NegativeExponentialTimer


1   /*
2   * CLIF is a Load Injection Framework
3   * Copyright (C) 2003 France Telecom R&D
4   * Copyright (C) 2003 INRIA
5   *
6   * This library is free software; you can redistribute it and/or
7   * modify it under the terms of the GNU Lesser General Public
8   * License as published by the Free Software Foundation; either
9   * version 2 of the License, or (at your option) any later version.
10  *
11  * This library is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with this library; if not, write to the Free Software
18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19  *
20  * CLIF $Name:  $
21  *
22  * Contact: clif@objectweb.org
23  *
24  * @authors: Julien Buret
25  * @authors: Nicolas Droze
26  */
27  
28  package org.objectweb.clif.scenario.util.timers;
29  
30  import java.util.Random  ;
31  
32  /**
33   * This class represents a timer with a negative exponential random distribution.
34   */
35  public class NegativeExponentialTimer extends RandomTimer {
36  
37      private long rand;
38      private Random   random = new Random  ();
39      private int mean;
40  
41      /**
42       * The constructor with no parameters (no range)
43       */
44      public NegativeExponentialTimer() {
45      }
46  
47      /**
48       * The constructor with specific lower bound and upper bound.
49       * @param min The lower bound.
50       * @param mean The mean value.
51       * Typicals values are min=0.5 mean=7000
52       */
53      public NegativeExponentialTimer(int min, int mean) {
54          setMin(min);
55          this.mean = mean;
56      }
57  
58      /**
59       * This method calculate a random delay between the range of the timer.
60       * @return The random delay calculated with a negative exponential distribution.
61       */
62      public long getDelay() {
63          double r = random.nextDouble();
64          if (r < (double) 4.54e-5)
65              return ((long) (r + getMin()));
66          return ((long) ((((double) - mean) * Math.log(r)) + getMin()));
67      }
68  
69      /**
70       * This is the useful method to write a scenario.
71       * Calling this method will pause the thread of a random delay.
72       */
73      public void delay() {
74          try {
75              Thread.sleep(getDelay());
76          } catch (InterruptedException   e) {
77              e.printStackTrace();
78          }
79      }
80  
81  }
82
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