat(originalString, count);
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if (x.length() != (originalString.length() * count)) {
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throw new RuntimeException("Wrong length: " + x);
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}
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}
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}
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private static String martinRepeat(String string, int count) {
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final int len = string.length();
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final int size = len * count;
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final char[] array = new char[size];
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string.getChars(0, len, array, 0);
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int n;
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for (n = len; n < size - n; n <<= 1) {
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System.arraycopy(array, 0, array, n, n);
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}
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System.arraycopy(array, 0, array, n, size - n);
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return new String(array);
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}
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}
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