/*
* Copyright (C) 2012 The Guava Authors
*
* 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.
*/
package com.google.common.hash;
import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;
import java.util.Random;
import java.util.zip.Adler32;
import java.util.zip.CRC32;
import java.util.zip.Checksum;
/**
* Benchmarks for comparing {@link Checksum}s and {@link HashFunction}s that wrap {@link Checksum}s.
*
* <p>Parameters for the benchmark are: <ul> <li>size: The length of the byte array to hash. </ul>
*
* @author Colin Decker
*/
public class ChecksumBenchmark {
// Use a constant seed for all of the benchmarks to ensure apples to apples comparisons.
private static final int RANDOM_SEED = new Random().nextInt();
@Param({"10", "1000", "100000", "1000000"})
private int size;
private byte[] testBytes;
@BeforeExperiment
void setUp() {
testBytes = new byte[size];
new Random(RANDOM_SEED).nextBytes(testBytes);
}
// CRC32
@Benchmark byte crc32HashFunction(int reps) {
return runHashFunction(reps, Hashing.crc32());
}
@Benchmark byte crc32Checksum(int reps) throws Exception {
byte result = 0x01;
for (int i = 0; i < reps; i++) {
CRC32 checksum = new CRC32();
checksum.update(testBytes);
result ^= checksum.getValue();
}
return result;
}
// Adler32
@Benchmark byte adler32HashFunction(int reps) {
return runHashFunction(reps, Hashing.adler32());
}
@Benchmark byte adler32Checksum(int reps) throws Exception {
byte result = 0x01;
for (int i = 0; i < reps; i++) {
Adler32 checksum = new Adler32();
checksum.update(testBytes);
result ^= checksum.getValue();
}
return result;
}
// Helpers + main
private byte runHashFunction(int reps, HashFunction hashFunction) {
byte result = 0x01;
// Trick the JVM to prevent it from using the hash function non-polymorphically
result ^= Hashing.crc32().hashInt(reps).asBytes()[0];
result ^= Hashing.adler32().hashInt(reps).asBytes()[0];
for (int i = 0; i < reps; i++) {
result ^= hashFunction.hashBytes(testBytes).asBytes()[0];
}
return result;
}
}