/*
* Copyright (C) The Apache Software Foundation. All rights reserved.
*
* This software is published under the terms of the Apache Software
* License version 1.1, a copy of which has been included with this
* distribution in the LICENSE.txt file. */
package org.apache.log4j.performance;
/**
This program compares the cost of creating a new StringBuffer and
converting it to a String versus keeping the same StringBuffer,
setting its size to zero and then converting it to String.
<p>The table below gives some figures.
<p> <table border="1" cellpadding="4">
<tr BGCOLOR="#33CCFF">
<th BGCOLOR="#CCCCCC" rowspan="2">Total Message length
<th colspan="2" align="center">0
<th colspan="2" align="center">1
<th colspan="2" align="center">2
<th colspan="2" align="center">4
<th colspan="2" align="center">8
</tr>
<tr BGCOLOR="#3366FF">
<td>New Buffer</td> <td>setLength</td>
<td>New Buffer</td> <td>setLength</td>
<td>New Buffer</td> <td>setLength</td>
<td>New Buffer</td> <td>setLength</td>
<td>New Buffer</td> <td>setLength</td>
</tr>
<tr align="right">
<td BGCOLOR="#CCCCCC">256
<td>33 <td>22
<td>34 <td>22
<td>34 <td>22
<td>34 <td>22
<td>33 <td>23
</tr>
<tr align="right">
<td BGCOLOR="#CCCCCC">1024
<td>58 <td>41
<td>59 <td>45
<td>59 <td>48
<td>59 <td>51
<td>60 <td>44
</tr>
<tr align="right">
<td BGCOLOR="#CCCCCC">4096
<td>146 <td>132
<td>138 <td>132
<td>144 <td>126
<td>142 <td>132
<td>136 <td>132
</tr>
<tr align="right">
<td BGCOLOR="#CCCCCC">16384
<td>617 <td>593
<td>593 <td>609
<td>601 <td>617
<td>601 <td>632
<td>593 <td>632
</tr>
<tr align="right">
<td BGCOLOR="#CCCCCC">65536
<td>3218 <td>3281
<td>3093 <td>3125
<td>3125 <td>3156
<td>3125 <td>3281
<td>3062 <td>3562
</tr>
<tr align="right">
<td BGCOLOR="#CCCCCC">262144
<td>14750 <td>15125
<td>14000 <td>15500
<td>14000 <td>16125
<td>14000 <td>18000
<td>14000 <td>21375
</tr>
<tr align="right">
<td BGCOLOR="#CCCCCC">1048576
<td>87500 <td>80000
<td>60500 <td>82000
<td>57000 <td>93000
<td>57500 <td>118500
<td>57500 <td>168500
</tr>
<caption ALIGN="BOTTOM">Performance comparisons of new buffer
creation versus setLength(0) approach for various message sizes and
secondary loop lengths.
</caption>
</table>
<p>The tests copy a message to a destination string buffer and then
copy a 256 character buffer to another buffer the number of times
as specified by the secondary loop length.
<p>The <code>setLength(0)</code> method is usually faster. However,
after copying a large string it becomes slow even when copying
small strings.
<p>This is due to a peculiarity in the <code>copy</code> method in
StringBuffer class which creates a character array of the same
length as the old buffer even if the vast majority of those
characters are unused.
<p>The tests were performed on Linux using IBM's JDK 1.1.8.
<p>The test script is a crude model of what might happen in
reality. If you remain unconvinced of its results, then please send
your alternative measurement scenario.
*/
public class NewVsSetLen {
static String s;
static int BIGBUF_LEN = 1048576;
static int SBUF_LEN = 256;
static int RUN_LENGTH = BIGBUF_LEN/4;
static char[] sbuf = new char[SBUF_LEN];
static char[] bigbuf = new char[BIGBUF_LEN];
{
for(int i = 0; i < SBUF_LEN; i++) {
sbuf[i] = (char) (i);
}
for(int i = 0; i < BIGBUF_LEN; i++) {
bigbuf[i] = (char) (i);
}
}
static
public
void main(String[] args) {
int t;
for(int len = SBUF_LEN; len <= BIGBUF_LEN; len*=4, RUN_LENGTH /= 4) {
System.out.println("<td>"+len+"\n");
for(int second = 0; second < 16;) {
System.out.println("SECOND loop="+second +", RUN_LENGTH="
+RUN_LENGTH+", len="+len);
t = (int)newBuffer(len, second);
System.out.print("<td>" + t);
t = (int)setLen(len, second);
System.out.println(" <td>" + t + " \n");
if(second == 0) {
second = 1;
} else {
second *= 2;
}
}
}
}
static
double newBuffer(int size, int second) {
long before = System.currentTimeMillis();
for(int i = 0; i < RUN_LENGTH; i++) {
StringBuffer buf = new StringBuffer(SBUF_LEN);
buf.append(sbuf, 0, sbuf.length);
buf.append(bigbuf, 0, size);
s = buf.toString();
}
for(int x = 0; x < second; x++) {
StringBuffer buf = new StringBuffer(SBUF_LEN);
buf.append(sbuf, 0, SBUF_LEN);
s = buf.toString();
}
return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
}
static
double setLen(int size, int second) {
long before = System.currentTimeMillis();
StringBuffer buf = new StringBuffer(SBUF_LEN);
for(int i = 0; i < RUN_LENGTH; i++) {
buf.append(sbuf, 0, sbuf.length);
buf.append(bigbuf, 0, size);
s = buf.toString();
buf.setLength(0);
}
for(int x = 0; x < second; x++) {
buf.append(sbuf, 0, SBUF_LEN);
s = buf.toString();
buf.setLength(0);
}
return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;
}
}
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