NewVsSetLen


1   /*
2    * Copyright 1999-2005 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.apache.log4j.performance;
18  
19  /**
20  
21     This program compares the cost of creating a new StringBuffer and
22     converting it to a String versus keeping the same StringBuffer,
23     setting its size to zero and then converting it to String.
24  
25     <p>The table below gives some figures.
26  
27  <p>   <table border="1" cellpadding="4">
28     <tr BGCOLOR="#33CCFF">
29       <th BGCOLOR="#CCCCCC" rowspan="2">Total Message length
30       <th colspan="2" align="center">0
31       <th colspan="2" align="center">1
32       <th colspan="2" align="center">2
33       <th colspan="2" align="center">4
34       <th colspan="2" align="center">8
35     </tr>
36  
37     <tr BGCOLOR="#3366FF">
38       <td>New Buffer</td> <td>setLength</td> 
39       <td>New Buffer</td> <td>setLength</td>
40       <td>New Buffer</td> <td>setLength</td>
41       <td>New Buffer</td> <td>setLength</td>
42       <td>New Buffer</td> <td>setLength</td>
43     </tr>
44  
45     <tr align="right"> 
46     <td BGCOLOR="#CCCCCC">256 
47     <td>33 <td>22 
48     <td>34 <td>22
49     <td>34 <td>22
50     <td>34 <td>22 
51     <td>33 <td>23
52     </tr>
53  
54     <tr align="right"> 
55     <td BGCOLOR="#CCCCCC">1024 
56     <td>58 <td>41
57     <td>59 <td>45
58     <td>59 <td>48
59     <td>59 <td>51 
60     <td>60 <td>44
61     </tr>
62  
63     <tr align="right"> 
64     <td BGCOLOR="#CCCCCC">4096 
65     <td>146 <td>132
66     <td>138 <td>132
67     <td>144 <td>126
68     <td>142 <td>132
69     <td>136 <td>132 
70     </tr>
71  
72     <tr align="right"> 
73     <td BGCOLOR="#CCCCCC">16384 
74     <td>617 <td>593 
75     <td>593 <td>609
76     <td>601 <td>617
77     <td>601 <td>632 
78     <td>593 <td>632
79     </tr>
80  
81     <tr align="right"> 
82     <td BGCOLOR="#CCCCCC">65536 
83     <td>3218 <td>3281
84     <td>3093 <td>3125 
85     <td>3125 <td>3156
86     <td>3125 <td>3281 
87     <td>3062 <td>3562
88     </tr>
89  
90     <tr align="right"> 
91     <td BGCOLOR="#CCCCCC">262144 
92     <td>14750 <td>15125
93     <td>14000 <td>15500 
94     <td>14000 <td>16125 
95     <td>14000 <td>18000 
96     <td>14000 <td>21375 
97     </tr>
98  
99     <tr align="right"> 
100    <td BGCOLOR="#CCCCCC">1048576 
101    <td>87500 <td>80000
102    <td>60500 <td>82000 
103    <td>57000 <td>93000 
104    <td>57500 <td>118500 
105    <td>57500 <td>168500 
106    </tr>
107 
108    <caption ALIGN="BOTTOM">Performance comparisons of new buffer
109    creation versus setLength(0) approach for various message sizes and
110    secondary loop lengths.
111    </caption>
112    </table>
113 
114    <p>The tests copy a message to a destination string buffer and then
115    copy a 256 character buffer to another buffer the number of times
116    as specified by the secondary loop length.
117 
118 
119    <p>The <code>setLength(0)</code> method is usually faster. However,
120    after copying a large string it becomes slow even when copying
121    small strings.
122 
123 
124    <p>This is due to a peculiarity in the <code>copy</code> method in
125    StringBuffer class which creates a character array of the same
126    length as the old buffer even if the vast majority of those
127    characters are unused. 
128 
129    <p>The tests were performed on Linux using IBM's JDK 1.1.8.
130 
131    <p>The test script is a crude model of what might happen in
132    reality. If you remain unconvinced of its results, then please send
133    your alternative measurement scenario.
134 
135    
136 
137    
138 */
139 public class NewVsSetLen {
140 
141   static String   s;
142 
143   static int BIGBUF_LEN = 1048576;
144   static int SBUF_LEN = 256;
145   static int RUN_LENGTH = BIGBUF_LEN/4;
146 
147   static char[] sbuf = new char[SBUF_LEN];
148   static char[] bigbuf = new char[BIGBUF_LEN];
149 
150   {
151     for(int i = 0; i < SBUF_LEN; i++) {
152       sbuf[i] = (char) (i);
153     }
154 
155     for(int i = 0; i < BIGBUF_LEN; i++) {
156       bigbuf[i] = (char) (i);
157     }
158   }
159 
160 
161   static
162   public 
163   void main(String  [] args) {    
164  
165     int t;
166 
167     for(int len = SBUF_LEN; len <= BIGBUF_LEN; len*=4, RUN_LENGTH /= 4) {
168       System.out.println("<td>"+len+"\n");
169       for(int second = 0; second < 16;) {
170     System.out.println("SECOND loop="+second +", RUN_LENGTH="
171                +RUN_LENGTH+", len="+len);
172     t = (int)newBuffer(len, second);
173 
174     System.out.print("<td>" + t);
175     t = (int)setLen(len, second);
176     System.out.println(" <td>" + t + " \n");
177     if(second == 0) {
178       second = 1;
179     } else {
180       second *= 2;
181     }
182       }
183     }
184     
185   }
186 
187   static
188   double newBuffer(int size, int second) {    
189     long before = System.currentTimeMillis();
190 
191     for(int i = 0; i < RUN_LENGTH; i++) {
192       StringBuffer   buf = new StringBuffer  (SBUF_LEN);
193       buf.append(sbuf, 0, sbuf.length);
194       buf.append(bigbuf, 0, size);
195       s = buf.toString();
196     }
197 
198     for(int x = 0; x <  second; x++) {
199       StringBuffer   buf = new StringBuffer  (SBUF_LEN);
200       buf.append(sbuf, 0, SBUF_LEN);
201       s = buf.toString();
202     }
203     return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;    
204   }
205 
206   static
207   double setLen(int size, int second) {
208     long before = System.currentTimeMillis();
209 
210     StringBuffer   buf = new StringBuffer  (SBUF_LEN);
211 
212     for(int i = 0; i < RUN_LENGTH; i++) {
213       buf.append(sbuf, 0, sbuf.length);
214       buf.append(bigbuf, 0, size);
215       s = buf.toString();
216       buf.setLength(0);
217     }
218 
219     for(int x = 0; x < second; x++) {
220       buf.append(sbuf, 0, SBUF_LEN);
221       s = buf.toString();
222       buf.setLength(0);
223     }
224     return (System.currentTimeMillis() - before)*1000.0/RUN_LENGTH;    
225   }  
226 }
227
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