1 /*
   2  * Copyright (c) 2014 Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 package org.openjdk.bench.java.lang;
  26 
  27 import org.openjdk.jmh.annotations.BenchmarkMode;
  28 import org.openjdk.jmh.annotations.Fork;
  29 import org.openjdk.jmh.annotations.Benchmark;
  30 import org.openjdk.jmh.annotations.Mode;
  31 import org.openjdk.jmh.annotations.OutputTimeUnit;
  32 
  33 import java.util.concurrent.TimeUnit;
  34 
  35 /**
  36  * This benchmark assesses different hashCode strategies in HotSpot
  37  */
  38 @BenchmarkMode(Mode.AverageTime)
  39 @OutputTimeUnit(TimeUnit.NANOSECONDS)
  40 public class ObjectHashCode {
  41 
  42     @Benchmark
  43     @Fork
  44     public int mode_default() {
  45         return System.identityHashCode(new Object());
  46     }
  47 
  48     @Benchmark
  49     @Fork(jvmArgsPrepend = {"-XX:+UnlockExperimentalVMOptions", "-XX:hashCode=0"})
  50     public int mode_0() {
  51         return System.identityHashCode(new Object());
  52     }
  53 
  54     @Benchmark
  55     @Fork(jvmArgsPrepend = {"-XX:+UnlockExperimentalVMOptions", "-XX:hashCode=1"})
  56     public int mode_1() {
  57         return System.identityHashCode(new Object());
  58     }
  59 
  60     @Benchmark
  61     @Fork(jvmArgsPrepend = {"-XX:+UnlockExperimentalVMOptions", "-XX:hashCode=2"})
  62     public int mode_2() {
  63         return System.identityHashCode(new Object());
  64     }
  65 
  66     @Benchmark
  67     @Fork(jvmArgsPrepend = {"-XX:+UnlockExperimentalVMOptions", "-XX:hashCode=3"})
  68     public int mode_3() {
  69         return System.identityHashCode(new Object());
  70     }
  71 
  72     @Benchmark
  73     @Fork(jvmArgsPrepend = {"-XX:+UnlockExperimentalVMOptions", "-XX:hashCode=4"})
  74     public int mode_4() {
  75         return System.identityHashCode(new Object());
  76     }
  77 
  78     @Benchmark
  79     @Fork(jvmArgsPrepend = {"-XX:+UnlockExperimentalVMOptions", "-XX:hashCode=5"})
  80     public int mode_5() {
  81         return System.identityHashCode(new Object());
  82     }
  83 
  84 }