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From "Henri Yandell (JIRA)" <j...@apache.org>
Subject [jira] Closed: (LANG-345) Optimize HashCodeBuilder.append(Object)
Date Thu, 09 Aug 2007 02:00:59 GMT

     [ https://issues.apache.org/jira/browse/LANG-345?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Henri Yandell closed LANG-345.
------------------------------

    Resolution: Fixed

Optimization applied - thanks Venkatesh. Once I dug into it, I realized how simple your proposed
change was. Nice find.

> Optimize HashCodeBuilder.append(Object)
> ---------------------------------------
>
>                 Key: LANG-345
>                 URL: https://issues.apache.org/jira/browse/LANG-345
>             Project: Commons Lang
>          Issue Type: Improvement
>    Affects Versions: 2.3
>            Reporter: Venkatesh Prasad Ranganath
>            Priority: Minor
>             Fix For: 2.3.1
>
>         Attachments: Test.java
>
>
> In HashCodeBuilder.append(Object), java.lang.Class.isArray() is used to check if the
input argument is an array.  This check is expensive in comparison with an "instanceof" check.
 While a single instanceof check will not suffice, even the required 9 instance of checks
prove to be faster than this single check.  This is illustrated by the data from a profiling
session.
> CPU SAMPLES BEGIN (total = 71) Sat Jun 30 16:51:43 2007
> rank   self  accum   count trace method
>    1 45.07% 45.07%      32 300138 java.lang.Class.isArray
>    2 14.08% 59.15%      10 300141 java.util.AbstractList.hashCode
>    3 12.68% 71.83%       9 300142 java.util.AbstractList.hashCode
>    4  4.23% 76.06%       3 300030 sun.nio.cs.UTF_8$Decoder.decodeArrayLoop   
>    5  4.23% 80.28%       3 300144 java.util.AbstractList.hashCode
>    6  2.82% 83.10%       2 300143 Test.run2
>    7  2.82% 85.92%       2 300139 java.util.ArrayList.get
>    8  1.41% 87.32%       1 300140 java.util.AbstractList.hashCode
>    9  1.41% 88.73%       1 300145 java.util.AbstractList.hashCode
>   10  1.41% 90.14%       1 300027 sun.nio.cs.UTF_8$Decoder.<init>
>   11  1.41% 91.55%       1 300012 java.nio.DirectByteBuffer.<init>
>   12  1.41% 92.96%       1 300089 sun.security.provider.Sun.<clinit>
>   13  1.41% 94.37%       1 300132 sun.security.provider.Sun.<init>
>   14  1.41% 95.77%       1 300071 java.lang.StringCoding.decode
>   15  1.41% 97.18%       1 300031 sun.reflect.NativeConstructorAccessorImpl.newInstance
 
>   16  1.41% 98.59%       1 300048 java.net.URLClassLoader.defineClass
>   17  1.41% 100.00%       1 300137
> sun.net.www.ParseUtil.canonizeStringCPU SAMPLES END
> The profiled program is given below.  While run1() uses HashCodeBuilder.append(Object),
run2() uses an optimized version of the same code.  While 45% of the time is spent in Class.isArray()
(hence, in run1()), only ~3% of the time is spent in run2().  So,  we can replace the body
of HashCodeBuilder.append(Object) with that from OptimizedHashCodeBuilder.append(Object) and
improve the performance by 15x.
> import org.apache.commons.lang.builder.HashCodeBuilder;
> public class Test {
>   public static void main(String[] s) {
>     java.util.ArrayList o = new java.util.ArrayList();
>     o.add("Hello");
>     o.add("World");
>     run1(o);
>     run2(o);
>   }
>   static void run1(Object o) {
>     for (int i = 0; i < 10000; i++) {
>       HashCodeBuilder h = new HashCodeBuilder();
>       for (int k = 0; k < 100; k++) {
>         h = h.append(o);
>       }
>     }
>   }
>   static void run2(Object o) {
>     for (int i = 0; i < 10000; i++) {
>       HashCodeBuilder h = new OptimizedHashCodeBuilder();
>       for (int k = 0; k < 100; k++) {
>         h = h.append(o);
>       }
>     }
>   }
> }
> class OptimizedHashCodeBuilder extends HashCodeBuilder {
>         public HashCodeBuilder append(final Object object) {
>                 if (object == null) {
>                         super.append(object);
>                 } else {
>                         // 'Switch' on type of array, to dispatch to the correct handler
>                         // This handles multi dimensional arrays
>                         if (object instanceof long[]) {
>                                 append((long[]) object);
>                         } else if (object instanceof int[]) {
>                                 append((int[]) object);
>                         } else if (object instanceof short[]) {
>                                 append((short[]) object);
>                         } else if (object instanceof char[]) {
>                                 append((char[]) object);
>                         } else if (object instanceof byte[]) {
>                                 append((byte[]) object);
>                         } else if (object instanceof double[]) {
>                                 append((double[]) object);
>                         } else if (object instanceof float[]) {
>                                 append((float[]) object);
>                         } else if (object instanceof boolean[]) {
>                                 append((boolean[]) object);
>                         } else if (object instanceof Object[]) {
>                                 // Not an array of primitives
>                                 append((Object[]) object);
>                         } else {
>                                 // the simple case, not an array, just the element
>                                 append(object.hashCode());
>                         }
>                 }
>                 return this;
>         }
> }

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