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1   /**
2    * Copyright (c) 2004-2011 QOS.ch
3    * All rights reserved.
4    *
5    * Permission is hereby granted, free  of charge, to any person obtaining
6    * a  copy  of this  software  and  associated  documentation files  (the
7    * "Software"), to  deal in  the Software without  restriction, including
8    * without limitation  the rights to  use, copy, modify,  merge, publish,
9    * distribute,  sublicense, and/or sell  copies of  the Software,  and to
10   * permit persons to whom the Software  is furnished to do so, subject to
11   * the following conditions:
12   *
13   * The  above  copyright  notice  and  this permission  notice  shall  be
14   * included in all copies or substantial portions of the Software.
15   *
16   * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
17   * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
18   * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
19   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
20   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
21   * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
22   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23   *
24   */
25  package org.slf4j.helpers;
26  
27  import junit.framework.AssertionFailedError;
28  
29  /**
30   * BogoPerf is used to check that the time required to perform a certain
31   * operation does not deteriorate over time. BogoPerf adjusts to the CPU speed
32   * and capabilities of the host.
33   * 
34   * @author Ceki Gülcü
35   * 
36   */
37  public class BogoPerf {
38  
39      private static long NANOS_IN_ONE_SECOND = 1000 * 1000 * 1000;
40      private static int INITIAL_N = 1000;
41      private static int LAST_N = 100;
42      private static int SLACK_FACTOR = 3;
43  
44      static {
45          // let the JIT warm up
46          computeBogoIPS(INITIAL_N);
47          double bogo_ips = computeBogoIPS(INITIAL_N);
48          System.out.println("Host runs at " + bogo_ips + " BIPS");
49      }
50  
51      /**
52       * Compute bogoInstructions per second
53       * <p>
54       * on a 3.2 Ghz Pentium D CPU (around 2007), we obtain about 9'000 bogoIPS.
55       * 
56       * @param N
57       *                number of bogoInstructions to average over in order to
58       *                compute the result
59       * @return bogo Instructions Per Second
60       */
61      private static double computeBogoIPS(int N) {
62          long begin = System.nanoTime();
63  
64          for (int i = 0; i < N; i++) {
65              bogoInstruction();
66          }
67          long end = System.nanoTime();
68  
69          // duration
70          double D = end - begin;
71          // average duration per instruction
72          double avgDPIS = D / N;
73          // System.out.println(D + " nanos for " + N + " instructions");
74          // System.out.println(avgD + " nanos per instruction");
75  
76          double bogoIPS = NANOS_IN_ONE_SECOND / avgDPIS;
77          // System.out.println(bogoIPS + " bogoIPS");
78  
79          return bogoIPS;
80      }
81  
82      private static void bogoInstruction() {
83          // use our own random number generator, independent of the host JDK
84          MyRandom myRandom = new MyRandom(100);
85          int len = 150;
86          int[] intArray = new int[len];
87          for (int i = 0; i < len; i++) {
88              intArray[i] = myRandom.nextInt();
89          }
90          // use our own sort algorithm, independent of the host JDK
91          BubbleSort.sort(intArray);
92      }
93  
94      /**
95       * Computed the BogoIPS for this host CPU.
96       * 
97       * @return
98       */
99      public static double currentBIPS() {
100         return computeBogoIPS(LAST_N);
101     }
102 
103     static double min(double a, double b) {
104         return (a <= b) ? a : b;
105     }
106 
107     /**
108      * Assertion used for values that <b>decrease</b> with faster CPUs, typically
109      * the time (duration) needed to perform a task.
110      * 
111      * @param currentDuration
112      * @param referenceDuration
113      * @param referenceBIPS
114      * @throws AssertionFailedError
115      */
116     public static void assertDuration(double currentDuration, long referenceDuration, double referenceBIPS) throws AssertionFailedError {
117         double ajustedDuration = adjustExpectedDuration(referenceDuration, referenceBIPS);
118         if (currentDuration > ajustedDuration * SLACK_FACTOR) {
119             throw new AssertionFailedError("current duration " + currentDuration + " exceeded expected " + ajustedDuration + " (adjusted reference), "
120                             + referenceDuration + " (raw reference)");
121         }
122     }
123 
124     /**
125      * Assertion used for values that <b>increase<b> with faster CPUs, typically
126      * the number of operations accomplished per unit of time.
127      * 
128      * @param currentPerformance
129      * @param referencePerformance
130      * @param referenceBIPS
131      * @throws AssertionFailedError
132      */
133     public static void assertPerformance(double currentPerformance, long referencePerformance, double referenceBIPS) throws AssertionFailedError {
134         double ajustedPerf = adjustExpectedPerformance(referencePerformance, referenceBIPS);
135         if (currentPerformance * SLACK_FACTOR < ajustedPerf) {
136             throw new AssertionFailedError(currentPerformance + " below expected " + ajustedPerf + " (adjusted), " + referencePerformance + " (raw)");
137         }
138     }
139 
140     private static double adjustExpectedPerformance(long referenceDuration, double referenceBIPS) {
141         double currentBIPS = currentBIPS();
142         return referenceDuration * (currentBIPS / referenceBIPS);
143     }
144 
145     private static double adjustExpectedDuration(long referenceDuration, double referenceBIPS) {
146         double currentBIPS = currentBIPS();
147         System.out.println("currentBIPS=" + currentBIPS + " BIPS");
148         return referenceDuration * (referenceBIPS / currentBIPS);
149     }
150 }