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
17package com.google.common.hash;
18
19import com.google.caliper.BeforeExperiment;
20import com.google.caliper.Benchmark;
21import com.google.caliper.Param;
22
23import java.util.Random;
24import java.util.zip.Adler32;
25import java.util.zip.CRC32;
26import java.util.zip.Checksum;
27
28/**
29 * Benchmarks for comparing {@link Checksum}s and {@link HashFunction}s that wrap {@link Checksum}s.
30 *
31 * <p>Parameters for the benchmark are: <ul> <li>size: The length of the byte array to hash. </ul>
32 *
33 * @author Colin Decker
34 */
35public class ChecksumBenchmark {
36
37  // Use a constant seed for all of the benchmarks to ensure apples to apples comparisons.
38  private static final int RANDOM_SEED = new Random().nextInt();
39
40  @Param({"10", "1000", "100000", "1000000"})
41  private int size;
42
43  private byte[] testBytes;
44
45  @BeforeExperiment
46  void setUp() {
47    testBytes = new byte[size];
48    new Random(RANDOM_SEED).nextBytes(testBytes);
49  }
50
51  // CRC32
52
53  @Benchmark byte crc32HashFunction(int reps) {
54    return runHashFunction(reps, Hashing.crc32());
55  }
56
57  @Benchmark byte crc32Checksum(int reps) throws Exception {
58    byte result = 0x01;
59    for (int i = 0; i < reps; i++) {
60      CRC32 checksum = new CRC32();
61      checksum.update(testBytes);
62      result ^= checksum.getValue();
63    }
64    return result;
65  }
66
67  // Adler32
68
69  @Benchmark byte adler32HashFunction(int reps) {
70    return runHashFunction(reps, Hashing.adler32());
71  }
72
73  @Benchmark byte adler32Checksum(int reps) throws Exception {
74    byte result = 0x01;
75    for (int i = 0; i < reps; i++) {
76      Adler32 checksum = new Adler32();
77      checksum.update(testBytes);
78      result ^= checksum.getValue();
79    }
80    return result;
81  }
82
83  // Helpers + main
84
85  private byte runHashFunction(int reps, HashFunction hashFunction) {
86    byte result = 0x01;
87    // Trick the JVM to prevent it from using the hash function non-polymorphically
88    result ^= Hashing.crc32().hashInt(reps).asBytes()[0];
89    result ^= Hashing.adler32().hashInt(reps).asBytes()[0];
90    for (int i = 0; i < reps; i++) {
91      result ^= hashFunction.hashBytes(testBytes).asBytes()[0];
92    }
93    return result;
94  }
95}
96