Optimize HashCodeBuilder.append(Object)
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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
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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